Pharmacokinetics of isoxicam in the elderly.

Several studies are under way to determine the pharmacokinetics of isoxicam in the elderly; this report presents preliminary results of these studies. Data have been collected from: eight healthy subjects older than 65 years old receiving single oral doses of 200 mg; eight patients with rheumatoid arthritis, 61 to 69 years old, receiving oral doses of 400 mg per day; and the same eight patients with arthritis receiving 100 mg per day (four patients), 200 mg per day (one patient), or 300 mg per day (three patients). The plasma levels of isoxicam were determined in the subjects for 96 hours following administration. The results indicate that the mean half-life of isoxicam is approximately 24 hours and is independent of dosage. The results were compared with those in 30 healthy subjects aged 18 to 32 years. The comparison showed that the half-life of isoxicam appears to be independent of dosage, duration of treatment, and age of subject. On the basis of these preliminary results, it appears that elderly patients are not at risk of excessive accumulation of isoxicam during treatment with therapeutic dosages.