Diphenhydramine
Class
Antihistamine
Description
Diphenhydramine is a potent antihistamine that blocks H1 and H2 histamine
receptors.
Mechanism of Action
Diphenhydramine blocks the effects of H1 receptor stimulation (bronchoconstriction,
visceral contractions) and that of H2 receptor stimulation (peripheral
vasodilation and secretion of gastric acids). Diphenhydramine is also useful in
the treatment of dystonic reactions accompanying phenothiazine use.
Indications
Anaphylaxis, allergic reactions, dystonic (extrapyramidal) reactions due to
phenothiazines.
Contraindications
1. Asthma, nursing mothers
2. Hypersensitivity
Adverse Reactions
Sedation, dries bronchial secretions, blurred vision, headache, palpitations,
tachycardia
Drug Interactions
Potentiation can occur by the administration of CNS depressants, other
antihistamines,
narcotics, and alcohol.
Precautions
The primary drug for treatment of severe allergic reactions is epinephrine, as
it reverses the effects of histamines. Diphenhydramine will block histamine
receptors, preventing subsequent stimulation
Note: Feel free to discuss this medication and your experiences in administering it in an emergency or hospital based setting on our message board
