From the Guidelines
For adults with giardiasis, the recommended treatment is typically tinidazole, as it is listed as the first choice in the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1.
Treatment Options
- Tinidazole is the preferred treatment, with metronidazole as an alternative option, according to the guidelines 1.
- The guidelines recommend tinidazole as the first choice for treating Giardia lamblia, with metronidazole as an alternative, due to its high frequency of gastrointestinal side effects 1.
Important Considerations
- It is essential to note that metronidazole has a high frequency of gastrointestinal side effects and is not FDA-approved for the treatment of giardiasis 1.
- Tinidazole is approved in the United States for children aged ≥3 years and is available in tablets that can be crushed, making it a more convenient option for some patients 1.
Additional Recommendations
- Good hygiene practices, including thorough handwashing after using the bathroom and before handling food, are essential to prevent reinfection or transmission to others.
- Household contacts or sexual partners may need treatment as well, even if asymptomatic, to prevent reinfection.
From the FDA Drug Label
1.2 Giardiasis Tinidazole is indicated for the treatment of giardiasis caused by Giardia duodenalis (also termed G. lamblia) in both adults and pediatric patients older than three years of age [see Clinical Studies ( 14.2)] . 14. 2 Giardiasis Tinidazole (2 g single dose) use in giardiasis has been documented in 19 published reports from the world literature involving over 1,600 patients (adults and pediatric patients) In eight controlled studies involving a total of 619 subjects of whom 299 were given the 2 g × 1 day (50 mg/kg × 1 day in pediatric patients) oral dose of tinidazole, reported cure rates ranged from 80% (40/50) to 100% (15/15).
Giardiasis Treatment for Adults:
- The recommended treatment is Tinidazole with a single 2g dose, which has shown cure rates ranging from 80% to 100% in clinical studies 2.
- Alternatively, Nitazoxanide can be used, with a recommended dosage of one 500mg tablet taken orally every 12 hours with food for 3 days 3.
From the Research
Giardia Treatment for Adults
- The first-line drug treatment for giardiasis in adults is tinidazole, which requires only a single dose to cure infection in most individuals 4, 5.
- Metronidazole is also effective, but it requires 5 to 7 days of three times a day therapy 4, 5.
- Nitazoxanide appears to be as effective as tinidazole or metronidazole, and it does not have the bitter taste of nitroimidazoles 4.
- Albendazole may be of similar effectiveness to metronidazole, may have fewer side effects, and has the advantage of a simplified regimen 6.
- A single dose of tinidazole appears to give the highest clinical cure rate for giardiasis with relatively few adverse effects 7.
Treatment Options
- Tinidazole: single dose, high parasitological cure rate, relatively few adverse effects 4, 5, 7.
- Metronidazole: 5 to 7 days, three times a day, effective but may have more side effects than tinidazole 4, 5.
- Nitazoxanide: effective, but limited studies, does not have the bitter taste of nitroimidazoles 4.
- Albendazole: may be of similar effectiveness to metronidazole, may have fewer side effects, simplified regimen 6.
- Quinacrine: effective in refractory cases, but potentially severe side effects limit its use 8.
Refractory Giardiasis
- The prevalence of treatment refractory giardiasis is increasing, with 5-nitroimidazole refractory infection occurring in up to 50% of cases 8.
- Combination treatment with a 5-nitroimidazole and a benzimidazole may be more effective than repeated courses of 5-nitroimidazole or monotherapies in refractory cases 8.
- Quinacrine is effective in refractory cases, but potentially severe side effects limit its use 8.