Ninety-four children (aged 8 months to 15 years) with idiopathic intractable epilepsy received intravenous pyridoxal phosphate (PLP) at a dose of 10 mg/kg, followed by 10 mg/kg/day in 4 divided doses. If seizures recurred within 24 hours, another dose of 40 mg/kg was given, followed by 50 mg/kg/day in 4 divided doses. For patients whose seizures were totally controlled, PLP was replaced by the same dose of oral pyridoxine. If seizures recurred, intravenous PLP was infused followed by oral PLP (50 mg/kg/day). Eleven patients had a dramatic and sustained response to PLP; of these, 5 also responded to pyridoxine. The remaining six responders responded only to PLP. The average final oral dose of PLP was 30 mg/kg/day (range, 7-38 mg/kg/day), which was significantly higher than the average pyridoxine dose (18 mg/kg/day) in the pyridoxine responders.

Comment: This study demonstrates that PLP can successfully control epilepsy in some children who fail to respond to pyridoxine. PLP appeared to be particularly useful for patients with infantile spasms. Because PLP could replace pyridoxine, but perhaps not vice versa, PLP should be considered for first-line treatment of patients with intractable childhood epilepsy, particularly those with infantile spasms.

It has long been known that PLP is the major biologically active form of vitamin B6, and that pyridoxine must be converted to PLP in order to exert an effect in the body. However, virtually all previous clinical research on vitamin B6 has used pyridoxine. Parenterally administered PLP was reported to be beneficial in a few studies in which pyridoxine was not effective, but there has been uncertainty about whether orally administered PLP can be absorbed. The results of this study strongly suggest that sufficient amounts of PLP can be absorbed to exert a biological effect. Because some people may have a defect in their capacity to convert pyridoxine to its biologically active form, oral PLP should be considered for patients with potentially vitamin B6-responsive conditions that fail to respond to pyridoxine. Other disorders that may improve with vitamin B6 supplementation include asthma, carpal tunnel syndrome, premenstrual syndrome, autism, pregnancy nausea, and gestational diabetes.

Wang HS, et al. Pyridoxal phosphate is better than pyridoxine for controlling idiopathic intractable epilepsy. Arch Dis Child 2005;90:512-515.