**Abstract**

This chapter reports the study results to determine percutaneous absorption and pharmacokinetics of eflornithine following topical treatment with eflornithine hydrochloride 13.9% cream and "eflornithine–armenicum" composition in rats. The model of aerobic wounds was developed. Eflornithine hydrochloride cream (dose of 460 mg/kg) was applied in group I, and "eflornithine–armenicum" composition was applied in group II at a same dose of Eflornithine. The plasma concentration-time profile of racemic eflornithine following frequent sampling was determined by the HPLC method (LLOQ, 1.5 ng/ml). Eflornithine concentrations were measurable at 24 h, with peak concentrations in plasma 5.3 ng/ml after cream and 3.8 ng/ml after composition application (p < 0.001) and the average time to reach the maximum concentration of eflornithine increases from 2 h to 3.3 h. The area under the pharmacokinetic curve was decreased after composition application by 25%. Eflornithine was eliminated from plasma with a mean terminal half-life of 11.6 hours. It can be assumed that the use of "eflornithine–armenicum" composition allows for maintaining the optimal concentration of two anti-inflammatory compounds at the site of application for a long time, which can improve their pharmacological effect compared to separate use of eflornithine cream.

**Keywords:** Eflornithine, "Eflornithine–Armenicum," composition, pharmacokinetics, percutaneous absorption
