In earlier skin pharmacokinetic studies we have shown that terbinafine is rapidly delivered to the stratum corneum, nails and hair both through sebum and by direct diffusion through dermis-epidermis. In the present study the skin pharmacokinetic profile of terbinafine was studied in two groups of eight human male volunteers during and after 250 mg orally once daily for 7 and 14 days. In the 7-day study high terbinafine levels were found in sebum (19.0 micrograms/g) and stratum corneum (2.5 micrograms/g), and a concentration in stratum corneum above the minimal inhibitory concentration for most dermatophytes was still found 48 days after the last day of medication. Terbinafine was found in peripheral nail clippings after 7 days of medication and the concentration was, in the 7-day study, 0.5 microgram/g 1 day after stopping medication; it was still 0.2 microgram/g 90 days after stopping treatment. The results in the 14-day study were in parallel with, but higher than, in the 7-day study. The elimination of terbinafine from several compartments is biphasic, with a faster initial elimination followed by a slower secondary elimination. For nails, the elimination is slower compared with the other compartments. The results indicate that terbinafine may be effective in short-term treatment of several dermatophytoses. The concentration of 0.2 microgram/g of terbinafine found in nails 90 days after stopping medication, following 7 days of treatment, indicates that the duration of therapy, even in tinea ungium, may be shorter than is currently the case.

The pharmacokinetics of terbinafine and its inactive metabolites SDZ 86-621 (the N-demethyl form), SDZ 280-027 (the carboxybutyl form), and SDZ 280-047 (N-demethyl-carboxybutyl form) in plasma were characterized for 10 healthy male subjects receiving 250 mg of terbinafine orally once a day for 4 weeks and in the subsequent 8-week washout phase. Terbinafine concentrations were also measured in sebum, hair, nail, and stratum corneum samples. Concentrations of the parent compound and metabolites were determined by validated high-performance liquid chromatography methods. Terbinafine was rapidly absorbed, with peak concentrations in plasma of 1.70 ؎ 0.77 g/ml occurring 1.2 ؎ 0.3 h postdose. Concentrations subsequently exhibited a triphasic decline, with a terminal disposition half-life of 16.5 ؎ 2.8 days. Terbinafine accumulated approximately twofold over the 4-week dosing phase. The predominant metabolite in plasma samples was SDZ 280-027; specifically, the ratios of metabolite area under the curve to terbinafine area under the curve following the last dose were 1.25, 1.38, and 1.08 for metabolites SDZ 86-621, SDZ 280-027, and SDZ 280-047, respectively. Nonrenal elimination constituted the major route of clearance for terbinafine and all three metabolites, with renal elimination playing a minor additional role in the clearance of metabolite SDZ 280-047. Measurable concentrations of terbinafine were achieved in sebum and hair samples within the first week of administration and by week 3 in stratum corneum and nail samples. Fungicidal concentrations persisted in plasma and peripheral tissue samples for prolonged periods (weeks to months) after administration of the last dose. These pharmacokinetic properties are likely an underlying factor in the shorter treatment times and good clinical cure rates which have been reported for terbinafine in the therapy of onychomycoses and dermatomycoses.

No abstract

SummaryTrough and peak concentrations as well as the elimination kinetics of the antimycotic agent terbinafine and 3 metabolites were investigated following multiple-dose administration of terbinafine 250mg daily for 4, 12 and 48 weeks. Plasma, sebum and tissues such as the stratum corneum, dermis-epidermis, hair and nails were analysed. The elimination of all compounds was multiphasic, being faster initially. Mean terminal elimination half-lives of the parent drug determined in plasma and tissues ranged from 18 to 28 days, and were in the same range as those of the metabolites (21 to 28 days). The slowest terminal elimination of terbinafine was observed from the dermis-epidermis and from keratinic tissues like hair and nails. Trough plasma concentrations of terbinafine were highly consistent in all studies, indicating an accumulation (12.6-to 18.5-fold) after multiple-dose treatment. However, peak concentrations of terbinafine accumulated only slightly (1.3-fold).In plasma, the kinetics of the metabolites were similar with regard to their terminal elimination half-life. Like the parent drug, trough concentrations of the N-demethylated metabolite accumulated (8-to 12.9-fold) after multiple-dose administration, but the peak concentrations did not. In contrast, the 2 carboxy metabolites accumulated only slightly (1.6-to 2.7-fold) under the same conditions.Terbinafine is a synthetic antimycotic agent of the allylamine class.[l] The compound is highly active against dermatophytes such as Trichophyton spp., Microsporum spp. and Epidermophyton floccosum, with minimal inhibitory concentrations (MICs) ranging from 1.5 to 10 Ilg/L in vitro [2,3,4] based on its interference with ergosterol biosynthesis, especially by the inhibition of the fungal squalene epoxidase)5] Terbinafine is readily absorbed by humans following oral administration,l6] with peak plasma concentrations ranging from 0.8 to 1.5 mg/L being

We determined terbinafine levels in serum, stratum corneum, dermis-epidermis (without stratum corneum), hair, sebum and eccrine sweat before, during and after 250 mg doses orally to volunteers once daily. Terbinafine is concentrated rapidly in stratum corneum (up to 9.1 micrograms/g of tissue) primarily by diffusion from the vascular system through the dermisepidermis. It also reaches high concentration in sebum (up to 45.1 micrograms/ml) after several days and continue to concentrate in sebum for up to two days after discontinuation of drug. Hair concentration reach levels of 2.6 micrograms/g of tissue indicating high drug levels in and around the hair follicle. It is not found in sweat. Plasma levels range between 0.1 and 1.0 micrograms/ml. There is a tenfold accumulation of drug in stratum corneum by day 2. Elimination of drug from tissue occurs with a half-life of 4 to 5 days and with the potential for drug levels above fungicidal concentrations for dermatophytes for more than 3 weeks. The tissue pharmacokinetic profile of terbinafine is similar to that of another lipophilic drug, itraconazole, but is very different from ketoconazole and griseofulvin. Higher levels of terbinafine are achieved than of either of the imidazoles and remain longer than griseofulvin.