Clemastine
Mechanism :
Clemastine is a selective histamine H1 antagonist and binds to the histamine H1 receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine.
Indication :
- Allergic rhinitis
- Urticaria
- Angioedema.
Contraindications :
Documented hypersensitivity; Lower respiratory disease, e.g., asthma (controversial); Preemies & neonates; Nursing women.
Dosing :
Upto 12 years:
0.05 mg/kg/day as clemastine base in 8-12 hourly divided doses. Maximum dose: 1 mg/day base in children upto 6 years, 3 mg/day base in 6-12 years.
>12 years:
Adult dose:
1-2 mg PO 2-3 times daily. Max: 6 mg/day.
Adverse Effect :
CNS depression, drowsiness, dizziness, disturbed coordination, muscular weakness, anorexia, nausea, vomiting, diarrhea, hepatitis, pruritus, tachycardia, hypotension, dryness, dysuria, urinary retention, impotence, blurred vision, tinnitus, facial dyskinesia, thickening of bronchial secretions, agranulocytosis, hemolytic anemia, leukopenia, thrombocytopenia, pancytopenia.
Interaction :
Potassium Salts: May delay solid potassium passage through GI tract, increase risk of ulcerative/stenotic lesions.
Doxylamine: May increase risk of CNS depression, anticholinergic and other adverse effects.
Isocarboxazid: May prolong and intensify anticholinergic effects of antihistamines.
Pramlintide: Combination with anticholinergic agents may further delay gastric emptying/slow GI transit.
Phenelzine: May prolong and intensify anticholinergic effects of antihistamines.
Hepatic Dose :
Clemastine is metabolized in the liver. Preferably avoid in hepatic impairment or use a reduced dose.