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Pharmacologic class: Propylamine (nonselective)
Therapeutic class: Antihistamine; allergy, cold, and cough remedy
Pregnancy risk category B
Antagonizes effects of histamine at histamine2-receptor sites, preventing histamine-mediated responses
Capsules (sustained-release): 8 mg, 12 mg
Syrup: 1 mg/5 ml, 2 mg/5 ml, 2.5 mg/5 ml
Tablets: 4 mg, 8 mg, 12 mg
Tablets (chewable): 2 mg
Tablets (timed-release): 8 mg, 12 mg
Indications and dosages
➣ Allergy symptoms; management of anaphylaxis and transfusion reactions
Adults: 4 mg q 4 to 6 hours P.O. or 8 to 12 mg P.O. of sustained-release form q 8 to 12 hours. Maximum dosage is 24 mg/day.
Children ages 6 to 12: 2 mg P.O. q 4 to 6 hours daily. Maximum dosage is 12 mg/day.
• Gastric ulcer
• Heart disease
• Hypersensitivity to drug
• Acute asthma attacks
• Stenosing peptic ulcer
Use cautiously in:
• hepatic or renal disease, asthma, angle-closure glaucoma, prostatic hypertrophy
• elderly patients
• pregnant patients (safety not established).
• Don't crush or break timed-release tablets or sustained-release capsules.
• Discontinue drug 4 days before allergy skin tests. (Drug may cause false-negative reactions.)
CNS: dizziness, drowsiness, excitation (in children), sedation, poor coordination, fatigue, confusion, restlessness, nervousness, tremor, headache, hysteria, tingling sensation, sensation of heaviness and weakness in hands
CV: palpitations, hypotension, bradycardia, tachycardia, extrasystoles, arrhythmias
EENT: blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, nasal congestion, dry nose, dry throat, sore throat
GI: nausea, vomiting, diarrhea, constipation, epigastric distress, anorexia, dry mouth, GI obstruction
GU: urinary retention, urinary hesitancy, dysuria, early menses, decreased libido, erectile dysfunction
Hematologic: hemolytic anemia, hypoplastic anemia, thrombocytopenia, leukopenia, pancytopenia, agranulocytosis
Respiratory: thickened bronchial secretions, chest tightness, wheezing
Skin: urticaria, rash, photosensitivity, diaphoresis
Other: chills, increased appetite, weight gain, anaphylactic shock
Drug-drug. Anticholinergics, anti-cholinergic-like drugs (such as some antidepressants, atropine, haloperidol, phenothiazines, quinidine, disopyramide): additive anticholinergic effects
CNS depressants (such as opioids, sedative-hypnotics): additive CNS depression
MAO inhibitors: intensified, prolonged anticholinergic effects
Drug-diagnostic tests. Allergy skin tests: false-negative reactions
Drug-behaviors. Alcohol use: additive CNS depression
Sun exposure: photosensitivity
• Assess for urinary retention and frequency.
• Monitor respiratory status throughout therapy.
• Advise patient to take with full glass of water.
• Tell patient not to crush timed-release tablets or sustained-release capsules. Instruct him to swallow them whole.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Advise parents to give dose to children in evening, because morning doses may cause inattention in school.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.