SAN FRANCISCO, CA—A systematic review of 30 randomized controlled trials (RCTs) showed the 5-nitroimidazoles demonstrated efficacy in the treatment of giardiasis; however, a need remains for well-designed, high-quality RCTs to assess their safety and efficacy profiles, a study concluded at IDWeek 2013.

Read More of MPR’s Exclusive Coverage of IDWeek 2013

Noting that newer agents with potentially similar efficacies as the 5-nitroimidazoles are increasingly becoming available, Abhishek Deshpande, MD, PhD, from the division of infectious diseases, department of medicine, Case Western Reserve University, Cleveland, OH, and colleagues investigated whether this class of agents continues to represent the best available treatment option for giardiasis. 

Investigators conducted a comprehensive literature search using PubMed-Medline, Scopus, Web of Science, and Cochrane Collaboration Library for RCTs to evaluate the efficacy of 5-nitroimidazoles vs. control (eg, placebo, active, or another 5-nitroimidazole) in the treatment of giardiasis.

The primary efficacy outcome was parasitological cure. Meta-analysis used random effects models to account for heterogeneity, and Mantel-Haenszel method to account for scarcity of outcomes. In addition, subgroup analyses by type of drug, type of patient, quality of studies, type of analysis and sample size were performed. 

A total of 30 RCTs studying 3930 patients were included. “All trials were conducted in countries endemic to giardiasis,” Dr. Deshpande reported. Of the 30 trials included, 22 were in outpatients, 7 in inpatients, and 1 RCT did not report the study setting. The majority of the RCTs, 24, were in the pediatric population; 4 were in both adult and pediatric populations and 2 trials in those aged >17 years. Post-treatment follow-up varied from 3 days to 5 weeks.

The analysis showed a significant and slightly higher response rate with 5-nitroimidazole in giardiasis treatment (risk ratio [RR] 1.06; 95% CI 1.02–1.11; P=0.005). There was also a high heterogeneity among studies (I2=72%).

When stratified by type of drug, they found that the efficacy of the 5-nitroimidazoles did not vary significantly: metronidazole (RR 1.05, 95% CI 1.01–1.09; P=0.01), tinidazole (RR 1.32, 95% CI 1.10–1.59; P=0.003), and secnidazole (RR 1.18, 95% CI 0.93–1.449; P=0.18). In addition, the high heterogeneity persisted (I2=57% to 80%).

No RCT compared ornidazole to a control group. When studies comparing two 5-nitroimidazoles were excluded, the pooled risk ratio did not vary significantly (RR 1.08, 95% CI 1.04–1.13; P<0.0001).