Enhanced potency of intravenous, but not intrathecal, morphine and morphine-6-glucuronide after burn trauma
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A Langlade1, D B Carr, A Serrie
1Department of Anesthesia, Massachusetts General Hospital, Boston 02114.
Abstract:
We examined the analgesic effect of morphine (M) and its metabolite morphine-6-glucuronide (M6G) in a rat model of acute thermal trauma. M or M6G were given by intrathecal (IT) or intravenous (i.v.) routes after brief burn or sham burn delivered during inhalational anesthesia. In the sham group, M6G was significantly less potent than M when given i.v., yet tended to be more potent than M when given IT. For both drugs, thermal injury increased i.v. potency, yet decreased (for M) or displayed a trend to decrease (for M6G) It potency. The increased potency seen with i.v. but not IT opioid administration may reflect pharmacokinetic (e.g., diminished clearance) and/or pharmacodynamic responses (e.g., activation of peripheral opioid receptors) after thermal injury.
Insights
This study on acute thermal trauma in rats found that morphine and morphine-6-glucuronide potency varied by administration route after injury. Intravenous administration potency increased, while intrathecal potency decreased.
Area of Science:
- Pharmacology
- Pain Management
- Toxicology
Background:
- Opioids like morphine are common analgesics.
- Morphine-6-glucuronide (M6G) is an active metabolite of morphine.
- Understanding opioid efficacy in trauma is crucial for pain management.
Purpose of the Study:
- To compare the analgesic effects of morphine (M) and morphine-6-glucuronide (M6G).
- To investigate the influence of acute thermal trauma on opioid potency.
- To evaluate the impact of different administration routes (intrathecal vs. intravenous) on M and M6G efficacy.
Main Methods:
- Utilized a rat model of acute thermal trauma.
- Administered M or M6G via intrathecal (IT) or intravenous (i.v.) routes.
- Compared drug potency in burned rats versus sham-burned controls.
Main Results:
- In non-injured rats, M6G was less potent than M i.v. but tended to be more potent IT.
- Thermal injury increased i.v. potency for both M and M6G.
- Thermal injury decreased (M) or tended to decrease (M6G) IT potency.
Conclusions:
- Opioid potency is significantly altered by acute thermal trauma.
- Route of administration critically influences M and M6G efficacy post-injury.
- Changes in potency may involve altered pharmacokinetics or peripheral opioid receptor activation.