**4. Pharmacokinetic study**

The aim of this study was to assign the range of values of α-MSH and met-enkephalin plasma concentrations before and after the Enkorten application and to determine pharmacokinetic parameters of the test preparation (Cmax, Tmax, AUC, T½). Cmax (Maximum Plasma Concentration) is the highest concentration of drug in the blood that is measured after a dose; Tmax (Time to Reach Cmax) is the time at which the highest plasma drug concentration occurs Cmax; AUC (Area Under the Curve) is the measure of total plasma exposure of drug over a given time period; T½ (Half-life) is the time required for a given drug concentration to decrease by 50%.

The study was carried out on a group of 14 healthy volunteers, ages from 18 to 30, males, of body weight and height within the standard values.

All volunteers received subcutaneously one dose of Enkorten preparation in the presumed therapeutic dose for human application. No serious side-effects were observed during the study. The available kit is not specific for the determination of α-MSH of the test preparation; thus, the cross-reactivity of physiologically present α-MSH and α-MSH component of the preparation was determined. Significant interindividual differences of α-MSH plasma concentration were found. Mean values were 21.31 - 47.56 pg/ml. Mean plasma concentration of endogenous met-enkephalin was 50.40 pg/ml. Maximum plasma concentration after Enkorten application, measured 5 minutes after the application, was 1551.86 pg/ml. The plasma half-life was 15 minutes. The concentration/time curve of metenkephalin implies first-order kinetics (Kusturica et al, 2009).
