Serum concentrations of mebendazole in patients with hydatid disease.

Mebendazole was administered to 22 patients, 17 of whom had developing or cured hydatid cysts, and to 5 volunteers. Then, at regular intervals, it was titrated by radioimmunoassay in the serum for 24 hours. Serum levels after the intake of 1 gram were perceptible on an empty stomach; they were higher when the drug was taken with a rich meal, but the difference was not statistically significant. The administration of increasing therapeutic doses (3, 4.5, 6 and 12 g a day) led to a concomitant increase of the average serum levels of mebendazole; concentrations varied between a minimum of 7.6 ng/ml and a maximum of 483 ng/ml. The difference between the various average concentrations was only significant after 8 hours when increasing from 3 to 6 g a day. The absence of a significant difference for the other average concentrations was due to the large interindividual variations. However, analysis of the individual results shows an increase of the serum concentrations parallel with that of the dose in 10 out of 12 patients. The effect of the dose seems to vary with the patient and the dose received. Blood samples taken 2 hours after each of the 3 daily drug intakes could give more information as to the serum concentrations susceptible to influence the parasite. The drug's half life, lying between 3.3 and 11.5 hours in 5 patients, is longer in case of major hepatic dysfunction, due to established hepatopathy. During the monitoring of 7 patients, the average serum levels were comparable with or higher than the initial concentration.