Drug interaction

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Drug_interaction 

 

A drug interaction is a change in the action or side effects of a drug caused by concomitant administration with a food, beverage, supplement, or another drug.

There are many causes of drug interactions. For example, one drug may alter the pharmacokinetics of another. Alternatively, drug interactions may result from competition for a single receptor or signaling pathway.

The risk of a drug-drug interaction increases with the number of drugs used. Over a third (36%) of the elderly in the U.S. regularly use five or more medications or supplements, and 15% are at risk of a significant drug-drug interaction.

Pharmacodynamic interactions

When two drugs are used together, their effects can be additive (the result is what you expect when you add together the effect of each drug taken independently), synergistic (combining the drugs leads to a larger effect than expected), or antagonistic (combining the drugs leads to a smaller effect than expected). There is sometimes confusion on whether drugs are synergistic or additive, since the individual effects of each drug may vary from patient to patient. A synergistic interaction may be beneficial for patients, but may also increase the risk of overdose. 

Both synergy and antagonism can occur during different phases of the interaction between a drug, and an organism. For example, when synergy occurs at a cellular receptor level this is termed agonism, and the substances involved are termed agonists. On the other hand, in the case of antagonism, the substances involved are known as inverse agonists. The different responses of a receptor to the action of a drug has resulted in a number of classifications, such as "partial agonist", "competitive agonist" etc. These concepts have fundamental applications in the pharmacodynamics of these interactions. The proliferation of existing classifications at this level, along with the fact that the exact reaction mechanisms for many drugs are not well-understood means that it is almost impossible to offer a clear classification for these concepts. It is even possible that many authors would misapply any given classification.

Direct interactions between drugs are also possible and may occur when two drugs are mixed prior to intravenous injection. For example, mixing thiopentone and suxamethonium in the same syringe can lead to the precipitation of thiopentone.

The change in an organism's response upon administration of a drug is an important factor in pharmacodynamic interactions. These changes are extraordinarily difficult to classify given the wide variety of modes of action that exist, and the fact that many drugs can cause their effect through a number of different mechanisms. This wide diversity also means that, in all but the most obvious cases it is important to investigate, and understand these mechanisms. The well-founded suspicion exists that there are more unknown interactions than known ones. 

Effects of the competitive inhibition of an agonist by increases in the concentration of an antagonist. A drugs potency can be affected (the response curve shifted to the right) by the presence of an antagonistic interaction.pA₂ known as the Schild representation, a mathematical model of the agonist:antagonist relationship or vice versa. NB: the x-axis is incorrectly labelled and should reflect the agonist concentration, not antagonist concentration.

 

Pharmacodynamic interactions can occur on:

1. Pharmacological receptors: Receptor interactions are the most easily defined, but they are also the most common. From a pharmacodynamic perspective, two drugs can be considered to be:
   1. Homodynamic, if they act on the same receptor. They, in turn can be:
      1. Pure agonists, if they bind to the main locus of the receptor, causing a similar effect to that of the main drug.
      2. Partial agonists if, on binding to one of the receptor's secondary sites, they have the same effect as the main drug, but with a lower intensity.
      3. Antagonists, if they bind directly to the receptor's main locus but their effect is opposite to that of the main drug. These include:
         1. Competitive antagonists, if they compete with the main drug to bind with the receptor. The amount of antagonist or main drug that binds with the receptor will depend on the concentrations of each one in the plasma.
         2. Uncompetitive antagonists, when the antagonist binds to the receptor irreversibly and is not released until the receptor is saturated. In principle the quantity of antagonist and agonist that binds to the receptor will depend on their concentrations. However, the presence of the antagonist will cause the main drug to be released from the receptor regardless of the main drug's concentration, therefore all the receptors will eventually become occupied by the antagonist.
   2. Heterodynamic competitors, if they act on distinct receptors.
2. Signal transduction mechanisms: these are molecular processes that commence after the interaction of the drug with the receptor. For example, it is known that hypoglycaemia (low blood glucose) in an organism produces a release of catecholamines, which trigger compensation mechanisms thereby increasing blood glucose levels. The release of catecholamines also triggers a series of symptoms, which allows the organism to recognise what is happening and which act as a stimulant for preventative action (eating sugars). Should a patient be taking a drug such as insulin, which reduces glycaemia, and also be taking another drug such as certain beta-blockers for heart disease, then the beta-blockers will act to block the adrenaline receptors. This will block the reaction triggered by the catecholamines should a hypoglycaemic episode occur. Therefore, the body will not adopt corrective mechanisms and there will be an increased risk of a serious reaction resulting from the ingestion of both drugs at the same time.
3. Antagonic physiological systems: Imagine a drug A that acts on a certain organ. This effect will increase with increasing concentrations of physiological substance S in the organism. Now imagine a drug B that acts on another organ, which increases the amount of substance S. If both drugs are taken simultaneously it is possible that drug A could cause an adverse reaction in the organism as its effect will be indirectly increased by the action of drug B. An actual example of this interaction is found in the concomitant use of digoxin and furosemide. The former acts on cardiac fibres and its effect is increased if there are low levels of potassium (K) in blood plasma. Furosemide is a diuretic that lowers arterial tension but favours the loss of K⁺. This could lead to hypokalemia (low levels of potassium in the blood), which could increase the toxicity of digoxin.

