Antipyrine absorption and disposition in the elderly.

Twelve young (24-41 years) and 11 elderly (62-77 years) volunteer subjects received a single 1.0-gram dose of antipyrine on three occasions: intravenously, orally in the fasting state and orally following a standard breakfast. Plasma antipyrine concentrations were determined for 24 h after each dose. Compared to young males, elderly men had significantly prolonged elimination half-life (17 vs. 11 h, p less than 0.025) and reduced clearance (32 vs. 54 ml/min, p less than 0.06). However, elderly and young women did not differ in half-life (12 vs. 11 h) or clearance (37 vs. 44 ml/min). After oral dosage in the fasting state, young and elderly groups (regardless of gender) did not differ in peak plasma antipyrine concentration (Cmax) or time of peak concentration (Tmax). Absolute bioavailability was not significantly less than 100% and was not related to age. Postprandial oral dosage of antipyrine caused reduced Cmax and prolonged Tmax in all groups, but absolute bioavailability was not significantly less than 100%. Again, there were no age-related differences. Although aging may lead to reduced clearance of antipyrine among men, there is no evidence that old age is associated with impairment of the rate or extent of antipyrine absorption from the gastrointestinal tract.