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Pharmacodynamics of Procainamide in Patients With Ventricular Tachyarrhythmias
Author(s) -
Liem L. Bing,
Yee Y. Gail,
Swerdlow Charles D.,
Kates Robert E.
Publication year - 1988
Publication title -
the journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 116
eISSN - 1552-4604
pISSN - 0091-2700
DOI - 10.1002/j.1552-4604.1988.tb03118.x
Subject(s) - procainamide , pharmacodynamics , qrs complex , plasma concentration , washout , anesthesia , pharmacokinetics , medicine , linear regression , cardiology , chemistry , mathematics , statistics
The onset and offset of the electropharmacologic effect of procainamide was studied in nine patients with ventricular arrhythmias. Procainamide was given at a constant infusion rate of 0.27 ± 0.05 mg/kg/min for 50 to 60 minutes to an average total dose of 15.5 ± 4.4 mg/kg. The QRS interval (used as an index of electropharmacologic effect) at a paced cycle length of 500 ms, and the plasma procainamide concentration were measured simultaneously every 5 minutes during infusion and at frequent intervals for up to 4 hours during a washout period. The average peak plasma concentration was 15.8 ± 9.6 μg/ml and the average maximum QRS interval prolongation was 23.9 ± 6.8% from baseline. The temporal and static plasma concentration‐effect relationships were evaluated by pharmacodynamic modeling and linear regression. For six patients, there was a minimal (<2 minutes) delay in the plasma concentration‐effect relationship, and the data fit a linear relationship with an average slope of 3.2 ± 1.1 msec/μg/ml. For the other three patients, there was a significant delay (3, 10, and 18 minutes respectively) in the plasma concentration‐ejfect relationship. In most patients, the electropharmacologic effect of procainamide is rapid and proportional to plasma concentration; but in a minority of patients, significant delay occurs and could influence the results and interpretation of electropharmacologic studies.