Pharmacokinetic interactions

Modifications in the effect of a drug are caused by differences in the absorption, transport, distribution, metabolism or excretion of one or both of the drugs compared with the expected behavior of each drug when taken individually. These changes are basically modifications in the concentration of the drugs. In this respect, two drugs can be homergic if they have the same effect in the organism and heterergic if their effects are different.

Absorption interactions

Changes in motility

Some drugs, such as the prokinetic agents increase the speed with which a substance passes through the intestines. If a drug is present in the digestive tract's absorption zone for less time its blood concentration will decrease. The opposite will occur with drugs that decrease intestinal motility.

• pH: Drugs can be present in either ionised or non-ionised form, depending on their pKa (pH at which the drug reaches equilibrium between its ionised and non-ionised form). The non-ionized forms of drugs are usually easier to absorb, because they will not be repelled by the lipidic bylayer of the cell, most of them can be absorbed by passive diffusion, unless they are too big or too polarized (like glucose or vancomycin), in which case they may have or not have specific and non specific transporters distributed on the entire intestine internal surface, that carries drugs inside the body. Obviously increasing the absorption of a drug will increase its bioavailability, so, changing the drug's state between ionized or not, can be useful or not for certain drugs.

Certain drugs require an acid stomach pH for absorption. Others require the basic pH of the intestines. Any modification in the pH could change this absorption. In the case of the antacids, an increase in pH can inhibit the absorption of other drugs such as zalcitabine (absorption can be decreased by 25%), tipranavir (25%) and amprenavir (up to 35%). However, this occurs less often than an increase in pH causes an increase in absorption. Such as occurs when cimetidine is taken with didanosine. In this case a gap of two to four hours between taking the two drugs is usually sufficient to avoid the interaction.

• Drug solubility: The absorption of some drugs can be drastically reduced if they are administered together with food with a high fat content. This is the case for oral anticoagulants and avocado.
• Formation of non-absorbable complexes:
  • Chelation: The presence of di- or trivalent cations can cause the chelation of certain drugs, making them harder to absorb. This interaction frequently occurs between drugs such as tetracycline or the fluoroquinolones and dairy products (due to the presence of Ca⁺⁺).
  • Binding with proteins. Some drugs such as sucralfate binds to proteins, especially if they have a high bioavailability. For this reason its administration is contraindicated in enteral feeding.
  • Finally, another possibility is that the drug is retained in the intestinal lumen forming large complexes that impede its absorption. This can occur with cholestyramine if it is associated with sulfamethoxazol, thyroxine, warfarin or digoxin.
• Acting on the P-glycoprotein of the enterocytes: This appears to be one of the mechanisms promoted by the consumption of grapefruit juice in increasing the bioavailability of various drugs, regardless of its demonstrated inhibitory activity on first pass metabolism.

Transport and distribution interactions

The main interaction mechanism is competition for plasma protein transport. In these cases the drug that arrives first binds with the plasma protein, leaving the other drug dissolved in the plasma, which modifies its concentration. The organism has mechanisms to counteract these situations (by, for example, increasing plasma clearance), which means that they are not usually clinically relevant. However, these situations should be taken into account if other associated problems are present such as when the method of excretion is affected.

Metabolism interactions

Diagram of cytochrome P450 isoenzyme 2C9 with the haem group in the centre of the enzyme.

 

Many drug interactions are due to alterations in drug metabolism. Further, human drug-metabolizing enzymes are typically activated through the engagement of nuclear receptors. One notable system involved in metabolic drug interactions is the enzyme system comprising the cytochrome P450 oxidases.

CYP450

Cytochrome P450 is a very large family of haemoproteins (hemoproteins) that are characterized by their enzymatic activity and their role in the metabolism of a large number of drugs. Of the various families that are present in human beings the most interesting in this respect are the 1, 2 and 3, and the most important enzymes are CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4. The majority of the enzymes are also involved in the metabolism of endogenous substances, such as steroids or sex hormones, which is also important should there be interference with these substances. As a result of these interactions the function of the enzymes can either be stimulated (enzyme induction) or inhibited.

Enzymatic inhibition

If drug A is metabolized by a cytochrome P450 enzyme and drug B inhibits or decreases the enzyme's activity, then drug A will remain with high levels in the plasma for longer as its inactivation is slower. As a result, enzymatic inhibition will cause an increase in the drug's effect. This can cause a wide range of adverse reactions.

