Pharmacologic and clinical control of antiarrhythmic drugs

Quantitation of lidocaine and its deethylated metabolites in plasma and urine by gas chromatography-mass fragmentography

A sensitive, precise and accurate method for simultaneous quantitation of lidocaine and its deethylated metabolites by gas chromatography-mass fragmentography has been developed. Propyl derivatives of the deethylated metabolites are formed directly in either plasma or urine by treatment with propionaldehyde and sodium cyanoborohydride. The propyl derivatives and unchanged lidocaine are extracted, separated by gas chromatography and quantitated by mass fragmentography using mepivacaine as the internal standard. Quantitation of these compounds to levels as low as 50 ng/ml body fluid has been achieved with coefficients of variation less than 10%.

Correlation between serum concentration and pharmacological effect on atrioventricular conduction time of the antiarrhythmic drug propafenone

Seven patients with cardiac dysrhythmias received a single, oral, therapeutically effective dose of the antiarrhythmic drug propafenone. The serum levels correlated well with changes in atrioventricular conduction times during the postabsorptive elimination phase (r = 0.8610, p less than 0.001). The mean half-lives of the serum level and the electrocardiographic effect (PQ-time) were 3.6 +/- .2 h and 3.8 +/- 0.6 h, respectively.

Adverse reactions to procainamide

1 Data from a comprehensive drug surveillance programme are analysed to provide details of procainamide use and toxicity in medical wards of teaching hospitals in five countries. 2 Out of a total of 488 recipients 9.2% had one or more adverse effect attributed to the drug; common effects being arrhythmias, gastro-intestinal upsets and drug fever. Although occasionally of major severity, no patient died as a consequence of procainamide toxicity. 3 Toxicity was directly related to total daily dose and duration of hospitalization but was not related to age, weight of the patient or presenting urea or albumin concentrations.

Clinical efficacy and pharmacokinetics of a new orally effective antiarrhythmic, tocainide

Tocainide, a new oral antiarrhythmic agent, was studied in man in a short-term protocol designed to evaluate the efficacy, kinetics, and toxicity of this compound. Premature ventricular contractions (PVCs) were suppressed by less than 70% in 11 of 15 patients compared with pre-drug placebo controls. For these 11 responders, there was an average PVC reduction of 91% +/- 10 (range 70 to 100%) at tocainide doses not associated with side effects. Mild transient central nervous system toxicity was observed in some patients near the time of peak concentrations during the highest dose administered. The drug was found to have linear kinetics over the dose range studied and a plasma half-life of 13.5 +/- 2 hours. Plasma concentration-response curves indicate antiarrhythmic activity over all plasma concentrations, with 70% PVC reduction above 6.0 mug/ml. This study suggests that tocainide is a safe and effective antiarrhythmic agent during short-term administration and is worthy of further clinical trials.