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S M Dobbs

Publications and source records attributed to S M Dobbs.

67 records · Page 4Linked to original sources

Maintenance digoxin.

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Arrhythmias, Cardiac↗

Maintenance digoxin after an episode of heart failure: placebo-controlled trial in outpatients.

The need for maintenance digoxin treatment was assessed in a double-blind, variable-dose, crossover comparison with placebo. Forty-six outpatients who had been prescribed the drug for heart failure were studied; 33 were in sinus rhythm and the remainder in atrial fibrillation. Mean serum digoxin concentrations in those with sinus rhythm averaged 1-33 nmol/l, but a lower concentration, averaging 0-97 nmol/l, was accepted in those with atrial fibrillation as six of them developed bradycardia. Sixteen of the 46 patients deteriorated on placebo, and eight completely recovered when digoxin was reintroduced; in the remainder additional diuretics were required temporarily. Spirometric values deteriorated on changing to placebo whether or not the patient showed clinical evidence of recurrence of heart failure. In a separate study of nine patients who showed no clinical evidence of deterioration on placebo, reintroduction of digoxin caused a shortening of left ventricular ejection time, which persisted for at least a month. This suggests that the inotropic response to digoxin is sustained during maintenance treatment.

Atrial Fibrillation↗

Intravenous injection of gentamicin and tobramycin without impairment of hearing.

The aminoglycoside antibiotics gentamicin and tobramycin were given to six healthy volunteers by intravenous injection. A dose of 80 mg was injected within 1 min. The curves relating serum concentration to time did not differ significantly for the two drugs. The maximal serum concentrations of drug exceeded 10 mug/ml on seven of 12 occasions. Despite these high concentrations, loss of hearing was not significant at any frequency (1,000-8,000 Hz) up to one month after injection. It is suggested that the aminoglycoside antibiotics penetrate into the inner ear lymph very slowly and that the concentration at that site is relatively unaffected by transient high concentrations of antibiotic in the blood plasma.

Adult↗

Can digoxin dose requirements be predicted?

A search for patient variables relevant to digoxin dose requirements was made in fourty-three patients with a wide range of renal and hepatic function. The daily dose of digoxin to achieve a mean serum concentration of 1.5 ng/ml, the standardized dose, was calculated for each patient. The standardized dose correlated significantly with the following variables, in descending order of correlation coefficient; creatinine clearance, serum creatinine concentration, body weight and serum albumin concentration. An equation containing the two independent variables, creatinine clearance and serum albumin concentration, had a significantly stronger correlation with standardized dose than creatinine clearance alone. Attempts were made in each patient to predict the standardized dose using both empirical prescribing methods and the published nomograms. Although a maximum of 70% of the variance of the standardized dose was explained, this corresponded approximately to one patient in three having a predicted dose outside the 95% confidnece limits for the standardized dose. There remain important sources of individual variation in digoxin dose requirements yet to be identified. Future application of empirical prescribing methods, such as multiple linear regression and Bayes' theorem, to prescription for large, defined patient groups may improve dose prediction for individual patients.

Digoxin↗