Plasma, heart, and extracardiac tissue verapamil concentrations were measured after sustained intravenous infusions in 11 dogs to determine the differential tissue accumulation of verapamil. A steady state verapamil concentration of 327 ± 50 ng/ml decreased the mean arterial blood pressure from 104 ± 9 to 90 ± 6 mm Hg (p = 0.08) and the P-R interval increased from 118 ± 4 to 176 ± 13 ms (p < 0.001) with second-degree atrioventricular block developing in 6 animals. Verapamil accumulated in organs in the following order: Lung >> kidney > spleen > ventricular myocardium = liver > atrial myocardium > cerebral cortex > fat = skeletal muscle. Levels in the ventricular free wall were consistently greater than atrial levels, but no difference was observed between left versus right-sided cardiac chambers. In summary, affinity of different organs for verapamil is highly variable and organ-specific; furthermore, differential intracardiac chamber accumulation occurs.
- Cardiac verapamil concentrations
- Tissue concentrations
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