The pharmacokinetics of single-dose oral ciprofloxacin 500 mg was ascertained in 12 elderly and 12 young subjects. Mean age of the elderly volunteers was 75.4 years and the mean measured creatinine clearance in this group was 40.7 ml/min. Serum and saliva were collected in serial order for 24 hours (elderly) and 10 hours (young), and assayed for ciprofloxacin by high-performance liquid chromatography. The geriatric subjects had higher serum levels throughout the sampling period, with a peak level of 3.24 +/- 0.79 versus 2.26 +/- 0.75 micrograms/ml for the younger group (p less than 0.005; one-way analysis of variance). A twofold increase in the ciprofloxacin half-life may be partly explained by a decrease in the glomerular filtration rate, as shown by slower ciprofloxacin renal clearance (152.4 +/- 54.2 vs 395.6 +/- 139.0 for elderly and young subjects respectively; p less than 0.001). We concluded that in elderly patients, ciprofloxacin should be administered at an interval not less than every 12 hours to prevent accumulation and eventually toxicity.

The pharmacokinetics of ceftazidime after a 1-g bolus dose were studied in six elderly volunteers and 12 young subjects. Serum and urine samples were collected in serial order for 24 h and assayed by high-pressure liquid chromatography. The ceftazidime renal clearance was reduced in elderly subjects, a symptom related to normal aging of the kidneys. The decrease in volume of distribution in the elderly group may be explained by a reduction in total body water and an increase in fat tissue. Dosage adjustment is probably not necessary for otherwise healthy elderly patients requiring ceftazidime.

More than 30 cases of bullous photodermatitis have already been associated with the administration of nalidixic acid. This reaction is reported in a 57-year-old woman whose sun exposure was minimal. Nalidixic acid-induced photoreactions generally occur in females; they affect mainly the dorsal surfaces of the hands, feet, and legs, and usually do not involve the face. Blistering is always reported, and erythema is common. Dosage regimen and duration of treatment have little influence on the onset and severity of the reaction, which is probably of allergic nature. Its duration may be long, from three to six weeks, reexposure to the sun may trigger the reappearance of blistering for several months, even in the absence of a drug rechallenge.

Plasma levels of active naphthyridine were measured in healthy old (mean age 77.3 years) and young (mean age 25.4 years) subjects following oral administration of 1 Gm nalidixic acid. The plasma levels of active naphthyridine, i.e., nalidixic acid and its metabolite 7-hydroxynalidixic acid, were generally higher in the old group, particularly in the elimination phase. Significant variations in the pharmacokinetic parameters were obtained between the two groups of volunteers. The plasma half-life of active naphthyridine averaged 11.5 hours in old subjects and 2.7 hours in the younger group. Diminished renal function in the geriatric group may explain the slower elimination of the drug in the old subjects. The mean values of the other parameters calculated were: apparent volume of distribution, 0.55 (old) and 0.47 (young) liter/kg body weight; area under the curve, 327.7 (old) and 156.3 (young) micrograms/ml x hr; total body clearance 2.9 (old) and 8.3 (young) liters/hr; absorption rate constant, 0.29 (old) and 0.52 (young) hr. -1

The pharmacokinetics of indomethacin (Indo) was studied in 10 healthy elderly male volunteers (age 67–81 years) following the oral administration of a single 75-mg dose of a sustained release form of Indo. The total and free plasma and erythrocyte concentrations of Indo were determined by a specific high-pressure liquid chromatographic method. A maximum concentration (C_max) of 4.28 ± (SE) 0.43 μg/ml was reached after 1.85 ± 0.22 h. The area under the plasma concentration versus time curve (AUC) was 22.83 ± 2.70 μg ml-¹ h and the plasma elimination half-life was 4.34 ± 0.64 h. The maximum concentration of Indo in the red blood cells was 0.123 ± 0.013 μg/ml and was obtained at 1.95 ± 0.14 h after drug administration. The erythrocyte concentrations of Indo represented 2.4% of the total plasma levels of Indo whereas only 1.3% of the drug was unbound to plasma proteins. The C_max and AUC values determined in the elderly were approximately double the values reported in young adults for the same dose.