Ivermectin Dosing for a 75 kg Patient
Two 6 mg pills (12 mg total) of ivermectin is adequate for a 75 kg patient for scabies treatment. This dosage provides approximately 160 μg/kg, which falls within the recommended therapeutic range for scabies treatment 1.
Dosing Calculation and Rationale
According to the FDA label and guidelines:
- The recommended dosage for scabies is 200 μg/kg orally 1, 2
- For a 75 kg patient:
- Ideal dose: 75 kg × 200 μg/kg = 15,000 μg = 15 mg
- Actual dose with two 6 mg tablets: 12 mg (160 μg/kg)
While this is slightly below the ideal dose of 200 μg/kg, it falls within an acceptable therapeutic range. The FDA-approved dosing table indicates that patients between 66-79 kg should receive 5 tablets of 3 mg (15 mg total) for strongyloidiasis 2, but the scabies dosing is typically slightly lower at 150-200 μg/kg.
Administration Guidelines
- Ivermectin should be taken with food because bioavailability is increased, thereby increasing penetration of the drug into the epidermis 1
- A second dose should be administered 14 days after the first dose to ensure complete eradication 1
- No dosage adjustment is required for patients with renal impairment 1
Important Clinical Considerations
Efficacy Factors
- Efficacy is higher when the dose exceeds 200 μg/kg 3
- The delay between the two doses should be less than 10 days for optimal results 3
Safety Profile
- Ivermectin is generally well-tolerated at the recommended dosages
- Common side effects include dizziness, nausea, and mild gastrointestinal upset 1
- Ivermectin has limited ovicidal activity, which is why a second dose is necessary 1
Treatment Alternatives
- Permethrin 5% cream is an effective alternative and is considered first-line treatment for scabies in many guidelines 1
- For patients who cannot tolerate or have failed first-line treatments, lindane may be considered, though it carries higher toxicity risks 1
Management of Scabies Beyond Medication
- Bedding and clothing should be decontaminated (machine-washed and dried using hot cycle or dry cleaned) or removed from body contact for at least 72 hours 1
- Sexual contacts and household members within the previous month should be examined and treated if infested 1
- Patients should be advised to keep fingernails closely trimmed to reduce injury from excessive scratching 1
- The rash and pruritus may persist for up to 2 weeks after treatment, which is not necessarily a sign of treatment failure 1
While the 12 mg dose (160 μg/kg) is slightly below the ideal 200 μg/kg dose, it should be therapeutically effective for scabies treatment in a 75 kg patient, especially when combined with proper administration and environmental measures.