What is the treatment for Giardia?

Treatment of Giardiasis

Tinidazole is the first-line treatment for giardiasis, administered as a single 2g oral dose in adults or 50 mg/kg in children ≥3 years, with cure rates of 80-100%. 1, 2, 3

First-Line Treatment: Tinidazole

Tinidazole is superior to other options due to its single-dose regimen and high efficacy. 2 The dosing is straightforward:

• Adults: 2g as a single oral dose 1
• Pediatric (≥3 years): 50 mg/kg as a single oral dose 1, 4, 3
• Tablets can be crushed for easier administration in children 2

The FDA has approved tinidazole specifically for giardiasis treatment in both adults and children over 3 years of age. 3

Second-Line Treatment: Metronidazole

When tinidazole is unavailable, metronidazole is the effective alternative, though it requires a longer treatment course. 1, 2 Dosing regimens include:

• Adults: 250 mg three times daily for 5 days (can use up to 750 mg three times daily for 5-7 days in severe cases) 1, 2
• Pediatric: 15 mg/kg/day divided into three doses for 5 days 1, 4

Note that commercial pediatric suspension is not available, but metronidazole can be compounded from tablets. 2

Alternative Treatment: Nitazoxanide

Nitazoxanide is FDA-approved for giardiasis and represents another treatment option, particularly useful in children. 5

• Pediatric (4-11 years): 200 mg twice daily 1, 4

This agent has the advantage of lacking the bitter taste characteristic of nitroimidazoles. 6

Special Populations

Children Under 3 Years

Consult with a pediatric specialist for children under 3 years, as tinidazole is only approved for children ≥3 years. 1, 2, 4

Immunocompromised Patients

Immunocompromised patients may require more aggressive treatment with higher doses and longer duration. 1 Consider:

• Metronidazole 750 mg three times daily for 5-10 days, potentially combined with diiodohydroxyquin or paromomycin 1

Pregnancy

Paromomycin is the preferred agent during pregnancy, though it has lower cure rates (60-100%). 6

Treatment Failure Management

If initial treatment fails, consider alternative medication regimens or combination therapy rather than simply repeating the same drug. 1 Important considerations include:

• Rule out reinfection, especially in endemic areas or with continued exposure 1
• Consider longer duration of therapy or combination therapy 1
• Recent evidence from Cuba demonstrates that 5-nitroimidazole resistance is increasingly common, with cross-resistance between metronidazole, secnidazole, and tinidazole 7
• For nitroimidazole-refractory cases, combination therapy with secnidazole plus high-dose mebendazole (200 mg every 8 hours for 3 days) achieved 87% cure rates 7
• Quinacrine can be reserved for multiply-refractory cases 7

Supportive Care

Maintain adequate oral hydration and continue age-appropriate diet during treatment. 1, 4 Specific measures include:

• Use reduced osmolarity oral rehydration solution (ORS) for mild to moderate dehydration 8
• Continue normal diet during or immediately after rehydration 4
• Emphasize hand washing after bathroom use and before food preparation/consumption 1, 4

Critical Pitfalls to Avoid

Never administer antimotility agents (like loperamide) to children under 18 years with acute diarrhea. 1, 4

Do not use empiric antimicrobial therapy for persistent watery diarrhea lasting 14 days or more without confirmed diagnosis. 8 Multiple stool examinations may be necessary as Giardia is shed intermittently. 1

Asymptomatic contacts should not receive empiric or preventive therapy, but should follow appropriate infection prevention and control measures. 8