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    DEA Class; Rx, OTC

    Common Brand Names; Dimetane, Respa-BR

    • Antihistamines, 1st Generation

    Histamine H1-receptor antagonist

    Indicated for the treatment of Allergies.

    Other Indications & Uses

    Perennial & seasonal allergic & vasomotor rhinitis, relief of symptoms from colds, urticaria, angioedema, anaphylactic reactions, pruritus, allergic conjunctivitis

    Documented hypersensitivity

    Lower respiratory disease, eg, asthma (controversial)

    Preemies & neonates

    Nursing women

    • CNS depression
    • Drowsiness
    • Sedation ranging from mild drowsiness to deep sleep (most frequent)
    • Dizziness
    • Lassitude
    • Disturbed coordination
    • Muscular weakness
    • Restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures is less common
    • Epigastric distress
    • Anorexia
    • Nausea
    • Vomiting
    • Diarrhea
    • Constipation
    • Cholestasis, hepatitis, hepatic failure, hepatic function abnormality, jaundice is rare
    • Tachycardia, palpitation ECG changes (eg, widened QRS)
    • Arrhythmias (eg, extrasystole, heart block)
    • Hypotension
    • Hypertension
    • Dizziness, sedation, and hypotension may occur in geriatric patients
    • Dryness of mouth, nose, and throat
    • Dysuria
    • Urinary retention
    • Impotence
    • Vertigo
    • Visual disturbances
    • Blurred vision
    • Diplopia; tinnitus
    • Acute labyrinthitis
    • Insomnia
    • Tremors
    • Nervousness
    • Irritability
    • Facial dyskinesia
    • Tightness of the chest
    • Thickening of bronchial secretions
    • Wheezing
    • Nasal stuffiness

    Caution in narrow angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, or bladder neck obstruction

    Pregnancy Category: C

    Lactation: excretion in milk unknown/contraindicated


    4 mg PO q4-6hr (no more than 24 mg qDay) PRN

    Extended release: 8-12 mg tablet PO q12hr or 12-24 mg capsule PO qDay


    <12 Years Old

    0.5 mg/kg/day divided q6hr PO 


    Nonanticholinergic antihistamines should be considered first when treating allergic reactions (Beers Criteria)

    Avoid use in elderly because of high incidence of anticholinergic effects

    Clearance reduced with advanced age, greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity

    May exacerbate existing lower urinary conditions or benign prostatic hyperplasia


    tablet extended release

    • 11mg

    oral suspension

    • 12mg/5mL

    oral liquid

    • 1mg/1mL
    • 2 mg/5mL