An investigation to determine the comparative value of pain-relieving drugs conducted on 94 private patients who had undergone orthopedic surgery was started 48 hours postoperatively and continued for three days. Four substances were used: dextro propoxyphene hydrochloride, 1 00 mg.; codeine phosphate, 65 mg.; meperidine hydrochloride, 100 mg.; and placebo. Capsules were administered at four-hour intervals. Intensity of pain was scored and interrogation of patients was done by a physician. The drugs were found to be significantly more pain-relieving than was the placebo. The analgesic effectiveness of the drugs in the doses used was indistinguishable. The over-all analgesic effectiveness of drugs and placebo- was similar to that found by other workers. A separate study on placebo effect showed that the patients discriminated more accurately between analgesics and placebos on the first day of study than on subsequent days.
Van Bergen WS, North WC, Karp M. EFFECT OF DEXTRO PROPOXYPHENE, MEPERIDINE, AND CODEINE ON POSTOPERATIVE PAIN. JAMA. 1960;172(13):1372-1375. doi:10.1001/jama.1960.03020130030008