It is possible that this can occasionally lead to a paradoxical situation, where the enzymatic inhibition causes a decrease in the drug's effect: if the metabolism of drug A gives rise to product A₂, which actually produces the effect of the drug. If the metabolism of drug A is inhibited by drug B the concentration of A₂ that is present in the blood will decrease, as will the final effect of the drug.

Enzymatic induction

If drug A is metabolized by a cytochrome P450 enzyme and drug B induces or increases the enzyme's activity, then blood plasma concentrations of drug A will quickly fall as its inactivation will take place more rapidly. As a result, enzymatic induction will cause a decrease in the drug's effect.

As in the previous case, it is possible to find paradoxical situations where an active metabolite causes the drug's effect. In this case the increase in active metabolite A₂ (following the previous example) produces an increase in the drug's effect.

It can often occur that a patient is taking two drugs that are enzymatic inductors, one inductor and the other inhibitor or both inhibitors, which greatly complicates the control of an individual's medication and the avoidance of possible adverse reactions.

An example of this is shown in the following table for the CYP1A2 enzyme, which is the most common enzyme found in the human liver. The table shows the substrates (drugs metabolized by this enzyme) and the inductors and inhibitors of its activity:

Drugs related to CYP1A2
Substrates	Inhibitors	Inductors
Caffeine Theophylline Phenacetin Clomipramine Clozapine Thioridazine	Omeprazole Nicotine Cimetidine Ciprofloxacin	Phenobarbital Fluvoxamine Venlafaxine Ticlopidine

Enzyme CYP3A4 is the enzyme that the greatest number of drugs use as a substrate. Over 100 drugs depend on its metabolism for their activity and many others act on the enzyme as inductors or inhibitors. 

Some foods also act as inductors or inhibitors of enzymatic activity. The following table shows the most common:

Foods and their influence on drug metabolism
Food	Mechanism	Drugs affected
Avocado Brassicas (brussel sprouts, broccoli, cabbage)	Enzymatic inductor	Acenocoumarol, warfarin
Grapefruit juice	Enzymatic inhibition	Calcium channel blockers: nifedipine, felodipine, nimodipine, amlodipine Cyclosporine, tacrolimus Terfenadine, astemizole Cisapride, pimozide Carbamazepine, saquinavir, midazolam, alprazolam, triazolam Main article: Grapefruit drug interactions
Soya	Enzymatic inhibition	Clozapine, haloperidol, olanzapine, caffeine, NSAIDs, phenytoin, zafirlukast, warfarin
Garlic	Increases antiplatelet activity	Anticoagulants NSAIDs, acetylsalicylic acid
Ginseng	To be determined	Warfarin, heparin, aspirin and NSAIDs
Ginkgo biloba	Strong inhibitor of platelet aggregation factor	Warfarin, aspirin and NSAIDs
Hypericum perforatum (St John's wort)	Enzymatic inductor (CYP450)	Warfarin, digoxin, theophylline, cyclosporine, phenytoin and antiretrovirals
Ephedra	Receptor level agonist	MAOI, central nervous system stimulants, alkaloids ergotamines and xanthines
Kava (Piper methysticum)	Unknown	Levodopa
Ginger	Inhibits thromboxane synthetase (in vitro)	Anticoagulants
Chamomile	Unknown	Benzodiazepines, barbiturates and opioids
Hawthorn	Unknown	Beta-adrenergic antagonists, cisapride, digoxin, quinidine

Grapefruit juice can act as an enzyme inhibitor.

 

Any study of pharmacological interactions between particular medicines should also discuss the likely interactions of some medicinal plants. The effects caused by medicinal plants should be considered in the same way as those of medicines as their interaction with the organism gives rise to a pharmacological response. Other drugs can modify this response and also the plants can give rise to changes in the effects of other active ingredients.

There is little data available regarding interactions involving medicinal plants for the following reasons:

St John's wort can act as an enzyme inductor.

1. False sense of security regarding medicinal plants. The interaction between a medicinal plant and a drug is usually overlooked due to a belief in the "safety of medicinal plants."
2. Variability of composition, both qualitative and quantitative. The composition of a plant-based drug is often subject to wide variations due to a number of factors such as seasonal differences in concentrations, soil type, climatic changes or the existence of different varieties or chemical races within the same plant species that have variable compositions of the active ingredient. On occasion, an interaction can be due to just one active ingredient, but this can be absent in some chemical varieties or it can be present in low concentrations, which will not cause an interaction. Counter interactions can even occur. This occurs, for instance, with ginseng, the Panax ginseng variety increases the Prothrombin time, while the Panax quinquefolius variety decreases it.
3. Absence of use in at-risk groups, such as hospitalized and polypharmacy patients, who tend to have the majority of drug interactions.
4. Limited consumption of medicinal plants has given rise to a lack of interest in this area.

They are usually included in the category of foods as they are usually taken as a tea or food supplement. However, medicinal plants are increasingly being taken in a manner more often associated with conventional medicines: pills, tablets, capsules, etc.

Excretion interactions

Renal excretion

Human kidney nephron.

