Metabolism and excretion of the antiepileptic/antimigraine drug, topiramate in animals and humans

The metabolism and excretion of 2,3:4,5-bis-0-(l-methylethylidene)-β-D-fructopyranose sulfamate (TOPAMAX®, topiramate, TPM) have been investigated in animals and humans. Radiolabeled [14C] TPM was orally administered to mice, rats, rabbits, dogs and humans. Plasma, urine and fecal samples were collected and analyzed. TPM and a total of 12 metabolites were isolated and identified in these samples. Metabolites were formed by hydroxylation at the 7- or 8-methyl of an isopropylidene of TPM followed by rearrangement, hydroxylation at the 10-methyl of the other isopropylidene, hydrolysis at the 2,3-{ie151-1}-isopropylidene, hydrolysis at the 4,5-{ie151-2}-isopropylidene, cleavage at the sulfamate group, glucuronide conjugation and sulfate conjugation. A large percentage of unchanged TPM was recovered in animal and human urine. The most dominant metabolite of TPM in mice, male rats, rabbits and dogs appeared to be formed by the hydrolysis of the 2,3-{ie151-3}-isopropylidene group.