Standard dosage 50 mg every 4 to 6 hours; do not exceed 200 mg/d. Use with caution in patients with convulsive, cardiovascular, respiratory, or hepatic disorders. Elderly patients may be more susceptible to adverse effects at the recommended adult dose. Contraindications Known hypersensitivity to cyclizine. Main drug interactions Alcohol, antianxiety drugs, anticoagulants, barbiturates, central nervous system depressants, heparin, monoamine oxidase inhibitors, narcotics, phenothiazines, procarbazine, sedative hypnotics, and tricyclic antidepressants. Main side effects Photosensitivity, excessive perspiration, dry mouth, dry nose, dry throat, palpitations, tachycardia, sedation, sleepiness, and fatigue. Special points Because of the anticholinergic action of cyclizine, this drug should be used with caution in elderly men with possible prostatic hypertrophy. Cost/cost effectiveness Information not available. Meclizine Standard dosage 25 to 50 mg/d in divided doses. Use with caution in patients with convulsive, cardiovascular, respiratory, or hepatic disorders. Contraindications Asthma, glaucoma, emphysema, chronic pulmonary disease, shortness of breath, difficulty breathing, difficulty urinating because of enlarged prostate (unless prescribed by physician), and known hypersensitivity to meclizine. Main drug interactions Alcohol, anticoagulants, tricyclic antidepressants, central nervous system depressants, antianxiety drugs, barbiturates, narcotics, phenothiazines, procarbazine, sedative hypnotics, heparin, and monoamine oxidase inhibitors. Main side effects Photosensitivity, excessive perspiration, dry mouth, dry nose, dry throat, palpitations, tachycardia, sedation, sleepiness, and fatigue. Special points In elderly patients, use the lowest adult dose. Cost/cost effectiveness In a strength of 25 mg, 100 tablets of meclizine cost $2.55.