Some problems in the interpretation of clinical trials: longterm parallel study of fenoprofen in rheumatoid arthritis.

Fenoprofen calcium was compared with acetylsalicylic acid in the treatment of 27 patients with definite or classic rheumatoid arthritis, over a period of one year. Both drugs appeared efficacious, with a slight edge to fenoprofen in the doses employed. Fewer side effects were noted with fenoprofen. Effectiveness continued undiminished throughout the year, and mean values of most parameters continued to improve in both groups over the entire period. Three problems which influence extrapolation of results from this and similar studies to the general setting are discussed. (1) Individual patients show great variation from the mean and from one observation point to another. Thus, expectations developed from mean values will seldom be accurate in a particular patient. (2) The relative doses chosen for two drugs in the clinical trial can profoundly influence both efficacy and toxicity. The qualification "at the doses employed" is seldom emphasized in clinical reports. (3) Patient compliance in the general clinical setting is importantly different from that in a clinical trial, and this potential problem must be assessed by the physician choosing an appropriate medication for a particular patient.