Terconazole

Terconazole, an azole antifungal agent, inhibits fungal cytochrome P-450-mediated 14 alpha-lanosterol demethylase enzyme. This enzyme functions to convert lanosterol to ergosterol. The accumulation of 14 alpha-methyl sterols correlates with the subsequent loss of ergosterol in the fungal cell wall and may be responsible for the antifungal activity of terconazole. Mammalian cell demethylation is less sensitive to terconazole inhibition.

Activity in vitro

Terconazole exhibits antifungal activity in vitro against Candida albicans and other Candida species. The MIC values of terconazole against most Lactobacillus spp. typically found in the human vagina were ≥128 mcg/mL; therefore these beneficial bacteria are not affected by drug treatment.

Absorption

Following a single intravaginal application of a suppository containing 240 mg ¹⁴C-terconazole to healthy women, approximately 70% (range: 64 to 76%) of terconazole remains in the vaginal area during the suppository retention period (16 hours); approximately 10% (range: 5 to 16%) of the administered radioactivity was absorbed systemically over 7 days. Maximum plasma concentrations of terconazole occur 5 to 10 hours after intravaginal application of the cream or suppository. Systemic exposure to terconazole is approximately proportional to the applied dose, whether as the cream or suppository. The rate and extent of absorption of terconazole are similar in patients with vulvovaginal candidiasis (pregnant or non-pregnant) and healthy subjects.

Distribution

Terconazole is highly protein bound (94.9%) in human plasma and the degree of binding is independent of drug concentration over the range of 0.01 to 5 mcg/mL.

Metabolism

Systemically absorbed terconazole is extensively metabolized (>95%).

Elimination

Across various studies in healthy women, after single or multiple intravaginal administration of terconazole as the cream or suppository/ovule, the mean elimination half-life of unchanged terconazole ranged from 6.4 to 8.5 hours. Following a single intravaginal administration of a suppository containing 240 mg ¹⁴C-terconazole to hysterectomized or tubal ligated women, approximately 3 to 10% (mean ± SD: 5.7 ± 3%) of the administered radioactivity was eliminated in the urine and 2 to 6% (mean ± SD: 4.2 ± 1.6%) was eliminated in the feces during the 7-day collection period.

Multiple Dosing

There is no significant increase in maximum plasma concentration or overall exposure (AUC) after multiple daily applications of the cream for 7 days or suppositories for 3 days.

Photosensitivity reactions were observed in some normal volunteers following repeated dermal application of terconazole 2% and 0.8% creams under conditions of filtered artificial ultraviolet light.

Photosensitivity reactions have not been observed in U.S. and foreign clinical trials in patients who were treated with terconazole suppositories or vaginal cream (0.4% and 0.8%).