From the Guidelines
For persistent scabies after two treatments with permethrin cream, oral ivermectin should be given at a dose of 200 micrograms per kilogram (0.2 mg/kg) of body weight, as recommended by the most recent guidelines 1. This dose is typically administered as a single dose, but a second dose is often recommended 7-14 days after the first to kill newly hatched mites.
- The medication should be taken with food to enhance absorption, as bioavailability is increased when taken with food 1.
- All household members and close contacts should be treated simultaneously to prevent reinfestation.
- Patients should also wash all bedding, clothing, and towels in hot water and dry on high heat on the day of treatment. Despite treatment, itching may persist for 2-4 weeks due to a hypersensitivity reaction to dead mites. Ivermectin works by paralyzing and killing the scabies mites by enhancing inhibitory neurotransmission, making it particularly useful for widespread infestations, treatment failures with topical agents, or when topical treatment is impractical 1. For example, a 70 kg adult would receive 14 mg of ivermectin. It's essential to note that ivermectin has limited ovicidal activity and may not prevent recurrences of eggs at the time of treatment; therefore, a second dose of ivermectin should be administered 14 days after the first dose 1.
From the Research
Treatment of Scabies with Ivermectin
- The standard dose of ivermectin for treating scabies is 200 μg/kg, as mentioned in the study 2.
- According to the study 3, a single dose of ivermectin provided a cure rate of 85.9% at a 2-week interval.
- The study 2 also suggests that oral ivermectin may lead to slightly lower rates of complete clearance after one week compared to permethrin 5% cream, but by week two there may be little or no difference.
- Another study 4 found that two applications of topical ivermectin provided a cure rate of 63.1% at the 2-week follow-up, which increased to 84.2% at the 4-week follow-up after repeating the treatment.
Comparison with Permethrin
- The study 2 compared the efficacy of topical permethrin and systemic ivermectin for scabies, and found that there is probably little or no difference in rates of complete clearance between the two treatments after four weeks.
- The study 3 found that twice application of permethrin with a 1-week interval is superior to a single dose of ivermectin.
- Another study 5 compared the efficacy of topical permethrin, crotamiton, and sulfur ointment, and found that permethrin cream showed faster improvement at first and second follow up.
Dosage and Administration
- The study 4 used a dose of 400 microg/kg of topical ivermectin, repeated once the following week.
- The study 3 used a single dose of oral ivermectin, while the study 2 used a standard dose of 200 μg/kg.
- The study 6 suggests that treatment failure is mainly caused by failure to properly implement the treatment recommendations by the patient and/or his or her contacts.