Catheter

From Wikipedia, the free encyclopedia

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

In medicine, a catheter (/ˈkæθətər/ KA-thə-tər) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Catheters are manufactured for specific applications, such as cardiovascular, urological, gastrointestinal, neurovascular and ophthalmic procedures. The process of inserting a catheter is called catheterization.

In most uses, a catheter is a thin, flexible tube (soft catheter) though catheters are available in varying levels of stiffness depending on the application. A catheter left inside the body, either temporarily or permanently, may be referred to as an "indwelling catheter" (for example, a peripherally inserted central catheter). A permanently inserted catheter may be referred to as a "permcath" (originally a trademark).

Catheters can be inserted into a body cavity, duct, or vessel, brain, skin or adipose tissue. Functionally, they allow drainage, administration of fluids or gases, access by surgical instruments, and also perform a wide variety of other tasks depending on the type of catheter. Special types of catheters, also called probes, are used in preclinical or clinical research for sampling of lipophilic and hydrophilic compounds, protein-bound and unbound drugs, neurotransmitters, peptides and proteins, antibodies, nanoparticles and nanocarriers, enzymes and vesicles.

Etymology

"Catheter" (from Greek καθετήρ kathetḗr) comes from the Greek verb καθίεμαι kathíemai, meaning "to thrust into" or "to send down" because the catheter allowed fluid to be "sent down" from the body.

Uses

In-line suction catheter used in ventilator circuit for delivering air into lungs

Single-use urinary catheter, 40 cm

Placement of a catheter into a particular part of the body may allow:

• Draining urine from the urinary bladder as in urinary catheterization, using intermittent catheters or Foley catheter inserted through urethra. When the urethra is damaged, suprapubic catheterisation is used instead. The suprapubic catheter is inserted through the lower part of the abdomen directly into the urinary bladder.
• drainage of urine from the kidney by percutaneous (through the skin) nephrostomy
• drainage of fluid collections, e.g. an abdominal abscess
• pigtail catheter: used to drain air from around the lung (pneumothorax)
• administration of intravenous fluids, medication or parenteral nutrition with a peripheral venous catheter or central venous catheter
• angioplasty, angiography, balloon septostomy, balloon sinuplasty, cardiac electrophysiology testing, catheter ablation. Often the Seldinger technique is used.
• direct measurement of blood pressure in an artery or vein
• direct measurement of intracranial pressure
• administration of anaesthetic medication into the epidural space, the subarachnoid space, or around a major nerve bundle such as the brachial plexus
• transfer of fertilized embryos, from in vitro fertilization, or sperm, during artificial insemination, into the uterus
• administration of oxygen, volatile anesthetic agents, and other breathing gases into the lungs using a tracheal tube
• subcutaneous administration of insulin or other medications, with the use of an infusion set and insulin pump

History

Ancient inventors

Catheters from the Roman Empire, 1st century AD

Ancient Chinese used onion stalks, the Romans, Hindus, and Greeks used tubes of wood or precious metals.

The ancient Egyptians created catheters from reeds.

Modern

The earliest invention of the flexible catheter was during the 18th century. Extending his inventiveness to his family's medical problems, Benjamin Franklin invented the flexible catheter in 1752 when his brother John suffered from bladder stones. Franklin's catheter was made of metal with segments hinged together with a wire enclosed to provide rigidity during insertion.

According to a footnote in his letter in Volume 4 of the Papers of Benjamin Franklin (1959), Franklin credits Francesco Roncelli-Pardino from 1720 as the inventor of a flexible catheter. In fact, Franklin claims the flexible catheter may have been designed even earlier.

An early modern application of the catheter was employed by Claude Bernard for the purpose of cardiac catheterization in 1844. The procedure involved entering a horse's ventricles via the jugular vein and carotid artery.

In 1929, Werner Forssman first performed central venous catheterization, work which led to the development of cardiac catherization as a treatment, for which he, André F. Cournand and Dickinson W. Richards would win the Nobel Prize for Medicine in 1959. Central venous catheterization allows for continuous administration of medications, fluids and blood products to a large vein, particularly in critically ill patients. Cardiac catheterization is the insertion of a catheter into one of the chambers of the heart, which is used for imaging, diagnosis, and the placement of devices such as stents.

David S. Sheridan invented the modern disposable catheter in the 1940s. Prior to this, some reusable catheters consisted of braided cotton tubes, which were varnished, heat-treated and polished. As these were primarily produced in France, the advent of World War II threatened the supply chain. Sheridan was dubbed the "Catheter King" by Forbes magazine in 1988. He also invented the modern "disposable" plastic endotracheal tube now used routinely in surgery.

Other reusable catheters consisted of red rubber tubes. Although sterilized prior to reuse, they still posed a high risk of infection and often led to the spread of disease.

