The basic action of a drug is twofold, including therapeutic action and adverse reactions. Drug action is the initial action of the drug on the organism and is specific, including therapeutic effects and adverse reactions. Specifically described as follows. 1. Therapeutic effect refers to the use of drugs to achieve a certain desired purpose, divided into the cause of treatment and symptomatic treatment of two kinds. Allopathic treatment is the treatment of the root cause of the disease, commonly known as the treatment of the root cause. Symptomatic treatment is the treatment of certain symptoms of the organism, commonly known as the treatment of the surface. 2. Adverse reactions are those that do not meet the therapeutic purpose of the drug and bring certain uncomfortable feelings to the patient, which can be gradually recovered by themselves after stopping the drug in general, including side effects, toxic effects, after-effects, withdrawal reaction, metamorphosis (allergic reaction), idiosyncratic reaction and secondary reactions. If there is any discomfort, it is recommended to consult a doctor in time, and the drug should be used according to the doctor’s instructions.