Comparative bioavailability of intravenous and oral chloramphenicol in adults

The comparative bioavailability of chloramphenicol from intravenous succinate, oral palmitate, and oral base preparations was studied in a crossover manner in 12 adult patients. Chloramphenicol was administered at a dose of 1 Gm every 6 hours, and blood samples were collected at steady state. For the succinate study, total urine output was also collected. The bioavailability of active chloramphenicol from the succinate preparation averaged 85.8 +/- 42.3 and 78.8 +/- 50.1 per cent of the free base and palmitate forms, respectively. This lower availability appeared to be due to variable excretion of unchanged succinate in the urine, averaging 27 +/- 11 per cent of the dose. Regardless of dosage form or route of administration, plasma chloramphenicol concentrations remained in the therapeutic range (5 to 25 mg/liter) for the entire dosage interval, implying that no change needs to be made when changing dosage form or route of administration. The interpatient variability, however, supports the need for monitoring of plasma chloramphenicol concentrations, especially in newborn infants, persons with liver disease, or those receiving other medications that alter chloramphenicol metabolism.