The caffeine CO2 breath test: dose response and route of N-demethylation in smokers and nonsmokers.

The optimal conditions for performing the caffeine CO2 breath test (CBT) were investigated in smokers and nonsmokers. Caffeine labeled with 13C or 14C in all three (1, 3, and 7) methyl groups or specifically in the 1-, 3-, or 7-methyl groups were orally administered to healthy adults and the expiration of labeled CO2 was measured for 8 or 24 hr. The absolute rate of labeled CO2 excretion from trilabeled caffeine was proportional to the dose up to 3 mg/kg in all subjects. In smokers, the rate of labeled CO2 excretion averaged twice that in nonsmokers at all doses. A correlation was observed between the 2-hr cumulative CO2 excretion from trilabeled caffeine and the apparent oral metabolic clearance rate (MCR) of caffeine (R = 0.90). Monolabeled CBTs in smokers and nonsmokers demonstrated that 80% +/- 4% of labeled CO2 expired in the breath during the first 2 hr of a trilabeled CBT was derived from the 3 position; at 6 to 8 hr equal amounts were derived from the 3 and 7 positions. Little N-demethylation was observed from the 1 position at any time during the 8-hr test. The results indicate that the 2-hr cumulative excretion of labeled CO2 could be used to accurately predict the metabolic clearance rate of caffeine is the best CBT parameter for detecting the effect of smoking on caffeine N-demethylation. The data suggest that the primary routes of caffeine metabolism are 3-N-demethylation and ring hydroxylation and confirm that caffeine metabolites are N-demethylated primarily in the 3 and 7 positions.

[On the influence of a special preparation of oxytetracycline and sodiumbituminosulfonates on amount and composition of skin surface lipids in acne vulgaris (author's transl)]. / Uber den Einfluss einer speziellen Zubereitung von Oxytetracyclin und Natriumbituminosulfonaten auf Menge und Zusammensetzung der Hautoberflächenlipide bei acne vulgaris

Two groups of 27 and 23 patients with acne vulgaris were first treated for a period of one week with 1 g oxytetracycline a day p.o. In a second treatment period of 6 weeks the first group received 100 mg oxytetracycline a day p.o. and the second group a combination of 100 mg oxytetracycline and 1.2 g sodiumbituminosulfonates a day p.o. In the third treatment period, similarly continued for 6 weeks, the method was reversed. Gastric juice-insoluble preparations were used for the investigation. All criteria for a double-blind study were considered. Amount and composition of the skin surface lipids were analysed before beginning the treatment, at the end of the 2nd and at the end of the 3rd treatment period. The combination of both agents in gastric juice-insoluble preparations suppresses to a great extent the known effects brought about by the substances separately, namely the reduction in free fatty acids and the decrease in the skin surface lipids. The findings also show that the reduction of the free fatty acids was in a limited time observed only in patients treated with 100 mg oxytetracycline a day p.o. if they had been treated in the beginning of this therapy with a higher dosage of tetracycline.