Following topical application, tazarotene undergoes esterase hydrolysis to form its active metabolite, tazarotenic acid. Little parent compound could be detected in the plasma. Tazarotenic acid was highly bound to plasma proteins (greater than 99%). Tazarotene and tazarotenic acid were metabolized to sulfoxides, sulfones and other polar metabolites which were eliminated through urinary and fecal pathways. The half-life of tazarotenic acid was approximately 18 hours, following topical application of tazarotene to normal, acne or psoriatic skin.

In a multiple dose trial with a once daily dose for 14 consecutive days in 9 psoriatic subjects (male=5; female=4), measured doses of tazarotene cream, 0.1% were applied by medical staff to involved skin without occlusion (5 to 35% of total body surface area: mean ± SD: 14 ± 11%). The Cmax of tazarotenic acid was 2.31 ± 2.78 ng/mL occurring 8 hours after the final dose, and the AUC0-24h was 31.2 ± 35.2 ng∙hr/mL on day 15 in the five subjects who were administered clinical doses of 2 mg cream/cm2.

During clinical trials with tazarotene cream, 0.05% or 0.1% treatment for plaque psoriasis, three out of 139 subjects with their systemic exposure monitored had detectable plasma tazarotene concentrations, with the highest value at 0.09 ng/mL. Tazarotenic acid was detected in 78 out of 139 subjects (LLOQ = 0.05 ng/mL). Three subjects using tazarotene cream 0.1% had plasma tazarotenic acid concentrations greater than 1 ng/mL. The highest value was 2.4 ng/mL. However, because of the variations in the time of blood sampling, the area of psoriasis involvement, and the dose of tazarotene applied, actual maximal plasma levels are unknown.

Tazarotene cream 0.1% was applied once daily to either the face (N=8) or to 15% of body surface area (N=10) of female subjects with moderate to severe acne vulgaris. The mean Cmax and AUC values of tazarotenic acid peaked at day 15 for both dosing groups during a 29 day treatment period. Mean Cmax and AUC0-24h values of tazarotenic acid from subjects in the 15% body surface area dosing group were more than 10 times higher than those from subjects in the face-only dosing group. The single highest Cmax throughout the trial period was 1.91 ng/mL on day 15 in the exaggerated dosing group. In the face-only group, the mean ± SD values of Cmax and AUC0-24h of tazarotenic acid on day 15 were 0.10 ± 0.06 ng/mL and 1.54 ± 1.01 ng∙hr/mL, respectively, whereas in the 15% body surface area dosing group, the mean ± SD values of Cmax and AUC0-24h of tazarotenic acid on day 15 were 1.20 ± 0.41 ng/mL and 17.01 ± 6.15 ng∙hr/mL, respectively. The steady state pharmacokinetics of tazarotenic acid had been reached by day 8 in the face-only and by day 15 in the 15% body surface area dosing groups.

In a Phase 3 clinical trial, tazarotene cream, 0.1% was applied once daily for 12 weeks to each of 48 subjects (22 females and 26 males) with facial acne vulgaris. The mean ± SD values of plasma tazarotenic acid at weeks 4 and 8 were 0.078 ± 0.073 ng/mL (N=47) and 0.052 ± 0.037 ng/mL (N=42), respectively. The highest observed individual plasma tazarotenic acid concentration was 0.41 ng/mL at week 4 from a female subject. The magnitude of plasma tazarotenic acid concentrations appears to be independent of gender, age, and body weight.