Only the free fraction of a drug that is dissolved in the blood plasma can be removed through the kidney. Therefore, drugs that are tightly bound to proteins are not available for renal excretion, as long as they are not metabolized when they may be eliminated as metabolites. Creatinine clearance is used as a measure of kidney functioning but it is only useful in cases where the drug is excreted in an unaltered form in the urine. The excretion of drugs from the kidney's nephrons has the same properties as that of any other organic solute: passive filtration, reabsorption and active secretion. In the latter phase the secretion of drugs is an active process that is subject to conditions relating to the saturability of the transported molecule and competition between substrates. Therefore, these are key sites where interactions between drugs could occur. Filtration depends on a number of factors including the pH of the urine, it having been shown that the drugs that act as weak bases are increasingly excreted as the pH of the urine becomes more acidic, and the inverse is true for weak acids. This mechanism is of great use when treating intoxications (by making the urine more acidic or more alkali) and it is also used by some drugs and herbal products to produce their interactive effect.

Drugs that act as weak acids or bases
Weak acids	Weak bases
Acetylsalicylic acid Furosemide Ibuprofen Levodopa Acetazolamide Sulfadiazine Ampicillin Chlorothiazide Paracetamol Chloropropamide Cromoglicic acid Ethacrynic acid alpha-Methyldopamine Phenobarbital Warfarin Theophylline Phenytoin	Reserpine Amphetamine Procaine Ephedrine Atropine Diazepam Hydralazine Pindolol Propranolol Salbutamol Alprenolol Terbutaline Amiloride Chlorpheniramine[23]

Bile excretion

Bile excretion is different from kidney excretion as it always involves energy expenditure in active transport across the epithelium of the bile duct against a concentration gradient. This transport system can also be saturated if the plasma concentrations of the drug are high. Bile excretion of drugs mainly takes place where their molecular weight is greater than 300 and they contain both polar and lipophilic groups. The glucuronidation of the drug in the kidney also facilitates bile excretion. Substances with similar physicochemical properties can block the receptor, which is important in assessing interactions. A drug excreted in the bile duct can occasionally be reabsorbed by the intestines (in the enterohepatic circuit), which can also lead to interactions with other drugs.

Herb-drug interactions

Herb-drug interactions are drug interactions that occur between herbal medicines and conventional drugs. These types of interactions may be more common than drug-drug interactions because herbal medicines often contain multiple pharmacologically active ingredients, while conventional drugs typically contain only one. Some such interactions are clinically significant, although most herbal remedies are not associated with drug interactions causing serious consequences. Most herb-drug interactions are moderate in severity. The most commonly implicated conventional drugs in herb-drug interactions are warfarin, insulin, aspirin, digoxin, and ticlopidine, due to their narrow therapeutic indices. The most commonly implicated herbs involved in such interactions are those containing St. John’s Wort, magnesium, calcium, iron, or ginkgo.

Examples

Examples of herb-drug interactions include, but are not limited to:

• St. John's wort affects the clearance of numerous drugs, including cyclosporin, SSRI antidepressants, digoxin, indinavir, and phenprocoumon. It may also interact with the anti-cancer drugs irinotecan and imatinib.
• Salvia miltiorrhiza may enhance anticoagulation and bleeding among people taking warfarin.
• Allium sativum has been found to decrease the plasma concentration of saquinavir, and may cause hypoglycemia when taken with chlorpropamide.
• Ginkgo biloba can cause bleeding when combined with warfarin or aspirin.
• Concomitant ephedra and caffeine use has been reported to, in rare cases, cause fatalities.

Mechanisms

The mechanisms underlying most herb-drug interactions are not fully understood. Interactions between herbal medicines and anticancer drugs typically involve enzymes that metabolize cytochrome P450. For example, St. John's Wort has been shown to induce CYP3A4 and P-glycoprotein in vitro and in vivo.

Underlying factors

It is possible to take advantage of positive drug interactions. However, the negative interactions are usually of more interest because of their pathological significance, and also because they are often unexpected, and may even go undiagnosed. By studying the conditions that favor the appearance of interactions, it should be possible to prevent them, or at least diagnose them in time. The factors or conditions that predispose the appearance of interactions include:

• Old age: factors relating to how human physiology changes with age may affect the interaction of drugs. For example, liver metabolism, kidney function, nerve transmission or the functioning of bone marrow all decrease with age. In addition, in old age there is a sensory decrease that increases the chances of errors being made in the administration of drugs.
• Polypharmacy: The use of multiple drugs by a single patient, to treat one or more ailments. The more drugs a patient takes the more likely it will be that some of them will interact.
• Genetic factors: Genes synthesize enzymes that metabolize drugs. Some races have genotypic variations that could decrease or increase the activity of these enzymes. The consequence of this would, on occasions, be a greater predisposition towards drug interactions and therefore a greater predisposition for adverse effects to occur. This is seen in genotype variations in the isozymes of cytochrome P450.
• Hepatic or renal diseases: The blood concentrations of drugs that are metabolized in the liver and/or eliminated by the kidneys may be altered if either of these organs is not functioning correctly. If this is the case an increase in blood concentration is normally seen.
• Serious diseases that could worsen if the dose of the medicine is reduced.
• Drug dependent factors:
  • Narrow therapeutic index: Where the difference between the effective dose and the toxic dose is small. The drug digoxin is an example of this type of drug.
  • Steep dose-response curve: Small changes in the dosage of a drug produce large changes in the drug's concentration in the patient's blood plasma.
  • Saturable hepatic metabolism: In addition to dose effects the capacity to metabolize the drug is greatly decreased

