Interaction of phenylbutazone and tolbutamide in man.

: Phenylbutazone pretreatment increases tolbutamide half-life, whereas tolbutamide pretreatment decreases phenylbutazone half-life in man. Clinically, phenylbutazone may enhance the hypoglycemic action of tolbutamide, and tolbutamide may reduce the therapeutic effect of phenylbutazone.