Premarketing clinical trials

At one end of the spectrum, the event may be a simple dosage problem which could be an error on the part of the prescriber or an unanticipated hypersensitivity for that particular patient. At the other end of the spectrum, is an uncommon, serious adverse reaction not revealed in premarketing clinical trials. Somewhere between those two extremes are more or less serious adverse events which are not entirely unexpected but appear to be more common than is accepted for comparable products in the same therapeutic category. This maybe a real increase in frequency or may be due to patient selection bias. The later has arisen with new products which claim a lower incidence of certain adverse reactions which encourages doctors to precribe them preferentially for patients who have suffered such reactions with older products. 

The FDA s June 1995 publication A MedWatch Continuing Education Article replicated the poster and made the following points in a section called Limitations of Premarketing Clinical Trials ... 

In addition to the larger numbers of patients involved and the longer treatment periods, the postmarketing SRS has a number of advantages over the premarketing clinical trials. 

Successful postmarket data collection, like premarket clinical trials, relies on physicians and patients to follow prescribed social norms. Each of the institutions described here tried to structure the doctor-patient relationship to produce objective and interpretable reports about drugs outside of the controlled clinical setting. In both countries, government authorities and the medical profession expected patients to recognize adverse reactions, assist physicians in reporting them to central authorities, and then continue to take other prescription drugs. However difficult it may be to discipline patients to report adverse reactions, physicians too must be trained to complete and submit forms. A standardized product requires a standardized producer. Authorities... 

Even more troubling would be underreporting of ADRs observed during premarketing clinical trials. During these studies it is vital to report all likely ADRs... 

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