To prevent clotting, catheters that are not in use may be filled with catheter lock solution.

Materials

Urinary catheters

A range of polymers are used for the construction of catheters, including silicone rubber, nylon, polyurethane, polyethylene terephthalate (PET), latex, and thermoplastic elastomers. Silicone is one of the most common implantable choices because it is inert and unreactive to body fluids and a range of medical fluids with which it might come into contact. On the other hand, the polymer is weak mechanically, and a number of serious fractures have occurred in catheters. For example, silicone is used in Foley catheters where fractures have been reported, often requiring surgery to remove the tip left in the bladder.

Catheters used in interventional procedures

Depending on the mechanical characteristics required, assorted polymers and polymer-metal composites can be used to build catheters used for interventional purposes. Common materials include polyamide (nylon), polyether block amide, polyuerathane, polyethylene terephthalate, and polyimides. These materials are often used in combination with each other and are frequently layered on top of stainless steel braiding, laser-cut stainless steel tubing, or other scaffold-like structures to impart desirable handling characteristics to the catheter, all dependent on the intended application. For example, the materials and the architectures used to manufacture vascular catheters for neurological applications might differ significantly from catheters destined for cardiovascular use.

Guiding catheters (catheters that guides angioplasty balloons and stents) is made up of polytetrafluoroethylene (PTFE) innermost layer which is lubricious, followed by stainless steel braid wire outer layer which helps to provide support for the catheter and prevent kinking while travelling through blood vessels, and Nylon elastomer outermost layer which provides extra support for the catheter and preserve the curvature of the catheter while passing through tortuous vessels.

To enhance ease of insertion, some catheters have a lubricious surface coating to lessen friction. A lubricious coating creates a smooth, slippery film making the catheter easier to insert.

Interventional procedures

Various settings of a 6 French pigtail catheter with locking string, obturator (also called stiffening cannula) and puncture needle.
A. Overview.
B. Both puncture needle and obturator engaged, allowing for direct insertion.
C. Puncture needle retracted. Obturator engaged. Used for example in steady advancement of the catheter on a guidewire.
D. Both obturator and puncture needle retracted, when the catheter is in place.
E. Locking string is pulled (bottom center) and then wrapped and attached to the superficial end of the catheter.

Diagnostic catheters

There are various catheters used in angiography procedures. Diagnostic catheters direct wires through blood vessels. Radiocontrast agent is then injected through the catheter to visualise the vessels via various imaging methods such as computed tomography (CT), projectional radiography, and fluoroscopy. Pigtail catheter is a non-selective catheter with multiple side holes that can deliver large volumes of contrast into a blood vessel for imaging purposes. Cobra catheter is a selective catheter used to catheterise downgoing vessels in the abdomen. Cobra catheters move forward by pushing and are removed by pulling. Sidewinder catheter is a selective catheter is used to navigate the aorta. Headhunter, Newton, Simmons, Bentson, and Berenstein catheters are used to navigate them into one of the three branches of the arch of aorta. Yashiro Catheter is a selective, hydrophilic catheter designed for optimal entry into celiac trunk. Whereas endothelial cell sampling through endovascular sampling with coils, stents, stent retrievers, or guidewires suffer from poor selectivity and a low or highly variable cell yield, a micro-3D-printed device adapted for endovascular techniques can harvest endothelial cells for transcriptomic analysis.

Balloon catheters

Main article: Balloon catheter

There are also balloon catheters used in angioplasty procedures such as plain balloon catheters that is useful in passing tight vessel stenosis, drug coated balloons that contains paclitaxel on the surface to prevent smooth muscle cells proliferation of the vessel walls, thus reducing the likehood of vessel blockage in the future, high pressure balloons that can open stubborn vessel stenoses in veins and arteriovenous fistula, and cutting balloon angioplasty that contains 3 to 4 small blades on its surface (endotomes) that helps to control the distribution of balloon dilatation more uniformly and cut through resistant stenosis due to fibrous scar tissue.

Dialysis catheters

Main article: Dialysis catheter

There is no difference in achieving adequacy of blood flow, period of catheter usage, infection, and thromboembolic risk whether the dialysis catheter has step-tip, split-tip, or symmetrical tip. The Palindrome catheter is superior to Permcath catheter in terms of maximum blood flow, dialysis adequacy, and annual patency rate. Similar to Permcath, Palindrome catheter has a high infection and thromboembolism rate.

Adverse effects

In interventional procedures, Teflon catheters (which are hydrophobic) have higher risk of thrombus formation when compared to polyurethane catheters. The longer the duration of the catheter left inside the body, the higher the risk of thrombus formation. Larger catheters increase the risk of thrombus formation around the catheter, because they can block the flow of blood.

"Any foreign object in the body carries an infection risk, and a catheter can serve as a superhighway for bacteria to enter the bloodstream or body", according to Milisa Manojlovich, a professor at the University of Michigan School of Nursing.

