Tinidazole Found to Be Better Than Metronidazole for Giardiasis

Single-dose tinidazole is the best available treatment for giardiasis in children and adults, a new study shows.

José M. Ordóñez-Mena, MSc, Dr. sc. hum, from the University of Oxford, United Kingdom, and colleagues published the results of their study November 27, 2017, in the Journal of Antimicrobial Chemotherapy.

“In this comprehensive investigation of all giardiasis treatments we provide strong evidence in favor of the adoption of tinidazole as a first-line treatment, given its higher efficacy and comparable side effects to the current mainstay therapy, metronidazole,” the authors write.

Giardiasis is caused by Giardia lamblia, the most common intestinal protozoal parasite isolated worldwide. Recognized as a neglected tropical disease owing to its burden and association with poverty, this important public health problem is highly associated with poor hygiene, contaminated water, and poor sanitation.

Although giardiasis occurs more commonly in children, it also arises in adults and may manifest as “travelers’ diarrhea” in those who travel to countries where the disease is endemic.

Effective treatment thus plays an important role in reducing the prevalence and burden of Giardia infection in these areas.

Metronidazole, a 5-nitroimidazole (5-NI), is the current first-choice treatment for giardiasis, but other drugs with potentially higher efficacy or with fewer and milder side effects have also emerged.

However, limited evidence exists for optimal treatment of this disease. Randomized controlled trials (RCTs) comparing the many available treatment options are scarce, and previous systematic reviews and traditional meta-analyses have neither evaluated all treatments nor compared their efficacies.

Dr. Ordóñez-Mena and colleagues, therefore, aimed to further examine the evidence base of treatments for giardiasis.

They performed a systematic review and network meta-analysis of studies investigating the efficacy and side effects of all available drugs for the treatment of giardiasis in children and adults. Their study included 6714 patients in 60 RCTs investigating 18 treatments and 42 treatment comparisons.

According to the authors, most treatments had an efficacy of greater than 80%. But tinidazole was the only 5-NI associated with a higher parasitological cure rate than metronidazole (relative risk [RR], 1.23; 95% confidence interval [CI], 1.12 to 1.35) and albendazole (RR, 1.35; 95% CI, 1.21 to 1.50).

Although tinidazole was associated with a higher incidence of side effects (such as metallic taste, nausea, and vomiting) than albendazole, mebendazole, and secnidazole, these were typically mild and occurred after completion of treatment. Therefore, the authors believe they are unlikely to affect compliance.

“Balancing the evidence for drug efficacy and side effects, tinidazole appears to be the best available treatment for giardiasis,” Dr. Ordóñez-Mena and colleagues wrote. “The better adherence possible with a single-dose regimen, which is usual for tinidazole, is likely to be even more important in clinical and public health practice than in the more controlled settings of RCTs.”

Given the findings of this study, the authors suggest that tinidazole should be included in the World Health Organization Essential Medicines List for treatment of giardiasis. However, they also stress the need for additional research to determine whether newer therapies such as sausalin may be more effective, particularly because nitroimidazole resistance has become an emerging issue.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.