Metyrapone transiently blocks glucocorticoid production in the adrenal cortex. The 118G allele blunted the ACTH response to metyrapone in healthy subjects (Ducat et al. 2011). 118G carriers in buprenorphine maintenance treatment showed even greater attenuated response to metyrapone compared to 118A carriers, indicating more potent HPA axis suppression by buprenorphine in 118G carriers (Kakko et al. 2008).
