A Cochrane review included 30 studies with a total of 8 165 subjects.
Praziquantel. On average, a single 40 mg/kg dose of praziquantel reduced the proportion of people still excreting eggs in their urine by around 60% compared to placebo at one to two months after treatment (treatment failure: RR 0.42, 95% CI 0.29 to 0.59, 864 participants, 7 trials). The proportion of people cured with praziquantel varied substantially between trials, from 22.5% to 83.3%, but was higher than 60% in five of the seven trials. At one to two months following praziquantel treatment at 40 mg/kg, the mean number of schistosome eggs in the urine was reduced by over 95% in five out of six trials (678 participants, 6 trials). Splitting praziquantel 40 mg/kg into two doses over 12 hours probably has no benefits over a single dose, and in a single trial of 220 participants the split dose caused more vomiting (RR 0.5, 95% CI 0.29 to 0.86) and dizziness (RR 0.39, 95% CI 0.16 to 0.94).
Metrifonate. A single dose of metrifonate 10 mg/kg reduced egg excretion (210 participants, 1 trial, at 8 months), but was only marginally better than placebo at achieving cure at one month (RR 0.83, 95% CI 0.74 to 0.94, 142 participants, 1 trial). In a single trial comparing one, two and three doses, the absolute number of participants cured improved from 47% after one dose to 81% after three doses (93 participants, 1 trial). Two small trials compared 40 mg/kg single dose praziquantel with two or three doses of 10 mg/kg metrifonate and found no clear evidence of differences in cure (metrifonate 2 x 10 mg/kg at one month: RR 1.03, 95% CI 0.8 to 1.34, 72 participants,1 trial; metrifonate 3 x 10 mg/kg at three months: RR 0.33, 95% CI 0.07 to 1.57, 100 participants, 1 trial. In one trial both drugs performed badly and in one trial both performed well.
Compared with placebo, participants receiving metrifonate had fewer parasitological failures at follow up at one to three months (1 trial) and three to 12 months (3 trials). Egg reduction rate was over 90%, and no adverse events were reported (1 trial). One metrifonate dose was inferior to three doses given fortnightly (both used 10 mg/kg). Praziquantel (standard single 40 mg/kg oral dose) was more effective than placebo at reducing parasitological failure at one to three months' follow up and three to 12 months. Egg reduction rates were improved with praziquantel (over 95% versus 5.3% to 64% with placebo). Mild to moderate adverse events were recorded in two trials. A comparison of metrifonate (10 mg/kg x 3, once every 4 months for one year) with praziquantel (standard dose) showed little difference in parasitological failure. For praziquantel, there was no significant difference in effect between 20 mg/kg x 2, 30 mg/kg x 1, and 20 mg/kg x 1, and the standard dose for all outcomes. One small trial of artesunate showed no obvious benefit compared with placebo, and the artesunate-praziquantel combination was similar to praziquantel alone.