Epidemiology

Among US adults older than 55, 4% are taking medication and or supplements that put them at risk of a major drug interaction. Potential drug-drug interactions have increased over time and are more common in the low educated elderly even after controlling for age, sex, place of residence, and comorbidity.

Universal Networking Language

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Universal_Networking_Language 

 

Universal Networking Language (UNL) is a declarative formal language specifically designed to represent semantic data extracted from natural language texts. It can be used as a pivot language in interlingual machine translation systems or as a knowledge representation language in information retrieval applications.

Scope and goals

UNL is designed to establish a simple foundation for representing the most central aspects of information and meaning in a machine- and human-language-independent form. As a language-independent formalism, UNL aims to code, store, disseminate and retrieve information independently of the original language in which it was expressed. In this sense, UNL seeks to provide tools for overcoming the language barrier in a systematic way.

At first glance, UNL seems to be a kind of interlingua, into which source texts are converted before being translated into target languages. It can, in fact, be used for this purpose, and very efficiently, too. However, its real strength is knowledge representation and its primary objective is to provide an infrastructure for handling knowledge that already exists or can exist in any given language.

Nevertheless, it is important to note that at present it would be foolish to claim to represent the “full” meaning of any word, sentence, or text for any language. Subtleties of intention and interpretation make the “full meaning,” however we might conceive it, too variable and subjective for any systematic treatment. Thus UNL avoids the pitfalls of trying to represent the “full meaning” of sentences or texts, targeting instead the “core” or “consensual” meaning most often attributed to them. In this sense, much of the subtlety of poetry, metaphor, figurative language, innuendo, and other complex, indirect communicative behaviors is beyond the current scope and goals of UNL. Instead, UNL targets direct communicative behavior and literal meaning as a tangible, concrete basis for most human communication in practical, day-to-day settings.

Structure

In the UNL approach, information conveyed by natural language is represented sentence by sentence as a hypergraph composed of a set of directed binary labeled links (referred to as relations) between nodes or hypernodes (the Universal Words, or simply UWs), which stand for concepts. UWs can also be annotated with attributes representing context information. 

As an example, the English sentence ‘The sky was blue?!’ can be represented in UNL as follows:

In the example above, "sky(icl>natural world)" and "blue(icl>color)", which represent individual concepts, are UWs; "aoj" (= attribute of an object) is a directed binary semantic relation linking the two UWs; and "@def", "@interrogative", "@past", "@exclamation" and "@entry" are attributes modifying UWs.

UWs are intended to represent universal concepts, but are expressed in English words or in any other natural language in order to be humanly readable. They consist of a "headword" (the UW root) and a "constraint list" (the UW suffix between parentheses), where the constraints are used to disambiguate the general concept conveyed by the headword. The set of UWs is organized in the UNL Ontology, in which high-level concepts are related to lower-level ones through the relations "icl" (= is a kind of), "iof" (= is an instance of) and "equ" (= is equal to).

Relations are intended to represent semantic links between words in every existing language. They can be ontological (such as "icl" and "iof," referred to above), logical (such as "and" and "or"), and thematic (such as "agt" = agent, "ins" = instrument, "tim" = time, "plc" = place, etc.). There are currently 46 relations in the UNL Specs. They jointly define the UNL syntax.

Attributes represent information that cannot be conveyed by UWs and relations. Normally, they represent information concerning time ("@past", "@future", etc.), reference ("@def", "@indef", etc.), modality ("@can", "@must", etc.), focus ("@topic", "@focus", etc.), and so on.

Within the UNL Program, the process of representing natural language sentences in UNL graphs is called UNLization, and the process of generating natural language sentences out of UNL graphs is called NLization. UNLization, which involves natural language analysis and understanding, is intended to be carried out semi-automatically (i.e., by humans with computer aids); and NLization is intended to be carried out fully automatically.

History

The UNL Programme started in 1996, as an initiative of the Institute of Advanced Studies of the United Nations University in Tokyo, Japan. In January 2001, the United Nations University set up an autonomous organization, the UNDL Foundation, to be responsible for the development and management of the UNL Programme. The foundation, a non-profit international organisation, has an independent identity from the United Nations University, although it has special links with the UN. It inherited from the UNU/IAS the mandate of implementing the UNL Programme so that it can fulfil its mission.

