What are the adverse drug reactions?

In the process of using commonly used drugs in the prevention or diagnosis of diseases, various reactions that are unrelated to the purpose of taking the medicine and are harmful to the patient are caused by the effects of the drugs themselves or the interactions between drugs. Including side effects, toxic and adverse reactions, sequelae, hypersensitivity reactions, secondary reactions and idiosyncratic reactions, etc. There are many ways to classify drug side effects, which are generally divided into two categories according to whether they are related to medicinal value: Type A and Type B.

Type A drug side effects are also known as dosage-related side effects. This reaction is caused by an increase in medicinal value, is often related to the dosage, can be predicted, has a high morbidity rate and a low mortality rate, such as drowsiness caused by benzodiazepines and bleeding caused by anticoagulants. Type A is mainly caused by the medicinal value process of the drug. Its characteristics are predictable, related to usage, high efficiency, but low mortality rate.

Type B is an abnormal reaction that is completely unrelated to normal medicinal value. It is difficult to predict, has a very low incidence rate, but a high mortality rate. Type B side effects can be divided into two types: drug abnormalities and patient abnormalities. The former includes abnormal effects caused by drug ingredients, solvents, and preservatives, solubilizers, thickeners, additives, excipients and residues of the drug; the latter is mainly related to the patient's specific genetic predisposition, such as hemolytic anemia caused by deficiency of 6-sulfate glucose dehydrogenase in blood cells.

In addition, drug allergies, carcinogens and fetal malformations are also Type B side effects. Type B drug side effects, also known as dosage-independent side effects. It is an abnormal reaction unrelated to the normal medicinal value, generally unrelated to the dosage, difficult to predict, with a low incidence rate (according to foreign data, accounting for 20-25% of drug side effects) and a high mortality rate, such as malignant hyperthermia caused by halothane and anaphylactic shock caused by penicillin.

Among the side effects of drugs, side effects, toxic reactions, and excessive effects are Type A side effects. The effects of the first dose, withdrawal reactions, secondary reactions, etc., are also Type A reactions because they are related to medicinal value. Drug hypersensitivity reactions and idiosyncratic reactions are type B reactions.