To test if capsaicin could improve the bioavailability of ciprofloxacin (1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid, CAS 85721-33-1, Bay q 3939) in rats, 0.01, 0.1, 0.5 and 1% capsaicin ((E)-N-[(4-hydroxy-3-methoxyphenyl)methyl]-8-methyl-6-nonenamide, trans-8-methyl-N-vanillyl-6-nonenamide, CAS 404-86-4) dissolved in ethanol and mixed with 20 mg/kg of ciprofloxacin were orally administered to groups of 10 rats each. Control groups were dosed with capsaicin-free, ethanol-containing or ethanol-free ciprofloxacin. Reference intravenous pharmacokinetics of ciprofloxacin was also established. The results revealed that capsaicin increased ciprofloxacin bioavailability by approximately 70% in groups receiving preparations containing capsaicin at a rate of 0.01, 0.1 and 0.5%. Higher concentrations failed to further increase bioavailability. However, capsaicin appears to have little or no impact on the rate of absorption or clearance of ciprofloxacin. Considering that 0.01% or 0.1% capsaicin are unlikely to upset the gastrointestinal tract, it may be worth attempting to study if a similar effect occurs in man, and to evaluate if the addition of capsaicin can be used as a method to increase the area under the curve/minimum inhibitory concentration rate, a key variable to improve clinical efficacy of ciprofloxacin.