Why Oral Antifungal Drug Interactions With Psych Meds Can Be Dangerous

Have thrush? Athlete's foot? A vaginal infection? Jock itch? Before you treat yourself, you need to know whether any of the medications you are taking will interact with treatments for conditions like athlete's foot. Some antidepressants and antipsychotics, in particular, can react badly to antifungal medications.

Overview

Some antifungal drugs are designed to be taken orally -- for example, to treat yeast infections in the mouth and throat, such as thrush. The risk of drug interaction is higher with oral drugs than the topical applications sold over the counter.

Athlete's foot is caused by a fungus, as are vaginal infections and jock itch. The common treatments for these conditions, called antifungals, usually come in creams, sprays, and powders. There are dozens of over-the-counter medications for fungus, the best known including Lotrimin, Monistat, Lamisil, Tinactin, and Desenex.

Lesser-known brands abound, and major drugstore chains often have their own generic versions. The availability of antifungal medications makes it seem like they must be perfectly safe to use, and in fact, if you look up, for example, "Lotrimin warnings," you find that it says "no food and drug interactions have been reported." Yet if you look deeper, you'll find that there ​are known drug interactions and lots of them.

Active Ingredients

The most common active ingredients in antifungal medications are:

• Clotrimazole
• Miconazole
• Terbinafine
• Tolnaftate

Some fungus treatments have other active ingredients such as ketoconazole and butenafine.

Interactions With Psychiatric Medications

All the "azoles" can interact with certain psychiatric medications when used regularly. For example:

• Azoles used with Seroquel (quetiapine) can increase the plasma level to the point where the person using both may experience excessive drowsiness, fast or irregular heartbeat, dizziness, fainting, or extrapyramidal side effects.
• Azoles used with calcium channel blockers may cause such symptoms as swelling of the lower extremities, sudden, unexplained weight gain, difficulty breathing, chest pain or tightness, and dizziness or fainting.
• Ketoconazole used daily for 14 days increased the plasma concentration of Abilify (aripiprazole) about 70%.
• The product labels for Xanax (alprazolam) and Halcion (triazolam) both recommend against the use of any azole antifungal agent. Valium's label specifically mentions ketoconazole.
• These drugs may cause a significant increase in blood plasma levels of trazodone.

This is just a sampling of the possible interactions of azole fungus treatments for conditions like athlete's foot with psychiatric drugs.

In addition, the active ingredient terbinafine can increase plasma levels of several antidepressants, particularly the tricyclics. Nortriptyline intoxication has been noted after steady use of terbinafine antifungals.

The Bottom Line

Ask the pharmacist about possible interactions and/or check with your doctor. They may recommend that you use a treatment containing butenafine and tolnaftate, and/or it may be necessary to adjust the dosage of one or more medications you are currently taking during the time you need to use the antifungal treatment. If you are prescribed an oral antifungal drug, make sure your doctor knows about all your existing medications.