Phenylbutazone: a clinico-pharmacological study in rheumatoid arthritis

A clinical trial of phenylbutazone in high dose (300 mg daily) and low dose (50 mg daily) is presented. 2. By analysis of the data by different methods, significant differences in clinical efficacy were shown between the two therapeutic regimes. 3. A relationship between the clinical effect and plasma level of phenylbutazone was demonstrated. 4. Some problems in the interpretation of plasma level-clinical effect correlates are discussed.