%0 Journal Article
%T Gabapentin Increases Analgesic Effect of Chronic Use of Morphine while Decreases Withdrawal Signs
%A Manzumeh-Shamsi Meimandi
%A Mina-Mobasher
%A GholamReza-Sepehri
%A Ashrafganjooei Narges
%J International Journal of Pharmacology
%D 2005
%I Asian Network for Scientific Information
%X This study was performed to evaluate the role of gabapentin co-administration in morphine antinociception and withdrawal effect. Four groups of male rats were examined for latency time using tail flick test; control, morphine (M), gabapentin (GB) and gabapentin-morphine (GB-M) treated groups. Rats received morphine (10 mg kg < SUP>-1 < /SUP>, s.c.) or gabapentin (75 mg kg < SUP>-1 < /SUP>, i.p.) or both of them twice a day for 9 days. Control rats received normal saline as schedule time. Latency time was recorded 3 times (5 min of interval) before drug injection and in 60, 65 and 70 min after drug injection in days 1, 3, 5, 7 and 9 by tail flick test. Percentage of Maximal Possible Effect (%MPE) as antinociceptive effect was calculated for all groups. On 9th day, rats were challenged for withdrawal signs by administration of naloxone (2 mg kg < SUP>-1 < /SUP>, i.p.). Analysis of variance showed no significant difference of %MPE in control and GB groups while in M and GB-M groups the %MPE was changed significantly during the days of study. Gabapentin had no analgesic effect while morphine and gabapentin-morphine had significant analgesic effect compared to control. %MPE of GB-M treated rats was significantly higher than M in days 5, 7 and 9. Also this study showed that pre-treatment with gabapentin reduced most of the opioid withdrawal signs including jumping, weight loss and fore paw tremor. The mechanism(s) by which gabapentin enhances the analgesic effect of chronic use of morphine and attenuate opioid withdrawal signs remain to be establish.
%U http://docsdrive.com/pdfs/ansinet/ijp/2005/161-166.pdf