Background and Objective: Tolerance and
dependence are two major problems of chronic opioids use. Repeated application
of Lavandula officinalis has been recommended for a long time in Iranian
traditional medicine for some of nervous disorders like epilepsy and dementia.
Since anti-convulsant drugs are beneficial in treatment of morphine dependence
and with regard to anti-convulsant effects of Lavandula officinalis, the
effects of Lavandula officinalis extract (LOE) was studied on
acquisition and expression of morphine tolerance and dependence and it was
compared with methadone. 
Materials and
Methods: Morphine was injected either
acutely(100 mg/kg) or chronically, with gradually increasing doses twice daily
for 7 days, Exept in 8th day in which morphine was administrated in a single
dose (100 mg/kg). In either acutely or chronically with: saline, LOE 200 mg/kg,
LOE 400 mg/kg, methadone 5 mg/kg, methadone + LOE 200, methadone + LOE 400 was administrated 60 min prior
to morphine injection. Morphine tolerance was measured by tail immersion test,
before and after administration of morphine in test day. Morphine dependence
was also evaluated by counting the number of jumps after injection of naloxone
(5mg/kg) in test day. All drugs were given in a volume of 0.3 ml
intraperitoneally.   Results: LOE
and methadone, significantly decreased acquisition (but not expression) of
morphine tolerance and dependence (P < 0.05). Chronic administration of LOE
and (not methadone) reduced physical dependence induced by single dose of
morphine (P < 0.05).   Conclusion: Chronic
administration of Lavandula officinalis better than methadone inhibits
morphine tolerance and dependence in mice.