Drug Interactions:
Primidone

Trade Names
  • Mysoline

Like phenobarbital, to which it is closely related, primidone is used to control epileptic seizures.

Folate

Supplementation Possibly Helpful

Primidone can reduce folate levels perhaps by increasing the rate of breakdown of the vitamin. Over time, such a decrease can cause anemia.^1–5 Taking folate supplements will correct this anemia.⁶ Anticonvulsant-induced folate deficiency might also cause birth defects. Women who plan to become pregnant while on primidone should be sure to take a supplement to prevent deficiency.^7,8

Vitamin D

Supplementation Possibly Helpful

Primidone appears to interfere with the normal absorption or metabolism of vitamin D.^9,10 This in turn impairs calcium absorption, with many potential complications.¹¹ To help avoid this problem, you should make sure that you get enough vitamin D.

Vitamin K

Supplementation Possibly Helpful for Pregnant Women

Children born to women taking primidone while pregnant may be deficient in vitamin K.^12,13 This might lead to bleeding disorders and facial bone abnormalities. Supplementing with vitamin K during pregnancy should help; however, physician supervision is recommended.

Biotin

Supplementation Possibly Helpful, but Take at a Different Time of Day

Many antiseizure medications including primidone are believed to interfere with the absorption of biotin.^14,15 For this reason, individuals taking primidone 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.

Glutamine

Theoretical Harmful Interaction

Because many anti-epilepsy drugs, including primidone, work by blocking glutamate stimulation in the brain, high dosages of glutamine might counteract the drugs' effects, and pose a risk of increased seizures.

Vitamin B3

Potentially Dangerous Interaction

Niacinamide (a form of vitamin B₃) might increase blood levels of primidone, possibly requiring reduction in drug dosage.¹⁶

Dong Quai, St. John's Wort

Possible Harmful Interaction

Primidone 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.

Ginkgo

Possible Harmful Interaction

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.

Hops, Kava, Passionflower, Valerian

Possible Harmful Interaction

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 primidone, unless advised by your physician.

Last reviewed March 2002 by Medical Review Board

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