Catheters can be difficult to clean, and therefore harbor antibiotic resistant or otherwise pathogenic bacteria.

Physical Therapist: Strong Legs After 50 Comes Down To This

 By Raymond Calloway

Contributing Health Writer

August 29, 2026
👁 198,742

My father in his last year — sitting on the porch of the assisted living facility. The photo my mother could never bring herself to delete.

My father spent his last years in assisted living. The muscle loss destroyed him. I refused to follow that path.

And by the end of this, you're gonna be pissed.

Because there are three things happening right now:

One — Your legs are giving you a countdown to a walking frame that you don't want.

Two — The medical system is pushing you toward "just accept it" instead of fixing the root cause.

And three — You've probably been doing the “right things” for years… and it's rarely explained what to do when your body stops responding the same way.

So let me tell you what happened with my father, because his story is gonna open your eyes to how messed up this really is.

For 8 Years, My Father Wasted Away In Front Of Us

For 8 YEARS, and I mean almost a full decade, my father wasted away right in front of us.

It started with the stairs. He'd grip the railing with both hands and go down sideways, one step at a time. My mom would stand behind him with her hand on his back like he was a toddler learning to walk.

His doctor said it was "just part of getting older." Said he should "stay active" and "eat more protein."

So he did. He ate more protein. Eggs every morning. Chicken every night. Even started drinking those chalky protein shakes my sister bought him from Costco.

His legs? Got weaker.

He started physical therapy. Twice a week. Leg presses. Resistance bands. Balance drills. $180 a session.

His physical therapist kept saying "you need to build strength" like he wasn't trying.

The weakness got so bad he fell in the kitchen. Hit his hip on the counter. Another time getting out of the shower. My mom found him on the bathroom floor, soaking wet, too weak to pull himself up.

And you know what the doctors said when we told them he was still getting worse?

"That's normal for his age."
"He needs to keep doing the exercises."
"We can refer him to a different physical therapist."

So they switched his PT program.

The exercises changed. Great, right?

Wrong.

Now he ached for days after every session. Could barely walk the day after therapy.

And his legs were STILL getting weaker. Not stronger. Weaker.

He'd sleep 10 hours a night and still wake up exhausted. Couldn't stand at his grandson's baseball game. Lost interest in the things he used to love. Just… existing. Sitting in his chair. Going through the motions.

My mom said it was like watching the man she married slowly disappear.

And here's the part that made me sick to my stomach years later when I figured this out.

They had him doing the same things for EIGHT YEARS.

Eight years of protein that wasn't working. Eight years of exercises that made him worse. Eight years of doctor appointments where they'd adjust the program or switch the therapist but never once, not ONE TIME, did anyone say "Hey, maybe we should look at WHY his muscles aren't responding instead of just telling him to eat more protein and exercise."

And then one morning, my mom called me. Her voice was shaking.

" Something’s wrong with your father. He can’t get up, and I’m calling an ambulance."

That was the turning point.

Six weeks later, he was in assisted living.

The man who built our back deck with his bare hands. The man who carried me on his shoulders at football games. The man who taught me to change a tire in the rain.

Sitting in a facility with an activities calendar and nurses checking on him twice a day. My sister and I would visit on Sundays. Stay for an hour. Make small talk. Leave feeling gutted.

Those 14 months were all the time we had left.

I will never forgive myself for not knowing then what I know now.

The chair my father lived in for the last three years of his life.

Three Years Ago, It Started Happening To Me

So fast forward to three years ago.

I'm 68 years old. I get out of bed one morning and my legs feel heavy. Stiff. Unreliable.

I walk to the bathroom and halfway there, I realize I'm reaching for the wall.

And I stop dead.

Because I've seen this before.

Over the next few months, it gets worse.

My legs start shaking after short walks. I can't stand for more than 20 minutes without needing to sit. I can't carry the groceries from the car anymore. My grip is so weak I can barely open a jar of pickles.

One morning, I'm coming downstairs for breakfast. I miss the bottom step. Slam into the wall. Land flat on my back, gasping.

That night, I hear my wife on the phone with our daughter.

"I'm worried about your father. He's not safe on those stairs anymore."

I felt my chest tighten.

Because I knew EXACTLY what comes next.

I'd watched my father go through this. The weakness. The falls. The slow, humiliating slide from independent man to someone people make decisions for.

The grab bars. The "community." The nurses.

And I made a decision right there.

I am NOT ending up in assisted living.

I'm not following my father's path.

There has to be another way.

I Did Everything They Told Me. It Didn't Work.

So I did what they told me to do, right?

I doubled down on protein. Eggs every morning, chicken breast at lunch, protein shake after dinner. More protein than I'd eaten in my entire life.

I went to physical therapy. Twice a week. Leg presses. Resistance bands. Balance exercises.

