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Phenobarbital and its relative phenobarbitone are sometimes used to control seizures.
Phenobarbital can reduce folate levels, perhaps by increasing the rate of breakdown of the vitamin.1–6 Over time, such a decrease can cause anemia. Taking folate supplements can correct this anemia.7 Anticonvulsant-induced folate deficiency might also cause birth defects. Women who plan to become pregnant while on phenobarbital should be sure to take a supplement to prevent deficiency.8,9
Phenobarbital appears to interfere with the normal absorption or metabolism of vitamin D.10,11 In turn, this can impair calcium absorption.12 Making sure to get enough vitamin D (and calcium) should help prevent any problems from developing.
Children born to women taking phenobarbital while pregnant may be deficient in vitamin K.13,14 This might lead to bleeding disorders and facial bone abnormalities. Supplementing with vitamin K during pregnancy should help; however, physician supervision is recommended.
Many antiseizure medications, including phenobarbital, are believed to interfere with the absorption of biotin.15,16 For this reason, individuals taking phenobarbital may benefit from extra biotin. Biotin should be taken 2 to 3 hours apart from your antiseizure medication. Do not exceed the recommended daily intake, because it is possible that too much biotin might interfere with the effectiveness of the medication.
Phenobarbital has been reported to cause increased sensitivity to the sun, amplifying the risk of sunburn or skin rash. Because St. John's wort and dong quai may also cause this problem, taking them during treatment with this drug might add to this risk.
It may be a good idea to wear a sunscreen or protective clothing during sun exposure if you take one of these herbs while using this anticonvulsant.
The herb ginkgo (Ginkgo biloba) has been used to treat Alzheimer's disease and ordinary age-related memory loss, among many other conditions.
This interaction involves potential contaminants in ginkgo, not ginkgo itself.
A recent study found that a natural nerve toxin present in the seeds of Ginkgo biloba made its way into standardized ginkgo extracts prepared from the leaves.17 This toxin has been associated with convulsions and death in laboratory animals.18,19,20
Fortunately, the detected amounts of this toxic substance are considered harmless.21 However, given the lack of satisfactory standardization of herbal formulations in the United States, it is possible that some batches of product might contain higher contents of the toxin depending on the season of harvest.
In light of these findings, taking a ginkgo product that happened to contain significant levels of the nerve toxin might theoretically prevent an anticonvulsant from working as well as expected.
The herb kava (Piper methysticum) has a sedative effect and is used for anxiety and insomnia.
Combining kava with anticonvulsants, which possess similar depressant effects, could result in "add-on" or excessive physical depression, sedation, and impairment.
Because of the potentially serious consequences, you should avoid combining these herbs with anticonvulsants or other drugs that also have sedative or depressant effects, such as phenobarbital, unless advised by your physician.
Because phenobarbital works (at least in part) by blocking glutamate pathways in the brain, high dosages of glutamine might possibly overwhelm the drug and increase the risk of seizures.
1. Berg MJ, Stumbo PJ, Chenard CA, et al. Folic acid improves phenytoin pharmacokinetics. J Am Diet Assoc 95: 352–356, 1995.
2. Ono H, Sakamoto A, Eguchi T, et al. Plasma total homocysteine concentrations in epileptic patients taking anticonvulsants. Metabolism 46: 959–962, 1997.
3. Kishi T, Fujita N, Eguchi T, et al. Mechanism for reduction of serum folate by antiepileptic drugs during prolonged therapy. J Neurol Sci 145: 109–112, 1997.
4. Reynolds EH. Mental effects of anticonvulsants, and folic acid metabolism. Brain 91: 197–214, 1968.
5. McNamara J. Drugs effective in the therapy of the epilepsies. As cited in Goodman L and Gilman A. The pharmacological basis of therapeutics, 9th ed. Hardman J, et al., eds. New York: McGraw-Hill, 1996: 472.
6. Reynolds EH, Milner G, Matthews DM, et al. Anticonvulsant therapy, megaloblastic haemopoiesis and folic acid metabolism. Q J Med 35: 521–537, 1966.
7. Berg MJ, Stumbo PJ, Chenard CA, et al. Folic acid improves phenytoin pharmacokinetics. J Am Diet Assoc 95: 352–356, 1995.
8. Lewis DP, Van Dyke DC, Stumbo PJ, et al. Drug and environmental factors associated with adverse pregnancy outcomes. Part I: Antiepileptic drugs, contraceptives, smoking, and folate. Ann Pharmacother 32: 802–817, 1998.
9. Biale Y and Lewenthal H. Effect of folic acid supplementation on congenital malformations due to anticonvulsive drugs. Eur J Obstet Gynecol Reprod Biol 18: 211–216, 1984.
10. Holmes T and Kummerow F. The relationship of adequate and excessive intake of vitamin D to health and disease. J Am Coll Nutr 2: 173–199, 1983.
11. Shils M, et al., eds. Modern nutrition in health and disease. 9th ed. Baltimore: Williams and Wilkins, 1999: 1634.
12. Wahl TO, Gobrity AH, and Lukert BP. Long-term anticonvulsant therapy and intestinal calcium absorption. Clin Pharmacol Ther 30: 506–512, 1981.
13. Cornelissen M, Steegers-Theunissen R, Kolle L, et al. Increased incidence of neonatal vitamin K deficiency resulting from maternal anticonvulsant therapy. Am J Obstet Gynecol 168: 923–928, 1993.
14. Cornelissen M, Steegers-Theunissen R, Kolle L, et al. Supplementation of vitamin K in pregnant women receiving anticonvulsant therapy prevents neonatal vitamin K deficiency. Am J Obstet Gynecol 168: 884–888, 1993.
15. Krause K-H, Bonjour J-P, Berlit P, et al. Biotin status of epileptics. Ann N Y Acad Sci 447: 297–313, 1985.
16. Said HM, Redha R, and Nylander W. Biotin transport in the human intestine: inhibition by anticonvulsant drugs. Am J Clin Nutr 49: 127–131, 1989.
17. Arenz A, Klein M, Fiehe K, et al. Occurrence of neurotoxic 4'-O-methylpyridoxine in Ginkgo biloba leaves, ginkgo medications and Japanese ginkgo food. Planta Med 62: 548–551, 1996.
18. Mizuno N, Kawakami K, and Morita E. Competitive inhibition between 4'-substituted pyridoxine analogues and pyridoxal for pyridoxal kinase from mouse brain. J Nutr Sci Vitaminol (Tokyo) 26: 535–543, 1980.
19. Wada K, Ishigaki S, Ueda K, et al. An antivitamin B 6, 4'-methoxypyridoxine, from the seed of Ginkgo biloba L. Chem Pharm Bull (Tokyo) 33: 3555–3557, 1985.
20. Yagi M, Wada K, Sakata M, et al. Studies on the constituents of edible and medicinal plants. IV. Determination of 4-O-methylpyridoxine in serum of the patient with gin-nan food poisoning [in Japanese; English abstract]. Yakugaku Zasshi 113: 596–599, 1993.
21. Arenz A, Klein M, Fiehe K, et al. Occurrence of neurotoxic 4'-O-methylpyridoxine in Ginkgo biloba leaves, ginkgo medications and Japanese ginkgo food. Planta Med 62: 548–551, 1996.
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015