Abstract: Saunders and colleagues (March 22, p 833)1Saunders KB Amerasinghe AKCP Saunders KL Dose of digoxin prescribed in the UK compared with France and the USA.Lancet. 1997; 349: 833-836Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar describe international differences in the prescribing patterns of digoxin. At our hospital in Bombay, India, digoxin is available as a 0·25 mg tablet, and all patients with rheumatic valvular heart disease scheduled for cardiac surgery are routinely prescribed one tablet daily. We monitored digoxin concentrations in 62 consecutive patients (23 men, 38 women; mean age 33·2 [SE 1·5] years; weight 45 [1·9] kg), who were admitted to the cardiovascular and thoracic surgery unit for elective surgery. All the patients had received digoxin for at least 2 months. The study was approved by the institutional ethics committee and the patients gave their written informed consent to take part. On the day of surgery, blood samples were taken just before administration of the digoxin tablet. This time point corresponded to 24 h after the administration of the last dose of digoxin. Plasma was separated and stored at −20°C and concentrations of digoxin were measured by radioimmunoassay (RIA) with the monobind digoxin equilibrium RIA test system.All the patients had normal sinus rhythm and none had clinical evidence of cardiac failure. Concentrations of blood urea nitrogen, serum creatinine, and serum potassium were within the normal range (mean 0·455 [0·028] mmol/L, 86·63 [5·3] μmol/L, and 3·6 [0·1] mmol/L, respectively). Of the 62 patients, 48 (77%) had plasma concentrations of digoxin below 0·8 ng/mL, which is usually the lower cutoff point of the therapeutic range of digoxin.2Aronson J Digoxin—clinical aspects.in: Richens A Marks V Therapeutic drug monitoring. Churchill Livingstone, London1981: 404-414Google Scholar Even if 0·5 ng/mL is taken to be the lowest cutoff, 36 (58%) of our patients had digoxin concentrations below this value. In our series, all the patients received the same daily dose of digoxin (0·25 mg), and despite this high dose, which is similar to the French practice,1Saunders KB Amerasinghe AKCP Saunders KL Dose of digoxin prescribed in the UK compared with France and the USA.Lancet. 1997; 349: 833-836Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar there was no evidence of drug-related toxicity. Only one patient had a plasma concentration of digoxin slightly above the accepted safe level (2·1 ng/mL). Our findings show that despite adequate dosing, the plasma concentrations of digoxin were below the therapeutic range in most of our patients. Ethnic differences in the pharmacokinetics and response to digoxin deserve further investigation. Saunders and colleagues (March 22, p 833)1Saunders KB Amerasinghe AKCP Saunders KL Dose of digoxin prescribed in the UK compared with France and the USA.Lancet. 1997; 349: 833-836Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar describe international differences in the prescribing patterns of digoxin. At our hospital in Bombay, India, digoxin is available as a 0·25 mg tablet, and all patients with rheumatic valvular heart disease scheduled for cardiac surgery are routinely prescribed one tablet daily. We monitored digoxin concentrations in 62 consecutive patients (23 men, 38 women; mean age 33·2 [SE 1·5] years; weight 45 [1·9] kg), who were admitted to the cardiovascular and thoracic surgery unit for elective surgery. All the patients had received digoxin for at least 2 months. The study was approved by the institutional ethics committee and the patients gave their written informed consent to take part. On the day of surgery, blood samples were taken just before administration of the digoxin tablet. This time point corresponded to 24 h after the administration of the last dose of digoxin. Plasma was separated and stored at −20°C and concentrations of digoxin were measured by radioimmunoassay (RIA) with the monobind digoxin equilibrium RIA test system. All the patients had normal sinus rhythm and none had clinical evidence of cardiac failure. Concentrations of blood urea nitrogen, serum creatinine, and serum potassium were within the normal range (mean 0·455 [0·028] mmol/L, 86·63 [5·3] μmol/L, and 3·6 [0·1] mmol/L, respectively). Of the 62 patients, 48 (77%) had plasma concentrations of digoxin below 0·8 ng/mL, which is usually the lower cutoff point of the therapeutic range of digoxin.2Aronson J Digoxin—clinical aspects.in: Richens A Marks V Therapeutic drug monitoring. Churchill Livingstone, London1981: 404-414Google Scholar Even if 0·5 ng/mL is taken to be the lowest cutoff, 36 (58%) of our patients had digoxin concentrations below this value. In our series, all the patients received the same daily dose of digoxin (0·25 mg), and despite this high dose, which is similar to the French practice,1Saunders KB Amerasinghe AKCP Saunders KL Dose of digoxin prescribed in the UK compared with France and the USA.Lancet. 1997; 349: 833-836Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar there was no evidence of drug-related toxicity. Only one patient had a plasma concentration of digoxin slightly above the accepted safe level (2·1 ng/mL). Our findings show that despite adequate dosing, the plasma concentrations of digoxin were below the therapeutic range in most of our patients. Ethnic differences in the pharmacokinetics and response to digoxin deserve further investigation.