I started walking every morning. 30 minutes, rain or shine.

Three months later?

My legs were shakier than ever. I ached for days after every PT session. And I was still gripping the railing with both hands going down the stairs.

Barely any difference.

My physical therapist says: "These things take time. You need to be patient. Keep doing the exercises."

I looked at her and I felt rage building in my chest.

Because I'd DONE everything she told me to do. Everything the medical establishment says you're supposed to do. And it wasn't enough.

And now the only answer they have is the exact same advice that failed my father for eight years?

So at this point, I'm furious.

And I started asking questions that nobody wants you to ask.

Why are doctors so quick to tell you to "eat more protein and exercise" when it clearly doesn't work for men over 60?

Why do they act like muscle loss is just something you accept instead of something you can actually fix?

And why does nobody ever talk about what's ACTUALLY happening inside your muscles that's causing them to shut down?

I told my physical therapist I wanted to try something different. She wasn't happy about it. Gave me this whole speech about "the risks of deconditioning" and "consistency is key."

But I stood my ground.

1:14 AM. Four months into my own decline. The night I found Dr. Walding's research.

Down The Rabbit Hole — And What I Found Stopped Me Cold

And I went down a rabbit hole. I mean a DEEP rabbit hole.

I started researching everything about muscle loss after 60. What causes it. Why some men respond to protein and exercise and others don't. What actually controls muscle growth in the body at a cellular level.

And every mainstream medical site was giving me the same answers: "Eat more protein. Do resistance training. Stay active. That's all you can do."

So I kept digging. Reading clinical studies. Research papers. Talking to people in online forums who'd managed to rebuild their strength after 60.

And I found out there's actual RESEARCH on this. Real clinical trials.

That's when I came across the work of a doctor named Chad Walding.

Senior Nutrition Expert and Doctor of Physical Therapy. Florida-based. TEDx speaker. Men's performance specialist with over 25 years working with everyone from retired Olympic athletes to Fortune 500 CEOs to regular guys like me.

And what I read in his research stopped me cold.

Because Dr. Walding had been watching the exact same nightmare I'd watched my father live through. For TWENTY-FIVE YEARS:

"I see it all the time. A guy comes in at 65, complaining he can't open jars anymore. Within 12 months, he's fallen in the shower. Six months after that, his 'caring' relatives are touring nursing homes. A year on, he's the guy Dr. Walding sees on his hospital rounds. Sitting in a fluorescent-lit day room. Eating soft food off a plastic tray. Waiting for someone to remember to wheel him down to bingo." — Dr. Chad Walding

I read that paragraph three times.

Because that was my father. That was his exact arc.

And Dr. Walding had been watching it happen to hundreds of men in his practice. Strong, independent guys who were doing everything right — walking, lifting, eating protein — and watching their strength bleed out of them anyway. Just like my dad. Just like me.

For years, he couldn't explain it either. He'd attended every conference. Spoken to muscle loss experts across the country. Tried every nutritional intervention in the literature on his patients. Nothing moved the needle.

So he went deeper. Started collaborating with muscle physiology labs running protein synthesis experiments. Spent his nights buried in cellular biology research that had nothing to do with urology — just because he was determined to figure out what was actually breaking inside these men's bodies.

And eventually, the mechanism came into focus.

What was draining my father’s vitality — and was now silently affecting me — was something called anabolic resistance.

After 60, Your Muscles Stop Responding To Protein

You know what's insane?

We're told our whole lives that protein builds muscle. Eat protein, do exercise, muscles grow. Simple. But nobody, and I mean NOBODY, ever told us that after 60, your muscles develop a resistance to protein. They literally stop responding to the growth signal.

Here's what's happening:

When you're young, every time you eat protein, your body sends a signal to your muscle cells that says "build, grow, repair." That signal is called muscle protein synthesis — MPS for short. It's what turns the steak on your plate into the muscle on your body.

But after 50, something breaks.

Your body still produces the signal. You still eat the protein. The steak still goes in. But the signal no longer reaches your muscle cells the way it used to.

Your muscles become resistant to it.

One peer-reviewed study found that older men needed roughly TWICE the protein dose to trigger the same muscle-building response as men in their 30s. Another found that in some men over 60, the response had dropped to as little as 16% of what it was in their youth.

2×

The protein dose older men need to trigger the same response as men in their 30s

16%

How little of the youthful muscle-building response some men over 60 retain

84%

Of the muscle-building signal wasted — bouncing off the cells

Let me put that in plain English.

You could be eating chicken every night, drinking whey protein after the gym, doing everything the nutrition magazines tell you to do — and 84% of the muscle-building signal is being WASTED. Hitting the cells and bouncing off.

That's why my father did everything they told him for eight years and just kept getting weaker.

That's why the careful, disciplined ones end up in the day room with the ones who gave up.

