The respiratory depressant effects of mitragynine are limited by its conversion to 7-OH mitragynine.

Both the anti-nociceptive effects and the respiratory depressant effects of mitragynine are partly due to its metabolic conversion to 7-OH mitragynine. The limiting rate of conversion of mitragynine into its active metabolite results in a built-in ceiling effect of the mitragynine-induced respiratory depression. These data suggest that such 'metabolic saturation' at high doses may underlie the improved safety profile of mitragynine as an opioid analgesic.