What is isotretinoin? How does it interact with other drugs?

Vitamin A

Effect: Probable Harmful Interaction

Both vitamin
A and isotretinoin can cause toxic symptoms if taken in
excess. It is presumed that the simultaneous use of vitamin A and isotretinoin
would tend to amplify the risk. For this reason, persons using isotretinoin should
not take vitamin A at doses higher than the recommended daily allowance. Because
most people get enough vitamin A from the diet, it might be preferable to take no
vitamin A supplements at all. (Supplements that use beta-carotene to supply
vitamin A are probably safe.)

St. John’s Wort

Effect: Indirect Harmful Interaction

Because isotretinoin can cause birth defects, women who use it are often
advised to take oral contraceptives (birth control pills). The herb
St. John’s
wort is thought to interact with birth control pills and
reduce their effectiveness, raising the risk of pregnancy. For this reason, people
taking Accutane and oral contraceptives should avoid using St. John’s wort.

Vitamin E

Effect: Possible Helpful Interaction

One preliminary study hints that vitamin E might reduce the side effects
of isotretinoin.

Bibliography

Murphy, P. A., et al. “Interaction of St. John’s Wort with Oral Contraceptives: Effects on the Pharmacokinetics of Norethindrone and Ethinyl Estradiol, Ovarian Activity, and Breakthrough Bleeding.” Contraception 71 (2005): 402-408.

Pfrunder, A., et al. “Interaction of St. John’s Wort with Low-Dose Oral Contraceptive Therapy.” British Journal of Clinical Pharmacology 56 (2003): 683-690.