Ivermectin Dosing for 120-Pound Female, Age 58
For a 58-year-old woman weighing 120 pounds (54.5 kg), the appropriate ivermectin dose is 200 mcg/kg (approximately 11 mg total), which translates to four 3-mg tablets as a single oral dose on an empty stomach with water. 1
Indication-Specific Dosing
The exact dosing depends on the parasitic condition being treated:
For Strongyloidiasis (Intestinal Threadworm)
- Single dose of 200 mcg/kg (four 3-mg tablets for this patient)
- Take on empty stomach with water
- Follow-up stool examinations needed to verify eradication
- Additional doses generally not necessary unless follow-up shows persistent infection 1
For Onchocerciasis (River Blindness)
- Single dose of 150 mcg/kg (three 3-mg tablets for this patient)
- Take on empty stomach with water
- Retreatment may be considered at intervals as short as 3 months for individual patients
- Most mass distribution programs use 12-month intervals 1
For Scabies
- 200 mcg/kg as two doses, one week apart (four 3-mg tablets per dose)
- The double-dose regimen achieves 98% clearance versus only 58% with single dose 2
- Single-dose regimens are a main predictor of treatment failure (p < 0.001) 2
- For crusted scabies, combine oral ivermectin with topical preparations 3
For Loiasis (African Eye Worm)
- 150-200 mcg/kg as single dose or repeated doses
- May be given monthly, quarterly, or biannually depending on microfilarial load 4
- Critical threshold: use caution if microfilaremia exceeds 8,000 mf/ml
Administration Details
Key points for proper administration:
- Timing: Take on empty stomach with water 1
- Food effect: High-fat meals increase bioavailability 2.5-fold, which is generally undesirable for standard dosing 1
- Metabolism: Primarily metabolized by CYP3A4 in the liver 1
- Half-life: Approximately 18 hours 1
Weight-Based Dosing Table
For this 54.5 kg (120 lb) patient, FDA dosing guidelines indicate:
| Indication | Body Weight Range | Number of 3-mg Tablets |
|---|---|---|
| Strongyloidiasis (200 mcg/kg) | 51-65 kg | 4 tablets |
| Onchocerciasis (150 mcg/kg) | 45-64 kg | 3 tablets |
Important Caveats
Contraindications and precautions:
- Avoid in pregnancy and breastfeeding
- Use caution with severe liver disease
- Check for drug interactions with CYP3A4 inhibitors/inducers
- Not indicated for COVID-19 treatment (no clinical benefit demonstrated) 5
- Ensure correct parasitic diagnosis before treatment
Follow-up requirements:
- Strongyloidiasis: Stool examinations 3-4 weeks post-therapy 6
- Scabies: Clinical assessment 1-2 weeks after second dose 2
- Consider second dose if new lesions develop or parasites persist
Efficacy Evidence
The evidence strongly supports ivermectin's efficacy for approved parasitic indications. For strongyloidiasis, single-dose ivermectin achieves 96.8% cure rates compared to 63.3% with albendazole 6. Double-dose regimens may be more effective in immunocompromised patients with concomitant illness 6.