There is no known interaction between prednisone, a corticosteroid, and saw palmetto, a popular over the counter dietary supplement for BPH (benign prostatic hyperplasia) and hair loss.
However, based on the mechanism of action of both, there is a potential for a mild interaction if prednisone is being used long term. Long term use of prednisone is associated with a decrease in endogenous androgens, including testosterone and DHT (dihydrotestosterone). Saw palmetto acts to decrease conversion of testosterone to dihydrotestosterone. So overall, there could be potentially additive effects. However, this interaction has not been documented and would be considered mild, if clinically significant at all.
More Information On Prednisone With Saw Palmetto
Below, we go into a little more depth regarding the potential effects of prednisone and saw palmetto together.
Prednisone, when administered for prolonged periods, can cause hypothalamic-pituitary-adrenal (HPA) suppression. Basically, corticosteroids like prednisone can exert a negative feedback on the pituitary, inhibiting the secretion of adrenocorticotropin (ACTH). This can result in a decrease of endogenous corticosteroids and androgens (including testosterone) by the adrenal cortex, which are mediated by ACTH. In general, prednisone needs to be taken in high doses for extended periods of time for this to happen (>4 weeks of therapy).
Saw palmetto is thought to work like the prescription drug Proscar (finasteride), inhibiting an enzyme known as 5-alpha reductase. This enzyme is responsible for the conversion of testosterone to the more potent DHT (dihydrotestosterone). Elevated levels of DHT are associated with an enlarged prostate and hair loss.
As both saw palmetto and prednisone can cause changes to endogenous (i.e. naturally occurring) hormones, they theoretically can have additive effects. This hasn't been specifically reported in literature and most likely isn't clinically significant however as prednisone needs to be taken for long periods of time and saw palmetto is only a weak inhibitor of 5-alpha reductase.