Aging and drug disposition--metabolism

Measurement of drug utilization in Sweden: methodological and clinical implications

The available sources of information on drug utilization in the Swedish population at large are reviewed. They comprise whole-sale statistics, drug deliveries to hospitals and prescription data. Drug consumption is preferably expressed in defined daily doses (DDD) per capita, where DDD is the average recommended dose on the major indication of the drug. Under ideal circumstances--drugs used continuously on one indication--the number of DDDs per population ought to agree with morbidity data. This turned out to be the case with antidiabetic drugs. The pitfalls with this unit of measurement include major discrepancies between recommended and prescribed doses, and the use of the drug on vastly different indications (such as neurosis and psychosis in the case of neuroleptics). Nevertheless, the DDD methodology may serve as a therapeutic audit in attempts to follow and influence therapeutic habits of health personnel in hospitals and primary health care. Wholesale data combined with individual-based prescription data are particularly useful in this regard.

A multiple dose pharmacokinetic and tolerance study of once daily 200 mg sustained-release flurbiprofen capsules in young and very elderly patients

The pharmacokinetic profile of 200 mg sustained-release flurbiprofen capsules was compared in nine elderly (mean age 84.2 years) and 10 young (mean age 38.1 years) patients with arthritis. After a single capsule, a 48 h plasma concentration profile was performed. The patients then took 1 capsule daily for a further 13 days with plasma levels of the drug being measured pre-dose on alternate days. Following ingestion of the last capsule, a further 48 hour plasma concentration profile was performed. These results were compared with each other and with computer predicted data obtained from dosing with 200 mg conventional flurbiprofen (as 100 mg b.d.). In both young and elderly patients, the two 48 h plasma concentration profiles confirmed the sustained-release characteristics of the capsule. There was no evidence of dose-dumping, although, in one elderly patient with a partial gastrectomy, higher plasma concentrations were observed. Inter- and intra-patient variability was acceptable. A steady-state was achieved within the predicted four days in both groups and there was no evidence of accumulation with the daily dosing interval. A mean steady-state level of approximately 6 micrograms/ml was achieved for both populations. Computer predicted data for 200 mg conventional flurbiprofen (as 100 mg b.d.) showed a pre-dose/peak range of 1-12 micrograms/ml. The pre-dose/peak ranges for the young and old patients were 4-10 micrograms/ml and 4-8 micrograms/ml respectively. One young patient developed a hypersensitivity reaction of moderate severity; one young and four elderly patients developed a low haemoglobin concentration during the study. No other changes in haematological or biochemical parameters were seen.

Beta-blocking effect and pharmacokinetics of pindolol in young and elderly hypertensive patients

The pharmacokinetics and beta-blocking effect of pindolol has been compared in 20 patients with essential hypertension (WHO Stage I), 10 below 25 years of age and 10 older than 60 years. Each patient received pindolol 10 mg p.o. once a day for 5 days. The area under the curve (AUC) of pindolol was larger in the old than in the young patients both on the first (p less than 0.05) and the fifth (p less than 0.01) days. The AUC of pindolol was 14% higher on the fifth day compared to the first day in the elderly group, indicating minor accumulation at steady-state. There was no change in AUC in the young patients. Endogenous creatinine clearance was lower in the old (80 +/- 9 ml/min) than in the young patients (150 +/- 45 ml/min). The beta-blocking effect did not differ between the groups at 2 h after administration of pindolol on Days 1 or 5. However, 24 h after the first and fifth doses approximately 60% of the beta-blockade persisted in the old group whereas 17 and 19% of the beta-blockade, respectively, persisted in the young group; the difference between the groups was statistically significant (p less than 0.01). The most probable explanation for the more sustained beta-blocking effect in the elderly is the physiologically decrease in renal function, which results in a more sustained plasma level of pindolol in those patients.