Model Answer
0 min readIntroduction
Scabies is a contagious skin infestation caused by the mite *Sarcoptes scabiei*. It presents with intense pruritus, particularly at night, and characteristic burrows on the skin. Effective management requires both treating the affected individual and preventing its spread to close contacts. While historically treated with lindane, concerns regarding neurotoxicity have led to the development and increased use of alternative anti-scabetic drugs. This answer will enumerate these drugs and detail the necessary precautions to prevent further transmission, crucial for public health control.
Anti-Scabetic Drugs
Several medications are available for the treatment of scabies. The choice of drug depends on factors such as patient age, pregnancy status, and the presence of comorbidities.
1. Permethrin 5% Cream
Mechanism of Action: Acts as a neurotoxin to the mites and their eggs. It disrupts the sodium channels in the nerve cells of the scabies mites, leading to paralysis and death. Administration: Topical application to the entire body from the neck down, left on for 8-14 hours, then washed off. Repeat after one week. Side Effects: Mild skin irritation, burning sensation, and pruritus. Precautions: Avoid contact with eyes and mucous membranes. Flammable – keep away from open flames.
2. Ivermectin
Mechanism of Action: A broad-spectrum antiparasitic agent that acts by disrupting the neuromuscular function of the mites. Administration: Oral administration. Single dose is often sufficient, but may be repeated after 1-2 weeks. Side Effects: Mild gastrointestinal upset, dizziness, and fatigue. Rarely, neurological side effects. Precautions: Contraindicated in pregnancy and breastfeeding. Caution in patients with liver disease.
3. Lindane 1% Lotion (Use discouraged due to neurotoxicity)
Mechanism of Action: A neurotoxin that disrupts the nervous system of the scabies mite. Administration: Topical application, left on for 4-8 hours, then washed off. Repeat after one week. Side Effects: Neurotoxicity, seizures, and skin irritation. Precautions: Reserved for cases where other treatments have failed due to its potential toxicity. Not recommended for infants, children, pregnant or breastfeeding women.
4. Crotamiton 10% Cream
Mechanism of Action: Acts as both a scabicide and an antipruritic. Administration: Topical application twice daily for 3-7 days. Side Effects: Skin irritation and burning sensation. Precautions: Avoid contact with eyes and mucous membranes.
5. Sulfur Ointment (8-50%)
Mechanism of Action: The exact mechanism is not fully understood, but it is believed to disrupt the mite's metabolism. Administration: Topical application overnight for 3-7 days. Side Effects: Skin irritation, dryness, and odor. Precautions: Can stain clothing and bedding.
Precautions to Prevent the Spread of Scabies in Healthy Contacts
Preventing the spread of scabies requires a multi-pronged approach, including pharmacological treatment of contacts and non-pharmacological measures to reduce transmission.
1. Prophylactic Treatment of Close Contacts
All household members and close contacts should be treated simultaneously, even if asymptomatic. This prevents re-infestation of the treated individual. The same drug regimen should be used for contacts as for the index case.
2. Non-Pharmacological Measures
- Decontamination of Clothing and Bedding: Wash all clothing, bedding, and towels used in the 3 days prior to treatment in hot water (at least 60°C) and dry on a hot cycle. Items that cannot be washed should be sealed in a plastic bag for at least 72 hours.
- Avoid Skin-to-Skin Contact: Minimize close physical contact with infected individuals until treatment is completed.
- Environmental Cleaning: Vacuum carpets and upholstered furniture.
- Avoid Sharing Personal Items: Do not share clothing, towels, or bedding.
3. Public Health Measures
In institutional settings (e.g., nursing homes, childcare facilities), outbreaks require prompt investigation and treatment of all contacts. Education of staff and residents regarding scabies transmission and prevention is crucial.
4. Addressing Pruritus
Persistent pruritus after successful treatment is common. Antihistamines and emollients can help alleviate symptoms. Topical corticosteroids may be used for short periods to reduce inflammation.
| Drug | Mechanism of Action | Administration | Common Side Effects |
|---|---|---|---|
| Permethrin 5% | Neurotoxin (sodium channel disruption) | Topical | Skin irritation, burning |
| Ivermectin | Neuromuscular disruption | Oral | GI upset, dizziness |
| Lindane 1% | Neurotoxin | Topical | Neurotoxicity, seizures |
| Crotamiton 10% | Scabicide & Antipruritic | Topical | Skin irritation |
| Sulfur Ointment | Disrupts mite metabolism | Topical | Skin irritation, odor |
Conclusion
Effective management of scabies requires a combination of appropriate pharmacological treatment and diligent public health measures. Permethrin and ivermectin are the preferred first-line treatments, while lindane should be reserved for refractory cases due to its toxicity. Preventing re-infestation through prophylactic treatment of contacts and meticulous decontamination of the environment is paramount. Continued surveillance and education are essential for controlling scabies outbreaks and minimizing its public health impact.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.