The effect of antihistamines on stimulated blood platelet functions

: The histamine receptor H1-antagonists of cationic amphiphilic drug (CAD) structure BromadrylR (BRO) and DithiadenR (DIT) were investigated on stimulated functions of blood platelets in vitro. Both drugs dose-dependently decreased platelet aggregation. BRO significantly decreased aggregation in concentrations of 20 and 200 mumol/l in thrombin and ADP stimulated platelets, respectively. DIT was 10 times less active as compared with BRO. A dose-dependent inhibitory effect of BRO and DIT was demonstrated on thrombin stimulated production of malondialdehyde (MDA) and thromboxane (TXB2) generation in platelets. A significant decrease in MDA production and TXB2 generation was measured with BRO and DIT in 10 mumol/l concentration. Results showed that the antihistaminic drugs BRO and DIT inhibited stimulated aggregation in relation to membrane phospholipid peroxidation and arachidonic cascade activation in platelets. These data, along with results from studies on the effect of other CAD on platelets, revealed that antihistaminic drugs interfere with stimulated aggregation by inhibiting phospholipase A2 rather than the intraplatelet histamine receptor.