Alpha- but not beta-receptor blocking agents inhibit the antiarrhythmic effect of iloprost on ouabain-induced arrhythmia in guinea-pigs.

The effects of iloprost, prazosin and propranolol were tested on ouabain-induced arrhythmia in guinea-pigs. Each drug used alone showed an antiarrhythmic effect. In a second step, iloprost was given in combination with drugs blocking alpha- and beta-adrenergic receptors. Propranolol and iloprost caused a statistically significant and comparable increase of the threshold dose of ouabain for the onset of arrhythmia (OA), the occurrence of premature ventricular beats (PVB), ventricular flutter (VF) and ventricular fibrillation (FIB). The effect of a combination of iloprost and propranolol was comparable to the effect of each drug administered alone. Prazosin enhanced the threshold dose of ouabain for OA and PVB in a statistically significant manner. The effect of a combination of iloprost and prazosin was nearly the same for OA and PVB compared to the single effect of these drugs. The threshold dose of ouabain was decreased for VF and FIB when a combination of iloprost and prazosin was given, compared to iloprost used alone. These results support the assumption that the adrenergic nervous system is involved in the antiarrhythmic effect of iloprost.