Dose of digoxin prescribed in the UK compared with France and the USA.

ABSTRACT

BACKGROUND: Two trials in patients with heart failure showed that some patients grew worse if digoxin was withdrawn. The median daily dose of digoxin in these trials was 375 micrograms. We suspected that doses used in the UK were much lower. METHODS: We studied the prescription of digoxin to 119 patients who were discharged from St George's Hospital, London, UK, in April and May, 1994. We calculated the appropriate digoxin prescription dose by Jelliffe's formula. Appropriate doses were put into a scale of six levels 62.5 micrograms, 125 micrograms, 187.5 micrograms, 250 micrograms, 375 micrograms, or 500 micrograms. We compared our findings with information from a database of prescription records. These records, gathered during 1993-94, came from the UK (1085 prescriptions). France (1148), and the USA (2303). FINDINGS: In the St George's Hospital series, the median daily dose of digoxin was 125 micrograms (mean 170 [SD 80] micrograms). The dose was significantly higher in patients who had heart failure than those who did not, by a mean of 40 micrograms. Among the 100 patients for whom appropriate dose was calculated, the dose was as predicted in 28, one level too low in 34, two or more levels too low in 32, and one level too high in six. There was no difference between St George's Hospital and UK practice as a whole (p > 0.05), but the dosage was significantly higher in the USA and France than in the UK (p < 0.001 for both) and significantly higher in France than in the USA (p < 0.001). INTERPRETATION: Differences in dosage may be correlated to the range of tablet strengths available in each country in our analysis. Underdosing can be detected with certainty only if plasma digoxin concentration is measured. However, our study provides strong circumstantial evidence that many patients in the UK are receiving too little digoxin.