Plasma concentrations of beta-carotene and canthaxanthin during and after stopping intake of a combined preparation.

During 17 days two groups of 6 and 8 volunteers of the Department of Dermatology ingested 4 and 6 capsules per day of carotenoids (10 mg beta-carotene + 15 mg canthaxanthin per capsule; Phenoro). Heparinized blood was collected twice a week until day 21 and then weekly until day 77. Concentrations of beta-carotene and canthaxanthin in plasma were analyzed by high-performance liquid chromatography during 77 days. Plasma levels of carotenoids were higher in group 2 (6 capsules) than in group 1 (4 capsules) but reached maximum concentrations within the same time. Hence, therapeutic plasma levels of beta-carotene were reached earlier in group 2. According to blood levels, group 2 could be clearly divided in low and high responders. In contrast to canthaxanthin, beta-carotene exhibited a biphasic decline in both groups, with a monophasic asymptotic decrease which was expressed clinically by a pronounced orange to yellow pigmentation of the skin.