Steady-state plasma levels of salicylate in patients with rheumatoid arthritis: effects of dosing interval and tablet strength.

Forty patients who were admitted to hospital with rheumatoid arthritis received a total of 3.9 g/d of enteric-coated acetylsalicylic acid (ASA) (Entrophen) according to one of four dosing schedules: group 1 (n = 13), three 325-mg tablets four times daily; group 2 (n = 11), two 650-mg tablets three times daily; group 3 (n = 10), three 650-mg tablets twice daily; and group 4 (n = 6), two 975-mg tablets twice daily. Five to seven days after the start of therapy, when steady-state plasma salicylate levels had been achieved, 10 blood samples, 1 per hour, were collected. Three healthy volunteers who received plain ASA formed a control group. There was little fluctuation in the salicylate levels over the sampling period, regardless of the dosing interval, and no significant difference in the fluctuations between the five groups. Likewise, there was no significant difference in the mean salicylate levels at each sampling time, regardless of the dosing interval or tablet strength. These results suggest that different tablet strengths of enteric-coated ASA and different dosing intervals produce comparable plasma salicylate levels. Less frequent dosing may improve patient acceptance of salicylate therapy in the treatment of arthritis.