From the Guidelines
Giardia lamblia infections should be treated with tinidazole as the first-line therapy, due to its higher efficacy and lower frequency of gastrointestinal side effects compared to metronidazole. According to the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1, tinidazole is the recommended first-choice treatment for Giardia lamblia infections. The guidelines suggest that tinidazole is approved in the United States for children aged ≥3 years and is available in tablets that can be crushed.
Key Considerations
- Metronidazole is an alternative treatment option, but it has a high frequency of gastrointestinal side effects and is not FDA approved for the treatment of giardiasis 1.
- A pediatric suspension of metronidazole is not commercially available but can be compounded from tablets 1.
- Symptoms of Giardia lamblia infection include diarrhea, abdominal cramps, bloating, nausea, and fatigue, typically appearing 1-2 weeks after exposure.
- Prevention involves proper handwashing, drinking treated water, and avoiding swallowing water while swimming in potentially contaminated sources.
Treatment Options
- Tinidazole: single 2-gram dose for adults, or approved for children aged ≥3 years 1.
- Metronidazole: 250 mg three times daily for adults or 15 mg/kg/day divided into three doses for children, although not FDA approved for giardiasis 1.
- Nitazoxanide: twice daily for 3 days, although not the first-line therapy 1.
From the Research
Giardiasis Treatment
- The first-line drug treatment for giardiasis is tinidazole, which requires only a single dose to cure infection in most individuals 2.
- Metronidazole is also effective, but it requires 5 to 7 days of three times a day therapy 2.
- Nitazoxanide appears to be as effective as tinidazole or metronidazole, and it does not have the bitter taste of nitroimidazoles 2.
- Albendazole may be of similar effectiveness to metronidazole, may have fewer side effects, and has the advantage of a simplified regimen 3, 4.
- Tinidazole was associated with higher parasitological cure than metronidazole and albendazole, and was found to be the most effective drug 5.
Giardiasis Symptoms and Diagnosis
- Giardiasis infection may be asymptomatic, or can cause diarrhoea, weight loss, malabsorption, and failure to thrive in children 3.
- Direct fluorescent antibody tests, enzyme immunoassays, and multiplex real-time polymerase chain reaction assays have improved sensitivity and specificity for detecting Giardia trophozoites or cysts in stool samples 6.