The programme has already crossed important milestones. The overall architecture of the UNL System has been developed with a set of basic software and tools necessary for its functioning. These are being tested and improved. A vast amount of linguistic resources from the various native languages already under development, as well as from the UNL expression, has been accumulated in the last few years. Moreover, the technical infrastructure for expanding these resources is already in place, thus facilitating the participation of many more languages in the UNL system from now on. A growing number of scientific papers and academic dissertations on the UNL are being published every year.

The most visible accomplishment so far is the recognition by the Patent Co-operation Treaty (PCT) of the innovative character and industrial applicability of the UNL, which was obtained in May 2002 through the World Intellectual Property Organisation (WIPO). Acquiring the patents (US patents 6,704,700 and 7,107,206) for the UNL is a completely novel achievement within the United Nations.

Heritage language

From Wikipedia, the free encyclopedia

 

A heritage language is a minority language (either immigrant or indigenous) learned by its speakers at home as children, but never fully developed because of insufficient input from the social environment: in fact, the community of speakers grows up with a dominant language in which they become more competent. Polinsky & Kagan label it as a continuum (taken from Valdés definition of heritage language) that ranges from fluent speakers to barely-speaking individuals of the home language. In some countries or cultures in which they determine one's mother tongue by the ethnic group, a heritage language would be linked to the native language.

The term can also refer to the language of a person's family or community that the person does not speak or understand, but identifies with culturally.

Definitions and use

Heritage language is a language which is predominantly spoken by "nonsocietal" groups and linguistic minorities.

In various fields, such as foreign language education and linguistics, the definitions of heritage language become more specific and divergent. In foreign language education, heritage language is defined in terms of a student's upbringing and functional proficiency in the language: a student raised in a home where a non-majority language is spoken is a heritage speaker of that language if they possess some proficiency in it. Under this definition, individuals that have some cultural connection with the language but do not speak it are not considered heritage students. This restricted definition became popular in the mid 1990s with the publication of Standards for Foreign Language Learning by the American Council on the Teaching of Foreign Languages.

Among linguists, heritage language is an end-state language that is defined based on the temporal order of acquisition and, often, the language dominance in the individual. A heritage speaker acquires the heritage language as their first language through natural input in the home environment and acquires the majority language as a second language, usually when they start school and talk about different topics with people in school, or by exposure through media (written texts, internet, popular culture etc.). As exposure to the heritage language decreases and exposure to the majority language increases, the majority language becomes the individual’s dominant language and acquisition of the heritage language changes. The results of these changes can be seen in divergence of the heritage language from monolingual norms in the areas of phonology, lexical knowledge (knowledge of vocabulary or words), morphology, syntax, semantics and code-switching, although mastery of the heritage language may vary from purely receptive skills in only informal spoken language to native-like fluency.

Controversy in definition

As stated by Polinsky and Kagan: "The definition of a heritage speaker in general and for specific languages continues to be debated. The debate is of particular significance in such languages as Chinese, Arabic, and languages of India and the Philippines, where speakers of multiple languages or dialects are seen as heritage speakers of a single standard language taught for geographic, cultural or other reasons (Mandarin Chinese, Classical Arabic, Hindi, or Tagalog, respectively)."

One idea that prevails in the literature is that "[heritage] languages include indigenous languages that are often endangered. . . as well as world languages that are commonly spoken in many other regions of the world (Spanish in the United States, Arabic in France)". However, that view is not shared universally. In Canada, for example, First Nations languages are not classified as heritage languages by some groups whereas they are so classified by others.

The label heritage is given to a language based principally on the social status of its speakers and not necessarily on any linguistic property. Thus, while Spanish typically comes in second in terms of native speakers worldwide and has official status in a number of countries, it is considered a heritage language in the English-dominant United States and Canada. Outside the United States and Canada, heritage language definitions and use vary.

Speakers of the same heritage language raised in the same community may differ significantly in terms of their language abilities, yet be considered heritage speakers under this definition. Some heritage speakers may be highly proficient in the language, possessing several registers, while other heritage speakers may be able to understand the language but not produce it. Other individuals that simply have a cultural connection with a minority language but do not speak it may consider it to be their heritage language. It is held by some that ownership does not necessarily depend on usership: “Some Aboriginal people distinguish between usership and ownership. There are even those who claim that they own a language although they only know one single word of it: its name.”

Proficiency

Heritage learners have a fluent command of the dominant language and are comfortable using it in formal setting because of their exposure to the language through formal education. Their command of the heritage language, however, varies widely. Some heritage learners may lose some fluency in the first language after they begin formal education in the dominant language. Others may use the heritage language consistently at home and with family but receive little or no formal training in the heritage language and thus may struggle with literacy skills or with using it in broader settings outside of the home. An additional factor that affects the acquisition of learners is whether they show willingness or reluctance towards learning the heritage language.

