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Drug interactions
Terbinafine is an allylamine medicine used to treat fungal infections. It is especially effective against dermatophytes (tinea infections).
The original brand is Lamisil®. In New Zealand (2016) it is available as 250 mg tablets (Dr Reddy's Terbinafine, fully funded by PHARMAC) and Terbinafine-DRLA. The tablets require a doctor's prescription. Topical options include creams, gel, solution and spray from various manufacturers, and are available at a pharmacy without a prescription.
Terbinafine inhibits a fungal enzyme, squalene epoxidase, and stops the cells making ergosterol, the main component of the cell wall.
For children, the tablets can be hidden in food – the tablets taste unpleasant:
Sometimes, if the fungal infection does not clear, the dose in children may need to be increased.
Treatment can be repeated if necessary.
Terbinafine is absorbed well when taken orally, with or without food. It is bound to proteins such as albumin in the circulating blood and becomes concentrated in fat cells and within skin and nails. It is slowly eliminated in faeces and urine mostly after conversion by the liver into inactive compounds. It is a moderate CYP2D6 inhibitor. Doses may need to be reduced in the presence of kidney disease.
Skin concentrations may be up to 75-fold higher than those in the blood. It may persist in the skin for up to 8 weeks after the drug has been discontinued and in the nails for up to a year.
Terbinafine appears to be a relatively safe drug. Side effects, usually minor, arise occasionally. Serious side effects occur rarely. Routine blood test monitoring is not considered necessary [1].
Adverse reactions to terbinafine may include:
Oral terbinafine should not be taken in pregnancy or when breastfeeding. Topical terbinafine is regarded as safe to apply when breastfeeding provided the infant does not come into direct contact with the medication.
Terbinafine does not generally alter the concentration of other medications.
Rifampicin results in a slight decrease in the concentration of terbinafine. Cimetidine may slightly increase the concentration of terbinafine. Terbinafine may increase the concentration of aripiprazole, brexpiprazole, darifenacin, eliglustat, vortioxetine, tricyclics and several other medications. It may reduce the analgesic effectiveness of codeine and similar drugs. Terbinafine is not thought to interact with the oral contraceptive pill.
Approved datasheets are the official source of information for medicines, including approved uses, doses, and safety information. Check the individual datasheet in your country for information about medicines.
We suggest you refer to your national drug approval agency such as the Australian Therapeutic Goods Administration (TGA), US Food and Drug Administration (FDA), UK Medicines and Healthcare products regulatory agency (MHRA) / emc, and NZ Medsafe, or a national or state-approved formulary eg, the New Zealand Formulary (NZF) and New Zealand Formulary for Children (NZFC) and the British National Formulary (BNF) and British National Formulary for Children (BNFC).
