Abstract

The in vivo effects of caffeine and nicotinic acid, alone and combined, on serum free fatty acid (FFA) levels of dogs were studied as follows: sodium benzoate (25 mg/kg), caffeine sodium benzoate (50 mg/kg), nicotinic acid (40 mg/kg) and caffeine sodium benzoate (50 mg/kg) plus nicotinic acid (40 mg/kg) were administered i.v. to groups of eight dogs. Serial blood samples were obtained before and after administration of the drugs and were analyzed for FFA concentration. In the group receiving sodium benzoate a slight, but not statistically significant drop in FFA levels was observed; in the group receiving caffeine sodium benzoate a significant increase in FFA concentration occurred. In the group receiving 40 mg/kg of nicotinic acid a sharp drop in FFA levels occurred within 30 minutes and persisted without signs of rebound for at least four hours. When caffeinesodium bensoate plus nicotinic acid was given concomitantly, the FFA-lowering effect of nicotinic acid prevailed. However, maximum lowering of FFA levels did not appear during the first hour. These findings were believed to be of interest in two respects. 1) Nicotinic acid was able to completely abolish caffeine-induced rises in FFA; caffeine, in turn, seemed to attenuate, but could not prevent, the FFA-lowering effect of nicotinic acid 2) By increasing the doses of nicotinic acid administered, rebound of FFA above base-line values, reported by others, could be abolished for at least four hours. It is thus conceivable that FFA rebound can be completely blocked by administering appropriate doses of nicotinic acid at adequately spaced intervals.