The antifungal drug terbinafine is the active ingredient in Lamisil cream, a topical prescription drug for fungal skin infections. The drug works by interfering with a fungal cell’s ability to maintain its cell membrane, the protective membrane that surrounds the cell and holds it together. With repeated exposure to the drug, the fungus is unable to grow; it eventually dies and the infection is cured.

Currently, Lamisil is probably the best FDA-approved drug for the treatment of fungal infection. In addition to Lamisil cream, Lamisil tablets are available, recommended for treatment of fungal nail infections, which are difficult to cure with topical preparations. Studies have shown a better treatment success rate with terbinafine than with other available prescription drugs such as griseofulvin and itraconazole.

Both Lamisil cream and Lamisil tablets are used daily and usually need to be continued for a number of weeks to completely wipe out the fungus. Skin infections usually take from one to four weeks to resolve. Nail infections will often clear up in six weeks, while toe nail infections take four months or more to cure. It’s not uncommon, however, for much longer periods of treatment to be necessary, especially in the case of toe nail fungus infection. Complete replacement of the disfigured nail takes many months, even if the fungus is dead, because nails grow very slowly.

Systemic antifungal drugs have had a reputation for causing unpleasant side effects, most notably liver damage, and although clinical studies of Lamisil tablets have indicated that these side effects are relatively rare, and usually quite mild, they are still a concern. Patients taking Lamisil tablets should watch for signs of liver toxicity, such as fatigue, nausea, vomiting, yellowing of the eyes and skin, dark urine, or light colored stools. Any other unexpected symptom that appears during the course of treatment should also be reported to a doctor. Concerns are not as great with Lamisil cream because the cream is only applied locally and relatively little gets into the bloodstream.

Another concern with Lamisil tablets is the possibility of drug interactions, and there is a long list of drugs that should not be used together with Lamisil tablets, or that should be used only with caution. The Lamisil dose may need to be adjusted to prevent adverse drug interactions and side effects. Anyone taking any other prescription medication should check with their doctor and their pharmacist before taking Lamisil. Again, Lamisil cream does not carry the same concerns; however, it is always wise to ask an appropriate medical professional before mixing medication.