We have no important quarrel with any of Dr Cohen's comments regarding our meta-analysis of clinical trials comparing dipyridamole plus aspirin vs aspirin alone in cerebrovascular disease.
Regarding the issue of new drugs being required to demonstrate their benefits in at least 2 trials, we were simply stating the usual requirement of regulatory authorities that approve new drugs for marketing. Ticlopidine was approved by the Food and Drug Administration based on the results of TASS (ticlopidine vs aspirin) and CATS (Canadian American Ticlopidine Study)1 (ticlopidine vs placebo). Similarly, ESPS-12 and ESPS-2 compared dipyridamole plus aspirin vs aspirin alone and dipyridamole plus aspirin vs placebo, albeit with different formulations of the drugs in the 2 trials. Clopidogel was approved by the Food and Drug Administration based on the very large size of the CAPRIE trial (19,185 patients) and the demonstration of a consistent result in the North American and the European/Australian patients. Thus, we are not "holding the new medication to a different and higher standard than the prior medications." We do not "demand" that ESPS-2 be repeated.
Easton JD, Wilterdink JL. Dipyridamole Plus Aspirin in Cerebrovascular Disease—Reply. Arch Neurol. 2000;57(7):1087. doi: