Pyridoxal-5'-phosphate
PLP
What it isPyridoxal 5-phosphate, the active coenzyme form of vitamin B6.
Why it mattersIt is the cofactor for transaminases, decarboxylases and delta-aminolevulinic acid synthase, which is why B6 deficiency causes sideroblastic anemia and seizures.
What it changesIsoniazid, hydralazine and cycloserine deplete it, which is why pyridoxine is co-prescribed with them.
Off-label
- PLP-dependent epilepsy from PNPO deficiency
- pyridoxine-unresponsive neonatal seizures
NO BOXED WARNINGS
Principal riskIt is what isoniazid and hydralazine sequester, which is why pyridoxine is co-given with them