Do patients take digoxin?

Abstract

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 (1.02 nmol/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 originalgroup were studied at 4 weeks when 27per 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 andfor the treatment of disease, and suggest that a problem of communication exists between doctors and their patients.In a previous study of patients already taking digoxin when admitted to hospital as emergencies (Carruthers et al., 1974), it was found that only 42 per cent had plasma digoxin concentrations within the normal therapeutic range of 08 to 2-0 ng/ml (1-02-2*56 nmol/l) (Whiting et al., 1973); 33 per cent had levels below 08 ng/ml (1P02 nmol/l) and were presumably under-treated and 25 per cent had levels greater than 2-0 ng/ml (2-56 nmol/l) and may have been potentially at risk from digoxin toxicity (Chamberlain et al., 1970;Whiting et al., 1973). Factors responsible for the wide scatter of digoxin concentrations were not identified. A further group of patients have now been studied in which serial inpatient and outpatient plasma digoxin concentrations were used to investigate non-compliance as a possible explanation of the fact that so many levels lie outside the 'therapeutic range'. Patients and methodsConsecutive patients admitted as emergencies to a general medical ward in the Belfast City Hospital and receiving maintenance digoxin treatment before admission were studied. For each patient, a careful history relating to digoxin treatment was taken with particular reference to the dose, the

Digoxin compliance in patients from general practice.

“…In a recent study of sixty patients being admitted to hospital in emergency (Johnston, Kelly & McDevitt, 1978) in which plasma digoxin concentrations on admission were compared with levels obtained after seven days treatment with their pre-admission digoxin doses, it was found that almost one-half of the patients were taking their digoxin improperly-nearly onethird of the total group were considered to be taking too little digoxin and to be non-compliant.…”

Variations of plasma digoxin concentrations in the equilibrium state after multiple dosing.

“…The limits are larger than those previously selected, both in relation to plasma digoxin and serum creatinine (Johnston et al, 1977). Reanalysis of compliance in the original admission study (Johnston et al, 1977) using these new limits shows that of the 50 patients studied 17 (34%), instead of 18 previously, would be adjudged to have been taking less and 5 (10%), instead of 7 previously, more than the prescribed daily digoxin dose before admission to hospital.…”

“…Reanalysis of compliance in the original admission study (Johnston et al, 1977) using these new limits shows that of the 50 patients studied 17 (34%), instead of 18 previously, would be adjudged to have been taking less and 5 (10%), instead of 7 previously, more than the prescribed daily digoxin dose before admission to hospital. Overall these new standards would mean 44 (rather than 50) per cent were taking their digoxin improperly.…”

“…In the latter area, the scope includes aid to determining optimal doses in malabsorption syndromes and renal failure, in the diagnosis of toxicity, and as a guide to the treatment of refractory fast atrial fibrillation. Recently plasma digoxin concentration estimations have been used to evaluate drug compliance by measuring digoxin levels in a group of patients on admission to hospital, comparing them with the levels achieved after 7 days treatment with digoxin at the dose level prescribed before admission (Johnston, Kelly & McDevitt, 1977). It was assumed that equilibrium would have been attained within that period and that alterations in plasma digoxin concentrations indicated poor compliance, provided renal function had not changed.…”

Does the frequency of daily dosage influence compliance with digoxin therapy?

“…Conversely, improved compliance may not always be beneficial-we have shown previously that in some non-compliant patients, given their prescribed daily digoxin dosage in hospital, plasma digoxin concentrations rose into the potentally toxic range (Johnston, Kelly & McDevitt, 1978). Reduced frequency of daily dosage administration may not affect compliance greatly.…”