The run-in period in trial design: a comparison of two non-steroidal anti-inflammatory agents in psoriatic arthropathy.

Psoriatic arthropathy is a relatively uncommon arthritis that exists in a wide variety of clinical forms. These two features of the disease cause problems in the design of clinical trials. In a comparison of two non-steroidal anti-inflammatory agents in this condition we attempted to overcome the difficulties by using a run-in period during which the dosage of one of the trial drugs was adjusted to suit the individual patient. After two weeks on indomethacin (75 mg or 150 mg/day) patients were allocated to four-week periods of indomethacin in the chosen dosage or diclofenac (75 mg or 150 mg/day) in a double-blind randomized crossover trial that used double dummy packaging. Of the 35 patients that entered the study, 19 completed both study groups. No significant differences were observed between the clinical improvements due to both drugs during the course of the study. In general more side-effects were seen during indomethacin treatment, though the study design precluded exact comparison. In a study biased against diclofenac, patient preference was 9/19 for indomethacin, 4/19 for diclofenac and 7/19 expressing no choice. Advantages and disadvantages of the study design are discussed.