Is 70 mg a High Dose of Ivermectin?
Yes, 70 mg is a high dose of ivermectin that significantly exceeds standard therapeutic dosing for approved parasitic infections, and would only be appropriate in specific clinical scenarios such as treating a very heavy patient (>350 kg) or managing severe crusted scabies with combination therapy.
Standard Dosing Context
The approved therapeutic dose for ivermectin is 200 μg/kg (0.2 mg/kg) for most parasitic infections 1, 2, 3. To put 70 mg in perspective:
- For a 70 kg adult: Standard dose = 14 mg (70 kg × 0.2 mg/kg)
- 70 mg represents: 1 mg/kg for a 70 kg person, which is 5 times the standard dose 3
- Weight threshold: A patient would need to weigh approximately 350 kg (770 lbs) for 70 mg to be a standard 200 μg/kg dose
When Higher Doses Are Used
Crusted (Norwegian) Scabies
The only guideline-supported scenario approaching higher cumulative dosing involves crusted scabies, where the CDC recommends oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 (five total doses) combined with daily topical permethrin 2. However, each individual dose remains at the standard 200 μg/kg level—not a single 70 mg dose 2.
Dose-Response Studies
Historical research explored doses ranging from 100-200 μg/kg for onchocerciasis, with studies finding that 100 μg/kg was sufficient for ocular microfilarial clearance 4, 5. A safety study evaluated doses up to 2000 μg/kg (2 mg/kg) in healthy volunteers, showing approximately proportional plasma concentrations with dose, but these were research settings, not clinical recommendations 3.
Pharmacokinetic Considerations
- Bioavailability: Taking ivermectin with food increases bioavailability approximately 2.5-fold, which is clinically relevant for dosing 1, 3
- Metabolism: Primarily metabolized by CYP3A4 in the liver 3
- Half-life: Approximately 18 hours following oral administration 3
- Clearance in children: Pre-school and school-aged children have higher clearance (0.346 and 0.352 L/hour/kg respectively) compared to adults (0.199 L/hour/kg), requiring weight-adjusted dosing 6
Safety Concerns at High Doses
The safety profile of ivermectin at doses that might achieve 70 mg in average-weight adults has not been established for routine clinical use 7. Key safety considerations include:
- Hepatic impairment: Safety of multiple or high doses in severe liver disease is not well established 1, 7
- Neurotoxicity risk: Ivermectin can cross the blood-brain barrier and should not be used in children weighing <15 kg due to potential neural transmission blockade 1
- Weight-based contraindications: Children <10 years should not receive certain formulations 1
Clinical Pitfalls to Avoid
- Do not assume higher doses are better: For strongyloidiasis, double-dosing at standard 200 μg/kg (two weeks apart) achieved 93.1% cure rates, while single doses achieved 96.8%—both far superior to higher-dose albendazole 8
- Verify patient weight accurately: A dosing error based on incorrect weight could result in significant overdosing
- Consider indication carefully: No current medical guidelines support ivermectin dosing that would result in 70 mg for average-weight adults outside of extreme obesity 7