What is the recommended dose of the ivermectin‑albendazole fixed‑dose combination for a patient weighing ≥ 15 kg, and who are the contraindicated groups?

Ivermectin-Albendazole Fixed-Dose Combination Dosing

The recommended dose of the ivermectin-albendazole fixed-dose combination (FDC) for patients weighing ≥15 kg is albendazole 400 mg plus ivermectin 18 mg as a single oral dose, with contraindications including pregnancy, children under 15 kg body weight, and individuals with Loa loa co-infection. 1, 2, 3, 4

Dosing Regimen

Standard Single-Dose Treatment

• The FDC contains albendazole 400 mg combined with ivermectin 18 mg in a single tablet for patients weighing ≥15 kg 5, 6, 4
• This combination is administered as a single oral dose taken on an empty stomach with water to optimize bioavailability 3
• For enhanced efficacy against certain parasites (particularly Trichuris trichiura), the FDC can be given as three consecutive daily doses (FDC×3), which demonstrated superior cure rates of 97.2% compared to 82.9% with single-dose treatment 4

Weight-Based Considerations

• The minimum weight requirement is 15 kg for safe administration of the FDC 5, 4
• The ivermectin component is dosed at approximately 200 mcg/kg when using the 18 mg formulation in patients weighing 15-45 kg 1, 3, 5
• Some formulations contain 9 mg ivermectin for lighter patients, though the 18 mg formulation is preferred for optimal efficacy 5, 4

Absolute Contraindications

Loa loa Co-infection (Critical Safety Warning)

• Always exclude Loa loa infection before administering ivermectin to anyone who has traveled to endemic regions (Central and West Africa) 7, 1, 3
• Patients with hypermicrofilaremia (>8,000 microfilariae/mL) are at high risk for severe adverse events including encephalitis and death when treated with ivermectin 7, 3
• This is the most critical contraindication and failure to screen can result in fatal outcomes 7

Age and Weight Restrictions

• Children weighing <15 kg should not receive the FDC 5, 4
• Children aged 12-24 months require expert consultation before any treatment with this combination 1
• Children under 10 years should not receive ivermectin for scabies (permethrin cream is preferred) 3

Pregnancy and Lactation

• Ivermectin is classified as "human data suggest low risk" in pregnancy but should be used with caution 3
• The combination is probably compatible with breastfeeding, though individual risk-benefit assessment is warranted 3

Onchocerciasis Co-infection

• Exclude onchocerciasis before treating with this combination, as rapid microfilarial death can precipitate severe Mazzotti reactions including pruritis, erythema, hypotension, and blindness 7
• A test dose of 50 mg diethylcarbamazine can be used to screen for onchocerciasis if skin snips are unavailable 7

Safety Profile and Adverse Events

Common Mild-to-Moderate Effects

• Gastrointestinal symptoms (nausea, abdominal pain, diarrhea) are the most common adverse events, occurring in 20-23% of patients receiving the FDC 4
• These symptoms typically resolve within 48 hours without intervention 4
• Albendazole alone causes adverse events in 14% of patients, demonstrating the FDC has an acceptable incremental safety burden 4

Serious Adverse Events

• No serious adverse events occurred in the largest phase 2/3 trial of 1,001 participants 4
• One historical study reported increased mortality in elderly, debilitated persons receiving ivermectin, though this has not been confirmed in subsequent reports 3
• Hepatotoxicity and leukopenia monitoring is recommended if treatment extends beyond 14 days 1

Clinical Efficacy by Parasite

Superior Efficacy Profile

• For Trichuris trichiura: FDC×3 achieves 97.2% cure rate versus 35.9% with albendazole alone (absolute difference 61.3%) 4
• For hookworms: FDC×3 achieves 95.0% cure rate versus 65.1% with albendazole alone (absolute difference 29.9%) 4
• For Strongyloides stercoralis: Single-dose ivermectin achieves 83% cure rate versus 45% with three-day albendazole 8
• For Ascaris lumbricoides: Both components are highly effective 8

Limitations

• Ivermectin alone is ineffective against hookworms, making the combination essential for broad-spectrum coverage 8
• Sample size for S. stercoralis efficacy evaluation was not met in the largest trial, though historical data supports efficacy 4

Administration Guidelines

Timing and Food Interactions

• Administer on an empty stomach with water only 3
• No dose adjustments required for renal impairment 3
• Safety of multiple doses in severe liver disease is not established 3

Follow-up Recommendations

• Repeat stool examination 2-3 weeks after treatment if symptoms persist 1
• For empirical treatment in endemic-exposed individuals with negative stool tests, a single dose is sufficient for prophylaxis 1
• Retreatment 1 month after symptom resolution may be needed to ensure adult worms are eliminated 1

Common Pitfalls to Avoid

• Never administer ivermectin without excluding Loa loa in anyone with Central/West African exposure 7, 1, 3
• Do not use this combination for Taenia solium (pork tapeworm) without first excluding neurocysticercosis 2
• Do not assume negative stool microscopy rules out infection—sensitivity is poor even with multiple samples 1
• For schistosomiasis, this combination is ineffective; praziquantel is required 2