The effect of gastric acidity on the oral absorption of the quinolone antibiotic enoxacin was evaluated in 12 healthy volunteers. In a randomized, crossover design, single 400 mg oral enoxacin doses were administered on four occasions: alone, after 50 mg intravenous ranitidine, after 2 micrograms/kg subcutaneous pentagastrin, and after combined ranitidine and pentagastrin treatment. Gastric pH was monitored by radiotelemetry capsule for 4 hours after enoxacin administration. Ranitidine pretreatment reduced enoxacin oral bioavailability by an average of 26%. This effect was abolished when pentagastrin was used to maintain low gastric pH. Thus the ranitidine-induced decrease in enoxacin oral bioavailability probably results from a decrease in gastric acidity rather than from an interaction with ranitidine itself.

1. Absorption and metabolism of 14C-labelled sunset yellow (FD & C Yellow No. 6), tartrazine (FD & C Yellow No. 5) and high molecular weight polymeric derivatives of the two azo dyes were compared in rats. 2. A trace to 1.5 percent of unchanged monomeric dyes was excreted in urine and bile during the first 24 h after dosing. No unchanged dye was absorbed after administration of the polymeric derivatives. 3. In animals dosed with sunset yellow and its polymer derivative, absorption of the azo-bound cleavage product 1-amino-2-naphthol-6-sulphonic acid was 8.5 and 6.9 percent, respectively, while absorption of the cleavage product sulphanilic acid was 37.4 and 0 percent, respectively. 4. In animals dosed with tartrazine and its polymer derivative, absorption of the cleavage product aminopyrazolone and its metabolites was 4.0 and 4.6 percent, respectively. 5. Azo bond cleavage did not appear to be decreased in the polymer derivatives. However, the sulphanilic acid moiety of both dyes remained attached to the polymer backbone, resulting in a 95 percent decrease in sulphanilic acid absorption with polymeric tartrazine. 6. Decreased absorption of unchanged dyes and certain metabolites with the stable, non-absorbed polymeric derivatives may be significant in developing non-sensitizing substitutes for these two commonly used food colourants.

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