Cardioactive bipyridines: Inamrinone, Milrinone
All PDE inhibitors are arrhythmogenic. Milirnone is more potent and has fewer side effects.
Mechanism:
They inhibit PDE enzyme (type 3) → ↑ cAMP → ↑ Ca2+ influx in myocardial cells → ↑ myocardial contractility.
They have VD properties → reduction of PR with no effect on HR.
Uses:
they are used in acute HF when other drugs fail.
Side effects:
- Thrombocytopenia.
- Cardiac arrhythmia.
- Hepatotoxicity.