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Biomedical subjects

E M Rodgers

Publications and source records attributed to E M Rodgers.

13 recordsLinked to original sources
PubMed1981

Evaluation of medigoxin in outpatients.

We compared our ability to predict the dose of medigoxin and of digoxin required to achieve a fixed serum concentration (the dose requirement) in 33 outpatients. Preliminary work supported the assumptions that the steady state glycoside concentration achieved was proportional to the daily dose given to an individual, and that the bioavailability of the different tablet presentations was similar for either glycoside. We were not able to predict the dose requirement from patient characteristics with any more certainty for medigoxin than for digoxin. Not only the between-patient variability in dose requirement, but also the within-patient variability, was similar for the two glycosides. However the digoxin used had a dissolution rate of over 90% in 1 h. When comparing medigoxin with digoxin of lower, or more variable dissolution rate, medigoxin may be preferable.

Analysis of Variance↗
PubMed1980

Ideal sampling time for drug assays.

Estimation of the mean steady state serum concentration of a drug from an isolated sample apparently requires a knowledge of both the timing of the sample within the dose interval and of the pharmacokinetic constants of the drug in the individual. Data from 80 general medical outpatients receiving maintenance digoxin has been used to derive a relationship between the serum digoxin concentration at any given time (C) and the mean steady state concentration (C), but this did not allow for individual variation in drug handling. It can be demonstrated theoretically that, for a one compartment model with instantaneous drug distribution and first order elimination, the ratio, C/C, is dependent on the half time of the drug, the dose interval and the time of sampling. Moreover, for higher values of half time the ratio is virtually constant at 11 h after a daily dose. This, then, would be an ideal sampling time. The above approach can be extended to any drug provided that its half time is at least 15 h in healthy subjects and that the concentration/time curve approximates to a simple exponential decay during virtually the entire dose interval. Orally administered digoxin meets both of these provisions, the ratio at 11 h being 0.97, which is only slightly different from the 1.02 of the theoretical model. Ideal sampling times and the conditions under which they apply may be derived for other dose intervals.

Blood Specimen Collection↗
PubMed1978

A score for prescribing digoxin.

A simple method of selecting a maintenance dose of digoxin, suitable for an adult patient, was derived from data on 129 patients taking digoxin. Eight items of readily available information are required for entry into the prescribing aid: out/inpatient status, sex, age (less/not less than 70 years), weight (allocated to one of four ranges), whether or not chronically house/chair bound, cardiac rhythm (sinus/other), serum creatinine concentration (allocated to one of four ranges), and diuretic therapy (prescribed/not prescribed). The recommended dose is given in terms of size and number of tablets to be prescribed. Using this method 72.3 per cent of patients are expected to achieve mean steady state serum digoxin concentrations within the therapeutic range, 6.5 per cent above and 21.2 per cent below. This performance would be considerably better than that expected from the use of other prescribing aids. If available, routine measurement of the serum digoxin concentration during follow-up is recommended to detect those who might benefit from a change, usually an increase, in dose.

Aged↗