Comparison of four dosage schedules in the treatment of giardiasis with metronidazole.

Sixty patients with parasitologically confirmed giardiasis were treated with metronidazole using four different regimens administered to four groups of 15 patients each. A seven-day course of 200 mg thrice daily successfully eliminated the organism in 11 patients. A repetition of the seven-day course after an interval of one week was successful in 14 patients, a single dose of 2400 mg in nine patients, and two 2400 mg doses on successive days in 12 patients. Late relapses, detected more than one month after therapy, were relatively common in the single-dose groups. Side-effects associated with the 2400 mg dosages were frequent but tolerable.