Age-related changes in the pharmacokinetics and pharmacodynamics of nifedipine.

1. The effects of age on the pharmacology of nifedipine were investigated in 11 young and six elderly normotensive volunteers. 2. Following 2.5 mg of nifedipine i.v. the plasma clearance of nifedipine was 348 +/- 83 (s.d.) ml min-1 in the elderly compared with 519 +/- 125 ml min-1 in the young (P less than 0.05) and the AUC in the elderly was significantly greater at 125 +/- 28 ng ml-1 h compared with 83.9 +/- 19 ng ml-1 h (P less than 0.05). The Vss was similar in both age groups. 3. Following 10 mg oral sustained release nifedipine the AUC was 281 +/- 64 ng ml-1 h in the elderly compared with 136 +/- 56 ng ml-1 h in the young (P less than 0.002) and Cmax in the elderly was significantly greater at 36.8 +/- 11.8 ng ml-1 compared with 22.3 +/- 5.8 ng ml-1 (P less than 0.05). The trend towards an increased bioavailability in elderly subjects (36%) was supported by a significantly lower nitropyridine metabolite/nifedipine ratio in the elderly. 4. Absorption rate limited kinetics of the sustained release formulation were indicated by the prolonged t1/2 compared with i.v. administration. In the elderly t1/2 (oral) was significantly greater than in the young (elderly 6.7 +/- 2.2 h, young 3.8 +/- 1.4 h, P less than 0.05). 5. Haemodynamic changes in the young were confined to a tachycardia following i.v. administration. In the elderly, supine BP fell significantly following both oral and i.v. nifedipine while the heart rate remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)