anticonvulsant
11 interactions related to anticonvulsant
carbamazepine + biotin
Carbamazepine reduces biotin status by inhibiting sodium-dependent biotin uptake in the intestine, decreasing renal reabsorption, and accelerating biotin catabolism through enzyme induction; long-term users often have measurably lower plasma biotin and elevated organic-acid markers of biotin insufficiency.
valproate + carnitine
Valproate (valproic acid) depletes carnitine by sequestering it as valproyl-carnitine for mitochondrial transport and by inhibiting renal tubular reabsorption, which can impair the urea cycle and contribute to hyperammonemia, hepatotoxicity, and encephalopathy.
lamotrigine + folate
Lamotrigine inhibits dihydrofolate reductase, the enzyme that converts dihydrofolate to active tetrahydrofolate, and high-dose folic acid supplementation has been shown to blunt lamotrigine's antidepressant effect in bipolar depression (CEQUEL trial), particularly in COMT Met allele carriers. The interaction is pharmacodynamic rather than pharmacokinetic, so lamotrigine blood levels remain unchanged.
phenobarbital + vitamin d
Phenobarbital activates the pregnane X receptor and constitutive androstane receptor, strongly inducing hepatic CYP3A4 while also directly suppressing CYP27A1 (a 25-hydroxylase), so it both accelerates breakdown of 25-hydroxyvitamin D and slows its formation; serum 25(OH)D drops substantially over weeks to months of therapy, with osteomalacia and increased fracture risk documented in long-term users.
grapefruit + carbamazepine
Grapefruit juice irreversibly inhibits intestinal CYP3A4, reducing first-pass metabolism of carbamazepine and increasing its bioavailability. Clinical study in epilepsy patients showed AUC rose by roughly 40 percent with concomitant grapefruit juice, pushing plasma levels toward the toxic range.
phenytoin + folate
Phenytoin lowers serum and red-cell folate through enzyme induction and impaired absorption of polyglutamate folates, but high-dose folate supplementation in turn accelerates phenytoin metabolism and can drop drug levels enough to cause seizure breakthrough.
phenytoin + vitamin d
Phenytoin induces hepatic CYP3A4 and CYP24A1, accelerating conversion of 25-hydroxyvitamin D to inactive metabolites and lowering circulating 25(OH)D, which over time produces secondary hyperparathyroidism, reduced calcium absorption, and a measurably increased risk of osteomalacia and fractures.
phenytoin + calcium
Phenytoin reduces calcium absorption by accelerating vitamin D catabolism and by directly inhibiting active transcellular calcium transport in intestinal enterocytes; separately, calcium-containing antacids and supplements can chelate phenytoin in the gut and lower its absorption when taken simultaneously.
valproate + biotin
Valproate appears to reduce biotinidase activity and impair mitochondrial biotin handling, leading to subnormal biotin status that has been linked to the drug's signature alopecia (hair loss) and brittle nails; biotin supplementation has reversed hair loss in case reports.
carbamazepine + vitamin d
Carbamazepine activates the pregnane X receptor and strongly induces hepatic CYP3A4 and CYP24A1, accelerating catabolism of 25-hydroxyvitamin D into inactive metabolites; meta-analyses confirm consistently lower 25(OH)D in long-term users along with secondary hyperparathyroidism and reduced bone mineral density.
levetiracetam + vitamin b6
Levetiracetam (Keppra) commonly causes behavioral side effects including irritability, agitation, anxiety, and mood changes (sometimes called 'Keppra rage'). Several observational studies and case series in both pediatric and veteran populations suggest that adjunctive pyridoxine (vitamin B6) supplementation reduces these behavioral symptoms in roughly 40-50% of patients, though randomized controlled trial data are mixed.