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Sustained-release morphine for epidural analgesia in rats
1DepoTech Corporation, San Diego, California 92121, USA. taehee_kim@depotech.com
Background:
Epidural opioid analgesia often requires either continuous infusion or repeated injections, which are inconvenient for patients, increase risk of infection, and consume expensive physician and nursing time. In addition, potential respiratory depression is a major safety concern. The authors studied whether a single dose of epidurally administered, sustained-release morphine could prolong analgesia and reduce toxic effects in rats.
Methods:
Sustained-release morphine (DTC401) was prepared by encapsulating morphine sulfate in DepoFoam (Dep. Tech, San Diego, CA), a lipid-based, sustained-release drug delivery system. A standard hot-plate test for analgesia, pulse oximetry for hemoglobin oxygen saturation, corneal-reflex loss, and incidence of catalepsy were used to assess efficacy and toxicities. Cerebrospinal fluid and serum pharmacokinetic studies were performed after a single epidural dose, using a commercially available radioimmunoassay kit.
Results:
Single epidural doses of DTC401 resulted in equivalent onset time to peak analgesia but significantly prolonged analgesia compared with morphine sulfate. Hemoglobin oxygen saturation was decreased minimally, and the incidences of catalepsy and corneal-reflex loss were minimal, even at large doses of DTC401. In contrast, the larger doses of morphine sulfate significantly decreased hemoglobin oxygen saturation, and caused catalepsy and loss of the corneal-reflex. The Cmax for DTC401 was 32% in cerebrospinal fluid and 6% in serum, relative to morphine sulfate. The terminal half-life for DTC401 was increased 32 fold in the cerebrospinal fluid compared with morphine sulfate.
Conclusions:
A single epidural dose of DTC401, compared with morphine sulfate, prolonged duration of analgesia, with minimal supraspinal toxic effects, in rats.
Insights
A single epidural dose of sustained-release morphine (DTC401) in rats significantly prolonged pain relief compared to standard morphine. This new formulation minimized respiratory depression and other toxic effects, offering a safer, more effective analgesia option.
Area of Science:
- Pharmacology
- Drug Delivery Systems
- Pain Management
Background:
- Epidural opioid analgesia typically involves frequent administration, posing risks like infection and requiring significant healthcare resources.
- Concerns regarding respiratory depression limit the safety and efficacy of conventional epidural opioids.
- Developing sustained-release formulations aims to improve patient convenience and safety profiles.
Purpose of the Study:
- To evaluate the efficacy and safety of a single epidural dose of sustained-release morphine (DTC401) in rats.
- To compare the analgesic duration and toxic effects of DTC401 with standard epidural morphine sulfate.
- To assess the pharmacokinetic profile of DTC401 in cerebrospinal fluid and serum.
Main Methods:
- Sustained-release morphine (DTC401) was formulated using a lipid-based DepoFoam delivery system.
- Analgesia was assessed using the hot-plate test; toxicities were evaluated via pulse oximetry, corneal-reflex testing, and catalepsy observation.
- Pharmacokinetic studies involved measuring drug concentrations in cerebrospinal fluid and serum using radioimmunoassay.
Main Results:
- DTC401 provided analgesia with a similar onset but significantly longer duration compared to morphine sulfate.
- Minimal decreases in hemoglobin oxygen saturation and low incidences of catalepsy and corneal-reflex loss were observed with DTC401, even at high doses.
- Morphine sulfate at higher doses caused significant decreases in oxygen saturation and notable toxic effects.
Conclusions:
- A single epidural administration of DTC401 offers prolonged analgesia in rats.
- DTC401 demonstrates a favorable safety profile with minimal supraspinal toxic effects compared to morphine sulfate.
- Sustained-release epidural morphine holds potential for improved pain management strategies.