Cyproheptadine is an orally active serotonin 5-HT2A receptor antagonist with multiple pharmacological properties including antidepressant, anti-serotonin, antiplatelet, and antithrombotic effects. Cyproheptadine is used as a research compound for investigating thromboembolic diseases, serotonergic signaling, and potential links between serotonin modulation and metabolic disorders such as diabetes.

In in vitro experiments, Cyproheptadine (0.01–100 nM, 1 minute) dose-dependently inhibited serotonin-enhanced ADP-induced mouse platelet aggregation [2]; at a concentration of 10 nM, Cyproheptadine suppressed 15 μM serotonin-potentiated 1 μM ADP-induced platelet tyrosine phosphorylation [2]; Cyproheptadine also inhibited activation markers of homo sapiens platelets, including phosphatidylserine (PS) exposure (detected by annexin V), P-selectin (CD62P), and the GPIIb-IIIa complex (assessed via PAC-1 binding) [2].

Cyproheptadine (1 mg/kg, intraperitoneal injection, once daily for 5 consecutive days) significantly prolonged the arterial occlusion time and tail bleeding time in C57BL/6 mice [2].