Does high hepatic bioavailability enhance the effect of oral compared to subcutaneous glucocorticoids?

Glucocorticoids (GC) are important in the treatment of autoinflammatory disorders. Oral prednisolone ≤5 mg/day can be effective, but such doses are at or even below physiological daily endogenous GC production. We hypothesised that their immunosuppressive effect might be explained by high hepatic bioavailability of oral GC, exposing the liver to supraphysiological GC via the portal circulation. We tested this by comparing the effect of oral versus subcutaneous low-dose prednisolone, on erythrocyte sedimentation rate (ESR).

Patients with rheumatoid arthritis or psoriatic arthritis, elevated ESR (≥30 mm/h) and no current or recent GC therapy were eligible. In a pilot study (n=5), 5 mg/day oral prednisolone decreased ESR significantly, suggesting a sample size of 10 patients for a randomised, non-blinded crossover trial. Patients received 5 mg/day prednisolone for 2 periods of 4 days: one treatment period orally and one subcutaneously with a 10-day washout period between treatments. ESR was measured before (day 1 and 15) and after (day 5 and 19) each treatment course.

10 patients were included. ESR decreased after both oral and subcutaneous prednisolone, by -5.6 (20.9) and -5.8 (3.0) mm/h, respectively (p=0.98). The treatment order had no effect on the outcome.

. Short-term oral low-dose GC therapy is not more effective than parental GC in decreasing ESR, arguing against therapeutic high hepatic bioavailability effects. More likely, systemic concentration peaks following administration explain why oral physiological steroid doses are clinically effective.