PHENYTOIN AND PYRIDOXINE
Daily doses of pyridoxine 80 to 400 mg can cause reductions of about 35% in phenytoin levels in some patients. The effect on fosphenytoin, a prodrug of phenytoin, does not appear to have been studied, but it may be prudent to assume it may interact similarly.
Concurrent use should be monitored if large doses of pyridoxine are used, being alert for the need to increase the phenytoin dosage. It seems unlikely that small doses (as in multivitamin preparations) will interact to any great extent.
Concurrent use should be monitored if large doses of pyridoxine are used, being alert for the need to increase the phenytoin dosage. It seems unlikely that small doses (as in multivitamin preparations) will interact to any great extent.