Factors influencing procainamide total body clearance in the immediate postmyocardial infarction period.
Fifteen acute myocardial infarction patients (only one of whom had evidence of significant renal dysfunction) received a constant-rate intravenous infusion of procainamide at one rate for a least 24 hours. Steady-state plasma levels achieved during these infusions were used to calculate total body clearance (C/B). Linear regression analysis of C/B versus a variety of clinical and laboratory patient characteristics yielded only body weight (or parameters derived from it) as a significant covariant (r = 0.713, P less than or equal to 0.005). Interestingly, the data from these 15 patients suggest that the presence of a significant degree of heart failure at the start of therapy did not result in a significant decrease in C/B (C/B = 5.9 ml/min/kg when class 0-I failure was present at the start of therapy and C/B = 5.5 ml/min/kg when class III-IV failure was present). If the data from five other patients who were studied previously are added to the group reported here, the conclusions reached would be the same. These data suggest that in patients with good renal and hepatic function, initial procainamide infusion rate could be selected on the basis of body weight and need not consider the initial presence of moderate heart failure. However, intense clinical monitoring for signs of impeding serious toxicity is strongly recommended since the observed regression line did not predict total body clearance accurately in 10-15 per cent of the patients studied.