It's not the exercise. It's not the protein. It's the signal.

And without fixing the signal, no amount of training or eating will ever bring back the muscle you've lost.

I sat at my kitchen table the night I figured this out and I felt sick.

Because if I’d known this eight years ago — if this information had been widely understood back then — my father wouldn't have spent his final years in that facility. He'd still be here.

Why “more protein and exercise” isn’t enough after 50

Because anabolic resistance isn’t something most people ever hear explained in plain English. In a normal appointment, you usually get broad advice that helps a lot of people: move more, eat more protein, lift when you can.

But when your muscle-building response slows down with age, the missing piece is the signal — not just the workouts.

The Two Compounds That Break Through Anabolic Resistance

OK. So here's what I learned next.

Once Dr. Walding had identified anabolic resistance as the mechanism, he set out to find compounds that could break through it. Compounds that amplified the signal at the cellular level. Compounds that forced the muscle cells to listen again.

He started testing. Most failed. But two kept showing up in the research, again and again, with peer-reviewed clinical backing behind both.

01

Hero Ingredient

Leucine

A specific amino acid that triggers MPS at the mTOR pathway. The mTOR pathway is the master switch for muscle building. Leucine is the only amino acid that flips it on.

The research from the University of Illinois shows that consuming L-leucine can actually boost mTOR and stimulate muscle growth.

02

Amplifier

L-carnitine

L-carnitine is another vital amino acid for good muscle strength after 50. It supports lean muscle mass and stamina by boosting mitochondrial function.

Mitochondria are the “power plants” of our cells. And muscle cells in particular need a ton of mitochondrial energy to keep you strong.

In a 2016 study, seniors who took a little L-carnitine each day for just 10 weeks…

Improved their strength and endurance…

Restored their energy and stamina back to normal levels…

Boosted their mobility, fitness, and speed…

Increased their lung power…

And other research shows that L-carnitine can even help prevent muscle soreness after exercise.

Beyond that, it’s been scientifically shown to support healthy blood pressure, brain function and memory, cholesterol, blood sugar, mood, fat burning, and so much more.

By fueling our mitochondria, L-carnitine energizes the entire body to work more like it did when it was younger.

Route of administration

From Wikipedia, the free encyclopedia

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

Oral administration of a liquid.

In pharmacology and toxicology, a route of administration (ROA) is the way by which a drug, fluid, poison, or other substance is introduced into the body.

Routes of administration are generally classified by the location at which the substance is applied. Common examples include oral and intravenous administration. Routes can also be classified based on where the target of action is. Action may be topical (local), enteral (system-wide effect, but delivered through the gastrointestinal tract), or parenteral (systemic action, but is delivered by routes other than the GI tract). Route of administration and dosage form are aspects of drug delivery.

Classification

Routes of administration are usually classified by application location (or exposition).

The route or course the active substance takes from application location to the location where it has its target effect is usually rather a matter of pharmacokinetics (concerning the processes of uptake, distribution, and elimination of drugs). Exceptions include the transdermal or transmucosal routes, which are still commonly referred to as routes of administration.

The location of the target effect of active substances is usually rather a matter of pharmacodynamics (concerning, for example, the physiological effects of drugs). An exception is topical administration, which generally means that both the application location and the effect thereof is local.

Topical administration is sometimes defined as both a local application location and local pharmacodynamic effect, and sometimes merely as a local application location regardless of location of the effects.

By application location

Enteral/gastrointestinal route

Through the gastrointestinal tract is sometimes termed enteral or enteric administration (literally meaning 'through the intestines'). Enteral/enteric administration usually includes oral (through the mouth) and rectal (into the rectum) administration, in the sense that these are taken up by the intestines. However, uptake of drugs administered orally may also occur already in the stomach, and as such gastrointestinal (along the gastrointestinal tract) may be a more fitting term for this route of administration. Furthermore, some application locations often classified as enteral, such as sublingual (under the tongue) and sublabial or buccal (between the cheek and gums/gingiva), are taken up in the proximal part of the gastrointestinal tract without reaching the intestines. Strictly enteral administration (directly into the intestines) can be used for systemic administration, as well as local (sometimes termed topical), such as in a contrast enema, whereby contrast media are infused into the intestines for imaging. However, for the purposes of classification based on location of effects, the term enteral is reserved for substances with systemic effects.

A medical professional injects medication into a gastric tube.

Many drugs as tablets, capsules, or drops are taken orally. Administration methods directly into the stomach include those by gastric feeding tube or gastrostomy. Substances may also be placed into the small intestines, as with a duodenal feeding tube and enteral nutrition. Enteric coated tablets are designed to dissolve in the intestine, not the stomach, because the drug present in the tablet may either cause irritation in the stomach or else be degraded by stomach acids/enzymes.