One factor that has been shown to influence the loss of fluency in the heritage language is age. Studies have shown that younger bilingual children are more susceptible to fluency loss than older bilingual children. The older the child is when the dominant language is introduced, the less likely he/she is going to lose ability in using his/her first language (the heritage language). This is because the older the child is, the more exposure and knowledge of use the child will have had with the heritage language, and thus the heritage language will remain as their primary language.

Researchers found that this phenomenon primarily deals with the memory network of an individual. Once a memory network is organized, it is difficult for the brain to reorganize information contrary to the initial information, because the previous information was processed first. This phenomenon becomes a struggle for adults who are trying to learn a different language. Once an individual has learned a language fluently, they will be heavily influenced by the grammatical rules and pronunciations of their first language they learned, while learning a new language.

An emerging effective way of measuring the proficiency of a heritage speaker is by speech rate. A study of gender restructuring in heritage Russian showed that heritage speakers fell into two groups: those who maintained the three-gender system and those who radically reanalyzed the system as a two-gender system. The heritage speakers who reanalyzed the three-gender system as a two-gender system had a strong correlation with a slower speech rate. The correlation is straightforward—lower proficiency speakers have more difficulty accessing lexical items; therefore, their speech is slowed down.

Although speech rate has been shown to be an effective way of measuring proficiency of heritage speakers, some heritage speakers are reluctant to produce any heritage language whatsoever. Lexical proficiency is an alternative method that is also effective in measuring proficiency. In a study with heritage Russian speakers, there was a strong correlation between the speaker's knowledge of lexical items (measured using a basic word list of about 200) and the speaker's control over grammatical knowledge such as agreement, temporal marking, and embedding.

Some heritage speakers explicitly study the language to gain additional proficiency. The learning trajectories of heritage speakers are markedly different from the trajectories of second language learners with little or no previous exposure to a target language. For instance, heritage learners typically show a phonological advantage over second language learners in both perception and production of the heritage language, even when their exposure to the heritage language was interrupted very early in life. Heritage speakers also tend to distinguish, rather than conflate, easily confusable sounds in the heritage language and the dominant language more reliably than second language learners. In morphosyntax as well, heritage speakers have been found to be more native-like than second language learners, although they are typically significantly different from native speakers. Many linguists frame this change in heritage language acquisition as “incomplete acquisition” or "attrition." "Incomplete acquisition," loosely defined by Montrul, is "the outcome of language acquisition that is not complete in childhood." In this incomplete acquisition, there are particular properties of the language that were not able to reach age-appropriate levels of proficiency after the dominant language has been introduced. Attrition, as defined by Montrul, is the loss of a certain property of a language after one has already mastered it with native-speaker level accuracy. These two cases of language loss have been used by Montrul and many other linguists to describe the change in heritage language acquisition. However, this is not the only viewpoint of linguists to describe heritage language acquisition.

One argument against incomplete acquisition is that the input that heritage speakers receive is different from monolinguals (the input may be affected by cross-generational attrition, among other factors), thus the comparison of heritage speakers against monolinguals is weak. This argument by Pascual and Rothman claims that the acquisition of the heritage language is therefore not incomplete, but complete and simply different from monolingual acquisition of a language. Another argument argues for a shift in focus on the result of incomplete acquisition of a heritage language to the process of heritage language acquisition. In this argument, the crucial factor in changes to heritage language acquisition is the extent to which the heritage speaker activates and processes the heritage language. This new model thus moves away from language acquisition that is dependent on the exposure to input of the language and moves towards dependence on the frequency of processing for production and comprehension of the heritage language.

Some colleges and universities offer courses prepared for speakers of heritage languages. For example, students who grow up learning some Spanish in the home may enroll in a course that will build on their Spanish abilities.

First language

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/First_language

The monument for the mother tongue ("Ana dili") in Nakhchivan, Azerbaijan

A first language, native language or mother/father/parent tongue (also known as arterial language or L1), is a language that a person has been exposed to from birth or within the critical period. In some countries, the term native language or mother tongue refers to the language of one's ethnic group rather than one's first language.

Sometimes, the term "mother tongue" or "mother language"(or "father tongue" / "father language") is used for the language that a person learned as a child (usually from their parents). Children growing up in bilingual homes can, according to this definition, have more than one mother tongue or native language. 

The first language of a child is part of that child's personal, social and cultural identity. Another impact of the first language is that it brings about the reflection and learning of successful social patterns of acting and speaking. It is basically responsible for differentiating the linguistic competence of acting. While some argue that there is no such thing as a "native speaker" or a "mother tongue", it is important to understand the key terms as well as to understand what it means to be a "non-native" speaker, and the implications that can have on one's life. Research suggests that while a non-native speaker may develop fluency in a targeted language after about two years of immersion, it can take between five and seven years for that child to be on the same working level as their native speaking counterparts.

On 17 November 1999, UNESCO designated 21 February as International Mother Language Day.

