Influence of nutritional status on plasma levels and relative bioavailability of tetracycline.

Relative bioavailability after oral administration of a single dose and Cmin levels of tetracycline in plasma after multiple doses were determined in groups of well-nourished and under-nourished subjects. The relative bioavailability of tetracycline, assessed by the area under serum concentration time-curves, did not differ in under-nourished and well-nourished patients. The plasma levels were not different in the two groups after the conventional dose of tetracycline HCL 250 mg at 6 hour intervals. However, in these studies under-nourished subjects received a higher dose per kg body weight, which could have compensated for any effect of a shortened half life of the drug. When the dose per kg body weight was reduced, the Cmin levels were lower. On the other hand, with the same dose per kg body weight at more frequent intervals, the plasma concentrations were similar to those in well-nourished subjects. These studies indicate that the dosage regimen should be based both on body weight and on the nutritional status of the individual.