Background: Development of tolerance to analgesic effect, on chronic administration of morphine, limits its clinical usefulness in pain management. S-adenosyl methionine (SAM) used for arthritis and approved as a supplement in many countries including United States was evaluated for reducing morphine tolerance.
Methods: Male 'Wistar' rats were used. The analgesic activity was determined using tail flick analgesiometer (Columbus Instruments, USA). Rats given morphine (7mg/kg), intraperitoneally (i.p.), once daily for 5days developed tolerance to analgesic effect. To evaluate the effect of SAM on morphine tolerance, SAM 800mg/kg was administered orally (p.o.), 45min prior to each dose of morphine. The analgesic activity of SAM and opioidergic component in its activity was also evaluated.
Results: Co-administration of morphine and SAM reversed morphine tolerance. SAM exhibited analgesic effect after repeated administration which was reversed by naloxone administration.
Conclusion: Since safety of SAM on chronic use is documented it can be a good option in morphine tolerance. Role in drug addiction and withdrawal should also be evaluated.
Keywords: Morphine; Pain; S-adenosylmethionine (SAM); Tail flick latency; Tolerance.
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