title: Effects of methaqualone on blood platelet function.
abstract: To study the mechanism whereby toxic doses of methaqualone cause a bleeding tendency in humans, the effects of methaqualone, diphenhydramine, and the combination of methaqualone plus diphenhydramine on blood platelet function were investigated. Exposure of human platelets in platelet-rich plasma in vitro to final concentrations of methaqualone ranging from 1.1 to 4.5 X 10(-4)) M resulted in nearly complete inhibition of the secondary phase and significant inhibition of the primary phase of adenosine diphosphate (ADP)--induced aggregation. Both the slope and height of collagen-induced aggregation responses were reduced significantly in vitro by the drug. When methaqualone final concentrations of 1.1, 2.3, and 4.5 X 10(-4) M were studied in the presence of diphenhydramine (1.1, 2.3, and 4.5 X 10(-5) M, respectively), the degree of inhibition of ADP-induced aggregation was only slightly greater (not significant) than that observed with methaqualone. The platelets of rabbits injected intravenously with methaqualone, 10 mg/kg, demonstrated a significantly decreased ability to aggregate with ADP and collagen 30 and 60 min after administration of the drug. These results suggest that a drug-induced defect of blood platelet function may play a role in the bleeding associated with methaqualone toxicity.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D000818:Animals; D003094:Collagen / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D004338:Drug Combinations; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008702:Methaqualone / Q000097:blood / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits
chemical_list: D004338:Drug Combinations; D000244:Adenosine Diphosphate; D008702:Methaqualone; D004155:Diphenhydramine; D003094:Collagen