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Biomedical subjects

D G McDevitt

Publications and source records attributed to D G McDevitt.

At least 19 recordsLinked to original sources
PubMed1979

Is maintenance digoxin necessary in patients with sinus rhythm?

Discontinuation of digoxin in 56 patients with sinus rhythm who had been taking it for a long time did not produce clinical deterioration in 33 of 34 patients whose pre-withdrawal steady-state plasma-digoxin concentration was less than 0.8 ng/ml; fast atrial fibrillation developed in the other patient. 22 patients had plasma-digoxin levels between 0.8 and 2.0 ng/ml before withdrawal--of these, 7 deteriorated without digoxin (5 had atrial fibrillation, which was associated with congestive heart-failure, measurement of the pre-injection period/left-ventricular ejection time (P.E.P./L.V.E.T.) ratio suggested that digoxin did exert a sustained positive inotropic effect. Thus, successful discontinuation of digoxin was possible in 86% of the total group and was more likely when the plasma-digoxin concentration was below 0.8 ng/ml. Unexpected atrial fibrillation was the commonest development inthe 8 patients in whom digoxin withdrawal was unsuccessful.

Adult↗
PubMed1978

Plasma protein binding of propranolol and isoprenaline in hyperthyroidism and hypothyroidism.

1. The possibility that thyroid disease might result in alterations in the plasma proteins binding of drugs has been investigated by studying the binding of propranolol and isoprenaline in patients with hyperthyroidism and hypothyroidism. 2. Plasma protein binding of propranolol and isoprenaline has been measured in seven hyperthyroid patients and ten hypothyroid patients. Plasma binding was estimated by equilibrium dialysis at 37 degree C using triatiated propranolol and isoprenaline, both when the patients had thyroid dysfunction and again when they were euthyroid. 3. In the hyperthyroid group, mean propranolol binding varied from 86 +/- 1.7% when hyperthyroid to 88.4 +/- 0.8% when euthyroid. The comparable isoprenaline figures were 65.1 +/- 3.2% and 68.1 +/- 1.4% respectively. Neither difference was significant. 4. Isoprenaline binding was significantly lower (64.3 +/- 1.6%) when patients were hypothyroid than when they became euthyroid (68.8 +/- 1.2%). Propranolol binding was not altered by hypothyroidism. 5. It is concluded that clinically important alterations in free drug concentrations of propranolol or isoprenaline do not occur in hyperthyroidism or hypothyroidism.

Adult↗
PubMed1978

Catecholamine sensitivity in hyperthyroidism and hypothyroidism.

1. Catecholamine sensitivity in hyper- and hypothyroidism has been studied using a standardised isoprenaline sensitivity test. 2. Seven patients with hyperthyroidism and seven with hypothyroidism were tested both when showing evidence of thyroid dysfunction and again when euthyroid. 3. No significant differences were seen in heart rate responses to isoprenaline when patients became euthyroid compared to their response when either hyperthyroid or hypothyroid. 4. These results indicate that sensitivity to catecholamines is not altered in thyroid dysfunction and, in particular, that hypersensitivity does not occur in spontaneous hyperthyroidism.

Adult↗
PubMed1978

Digoxin compliance in patients from general practice.

1. Compliance with digoxin therapy has been assessed in a group of fifty patients receiving the drug in general practice but not attending hospital. 2. Compliance was estimated by comparing plasma digoxin concentrations before and after a 10 day period of measured digoxin consumption and by tablet counting. 3. Twelve patients had plasma concentrations which increased by more than 0.4 ng/ml during monitored intake and eight other patients took less than 80% of their tablets. These twenty patients were considered non-compliant. 4. A further three patients in whom plasma digoxin levels were zero when first seen but increased substantially during the run-in period were also adjudged non-compliant. 5. Non-compliance with prescribed digoxin dosage occurred, therefore, in 46% of the patients studied.

Aged↗
PubMed1978

Comparative trial of atenolol and propranolol in hyperthyroidism.

1 The use of atenolol, a cardioselective beta-adrenoceptor antagonist, in the management of hyperthyroidism has been studied by comparing it with propranolol. 2 In a double-blind cross-over trial, atenolol (50 mg), propranolol (40 mg) and placebo 4 times daily for 1 week were compared in twenty-one hyperthyroid patients by sequential analysis. 3. Patients generally preferred atenolol or propranolol to placebo but this preference only achieved significance with propranolol. 4 Judged by their effect on the symptoms and signs of hyperthyroidism, both atenolol and propranolol were significantly better than placebo, but no distinction could be made between the two active compounds. 5 Atenolol and propranolol reduced mean heart rate by 29.8 and 27.1% respectively compared with placebo. 6 Atenolol appeared almost equally effective to propranolol in the management of the peripheral manifestations of hyperthyroidism.

Atenolol↗
PubMed1978

Do patients take digoxin?

Plasma digoxin concentrations on admission to hospital have been compared with levels on day 8 in a group of 50 patients who were maintained on their preadmission digoxin doses for 7 days. In the absence of a change in renal function, 18 patients (36%) had higher levels on day 8 and were considered to be non-compliant: a further 7 patients (14%) had lower levels on day 8 suggesting that before admission they had been taking more than their prescribed digoxin dose. Fifty per cent were, therefore, taking their digoxin improperly. In addition, an incorrect dose of digoxin may have been prescribed in 14 patients (28%) with plasma digoxin concentrations either below 0.8 ng/ml (1.02nmol/l) or above 2.0 ng/ml (2.56 nmol/l) on day 8. Long-term compliance was assessed by comparing day 8 'steady state' digoxin levels with those obtained at outpatient follow-up. Thirty of the original group were studied at 4 weeks when 27 per cent were considered non-compliant, and 20 at 3 months when 30 per cent were non-compliant. These results have serious implications both for drug prescribing and for the treatment of disease, and suggest that a problem of communication exists between doctors and their patients.

Aged↗
PubMed1978

Observations on intravenous administration of lignocaine in patients with myocardial infarction.

Lignocaine was administered intravenously to 36 patients with acute myocardial infarction. A bolus of 100 mg followed by an infusion of 2 mg/minute failed to maintain plasma levels above 2 microgram/ml. A bolus of 100 mg followed by 4 mg/minute also failed to maintain satisfactory plasma concentrations during the first hour of therapy. A bolus of 75 mg was combined with an infusion of 10 mg/minute for 20 minutes followed by 1.5 mg/minute. Satisfactory plasma concentrations during the first hour were observed in 94 per cent of the estimations. No important adverse side effects occurred during the infusion of 10 mg/minute.

Arrhythmias, Cardiac↗