Administering medication rectally

The rectal route is an effective route of administration for many medications, especially those used at the end of life. The walls of the rectum absorb many medications quickly and effectively. Medications delivered to the distal one-third of the rectum at least partially avoid the "first pass effect" through the liver, which allows for greater bio-availability of many medications than that of the oral route. Rectal mucosa is highly vascularized tissue that allows for rapid and effective absorption of medications. A suppository is a solid dosage form that fits for rectal administration. In hospice care, a specialized rectal catheter, designed to provide comfortable and discreet administration of ongoing medications provides a practical way to deliver and retain liquid formulations in the distal rectum, giving health practitioners a way to leverage the established benefits of rectal administration. The Murphy drip is an example of rectal infusion.

Parenteral route

Needle insertion angles for 4 types of parenteral administration of medication: intramuscular, subcutaneous, intravenous, and intradermal injection.

The parenteral route is any route that is not enteral (par- + enteral).

Parenteral administration can be performed by injection, that is, using a needle (usually a hypodermic needle) and a syringe, or by the insertion of an indwelling catheter.

Locations of application of parenteral administration include:

• Central nervous system:

• Epidural (synonym: peridural) (injection or infusion into the epidural space), e.g. epidural anesthesia.
• Intracerebral (into the cerebrum) administration by direct injection into the brain. Used in experimental research of chemicals and as a treatment for malignancies of the brain. The intracerebral route can also interrupt the blood brain barrier from holding up against subsequent routes.
• Intracerebroventricular (into the cerebral ventricles) administration into the ventricular system of the brain. One use is as a last line of opioid treatment for terminal cancer patients with intractable cancer pain.

A transdermal patch which delivers medication is applied to the skin. The patch is labelled with the time and date of administration as well as the administrator's initials.

A medical professional applies nose drops.

• Epicutaneous (application onto the skin). It can be used both for local effect as in allergy testing and typical local anesthesia, as well as systemic effects when the active substance diffuses through skin in a transdermal route.
• Sublingual and buccal medication administration is a way of giving someone medicine orally (by mouth). Sublingual administration is when medication is placed under the tongue to be absorbed by the body. The word "sublingual" means "under the tongue." Buccal administration involves placement of the drug between the gums and the cheek. These medications can come in the form of tablets, films, or sprays. Many drugs are designed for sublingual administration, including cardiovascular drugs, steroids, barbiturates, opioid analgesics with poor gastrointestinal bioavailability, enzymes and, increasingly, vitamins and minerals.
• Extra-amniotic administration, between the endometrium and fetal membranes.
• Nasal administration (through the nose) can be used for topically acting substances, as well as for insufflation of e.g. decongestant nasal sprays to be taken up along the respiratory tract. Such substances are also called inhalational, e.g. inhalational anesthetics.
• Intra-arterial (into an artery), e.g. vasodilator drugs in the treatment of vasospasm and thrombolytic drugs for treatment of embolism.
• Intra-articular, into a joint space. It is generally performed by joint injection. It is mainly used for symptomatic relief in osteoarthritis.
• Intracardiac (into the heart), e.g. adrenaline during cardiopulmonary resuscitation (no longer commonly performed).
• Intracavernous injection, an injection into the base of the penis.
• Intradermal, (into the skin itself) is used for skin testing some allergens, and also for mantoux test for tuberculosis.
• Intralesional (into a skin lesion), is used for local skin lesions, e.g. acne medication.
• Intramuscular (into a muscle), e.g. many vaccines, antibiotics, and long-term psychoactive agents. Recreationally the colloquial term 'muscling' is used.

Topical ocular administration

• Intraocular, into the eye, e.g., some medications for glaucoma or eye neoplasms.
• Intraosseous infusion (into the bone marrow) is, in effect, an indirect intravenous access because the bone marrow drains directly into the venous system. This route is occasionally used for drugs and fluids in emergency medicine and pediatrics when intravenous access is difficult.
• Intraperitoneal, (infusion or injection into the peritoneum) e.g. peritoneal dialysis.
• Intrathecal (into the spinal canal) is most commonly used for spinal anesthesia and chemotherapy.
• Intrauterine.
• Intravaginal administration, in the vagina.
• Intravenous (into a vein), e.g. many drugs, total parenteral nutrition.
• Intravesical infusion is into the urinary bladder.
• Intravitreal, through the eye.
• Subcutaneous (under the skin). This generally takes the form of subcutaneous injection, e.g. with insulin. Skin popping is a slang term that includes subcutaneous injection, and is usually used in association with recreational drugs. In addition to injection, it is also possible to slowly infuse fluids subcutaneously in the form of hypodermoclysis.
• Transdermal (diffusion through the intact skin for systemic rather than topical distribution), e.g. transdermal patches such as fentanyl in pain therapy, nicotine patches for treatment of addiction and nitroglycerine for treatment of angina pectoris.
• Perivascular administration (perivascular medical devices and perivascular drug delivery systems are conceived for local application around a blood vessel during open vascular surgery).
• Transmucosal (diffusion through a mucous membrane), e.g. insufflation (snorting) of cocaine, sublingual, i.e. under the tongue, sublabial, i.e. between the lips and gingiva, and oral spray or vaginal suppository for nitroglycerine.

