Highlights 
• There should be no debate about the need for new analgesic medications.
• Some studies reported that psychostimulant drugs could increase opioid-induced analgesia.
• We tested the analgesic effects of methamphetamine (Meth), Buprenorphine (BUP), and their coadministration in rats.
• The combination of Meth and BUP increased reaction time more than these two alone.
• Meth increases the analgesic effects of BUP.

Plain Language Summary 
There is no doubt about providing access to pain medications for those with a serious illness such as cancer, especially in a palliative care stage. Millions of people still lack access to drugs such as morphine, and millions more have access to ineffective drugs and continue to suffer from poorly-controlled symptoms. Additionally, because of some adverse effects of opioid medications, such as respiratory depression, especially in higher doses, we aimed to explore ways for increasing the analgesic effects of opiate medications without an increase in those adverse effects. Buprenorphine is approved as an opioid analgesic (painkiller) for various types of pain. In this study, we tested the analgesic effects of methamphetamine, buprenorphine, and their coadministration in rats to find new medications and compounds for effective controlling of pain in end-stage patients. We proved that methamphetamine decreases pain sensation in rats. Also, methamphetamine increases the analgesic effects of buprenorphine, and this combination can be used for more analgesic effects. Furthermore, our study results implicate that psycho-stimulant drugs, such as methamphetamine are good candidates for enhancing the analgesic effects of opioid medications.