Finasteride, a 5α-Reductase Inhibitor, Potentiates Antinociceptive Effects of Morphine, Prevents the Development of Morphine Tolerance and Attenuates Abstinence Behavior in the Rat
 May 2007   
in “
 Hormones and Behavior 
”
 
     
   TLDR  Finasteride boosts morphine's pain relief, stops tolerance, and reduces withdrawal in rats.   
  The study found that finasteride, a 5α-reductase inhibitor, enhanced the pain-relieving effects of morphine, prevented the development of tolerance to morphine, and reduced withdrawal symptoms in rats. This suggests its potential use in pain management and as a treatment for opioid addiction.