Pharmacology procainamide

Pharmacology Procainamide, a class lA antiarrhythmic, increases the effective refractory period of the atria, and to a lesser extent the bundle of His-Purkinje system and ventricles of the heart. 

These changes substantially alter the pharmacological properties of procainamide however, flecainide maintains local anesthetic properties. 

Concurrent administration of propafenone with digoxin, warfarin, propranolol, or metoprolol increases the serum concentrations of the latter four drugs. Cimetidine slightly increases the propafenone serum concentrations. Additive pharmacological effects can occur when lidocaine, procainamide, and quinidine are combined with propafenone. 

You are asked to treat a 55-year-old patient for continuing ventricular arrhythmias. The patient is receiving timolol drops for glaucoma, daily insulin injections for diabetes melUtus, and an ACE inhibitor for hypertension. You decide to use phenytoin instead of procainamide because of what pharmacological effect of procainamide ... 

Disposition in the Body. Readily absorbed after oral administration and widely distributed throughout the body bioavailability 75 to 95%. The major metabolite, V-acetylprocainamide (ace-cainide), has similar pharmacological activity to procainamide the acetylation of procainamide is subject to genetic polymorphism. Up to about 80% of a dose is excreted in the urine of normal subjects in 24 hours, about 50 to 60% as unchanged drug and up to about 30% as V-acetylprocainamide (less in slow acetylators). Other metabolites include monodesethylprocainamide and monodesethyl-V-acetylprocainamide. 

For refractory cases consider additional pharmacological agents aminodarone. lidocaine, procainamide or sotalol ... 

Somogyi, A., McLean, A. Heinzow, B. (1983) Cimetidine-procainamide pharmacokinetic interaction in man evidence of competition for tubular secretion of basic drugs. European Journal of Clinical Pharmacology, 25, 339-345. 

Papich, M.G., Davis, L.E. Davis, C.A. (1986) Procainamide in the dog anti-arrhythmic plasma concentrations after intravenous administration. Journal of Veterinary Pharmacology and Therapeutics, 9, 359-369. 

The biotransformation of drugs may produce metabolites that are pharmacologically active. In such instances, the metabolite should also be measured because it is contributing to the effect of the drug on the patient. Primidone and procainamide are examples of such drugs. If the metabolite is inactive, it need not be measured, but steps should be taken to ensure that it does not interfere in the analytical process. 

Pharmacological Effects Procainamide is a blocker of open Na channels with an intermediate time constant of recovery from block. It also prolongs cardiac action potentials, probably by... 

Conjugates are usually pharmacologically inactive they are more hydrophilic than the parent compounds and are easily excreted by the kidneys or the bile. Some conjugates, e.g. morphine-6-glucuronide and acetyl procainamide, are pharmacologically active. 

Please note that it is the free acid or free base of a therapeutic agent that provides the pharmacological effect. For instance, when procainamide hydrochloride is administered to a patient, it is procainamide (free base) that is responsible for its pharmacological effect and not the hydrochloride part of the molecule. The pharmacokinetic parameters reported in the literature are obtained by measuring the free acid or base of a particular drug. 

A) The pharmacological properties of the drug (hydralazine, diphenylhydantoin, procainamide, isonicotinic acid hydrazine and possibly sulphonamides)... 

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