Orally administered mebendazole is extensively metabolized primarily by the liver. Plasma concentrations of its major metabolites (amino and hydroxylated amino forms of mebendazole) are substantially higher than those of mebendazole. Impaired hepatic function, impaired metabolism, or impaired biliary elimination may lead to higher plasma levels of mebendazole.
Mebendazole, the conjugated forms of mebendazole, and its metabolites likely undergo some degree of enterohepatic recirculation and are excreted in the urine and bile. The apparent elimination half-life after an oral dose ranges from 3 to 6 hours in most patients.
Ovex® Summary of Product Characteristics, McNeil Products Ltd. Updated April 2011

In 8 patients, the [14C]-aminopyrine breath test (ABT) and maximum serum concentration of mebendazole following a dose of 1.5 g of mebendazole three times daily were determined before and after treatment with cimetidine (400mg three times daily for 30 days). Serum mebendazole concentrations were measured in blood samples taken 2 h after each drug intake. Cimetidine lowered the 14CO2 specific activity (SA) at 1 h and increased the maximum serum concentration of mebendazole (82.3ng/ml vs 55.7ng/ml).
Cimetidine increases serum mebendazole concentrations. Implications for treatment of hepatic hydatid cysts. Bekhti A, Pirotte J. Br J Clin Pharmacol. 1987;24:390-2.