Effects of enzyme induction on metabolism of prednisolone. Clinical and laboratory study.

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.