The physical dependence liabilities of oxybutynin and morphine in rats

The anticholinergic/antispasmodic agent oxybutynin does not induce physical dependence in rats when administered by oral gavage twice daily for 40 days; nor did challenge with naloxone precipitate withdrawal signs in these (oxybutynin-treated) animals. In contrast, morphine treatment resulted in a high degree of physical dependence as evidenced by the withdrawal signs noted after treatment was halted. Challenge with naloxone also induced severe withdrawal signs in morphine-treated rats. Withdrawal signs characterised by squealing, teeth chattering and "wet-dog" shakes were seen in one from five morphine-treated rats challenged with oxybutynin.