Name: Diphenhydramine (Benadryl)
Class: H1-Histamine Antagonist (OTC)
Mechanism: Competitive inhib. of histamine and histamine receptor interaction.
Absorption:
Dist.: Enters CNS
Excretion, t½:
Toxicity/S.E.s: Sedation (not in everyone). Taken w/alcohol ® enhanced CNS depression. Local anesthetic activity. Acute poisoning in kids ® complex CNS excitatory and depressant effects (convulsions, hyperpyrexia). Topical use = highest risk of sensitization, \ shouldn’t be applied topically.
Utility: Treat allergic rxns (e.g., hay fever). Prevent motion sickness. Can be used for morning sickness. Treat PD symptoms (esp. geriatric patients).
Special Features: Most effective if taken prophylactically. Can’t reverse effects once histamine has bound to receptor. Therapeutically effective dose related to amount of antigen.