Psychomotor performance of patients with rheumatoid arthritis: cross-over comparison of dextropropoxyphene, dextropropoxyphene plus amitriptyline, indomethacin, and placebo.

Actions on performance of dextropropoxyphene (DXP) alone and in combination with amitriptyline (AMI), indomethacin (IN), and placebo were compared in 15 patients with rheumatoid arthritis. The patients were on their prescribed maintenance regimen excluding analgesics. In four randomized test sessions at two-week intervals, they received double blind and crossover single oral doses of DXP 130 mg, IN 50 mg, DXP 65 mg + AMI 25 mg or placebo, each after two days' pretreatment with the same drug. Objective and subjective effects were measured at baseline and 2 and 4 hours after drug administration. DXP impaired critical flicker discrimination, symbol copying and body balance without modifying tracking, choice reactions or attention. It rendered the subjects elated, muzzy, mentally slow and calm. Actions of AMI + DXP were about the same. IN impaired body balance and critical flicker recognition. Plasma concentrations of DXP were moderate to high whilst those of IN and AMI were fairly low. We conclude that therapeutic doses of DXP and IN are relatively safe in regard to driving skills. Small doses of AMI may not enhance the mild psychomotor effects of DXP. Earlier single dose studies carried out with healthy volunteers might have overestimated the decremental effects of analgesics on psychomotor performance.