anticonvulsant
11 interactions related to anticonvulsant
carbamazepine + biotin
Carbamazepine gradually lowers biotin (vitamin B7) status by reducing intestinal absorption, increasing urinary loss, and accelerating breakdown of the vitamin. The effect is biomarker-level and well documented over decades; frank deficiency and serious adult harm are uncommon.
valproate + carnitine
Valproate (valproic acid) depletes carnitine by sequestering it as valproyl-carnitine for mitochondrial transport and by reducing renal reabsorption of free carnitine. Carnitine depletion can impair fatty-acid oxidation and the urea cycle, contributing to raised blood ammonia (hyperammonemia), liver stress, and in some cases encephalopathy.
lamotrigine + folate
In a randomized controlled trial of bipolar depression (CEQUEL), adding folic acid to lamotrigine appeared to blunt lamotrigine's antidepressant benefit, an effect seen mainly in people carrying the COMT Met allele. The interaction is pharmacodynamic, not pharmacokinetic, so lamotrigine blood levels stay unchanged. The exact mechanism is not established, and the signal is limited to bipolar depression rather than epilepsy.
phenobarbital + vitamin d
Phenobarbital is a strong inducer of liver enzymes that speed the breakdown of vitamin D, so long-term use can lower 25-hydroxyvitamin D and, over months to years, contribute to softened bones (osteomalacia in adults, rickets in children) and higher fracture risk. Children and older or housebound adults are most vulnerable. The drop in vitamin D is well documented; some experimental work also suggests phenobarbital may slow vitamin D activation, though that mechanism rests on animal and cell studies. Have vitamin D and bone-related labs reviewed and discuss ongoing vitamin D with your doctor or pharmacist.
grapefruit + carbamazepine
Grapefruit juice inhibits the intestinal CYP3A4 enzyme that performs first-pass metabolism of carbamazepine, allowing more of each oral dose to reach the bloodstream. A human study in epilepsy patients found grapefruit juice raised carbamazepine blood levels, which matters because carbamazepine has a narrow safety margin.
phenytoin + folate
Phenytoin and folate interact in both directions: long-term phenytoin lowers folate through enzyme induction and reduced absorption, while supplemental folate can speed phenytoin clearance and lower its blood level enough to allow seizures to return in some people. The interaction is real but monitorable, so changes should be coordinated with your neurologist rather than avoided.
phenytoin + vitamin d
Phenytoin induces the liver enzymes that break down vitamin D, accelerating clearance of 25-hydroxyvitamin D and lowering circulating levels over time. The downstream result can be reduced calcium absorption, a compensatory rise in parathyroid hormone, and an increased risk of softened bones (osteomalacia) and fractures with long-term use.
phenytoin + calcium
Calcium-containing supplements and antacids can bind phenytoin in the gut and lower how much of the drug is absorbed when the two are taken together, which can reduce phenytoin's blood level. Separately, long-term phenytoin use can reduce calcium absorption by speeding up the breakdown of vitamin D, which is relevant to bone health over time.
valproate + biotin
Valproate appears to lower biotinidase activity and may impair mitochondrial biotin handling, contributing to subnormal biotin status that has been linked to the drug's characteristic hair thinning and brittle nails. Case reports describe biotin supplementation reversing valproate-related hair loss, though the underlying biotin-status studies are mixed.
carbamazepine + vitamin d
Carbamazepine activates the pregnane X receptor and induces the liver enzymes (including CYP3A4 and CYP24A1) that break down vitamin D, accelerating the clearance of 25-hydroxyvitamin D into inactive metabolites. A meta-analysis and observational studies consistently show lower 25(OH)D in long-term carbamazepine users, along with a secondary-hyperparathyroidism pattern and reduced bone density that raises fracture risk over years of therapy.
levetiracetam + vitamin b6
Levetiracetam (Keppra) commonly causes behavioral side effects including irritability, agitation, anxiety, and mood changes (sometimes called 'Keppra rage'). Randomized trials and case series in children and adults suggest that adding pyridoxine (vitamin B6) eases these behavioral symptoms in a meaningful subset of patients, though the evidence is mixed: two pediatric trials were positive while one adult trial was null. This is a potential benefit, not a harmful interaction.