Oral Treatment for Scabies
Ivermectin 200 μg/kg orally, repeated in 2 weeks, is the recommended oral medication for treating scabies 1.
Dosing and Administration
- Standard dose: 200 μg/kg body weight
- Timing: Two doses, 14 days apart 1
- Critical administration detail: Must be taken with food to increase bioavailability and enhance drug penetration into the epidermis 1
The two-dose regimen is essential because ivermectin has limited ovicidal activity and cannot prevent hatching of eggs present at the time of initial treatment 1. A single dose results in only 58% treatment success compared to 98% with two doses 2, making the second dose critical to prevent treatment failure and potential resistance development.
When to Use Oral Ivermectin
Ivermectin is particularly valuable in:
- Institutional outbreaks (nursing homes, hospitals, residential facilities) where treating entire populations is necessary 1
- Patients who cannot tolerate or have failed topical therapy 1
- Mass drug administration in endemic populations 3, 4
Important Contraindications and Precautions
Do not use ivermectin in:
- Children weighing <15 kg (safety not established) 1
- Patients with severe liver disease (safety of multiple doses unknown) 1
Use with caution in:
- Elderly, debilitated persons (one study showed increased mortality, though not confirmed in subsequent reports) 1
- Renal impairment (no dose adjustment needed, but monitor closely) 1
Pregnancy and lactation: Ivermectin is classified as "human data suggest low risk" and likely compatible with breastfeeding, but permethrin remains preferred due to more extensive safety data 1.
Comparative Efficacy
While topical permethrin 5% cream remains first-line therapy (more effective, safer, and less expensive than ivermectin) 1, recent meta-analysis shows oral ivermectin and topical benzyl benzoate have comparable cure rates 5. However, ivermectin demonstrates significantly better tolerability with fewer adverse events (RR: 0.27), particularly less burning/stinging (RR: 0.07) 5.
Special Situation: Crusted (Norwegian) Scabies
For severe crusted scabies, combination therapy is mandatory:
- Oral ivermectin 200 μg/kg on days 1,2,8,9, and 15
- PLUS topical permethrin 5% cream (full-body application daily for 7 days, then twice weekly until cure)
- Additional ivermectin doses on days 22 and 29 may be required for severe cases 1
Never use lindane in crusted scabies due to neurotoxicity risk with heavy applications or denuded skin 1.
Follow-Up and Treatment Failure
- Pruritus and rash may persist up to 2 weeks after successful treatment 1
- Retreatment at 2 weeks is indicated if: live mites are observed, new lesions develop, or symptoms persist beyond 2 weeks 1
- If initial regimen fails, switch to an alternative regimen 1
Essential Adjunctive Measures
- Decontaminate bedding and clothing (machine wash/dry on hot cycle or dry clean) or remove from body contact for 72 hours 1
- Treat all household and sexual contacts within the preceding month 1
- No fumigation of living areas is necessary 1
Common Pitfall to Avoid
The most critical error is administering only a single dose of ivermectin—this is a major predictor of treatment failure (P < 0.001) and may promote resistance 2. Always ensure patients understand the necessity of the second dose at 14 days.