PDE3A and cardiac arrhythmia: Notably, inhibition PDE3A’s PDE activity results in side effects like headache, diarrhea, unusual weakness/fatigue, hair loss, nausea, dizziness, and cardiac dysrhythmias, as well as affecting oocytes maturation, decreasing platelet formation, and increasing the risk of sudden death in patients with cardiac diseases; these side effects have greatly limited drug development efforts for targeting PDE336.