Topical route

Main article: Topical drug delivery

The definition of the topical route of administration sometimes states that both the application location and the pharmacodynamic effect thereof is local.

In other cases, topical is defined as applied to a localized area of the body or to the surface of a body part regardless of the location of the effect. By this definition, topical administration also includes transdermal application, where the substance is administered onto the skin but is absorbed into the body to attain systemic distribution.

If defined strictly as having local effect, the topical route of administration can also include enteral administration of medications that are poorly absorbable by the gastrointestinal tract. One such medication is the antibiotic vancomycin, which cannot be absorbed in the gastrointestinal tract and is used orally only as a treatment for Clostridioides difficile colitis.

Choice of routes

The choice of routes of drug administration is governed by various factors:

• Physical and chemical properties of the drug. The physical properties are solid, liquid and gas. The chemical properties are solubility, stability, pH, irritancy, etc.
• Site of desired action: the action may be localised and approachable or generalised and not approachable.
• Rate of extent of absorption of the drug from different routes.
• Effect of digestive juices and the first pass metabolism of drugs.
• Condition of the patient.

In acute situations, in emergency medicine and intensive care medicine, drugs are most often given intravenously. This is the most reliable route, as in acutely ill patients the absorption of substances from the tissues and from the digestive tract can often be unpredictable due to altered blood flow or bowel motility.

Convenience

Enteral routes are generally the most convenient for the patient, as no punctures or sterile procedures are necessary. Enteral medications are therefore often preferred in the treatment of chronic disease. However, some drugs can not be used enterally because their absorption in the digestive tract is low or unpredictable. Transdermal administration is a comfortable alternative; there are, however, only a few drug preparations that are suitable for transdermal administration.

Desired target effect

Identical drugs can produce different results depending on the route of administration. For example, some drugs are not significantly absorbed into the bloodstream from the gastrointestinal tract and their action after enteral administration is therefore different from that after parenteral administration. This can be illustrated by the action of naloxone (Narcan), an antagonist of opiates such as morphine. Naloxone counteracts opiate action in the central nervous system when given intravenously and is therefore used in the treatment of opiate overdose. The same drug, when swallowed, acts exclusively on the bowels; it is here used to treat constipation under opiate pain therapy and does not affect the pain-reducing effect of the opiate.

Oral

The oral route is generally the most convenient and costs the least. However, some drugs can cause gastrointestinal tract irritation. For drugs that come in delayed release or time-release formulations, breaking the tablets or capsules can lead to more rapid delivery of the drug than intended. The oral route is limited to formulations containing small molecules only while biopharmaceuticals (usually proteins) would be digested in the stomach and thereby become ineffective. Biopharmaceuticals have to be given by injection or infusion. However, recent research found various ways to improve oral bioavailability of these drugs. In particular permeation enhancers, ionic liquids, lipid-based nanocarriers, enzyme inhibitors and microneedles have shown potential.

Oral administration is often denoted as "PO" from "per os", the Latin word for "by mouth".

The bioavailability of oral administration is affected by the amount of drug that is absorbed across the intestinal epithelium and first-pass metabolism.

Oral mucosal

The oral mucosa is the mucous membrane lining the inside of the mouth.

Buccal

Buccally administered medication is achieved by placing the drug between gums and the inner lining of the cheek. In comparison with sublingual tissue, buccal tissue is less permeable resulting in slower absorption.

Sublabial

Sublabial administration is achieved by placing the drug between the lip and gum. The frenulum of the tongue may be irritated when in contact with corrosive materials but can be avoided with this route. It is usually used for medications such as nitroglycerin, for example.

Sublingual

Sublingual administration is fulfilled by placing the drug between the tongue and the lower surface of the mouth. The sublingual mucosa is highly permeable and thereby provides access to the underlying expansive network composed of capillaries, leading to rapid drug absorption.

Supralingual

Supralingual administration is achieved by placing the drug above the tongue. It is often the route of administration of choice when one would like the drug to bypass or alleviate the first pass effect on the drug after oral delivery.

Intranasal

Main article: Nasal administration

Drug administration via the nasal cavity yields rapid drug absorption and therapeutic effects. This is because drug absorption through the nasal passages does not go through the gut before entering capillaries situated at tissue cells and then systemic circulation and such absorption route allows transport of drugs into the central nervous system via the pathways of olfactory and trigeminal nerve.

