Ivermectin reaches peak plasma levels 5 hours after oral administration and has a half-life of 36 hours.1 It is currently assumed that the drug is delivered to infective organisms via ingested intraepidermal fluids. Whereas fertile tunneling mites die after a first oral dose, the eggs in the burrows are assumed to require a second dose 10 to 14 days later, when the larvae hatch.2 Since immature mites are known to move extensively over the body at night between molting periods, we investigated the possibility that they take up the drug from the skin surface. Because the drug is lipophilic, we compared seborrheic and dry skin regions for drug concentration.
Haas N, Lindemann U, Frank K, Sterry W, Lademann J, Katzung W. Rapid and Preferential Sebum Secretion of Ivermectin: A New Factor That May Determine Drug Responsiveness in Patients With Scabies. Arch Dermatol. 2002;138(12):1618. doi:10.1001/archderm.138.12.1613