Drugs for treating giardiasis

Giardiasis infection may be asymptomatic, or can cause diarrhoea (sometimes severe), weight loss, malabsorption, and, in children, failure to thrive. It is usually treated with metronidazole given three times daily for five to 10 days.

To evaluate the relative effectiveness of alternative antibiotic regimens for treating adults or children with symptomatic giardiasis.

We searched the Cochrane Infectious Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 6 2012); MEDLINE, EMBASE, LILACS and the International Clinical Trials Registry Platform Search Portal (3 July 2012).

We included randomized controlled trials (RCT) comparing metronidazole administered for five to 10 days with any of the following drugs: metronidazole (single dose), tinidazole, albendazole, mebendazole, and nitazoxanide. The primary outcomes were parasitological and clinical cure.

Two authors independently assessed studies for inclusion, performed the risk of bias assessment, and extracted data. We summarized data using risk ratios and mean differences and we presented the results in forest plots and performed meta-analyses where possible. We assessed heterogeneity using the Chi(2) test, I(2) statistic and visual inspection; and we explored this by using subgroup analyses.We assessed the quality of evidence by using the GRADE approach.

We included 19 trials, involving 1817 participants, of which 1441 were children. Studies were generally small, with poor methods reporting. . Most reported parasitological outcomes rather than clinical improvement.Ten trials, from India, Mexico, Peru, Iran, Cuba, and Turkey, compared albendazole (400 mg once daily for five to 10 days) with metronidazole (250 mg to 500 mg three times daily for five to 10 days). This once-daily regimen of albendazole is probably equivalent to metronidazole at achieving parasitological cure (RR 0.99, 95% CI 0.95 to 1.03; 932 participants, 10 trials; moderate quality evidence), and improving symptoms (RR 0.98, 95% confidence interval (CI) 0.93 to 1.04; 483 participants, five trials; moderate quality evidence), but the duration of follow-up was short (two to three weeks). Albendazole probably has fewer side effects than metronidazole (gastrointestinal side effects: RR 0.29, 95% CI 0.13 to 0.63; 717 participants, eight trials; moderate quality evidence; neurological side effects: RR 0.34, 95% CI 0.18 to 0.64; 453 participants, five trials; low quality evidence).Five trials from Turkey, Spain and the UK compared mebendazole (200 mg three times daily for five to 10 days) with metronidazole (5 mg/kg (or 250 mg) three times daily for five to 10 days). These trials were small in size, and at high risk of bias. Consequently, reliable conclusions on the relative effectiveness cannot be made (very low quality evidence).Five further trials, from Iran, Spain and Peru, have evaluated shortened regimens of tinidazole (single dose; 179 participants, three trials), metronidazole (single dose; 55 participants, one trial), and nitazoxanide (three days; 55 participants, one trial). Again, these trials were at high risk of bias and too small to reliably detect or exclude important differences (very low quality evidence).

Albendazole may be of similar effectiveness to metronidazole, may have fewer side effects, and has the advantage of a simplified regimen. Large, high quality trials, assessing clinical outcomes (such as diarrhoea) will help assess further alternatives.