Failure of diphenhydramine hydrochloride to prevent thrombosis at sites of endarterectomy in dogs.

Our previous work has shown that the addition of diphenhydramine hydrochloride to platelet-rich plasma is capable of causing disaggregation of platelet aggregates already induced by adenosine diphosphate as well as of inhibiting platelet aggregation when added prior to the aggregating agent. This led us to attempt to prevent arterial thrombosis in a canine experimental model. Ten dogs received an injection of diphenhydramine (approximately 3 mg/kg of body-weight) into the right common femoral artery 1 cm proximal to the proximal end of a 2 cm endarterectomy immediately after closure of the endarterectomy site and prior to performing an endarterectomy of the other common femoral and both common carotid arteries. The dogs which received diphenhydramine were compared with ten control dogs and found to have no protection against thrombosis at the sites of endarterectomy after 4 and 24 hours.