Determination of terbinafine in healthy Chinese human plasma using a simple and fast LC-MS/MS method and its application to a bioequivalence study.

A rapid, simple, and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was validated for the determination of terbinafine concentrations in the plasma of healthy Chinese subjects. Terbinafine-d7 was used as the internal standard (IS), and the acetonitrile protein precipitation method was selected. The processed samples were chromatographically separated with a C18 column. The mobile phases were 0.1% formic acid (FA) in water (A), and methanol (B), respectively, and the gradient elution program was used with a flow rate of 0.8 mL/min. Quantification was achieved by positive electrospray ionization containing multiple reaction monitoring (MRM) transitions of m/z 292.5 â†’ 141.1 for terbinafine and m/z 299.5 â†’ 148.1 for IS. The calibration curve range was 2.00-1200 ng/mL; the intra- and inter-batch precision (coefficient of variation, %CV) was <8.2%, with the accuracy deviation (relative error, %RE) of -6.5% to 10.2%. The selectivity, sensitivity, extraction recovery, matrix effect, dilution reliability, carryover, and stability were within the acceptable range. This method was successfully applied to a bioequivalence study that orally administered 125 mg of terbinafine hydrochloride tablets in 84 healthy Chinese subjects.

TERBINAFINE PHARMACOKINETICS FOLLOWING SINGLE-DOSE ORAL ADMINISTRATION IN RED-EARED SLIDER TURTLES (TRACHEMYS SCRIPTA ELEGANS): A PILOT STUDY.

In this pilot study, the pharmacokinetics of terbinafine were determined in six apparently healthy red-eared slider turtles (Trachemys scripta elegans) after a single PO administration. Terbinafine suspension (15 mg/kg, once) was administered via gavage tube to all turtles. Blood samples were collected immediately before (time 0) and at 1, 2, 4, 8, 24, and 48 h after drug administration. Plasma terbinafine concentrations were quantified by ultra-performance liquid chromatography-mass spectrometry, and noncompartmental pharmacokinetic analysis was performed. None of the animals showed any adverse responses following terbinafine administration. Mean area under the curve from time 0 to 24 h was 1,213 h × ng/ml (range 319-7,309), mean peak plasma concentration was 201.5 ng/ml (range 45.8-585.3), mean time to maximum plasma concentration was 1.26 h (range 1-4), mean residence time was 7.71 h (range 3.85-14.8), and mean terminal half-life was 5.35 h (range 2.67-9.83). The administration of terbinafine (15 mg/kg, PO) may be appropriate for treatment of select fungal organisms with low minimum inhibitory concentrations in red-eared slider turtles but may require q12h administration even for organisms with low minimum inhibitory concentrations. Multiple-dose studies as well as clinical studies are needed to determine ideal dosages and efficacy.

EFFICACY OF SUBCUTANEOUS IMPLANTS TO PROVIDE CONTINUOUS PLASMA TERBINAFINE IN HELLBENDERS (CRYPTOBRANCHUS ALLEGANIENSI) FOR FUTURE PROPHYLACTIC USE AGAINST CHYTRIDIOMYCOSIS.

Batrachochytrium dendrobatidis (Bd) is an important fungal pathogen present in wild hellbender (Cryptobranchus alleganiensis) populations that appears to cause disease during novel exposure and acute stress. Hellbender repatriation efforts are ongoing to combat declining populations, but mortality by chytridiomycosis (disease from Bd) after release has been reported. The goal was to determine whether a safe antifungal agent could be administered and provide prolonged plasma concentrations without repeated handling. A subcutaneous implant impregnated with 24.5 mg of terbinafine was tested in three juvenile eastern hellbenders (C. a. alleganiensis) raised in human care, and plasma terbinafine concentrations were recorded from weekly to biweekly for 141 days. Plasma concentrations were variable, with peak plasma concentrations of 1,610, 112, and 66 ng/ml between 28 and 56 days postimplant. Although all hellbenders achieved plasma concentrations above the published minimum inhibitory concentration for terbinafine against Bd zoospores (63 ng/ml) at several time points, only one individual remained above this threshold for more than two consecutive time intervals. Results show the potential for these implants as a prophylaxis for chytridiomycosis in captive-to-wild hellbender releases. However, further investigation will be needed to determine the plasma concentrations required to achieve prophylaxis in vivo and implant reliability.

Determination of terbinafine in human plasma using UPLC-MS/MS: Application to a bioequivalence study in healthy subjects.

A high-throughput and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method has been developed for the determination of terbinafine in human plasma. The method employed liquid-liquid extraction of terbinafine and terbinafine-d7 (used as internal standard) from 100 µL human plasma with ethyl acetate-n-hexane (80:20, v/v) solvent mixture. Chromatography was performed on a BEH C18 (50 × 2.1 mm, 1.7 µm) column using acetonitrile-8.0 mm ammonium formate, pH 3.5 (85:15, v/v) under isocratic elution. For quantitative analysis, MS/MS ion transitions were monitored at m/z 292.2/141.1 and m/z 299.1/148.2 for terbinafine and terbinafine-d7, respectively, using electrospray ionization in the positive mode. The method was validated according to regulatory guidance for selectivity, sensitivity, linearity, recovery, matrix effect, stability, dilution reliability and ruggedness with acceptable accuracy and precision. The method shows good linearity over the tested concentration range from 1.00 to 2000 ng/mL (r2 ≥ 0.9984). The intra-batch and inter-batch precision (CV) was 1.8-3.2 and 2.1-4.5%, respectively. The method was successfully applied to a bioequivalence study with 250 mg terbinafine in 32 healthy subjects. The major advantage of this method includes higher sensitivity, small plasma volume for processing and a short analysis time.