Biomedical subjects

B F Tregaskis

Publications and source records attributed to B F Tregaskis.

4 recordsLinked to original sources

PubMed1991

Comparison of hypokalaemic, electrocardiographic and haemodynamic responses to inhaled isoprenaline and salbutamol in young and elderly subjects.

The purpose of the study was to compare beta-adrenoceptor responsiveness to salbutamol (beta-2 selective agonist) and isoprenaline (non-selective) in young (n = 10, age 23 y) and elderly (n = 7, age 71 y) subjects. Subjects were given cumulative doubling doses of inhaled isoprenaline or salbutamol (500-4000 micrograms), and placebo, in a single-blind randomised cross-over design. Plasma potassium, electrocardiographic (R-R, T-wave, Q-Tc) and blood pressure responses were measured at baseline and at each dose step. There were no difference between baseline values for each of the three study days within each group of subjects. Hypokalaemia was significantly greater in response to salbutamol compared with isoprenaline in both the young (as change from baseline): -0.61 versus -0.10 mmol.l-1: and in the elderly: -0.68 versus -0.20 mmol.l-1. There were no differences between young and elderly responses. T-wave amplitude fell significantly in response to isoprenaline and salbutamol, although this effect was progressively attenuated with increasing doses of isoprenaline. Maximum T-wave response (change from baseline) was greater with salbutamol than isoprenaline in the young: -0.22 versus -0.11 mV: and in the elderly: -0.17 versus -0.08 mV, and there were no differences between the two groups. There were no differences between the effects of isoprenaline and salbutamol on Q-Tc prolongation or heart rate. Chronotropic responses to salbutamol were greater in the elderly: 39 versus 24 beats.min-1. There were larger increases in SBP with isoprenaline in both groups. Falls in DBP in response to isoprenaline and salbutamol were significantly greater in the elderly.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1990

Pharmacokinetics in old age.

All practising clinicians will be aware of the increased number of elderly patients requiring drug treatment as the proportion of people over the age of 65 increases in our Western society. The elderly as a group have much to benefit from modern drug therapy, but, historically, are also the group most prone to adverse drug reactions. Such reactions have often been due to inappropriate drug prescribing based on an incomplete knowledge of changes in drug handling with age. In recent years there has been an increased understanding of the physiological changes of ageing and the changes in drug handling consequent upon these changes. This review will concentrate on the clinical sequelae of changes in drug handling and suggest areas where modification in prescribing practice may yield clinical benefits and lessen the toll of adverse drug reactions.

Aged↗

PubMed1990

Beta-adrenoceptor-blocking drugs in the elderly.

Beta-adrenoceptor function appears to be diminished in the elderly, although the exact mechanisms are still uncertain. Some evidence suggests that this attenuation is predominantly of beta1-receptor activity, with beta2-receptor activity remaining intact. Pharmacokinetic changes also occur in the elderly with beta-blockers. Absorption is unchanged but bioavailability may be increased, particularly with lipophilic drugs such as propranolol that are subject to "first-pass" effects. Both hepatic and renal clearance may be diminished, and this suggests that, in general, elderly patients will require smaller doses than those normally given to younger ones. Although antihypertensive response to beta-blockers has been linked to renin status, clinical trial evidence indicates that beta-blockers are effective antihypertensive agents in the elderly, and clinical experience suggests that this is true also for ischemic heart disease. Provided attention is given to patient selection, associated diseases, and dosage, in general, beta-blockers appear to be well tolerated in the elderly. However, careful clinical supervision is required, particularly during treatment initiation.

Adrenergic beta-Antagonists↗

PubMed1989

Beta-adrenoceptor responses to inhaled salbutamol in the elderly.

The purpose of the present study was to evaluate and compare the responsiveness of beta 2-adrenoceptors in elderly and young subjects. Seven healthy elderly volunteers (72 +/- 3 years) were given cumulative doses of inhaled salbutamol (100 micrograms-4000 micrograms) or placebo, following pre-treatment with propranolol 40 mg or placebo. Finger tremor (Tr), plasma potassium (K), and heart rate (HR) were measured at each dose step. There were dose-dependent increases in Tr (P less than 0.001) and HR (P less than 0.001) and falls in K (P less than 0.001), which were completely attenuated by propranolol (P less than 0.001). Comparison with dose-response curves in a group of young (Y) subjects (24 +/- 3 years) given an identical dose protocol of salbutamol showed no evidence of subsensitivity of beta 2-adrenoceptor responses in the elderly (E) group (mean and 95% confidence intervals for maximum responses): delta K -0.90 (-1.1(-)-0.82) mmol l-1 Y, -0.82 (-1.04(-)-0.60) mmol l-1 E, delta Tr 274 (213-335)% Y, 269 (197-342)% E, delta HR 25 (21-28) beats min-1 Y, 26 (21-31) beats min-1 E.

Aged↗