Quercetin,a bioflavonoid,reverses development of tolerance and dependence to morphine

Quercetin, a bioflavonoid (25 and 50 mg/kg), when chronically administered for 9 days, failed to produce any significant change in tail flick latency as compared to control mice. However, repeated administration of quercetin (25 and 50 mg/kg) for 9 days attenuated the development of tolerance to the analgesic effect of morphine (10 mg/kg). Quercetin (25 and 50 mg/kg) also suppressed naloxone (2 mg/kg)‐precipitated withdrawal jumps on day 10 in morphine‐tolerant mice. Pretreatment of mice with quercetin (10–50, ip) significantly reversed the morphine (5 mg/kg)‐induced delay in gastric transit, whereas a higher dose of quercetin (100 mg/kg) did not have any significant effect on morphine‐induced delay in gastric transit. Quercetin per se had no effect on gastric transit. In conclusion, the results of the present study suggest potential use of quercetin in alleviating the adverse effects of opioid treatment. Drug Dev. Res. 57:167–172, 2002. © 2003 Wiley‐Liss, Inc.