Definitions

One of the more widely accepted definitions of native speakers is that they were born in a particular country (and) raised to speak the language of that country during the critical period of their development. The person qualifies as a "native speaker" of a language by being born and immersed in the language during youth, in a family in which the adults shared a similar language experience to the child. Native speakers are considered to be an authority on their given language because of their natural acquisition process regarding the language, as opposed to having learned the language later in life. That is achieved by personal interaction with the language and speakers of the language. Native speakers will not necessarily be knowledgeable about every grammatical rule of the language, but they will have good "intuition" of the rules through their experience with the language.

The designation "native language", in its general usage, is thought to be imprecise and subject to various interpretations that are biased linguistically, especially with respect to bilingual children from ethnic minority groups. Many scholars have given definitions of 'native language' based on common usage, the emotional relation of the speaker towards the language, and even its dominance in relation to the environment. However, all three criteria lack precision. For many children whose home language differs from the language of the environment (the 'official' language), it is debatable which language is their "native language".

Defining "native language"

• Based on origin: the language(s) one learned first (the language(s) in which one has established the first long-lasting verbal contacts).
• Based on internal identification: the language(s) one identifies with/as a speaker of;
• Based on external identification: the language(s) one is identified with/as a speaker of, by others.
• Based on competence: the language(s) one knows best.
• Based on function: the language(s) one uses most.

In some countries, such as Kenya, India, and various East Asian and Central Asian countries, "mother language" or "native language" is used to indicate the language of one's ethnic group in both common and journalistic parlance ("I have no apologies for not learning my mother tongue"), rather than one's first language. Also, in Singapore, "mother tongue" refers to the language of one's ethnic group regardless of actual proficiency, and the "first language" refers to English, which was established on the island under the British Empire, and is the lingua franca for most post-independence Singaporeans because of its use as the language of instruction in government schools and as a working language.

In the context of population censuses conducted on the Canadian population, Statistics Canada defines mother tongue as "the first language learned at home in childhood and still understood by the individual at the time of the census." It is quite possible that the first language learned is no longer a speaker's dominant language. That includes young immigrant children whose families have moved to a new linguistic environment as well as people who learned their mother tongue as a young child at home (rather than the language of the majority of the community), who may have lost, in part or in totality, the language they first acquired. According to Ivan Illich, the term "mother tongue" was first used by Catholic monks to designate a particular language they used, instead of Latin, when they were "speaking from the pulpit". That is, the "holy mother the Church" introduced this term and colonies inherited it from Christianity as a part of colonialism. J. R. R. Tolkien, in his 1955 lecture "English and Welsh", distinguishes the "native tongue" from the "cradle tongue". The latter is the language one learns during early childhood, and one's true "native tongue" may be different, possibly determined by an inherited linguistic taste and may later in life be discovered by a strong emotional affinity to a specific dialect (Tolkien personally confessed to such an affinity to the Middle English of the West Midlands in particular).

Children brought up speaking more than one language can have more than one native language, and be bilingual or multilingual. By contrast, a second language is any language that one speaks other than one's first language.

Bilingualism

International Mother Language Day Monument in Sydney, Australia, unveiling ceremony, 19 February 2006

 

A related concept is bilingualism. One definition is that a person is bilingual if they are equally proficient in two languages. Someone who grows up speaking Spanish and then learns English for four years is bilingual only if they speak the two languages with equal fluency. Pearl and Lambert were the first to test only "balanced" bilinguals—that is, a child who is completely fluent in two languages and feels that neither is their "native" language because they grasp both so perfectly. This study found that

• balanced bilinguals perform significantly better in tasks that require flexibility (they constantly shift between the two known languages depending on the situation),
• they are more aware of the arbitrary nature of language,
• they choose word associations based on logical rather than phonetic preferences.

Multilingualism

One can have two or more native languages, thus being a native bilingual or indeed multilingual. The order in which these languages are learned is not necessarily the order of proficiency. For instance, if a French-speaking couple have a child who learned French first but then grew up in an English-speaking country, the child would likely be most proficient in English. Other examples are India, Indonesia, the Philippines, Kenya, Malaysia, Singapore, and South Africa, where most people speak more than one language.

Defining "native speaker"

Defining what constitutes a native speaker is difficult, and there is no test which can identify one. It is not known whether native speakers are a defined group of people, or if the concept should be thought of as a perfect prototype to which actual speakers may or may not conform.

An article titled "The Native Speaker: An Achievable Model?" published by the Asian EFL Journal states that there are six general principles that relate to the definition of "native speaker". The principles, according to the study, are typically accepted by language experts across the scientific field. A native speaker is defined according to the following guidelines:

1. The individual acquired the language in early childhood and maintains the use of the language.
2. The individual has intuitive knowledge of the language.
3. The individual is able to produce fluent, spontaneous discourse.
4. The individual is communicatively competent in different social contexts.
5. The individual identifies with or is identified by a language community.
6. The individual does not have a foreign accent.