[Analgesic effect and clinical tolerability of the combination of paracetamol 500 mg and caffeine 50 mg versus paracetamol 400 mg and dextropropoxyphene 30 mg in back pain].

OBJECTIVES: A double-blind randomized multicentric study was performed to test the hypothesis that the analgesic effect of paracetamol-cafeine is equivalent to that of paracetamol-dextropropoxyphen in patients suffering from pain due to osteoarthritis of the spine.

METHODS: Rhumatologists included 124 patients who were randomized into two groups of 62 each. Pain was measured daily during the seven-day treatment Huskisson's Analog Visual Scales; 112 were per protocol and evaluable.

RESULTS: The two treatment groups were statistically similar for demographics, vital signs, medical and treatment history. A majority of them had pain located at the lumbar spine only; the other patients had either pain at the cervical or dorsal spine or at several sites. At the end of the week there was a major reduction in pain level: 51.2% in patients given paracetamol-cafeine and 47.0% in those given paracetamol-dextropropoxyphen. The main criteria of efficacy--the percentage of success (decrease of pain > 50%)--was similar in the two groups as well in the intention-to-treat population (p = 0.01) as the per protocol population (p = 0.028). Kinetics of pain decrease during the first day of treatment were assessed with an hourly evaluation during the six first hours and at the 12th hour. There was no difference between the two groups. There was no serious adverse event and the frequency and intensity of the adverse events were similar in the two groups.

CONCLUSION: The potentializing action of cafeine on paracetamol-induced pain relief enables a degree of pain relief equivalent to that of a combination using an analgesic with a peripheral action, paracetamol, and another with a central action, dextropoxyphen. The fact that the paracetamol-cafeine combination does not have a central action avoids secondary effects induced by central analgesics (drowsiness, constipation) in patients with osteoarthritis back pain.