d-Methadone blocks morphine tolerance and N-methyl-D-aspartate-induced hyperalgesia.

Pharmacology of methadone and its isomers.

UNLABELLED Methadone is a synthetic opioid analgesic that is used as an alternate to morphine and hydromorphone for patients with severe pain. It is increasingly being used in opioid rotation schedules. Methadone has an asymmetric carbon atom resulting in 2 enantiomeric forms, the d and l isomers. The racemic mixture (dl-methadone) is the form commonly used clinically. Recent studies have revea...

Author's response to reviews Title:Melatonin prevents morphine-induced hyperalgesia and tolerance in rats: role of protein kinase C and N-methyl-D-aspartate receptors Authors:

NMDA RECEPTOR ANTAGONISTS ATTENUATE TOLERANCE INDUCED BY MORPHINE AND NERVE LIGATION IN MICE

The effect of NMDA (N-methyl-D-aspartate) receptor antagonists on tolerance to morphine antinociception was investigated in mice. Daily subcutaneous administration of 50 mg/kg of morphine hydrochloride for three days induced tolerance to different (3,6 and 9 mg/kg) test doses of morphine. The tolerance obtained was decreased by pretreatment of animals with single or repeated doses of compe...

Melatonin prevents morphine-induced hyperalgesia and tolerance in rats: role of protein kinase C and N-methyl-D-aspartate receptors

BACKGROUND Morphine-induced hyperalgesia and tolerance significantly limits its clinical use in relieving acute and chronic pain. Melatonin, a pineal gland neurohormone, has been shown to participate in certain neuropsychopharmacological actions. The present study investigated the effect of melatonin on morphine-induced hyperalgesia and tolerance and possible involvement of protein kinase C (PK...

Repetitive opioid abstinence causes progressive hyperalgesia sensitive to N-methyl-D-aspartate receptor blockade in the rat.

The opioid abstinence syndrome is associated with spinal excitatory amino acid (EAA) release, hyperalgesia and long-term changes in dorsal horn cellular excitability. N-Methyl-D-aspartate (NMDA) receptor antagonism attenuates opioid tolerance but also blocks EAA release during abstinence. This study examines the effect of repetitive abstinence, and NMDA receptor antagonism during abstinence, on...