1. Class
    Antihistamine; anticholinergic.
  2. Mechanism of action
    Blocks cellular histamine receptors; decreases vasodilation; decrease motion sickness. Reverses extrapyramidal reactions
  3. Indications
    Symptomatic relief of allergies, allergic recations, anaphylaxis, acute dystonic reactions (phenothiazines). Blood administration reactions; used for motion sickness, hay fever.
  4. Contraindications
    Asthma, glaucoma, pregnancy, hypertension, narrow angle glaucoma, infants, patients taking monoamine oxidase inhibitors (MAOIs)
  5. Adverse reaction
    Sedation, hypotension seizures, seizures, visual disturbances, vomiting, urninary retention, palpitations, arrhythmias, dry mouth and throat, and paradoxical CNS excitation in children.
  6. Drug Interactions
    Potentiates effects of alcohol and other anticholinergics, may inhibit corticossteroid activity; MAOIs prolong anticholinergic effects of diphenhydramine.
  7. How supplied
    Tablets: 25, 50mg; Capsules: 25, 50mg; Prefilled syringes: 50- or 100-mg; vials (IV or IM); elixir, 12.5mg/5ml
  8. Dosage and administration
    Adult: 25-50mg IM or IV or PO. Pediactric: 1-2mg/kg IV,IO slowly or IM. If given PO: 5mg/kg/24 hours.
  9. Duration of action
    Onset: 15-30 minutes. Peak effect: 1 hour. Duration: 3-12 hours.
  10. Special considerations
    Not used in infants or in pregnancy: Catergory B. If used in anaphylaxis, will be in conjunction with epinephrine, corticosteroids.
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