THE EFFECT OF HIGH AND LOW-FAT MEALS ON THE ABSORPTION OF RIFAMPICIN FROM THE GASTROINTESTINAL-TRACT IN VOLUNTEER SUBJECTS

A combination of gamma scintigraphy and pharmacokinetic analysis has b een used to investigate whether the variable effect of food on bioavai lability of rifampicin could be attributed to lymphatic absorption, or to alteration of the gastrointestinal transit time of the drug. Seven healthy subjects participated in the study and were given a Tc-99m-la belled meal and two rifampicin capsules containing In-111-labelled res in and the gastrointestinal transit of both labels was measured. Rifam picin levels were measured in plasma by HPLC. Increasing the fat conte nt of the meal did not alter the gastric emptying of the meal or the r esin (T-50 emptying = 2.99 h law fat meal, 5.83 h high fat meal; T-50 = 3.14 h resin low fat meal, 2.70 h high fat meal); but it did signifi cantly delay the time for the meal to reach the colon (T-50 arrival = 9.11 h low fat meal, 10.99 h high fat meal). Surprisingly, it did not affect the arrival time of the co-administered indium-labelled resin ( T-50 arrival = 8.91 h low fat meal, 8.43 h high fat meal). The increas ed fat present in the meal did not alter the pharmacokinetic parameter s for rifampicin.