A 32-year-old woman presents with intense pruritus, worse at night, affecting the interdigital spaces, wrists, and axillae for 2 weeks. Examination reveals burrows and papules. Scabies is confirmed by dermoscopy. What is the drug of choice for treatment?

Question

Accepted Answer

B. Permethrin 5% cream. ## First-Line Treatment of Scabies **Key Point:** Permethrin 5% cream is the gold-standard first-line agent for scabies in adults and children >2 months of age, recommended by WHO, CDC, and Indian dermatology guidelines. ### Mechanism & Efficacy Permethrin is a synthetic pyrethroid that disrupts sodium channel function in the mite's nervous system, causing paralysis and death. It has excellent efficacy (cure rates >95% with proper application) and minimal systemic absorption. ### Application Protocol - Apply to entire body surface (neck to toes) after a warm bath - Leave on for 8–14 hours (overnight application preferred) - Repeat after 1–2 weeks to eliminate hatched mites - Treat all household contacts and sexual partners simultaneously ### Comparison with Alternatives | Agent | First-Line? | Advantages | Limitations | |-------|------------|-----------|-------------| | **Permethrin 5%** | ✓ Yes | Safe, effective, low toxicity, minimal absorption | Cost (higher than benzyl benzoate) | | **Benzyl benzoate 10%** | Acceptable alternative | Cheap, widely available in India | Irritant, requires multiple applications, higher relapse | | **Sulfur 5%** | No (reserve) | Safe in pregnancy & infants <2 months | Slow-acting, messy, cosmetically unacceptable | | **Lindane 1%** | ✗ No (contraindicated) | — | Neurotoxicity, seizures, banned in many countries | **High-Yield:** In resource-limited settings or when permethrin is unavailable, benzyl benzoate 10% lotion (applied for 24 hours on days 1, 3, 5) is an acceptable alternative, though inferior in efficacy and tolerability. **Clinical Pearl:** Sulfur 5% ointment is reserved for pregnant women, nursing mothers, and infants <2 months (permethrin is safe in infants >2 months). Lindane is now contraindicated due to risk of CNS toxicity and environmental persistence. **Warning:** Lindane should NOT be used — it carries risk of seizures, aplastic anemia, and is banned in the EU and restricted in the US. This is a common exam trap.

Answer

A. Lindane 1% lotion

Answer

C. Sulfur 5% ointment

Answer

D. Benzyl benzoate 10% lotion

A 32-year-old woman presents with intense pruritus, worse at night, affecting the interdigital spaces, wrists, and axillae for 2 weeks. Examination reveals burrows and papules. Scabies is confirmed by dermoscopy. What is the drug of choice for treatment?

Explanation

First-Line Treatment of Scabies

Mechanism & Efficacy

Application Protocol

Comparison with Alternatives

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Agent	First-Line?	Advantages	Limitations
Permethrin 5%	✓ Yes	Safe, effective, low toxicity, minimal absorption	Cost (higher than benzyl benzoate)
Benzyl benzoate 10%	Acceptable alternative	Cheap, widely available in India	Irritant, requires multiple applications, higher relapse
Sulfur 5%	No (reserve)	Safe in pregnancy & infants <2 months	Slow-acting, messy, cosmetically unacceptable
Lindane 1%	✗ No (contraindicated)	—	Neurotoxicity, seizures, banned in many countries