Characteristics of drugs absorbed from the gastrointestinal tract

In clinical practice today, there are many drugs that are absorbed mainly through the human digestive system, because this is the most natural and easy to use absorption route. However, gastrointestinal drug absorption also has certain advantages and disadvantages that patients need to be aware of in order to use the drug as effectively as possible.

The absorption of drugs in the patient's body is determined by the chemical, physical, and route of administration of certain drugs. Current dosage forms of drugs such as tablets, capsules, solutions... include drugs and other excipients and are introduced into the body by many different ways such as: oral, sucking, sublingual, etc. rectally, intravenously, applied topically, inhaled through the nose or mouth... No matter how the drug is given, it needs to be converted into a solution, so that the body can absorb it. .

For the absorption of drugs from the gastrointestinal tract, the drugs after being put into the body must exist in an environment with low pH as well as a lot of gastrointestinal secretions, including degrading enzymes. Some drugs that are peptides in nature, such as insulin, are easily degraded and cannot be used orally, so they are usually better absorbed when injected.
Basically the absorption of a drug orally will be closely related to the transmembrane transport of the drug in the gastrointestinal epithelium. Several factors can affect drug absorption in the small intestine:
pH difference along the gastrointestinal tract Surface area Blood transfusion Gastrointestinal bile and mucus Nature of the epithelium gastrointestinal

Some important features in the process of drug absorption through the gastrointestinal tract is that the human oral mucosa usually has a thin epithelial layer, rich in blood vessels, so it is able to help the drug absorb easily, however, because of the long too short, so the amount of drug absorbed is insignificant. Therefore, the method of sucking the medicine between the gums and cheeks or under the tongue helps the drug to be kept in the oral mucosa longer, thereby enhancing drug absorption.
The stomach is considered to be the first organ where strong contact between oral drugs and digestive juices takes place. The stomach is an organ with a thick epithelial layer and a relatively short drug delivery time, so it still causes limitations in drug absorption, preventing the drug from achieving maximum therapeutic effect. Because the drug is mainly absorbed in the small intestine, the gastric phase of drug should be limited to the rate of drug movement by gastric emptying. When eating foods high in fat, gastric emptying is slowed, which is why some medications taken on an empty stomach increase the rate of absorption. In addition, some drugs also affect gastric emptying, such as anti-parasympathetic drugs and affect the action of other drugs. Food also enhances absorption of poorly soluble drugs as well as reduces absorption of drugs that are broken down in the stomach such as Penicillin G.
The small intestine is home to a large surface area. This helps the drug to be absorbed the most here, and the membrane of the small intestine also helps the drug to be more permeable than the lining of the stomach. For this reason, the absorption of drugs from the small intestine is most common in the body, even non-ionized drugs easily pass through the small intestine membrane but are still more effective and faster when absorbed from the stomach. .

The absorption of drugs from the gastrointestinal tract takes place through several stages and at many different structures of the gastrointestinal tract. Because of the different anatomical and physicochemical characteristics of each organ, the absorption of drugs is also different at many times, in which the absorption of drugs in the small intestine is the most effective and fastest.
Because each drug has a different way of action and absorption mechanism, to ensure that the drug is safe and achieve certain effects, before taking prescription or non-prescription drugs, patients should consult opinions of doctors and pharmacists. Taking the medicine exactly as directed always brings the best results in terms of health.