Intranasal absorption features low lipophilicity, enzymatic degradation within the nasal cavity, large molecular size, and rapid mucociliary clearance from the nasal passages, which explains the low risk of systemic exposure of the administered drug absorbed via intranasal.

Involved subjects' positions.

Local

By delivering drugs almost directly to the site of action, the risk of systemic side effects is reduced.

Skin absorption (dermal absorption), for example, is to directly deliver drug to the skin and, hopefully, to the systemic circulation. However, skin irritation may result, and for some forms such as creams or lotions, the dosage is difficult to control. Upon contact with the skin, the drug penetrates into the dead stratum corneum and can afterwards reach the viable epidermis, the dermis, and the blood vessels.

Parenteral

The term parenteral is from para-1 'beside' + Greek enteron 'intestine' + -al. This name is due to the fact that it encompasses a route of administration that is not intestinal. However, in common English the term has mostly been used to describe the four most well-known routes of injection.

A peripheral IV placed on the hand.

A medical professional performs an intradermal (ID) injection.

The term injection encompasses intravenous (IV), intramuscular (IM), subcutaneous (SC or SQ) and intradermal (ID) administration.

Parenteral administration generally acts more rapidly than topical or enteral administration, with onset of action often occurring in 15–30 seconds for IV, 10–20 minutes for IM and 15–30 minutes for SC. They also have essentially 100% bioavailability and can be used for drugs that are poorly absorbed or ineffective when they are given orally. Some medications, such as certain antipsychotics, can be administered as long-acting intramuscular injections. Ongoing IV infusions can be used to deliver continuous medication or fluids.

Disadvantages of injections include potential pain or discomfort for the patient and the requirement of trained staff using aseptic techniques for administration. However, in some cases, patients are taught to self-inject, such as SC injection of insulin in patients with insulin-dependent diabetes mellitus. As the drug is delivered to the site of action extremely rapidly with IV injection, there is a risk of overdose if the dose has been calculated incorrectly, and there is an increased risk of side effects if the drug is administered too rapidly.

Respiratory tract

Mouth inhalation

A dummy wears a nebulizer mask, used to administer inhaled medications.

1. trachea (conducting zone)
2. main bronchus (conducting zone)
3. lobar bronchus (conducting zone)
4. segmental bronchus (conducting zone)
5. subsegmental bronchus (conducting zone)
6. conducting bronchiole (conducting zone)
7. terminal bronchiole (conducting zone)
8. respiratory bronchiole (transitional respiratory zone)
9. alveolar duct (transitional respiratory zone)
10. alveolar sac (transitional respiratory zone)
11. alveolus (transitional respiratory zone)

Inhaled medications can be absorbed quickly and act both locally and systemically. Proper technique with inhaler devices is necessary to achieve the correct dose. Some medications can have an unpleasant taste or irritate the mouth.

In general, only 20–50% of the pulmonary-delivered dose rendered in powdery particles will be deposited in the lung upon mouth inhalation. The remainder of 50-70% undeposited aerosolized particles are cleared out of lung as soon as exhalation.

An inhaled powdery particle that is >8 μm is structurally predisposed to depositing in the central and conducting airways (conducting zone) by inertial impaction.

An inhaled powdery particle that is between 3 and 8 μm in diameter tend to largely deposit in the transitional zones of the lung by sedimentation.

An inhaled powdery particle that is <3 μm in diameter is structurally predisposed to depositing primarily in the respiratory regions of the peripheral lung via diffusion.

Particles that deposit in the upper and central airways are generally absorbed systemically to great extent because they are only partially removed by mucociliary clearance, which results in orally mediated absorption when the transported mucus is swallowed, and first pass metabolism or incomplete absorption through loss at the fecal route can sometimes reduce the bioavailability. This should in no way suggest to clinicians or researchers that inhaled particles are not a greater threat than swallowed particles, it merely signifies that a combination of both methods may occur with some particles, no matter the size of or lipo/hydrophilicity of the different particle surfaces.

Further information: PM 2.5 and PM 10

Nasal inhalation

Inhalation by nose of a substance is almost identical to oral inhalation, except that some of the drug is absorbed intranasally instead of in the oral cavity before entering the airways. Both methods can result in varying levels of the substance to be deposited in their respective initial cavities, and the level of mucus in either of these cavities will reflect the amount of substance swallowed. The rate of inhalation will usually determine the amount of the substance which enters the lungs. Faster inhalation results in more rapid absorption because more substance finds the lungs. Substances in a form that resists absorption in the lung will likely resist absorption in the nasal passage, and the oral cavity, and are often even more resistant to absorption after they fail absorption in the former cavities and are swallowed.

Research

Neural drug delivery is the next step beyond the basic addition of growth factors to nerve guidance conduits. Drug delivery systems allow the rate of growth factor release to be regulated over time, which is critical for creating an environment more closely representative of in vivo development environments.