Where is medication absorbed in the body

Some drugs are rapidly absorbed in blood but might take a day to reach maximum levels in genital fluids. Some drugs have much higher concentrations in genital fluids than they in blood. Home Treatment training manual Learning resources What happens when you take a drug?

Treatment training manual What happens when you take a drug? What happens to drugs in the body? How a drug is absorbed by your body into the blood depends on the way it is taken: A pill is usually absorbed into the blood through the stomach walls after it is swallowed — these can become active in a few minutes but usually take an hour or two to reach the highest concentration in the blood. IV drugs are injected directly into the blood work much faster — sometimes in seconds or minutes.

For a pain reliever, the target organ might be a sore muscle in the leg; irritation of the stomach could be a side effect. Drugs destined for the central nervous system face a nearly impenetrable barricade called the blood-brain barrier that protects the brain from potentially dangerous substances such as poisons or viruses. Fortunately, pharmacologists have devised various ways to sneak some drugs past the blood-brain barrier. Other factors that can influence distribution include protein and fat molecules in the blood that can put drug molecules out of commission by latching onto them.

After a medicine has been distributed throughout the body and has done its job, the drug is broken down, or metabolized, the M in ADME. Decreased blood flow eg, in shock may lower the concentration gradient across the intestinal mucosa and reduce absorption by passive diffusion.

Intestinal transit time can influence drug absorption, particularly for drugs that are absorbed by active transport eg, B vitamins , that dissolve slowly eg, griseofulvin , or that are polar ie, with low lipid solubility; eg, many antibiotics.

To maximize adherence, clinicians should prescribe oral suspensions and chewable tablets for children 8 years of age. In adolescents and adults, most drugs are given orally as tablets or capsules primarily for convenience, economy, stability, and patient acceptance. Because solid drug forms must dissolve before absorption can occur, dissolution rate determines availability of the drug for absorption.

Dissolution, if slower than absorption, becomes the rate-limiting step. Eur J Pharm Sci , Drugs given IV enter the systemic circulation directly. However, drugs injected IM or subcutaneously sc must cross one or more biologic membranes to reach the systemic circulation.

In such cases, drug delivery to systemic circulation is slow and often incomplete because of first-pass metabolism metabolism of a drug before it reaches systemic circulation by proteolytic enzymes in the lymphatics.

Thus, injection site can affect absorption rate. Absorption after IM or sc injection may be delayed or erratic for salts of poorly soluble bases and acids eg, parenteral form of phenytoin and in patients with poor peripheral perfusion eg, during hypotension or shock.

Controlled-release forms are designed to reduce dosing frequency for drugs with a short elimination half-life and duration of effect.

These forms also limit fluctuation in plasma drug concentration, providing a more uniform therapeutic effect while minimizing adverse effects. Absorption rate is slowed by coating drug particles with wax or other water-insoluble material, by embedding the drug in a matrix that releases it slowly during transit through the gastrointestinal tract, or by complexing the drug with ion-exchange resins. Most absorption of these forms occurs in the large intestine.

Crushing or otherwise disturbing a controlled-release tablet or capsule can often be dangerous. Transdermal controlled-release forms are designed to release the drug for extended periods, sometimes for several days. Drugs for transdermal delivery must have suitable skin-penetration characteristics and high potency because the penetration rate and area of application are limited. Many non-IV parenteral forms are designed to sustain plasma drug concentrations. Absorption of antimicrobials can be extended by using their relatively insoluble salt form eg, penicillin G benzathine injected IM.

For other drugs, suspensions or solutions in nonaqueous vehicles eg, crystalline suspensions for insulin are designed to delay absorption. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. From the time the drug goes into your body to the time it leaves, a lot happens. Scientists have dubbed the process ADME, short for absorption, distribution, metabolism and, finally, excretion.

But how, exactly, does a drug go from point A absorption to point E excretion? We asked the experts. But most medications we take at home are in pill or capsule form, and those need to be absorbed in the stomach or gastrointestinal tract gut.

The acidity of the stomach and gut, as well as the makeup of the drug itself, can impact absorption. For example, fat-soluble drugs like prednisone , a steroid used to treat inflammation seek out fat cells where they easily dissolve and pass through cell membranes.

Water-soluble drugs, such as atenolol , used to treat high blood pressure, stick around in the blood and the fluids surrounding cells. Another factor affecting distribution is whether the drug is made up of large or small molecules.