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Objective: To evaluate the safety and pharmacokinetics of tazarotene cream 0.1% under standard (face only) or exaggerated (15% body surface area, including the face) application conditions after a single dose and after repeat topical applications once daily to patients with acne vulgaris or photodamaged skin. Methods: Two separate, randomised, single-centre, nonblinded, parallel-group pharmacokinetic studies were conducted. In one study, tazarotene cream 0.1% was applied either to the face of eight female patients with moderate acne or to 15% body surface area of ten female patients with severe acne. In the other study, tazarotene cream 0.1% was applied either to the face (six females, two males) or to 15% body surface area (8 females. 8 males) of patients with photodamaged skin. In both studies, tazarotene cream 0.1% was applied once daily (except on days 1 and 2) for 30 days. Blood was drawn for measurement of plasma concentrations of tazarotenic acid at defined time intervals after applicat ion of the cream. Plasma tazarotenic acid concentrations were determined by a validated gas chromatography-tandem mass spectrometry method with a lower limit of quantification of 0.005 μg/L. Results: At exaggerated application rates in patients with acne vulgaris, the maximum average peak concentration (C[submax]) and 24-hour area under the concentration-time curve (AUC) values of tazarotenic acid were (mean ± SD) 1.20 ± 0.41 μg/L (n = 10) and 17.0 ±6.1 μg · h/L (n = 10), respectively, and occurred on day 15. The single highest C[submax] was 1.91 μg/L. At standard application rates in patients with acne vulgaris, the maximum average C[submax] and AUC values of tazarotenic acid were 0.10 ± 0.06 μg/L (n = 8) and 1.54 ± 1.01 μg · h/L (n = 8), respectively, and occurred on day 15. At exaggerated application rates in patients with photodamaged skin, the maximum average C[submax] and AUC values of tazarotenic acid were (mean ± SD) 1.75 ± 0.53 μg/L (n = 16) and 23.8 ± 7.0 μg • h/L (n = 16), respectively, and occurred on day 22. The single highest C[submax] was 3.43 μg/L on day 29. At standard application rates in patients with photodamaged skin, the maximum average C[submax] and AUC values of tazarotenic acid were 0.236 ± 0.255 μg/L (n = 8) and 2.44 ± 1.38 μg · h/L (n = 8), respectively, and occurred on day 15. Gender had no influence on the systemic exposure of tazarotenic acid. The most common treatment-related adverse events were signs and symptoms of local irritation, of mild or moderate severity. Conclusions: The pharmacokinetics of tazarotene cream 0.1% in patients with acne vulgaris or photodamaged skin are similar. The maximum average plasma concentrations of tazarotenic acid after topical application of tazarotene cream 0.1% to the face were less than 0.25 μg/L. The maximum average plasma concentrations of tazarotenic acid following application to an exaggerated body surface area (15%) were less than 1.8 μg/L. [ABSTRACT FROM AUTHOR]