Medical knowledge: pharmacological action of promethazine

Promethazine is a phenothiazine antihistamine, which has a longer effect than diphenhydramine, and also has obvious central sedative effect, but is weaker than chlorpromazine; It can enhance the effect of anesthetics, hypnotics, analgesics and local anesthetics, reduce body temperature and have antiemetic effect. It is suitable for various allergies (such as asthma, urticaria, etc.), dizziness caused by vomiting during pregnancy, boating, etc. This article mainly introduces its pharmacological effects and side effects.

Key words: promethazine, pharmacological action

Pharmacological action of promethazine
Promethazine is a phenothiazine antihistamine, which is mainly used in the following symptoms: skin and mucous membrane allergy; Prevent carsickness, seasickness and aircraft sickness; It is used for anesthesia and adjuvant treatment before and after surgery, including sedation, hypnosis, analgesia and antiemesis; It is used to prevent and treat radiation-induced or drug-induced nausea and vomiting.

1) Antihistamine effect: compete with histamine released by tissue for H1 receptor, which can antagonize the contraction or contracture of histamine on smooth muscle of gastrointestinal tract, trachea, bronchus or bronchioles, and relieve the spasmogenic and hyperemic effect of histamine on smooth muscle of bronchus.

2) Antiemetic effect: it may be related to the inhibition of emetic chemoreceptor area in medulla oblongata.

3) Anti motion sickness: it may act on vestibular and vomiting centers and midbrain medullary texture receptors through central anticholinergic properties, mainly to block the excitation of cholinergic synaptic labyrinthine impulse in vestibular nucleus.

4) Sedative and hypnotic effect: it may indirectly reduce the stress of brainstem reticular ascending activation system.

After injection, the absorption is fast and complete, and the plasma protein binding rate is high. The onset time is 20 minutes after intramuscular injection and 3-5 minutes after intravenous injection. The antihistamine effect generally lasts for 6-12 hours, and the sedative effect lasts for 2-8 hours. It is mainly metabolized in the liver, and inactive metabolites are excreted through urine, with less excretion through feces.

Interaction between promethazine and other drugs

(1) Interference with diagnosis: increased glucose tolerance can be shown in glucose tolerance test. It can interfere with urine pregnancy immune test, and the result is false positive or false negative.

(2) Ethanol or other central nervous system inhibitors, especially anesthetics, barbiturates, monoamine oxidase inhibitors or tricyclic antidepressants, when used with this product, can increase the effect of promethazine or (and) these drugs, and the dosage should be adjusted separately.

(3) When anticholinergic drugs, especially atropine and promethazine are used together, the anti muscarinic effect of the latter increases.

(4) When the antihypertensive drugs such as benzylammonium bromide and guanidine were used together with promethazine, the antihypertensive effect of the former was enhanced. The effect of adrenaline and Promethazine on adrenaline α The effect can be blocked, so that β The role is dominant.


(5) The ototoxic symptoms of cisplatin, baronmycin, other aminoglycoside antibiotics, salicylic acid preparations, vancomycin and other ototoxic drugs can be masked when used with promethazine.


(6) It should not be mixed with aminophylline for injection.