Ivermectin uptake and distribution in the plasma and tissue of Sudanese and Mexican patients infected with Onchocerca volvulus.

Ten Sudanese patients with Onchocerca volvulus infection were treated with a single oral dose of 150 micrograms/kg of ivermectin. Plasma samples were collected before treatment, 0.5, 1, 3, 4, 6, 12 hours and 1, 2, 3, 7, and 30 days. Four patients were selected for nodulectomies and skin biopsies at 6, 18 and 30 hours and 3 days post treatment. Using these samples O. volvulus worm fragments were dissected free of host nodular tissues for ivermectin extraction. Ivermectin was present in the nodular tissue at 6 hr and persisted for 3 days. It was also detected in an individual worm tissue extract at a concentration similar to the nodule, but in subcutaneous fascial tissue higher concentrations were sometimes found. Ivermectin was detected by radioimmunoassay in the plasma of all patients at 1 hr and peak concentrations were reached in an average of 5.6 hr. The drug persisted at detectable levels for 7 days in 70% of the studied patients. Plasma samples were also collected from 16 treated Mexican onchocerciasis patients before ivermectin treatment and 4 hr treatment and from six individuals who served as controls. The Mexican patients had concentrations of ivermectin in their plasma similar to those in the Sudanese patients.