Ivermectin dose assessment without weighing scales.

Described are two alternatives to the weighing of patients for assessing the dose of ivermectin for use in mass chemotherapy campaigns against onchocerciasis. The first method uses height to separate patients into four dosing categories (1/2, 1, 11/2 and 2 tablets), while the second involves estimating one of these dosing categories according to an individual's physical appearance, without making any measurements. Data for the height-based method were obtained from 6373 people who were taking part in a placebo-controlled trial of ivermectin in northern Nigeria. Use of an arbitrary trade-off of approximately 100 people "overdosed" for every person "underdosed" would lead to 0.5% of the population being underdosed by 1/2 tablet, 46.5% being dosed correctly, 51.7% being overdosed by 1/2 tablet, and 1.2% being overdosed by 1 tablet. The physical appearance approach involved three observers and 779 subjects. A total of 82% of the observers' estimates were "correct", with all the incorrect dosing deviating by only 1/2 tablet from the dose that the subjects should have received.