High oral doses of
mebendazole have been only partly effective in the treatment of patients with alveolar or
cystic echinococcosis, possibly due to an inadequate plasma concentration of the
drug in some patients. In order to improve therapeutic results the influence of liver function on the plasma levels of
mebendazole was investigated during long term
therapy. Plasma
mebendazole concentrations measured before the morning dose (trough values) showed a highly significant, negative correlation both with the
aminopyrine breath test (ABT; rs = -0.78, n = 14, p less than 0.001) and the second exponential component of bromsulphthalein elimination (BSP- k2; rs = -0.74, n = 12, p less than 0.01). These relationships also applied over longer than a single day, since trough and peak
mebendazole levels observed over an interval of 6 months before and after testing liver function were equally well correlated with ABT and BSP-k2. The daily dosage and other liver function tests seemed to be of minor importance in determining the plasma levels. It was concluded that the microsomal function of the liver and/or
cholestasis might be important determinants of plasma
mebendazole levels. The results of the study imply that higher and more effective
mebendazole concentrations might be achieved by inhibition of the
drug metabolizing capacity of the liver rather than by increasing the dose of
mebendazole.