This information is for educational purposes only. It is not intended as medical advice. Always consult a qualified healthcare professional.
Diphenhydramine is a sedating, antiallergic, and anticholinergic active substance belonging to the first-generation antihistamines. It is used, among other purposes, for sleep disorders, the treatment of allergic conditions, prevention of motion sickness, and common cold symptoms. Its effects are based on inverse agonism at histamine receptors and antagonism at muscarinic acetylcholine receptors. When used as a sleep aid, the medication is taken 15 to 30 minutes before bedtime. The most common possible adverse effects include drowsiness, somnolence, and dizziness. Diphenhydramine may prolong the QT interval.
Diphenhydramine (ATC D04AA32, ATC R06AA02) has antihistamine, antiallergic, sedative, antiemetic, local anaesthetic, spasmolytic, and anticholinergic properties. Its effects are based on inverse agonism at peripheral and central histamine receptors and antagonism at muscarinic acetylcholine receptors. Additionally, diphenhydramine also blocks sodium channels, which produces local anaesthesia. The half-life is approximately 5 hours.
Diphenhydramine also inhibits the reuptake of serotonin. The antidepressant fluoxetine was derived from it.
Mechanism of action of antihistamines, click to enlarge. Illustration © PharmaWiki
