Brooks P M, Buchanan W W, Grove M, Downie W W
Ann Rheum Dis. 1976 Aug;35(4):339-43. doi: 10.1136/ard.35.4.339.
The addition of phenobarbitone in therapeutic dosage to the drug regimen of prednisolone-treated subjects with rheumatoid arthritis produced measurable deterioration in the clinical status of the patients associated with a more rapid clearance of prednisolone from plasma. It is considered that phenobarbitone induced the hepatic metabolism of prednisolone, effectively reducing the steady state plasma level and resulting in clinical relapse. A slight but significant improvement in the adrenocortical response to tetracosactrin (Synacthen) was noted after phenobarbitone therapy.