[Kinetics of digitoxin during antirheumatic therapy with azapropazone (author's transl)]

The effect of chronic therapy with 5-dimethylamino-9-methylamino-9-methyl-2-propyl-1H-pyrazolo[1,2-a] [1,2,4] benzotriazine-1,3-(2H)-dione-dihydrate (azapropazone-dihydrate; Prolixan 300) on the elimination of a single i.v. dose of digitoxin was studied in 8 patients with rheumatoid arthritis and osteoarthritis using a crossover design. 0.5 mg digitoxin were injected i.v. alone and together with a chronic oral therapy of azapropazone starting 3 weeks before digitoxin was given. Digitoxin plasma levels were determined by radioimmunoassay over a period of 19 days. The half-life for plasma digitoxin was 6.4 +/- 0.5 days after digitoxin alone and 7.0 +/- 0.6 days during azapropazone treatment. In two patients the half-life of digitoxin was increased by about one-third during azapropazone therapy. The areas under the plasma digitoxin curve were 2592 +/- 262 ng/ml X h and 2615 +/- 273 ng/ml X h, respectively. None of the differences were statistically significant. It was concluded that there was no clinically significant interaction between azapropazone and a single dose of digitoxin.