Treatment with digoxin and measurement of serum digoxin levels after myocardial infarction.

Forty-nine patients admitted to a Coronary Care Unit with myocardial infarction complicated by left ventricular failure, were treated with 1.75 mg Lanoxin over 36 hours. Serum digoxin levels were measured by radioimmunoassay at 8, 24, and 48 hours. No difference in serum levels was observed between those patients who received 'old' (reduced bioavailability) and those who received 'new' Lanoxin. Serum levels were significantly higher at 8 and 24 hours in those patients who received their first dose intramuscularly compared with those who received their first dose orally, irrespective of the bioavailability of the oral preparation used. No correlation was observed between serum digoxin levels and serum urea or creatinine during the 48-hour period of study. The incidence of arrhythmias is reported, but no conclusion can be drawn as to whether or not the glycoside contributed to this in any way. The use of digoxin in patients with acute myocardial infarction complicated by left ventricular failure is justifiable in the light of available evidence. However, in view of the possible predisposition of such patients to toxicity, lower serum levels than were achieved in many of our patients seem desirable and a modified dosage schedule is suggested.