Comparison of the Amount of Platelet Inhibition Produced by ASA with 4 Different NSAIDs Using the Platelet Aggregation Assay (PAA)

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Platelet Aggregation Assay and NSAID Detection

Comparison of the Amount of Platelet Inhibition Produced by ASA with Four Different NSAIDs Using the Platelet Aggregation Assay (PAA)

By A. Sami, J. Davis, K. Schwartz, R Miranda and D. Schwarts at the Department of Medicine, Michigan State University in East Lansing Michigan. First presented as an abstract at the American Society of Hematology Meeting, 1999.

Platelet function is inhibited by both aspirin (ASA) and other non-steroidal anti-inflammatory drugs (NSAIDs). The amount of aspirin induced inhibition is measured using a new platelet agonist, Platelet Aggregation Assay (PAA) for platelet aggregometry. The slope of the PAA performed 24 hours following ingestion of a single 325 mg ASA tablet completely separates normal from aspirinated platelets. Using the PAA, the inhibitory effect of a single 325 ASA tablet is measured up to 72 hours after ingestion. Our objective was to use the PAA to quantitate the platelet defect produced by NSAIDs and to compare the amount and duration of NSAIDs induced platelet function inhibition with ASA. We studied the effect of a single standard dose of five different classes of NSAIDs on platelet function.

Drug/Class	(n)	Dose	Aggregation Slope		Time to Recovery
			Pre Sample	2 hours Post
Aspirin (Salicylate)	20	325 mg	80	12	72 hours
Indomethacin (Indole)	4	50 mg	143	58	24 hours
Diclofenac (Phenylacetic Acid)	4	50 mg	79	53	6 hours
Ibuprofen (Propionic Acid)	3	400 mg	89	65	24 hours
Celecoxib (COX-2)	3	200 mg	No effect	No effect	No applicable

We conclude that: 1. PAA detects the platelet inhibitory effects of NSAIDs; 2. Inhibition of PAA platelet function is not produced by the COX-2 inhibitor, celecoxib; 3. The least amount of inhibition of platelet function was observed with diclofenac with return to normal in 6 hours, and; 4. The magnitude of platelet inhibition produced by ASA is much stronger than when compared to the other four NSAIDs.

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