Pharmacokinetics of fluorinated 4-quinolones in the aged.

Differences between the pharmacokinetics of the new fluoroquinolones in the young and in the elderly have been demonstrated for ciprofloxacin, enoxacin, norfloxacin, and ofloxacin. Comparative studies of the young and the elderly are still lacking for pefloxacin. With ofloxacin and norfloxacin, the age-related pharmacokinetic differences seem for the most part to be due to differences in the renal handling of the drugs. With ciprofloxacin and enoxacin more profound differences have been reported. The peak concentrations of ciprofloxacin and enoxacin in serum increase with age, without a concurrent increase in serum half-life. This cannot be explained by differences in the distribution of the drug or by reduced metabolism. The most probable explanation for the age-related differences in the disposition of ciprofloxacin is a more efficient absorption of the drug in the elderly. With enoxacin, an increase in the nonrenal clearance of the drug with age has been demonstrated. The clinical consequence of the age-related differences in the pharmacokinetics of ciprofloxacin and enoxacin is that these antibiotics should be administered at lower doses to the elderly.