Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.
Mode of Action
Diphenhydramine blocks histamine H1-receptors on effector cells of the GI tract, blood vessels and respiratory tract. It also causes sedation and has some anticholinergic action.
Interaction
Masks ototoxicity produced by aminoglycosides. Increases gastric degradation of levodopa and decreases its absorption by reduction of gastric emptying. Antagonises therapeutic effects of cholinergic agents e.g. tacrine, donezepil and neuroleptics. Valerian, St. John's wort, Kava Kava and gotu kola may increase CNS depression.
Potentially Fatal: Potentiates CNS depression with alcohol, barbiturates, analgesics, sedatives and neuroleptics. Additive antimuscarinic action with MAOIs, atropine and TCAs.
Pregnancy Category Note
Pregnancy category: B
Lactation: Drug enters breast milk; contraindicated
Adult Dose
Oral
Allergic conditions; Treatment and prophylaxis of motion sickness
Adult: 25-50 mg 3-4 times daily. For prevention of motion sickness, admin 30 min before exposure to motion. Max: 300 mg daily.
Parkinson's disease
Adult: Initially, 25 mg tid, may increase to 50 mg 4 times daily if necessary.
Short-term management of insomnia
Adult: 50 mg 30 min before bedtime as needed.
Hepatic impairment: No dosage adjustment needed.
Child Dose
Allergic Reaction
2-6 years: 6.25 mg q4-6hr; not to exceed 37.5 mg/day
6-12 years: 12.5-25 mg PO q4-6hr; not to exceed 150 mg/day
>12 years: 25-50 mg PO q4-6hr; not to exceed 300 mg/day
Occasional Insomnia
>12 years: 50 mg PO 30 minutes before bedtime
Cough
<12 years: Safety and efficacy not established
>12 years: 25-50 mg PO q4-6hr; not to exceed 300 mg/day
Motion Sickness
Administer 30 min before motion
12.5-25 mg PO q6-8hr or 150 mg/m? ; not to exceed 300 mg/day
Renal Dose
Renal impairment: No dosage adjustment needed.
Administration
May be taken with or without food.
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