Four children with pyridoxine dependent seizures beginning at 2 to 19 months are reported from the Loyola University Medical Center, Maywood, IL. Patients were identified out of 51 treated routinely with pyridoxine for refractory seizures and seen over a 6 year period. The dose of pyridoxine was 50 mg orally twice daily. The seizure types were atypical absence, myoclonic, generalized clonic and simple partial and complex partial. The authors suggest that pyridoxine should be tried in all children with seizure disorders with onset at any age who are poorly responsive to anticonvulsant drugs. 
COMMENT. Pyridoxine dependent epilepsy may present after the neonatal period and may be manifested by many seizure types. Many of us have been discouraged by failure to uncover pyridoxine dependency in drug resistant epilepsies in children. Obviously, persistence rewards, but the relationship between pyridoxine and epilepsy is complex.
The wide range of reactivity of vitamin B6 with a number of drugs and other chemicals encountered in the environment must be considered in the diagnosis. These interactions involve a condensation between the xenobiotic and pyridoxal phosphate, and vitamin B6 absorption, coenzymes, and specific vitamin B6-dependent enzymes can also be affected. Isoniazide is probably the most extensively studied drug with respect to effects on vitamin B6 metabolism. Other drugs reported to interact with vitamin B6 include ampicillin, anticonvulsants, levodopa, oral contraceptives and ethanol. The mechanism of anticonvulsant drug and vitamin B6 interaction is not well determined. One study showed that the vitamin was decreased only in males treated with anticonvulsants. Another showed that pyridoxine supplements resulted in lower plasma phenytoin and phenobarbital concentrations. An interaction between the vitamin and dyes added to medications during manufacture has also been demonstrated.