Distribution of lidocaine and digoxin in heart tissues and aorta following intrapericardial administration

The distribution of lidocaine and digoxin in myocardial and aorta tissues of open chest anesthetized dogs was studied, following the administration of 30 ml phosphate buffer solution of the drugs in the pericardial cavity where it was kept for increasing time intervals. Transfer of lidocaine (15 or 30 mg) from the solution to myocardium was almost complete within 60 min, while only 50% of digoxin (2 or 50 micrograms) was removed, and this occurred during the first 30 min. Accordingly, the absorption rate of lidocaine by heart tissues increased with time up to 60 min while that of digoxin decreased with time. Absorption of digoxin by the atria and absorption of both drugs by intrapericardial aorta were higher than that of other heart tissues, between 20 and 60 min. At 30 and 60 min, lidocaine was evenly distributed across the LV wall while digoxin 50 micrograms was mainly concentrated subepicardially. On the contrary, i.v. administration of digoxin resulted in even distribution in the LV wall without preferential concentration in the atria. The uptake of both drugs by aorta was several times lower compared to heart tissues after i.v. administration. Drug concentrations in LV wall almost at therapeutic level, were derived from solution of low concentration of the drug in the pericardial cavity. It is concluded that intrapericardial administration of the drugs may be used when increased concentration of them is desired in specific areas of the heart and the aorta.