Evaluation of whether acepromazine maleate causes fentanyl to decrease the minimum alveolar concentration of
American Journal of Veterinary Research
|April 27, 2021
Summary
Acepromazine enabled fentanyl to reduce isoflurane MAC in cats, an effect reversed by naltrexone. This suggests that opioid-induced catecholamine increases in cats counteract fentanyl's MAC-sparing effect.
Area of Science:
- Veterinary Anesthesia
- Pharmacology
- Neuroscience
Background:
- Fentanyl, an opioid, typically reduces the minimum alveolar concentration (MAC) of isoflurane.
- Some cats exhibit resistance to fentanyl's immobilizing effects, potentially due to altered pharmacodynamics.
- Acepromazine, a centrally acting catecholamine receptor antagonist, may influence fentanyl's anesthetic effects.
Purpose of the Study:
- To investigate if acepromazine could enable fentanyl to decrease isoflurane MAC in cats resistant to fentanyl alone.
- To determine if this potential MAC-sparing effect is reversible by naltrexone, an opioid antagonist.
Main Methods:
- Five healthy male cats were anesthetized with isoflurane.
- Baseline isoflurane MAC was determined.
- Fentanyl was administered to achieve a target plasma concentration.
- Acepromazine was coadministered with fentanyl.
- Isoflurane MAC was remeasured after each drug administration.
- Naltrexone was administered to assess reversibility of effects.
Main Results:
- Fentanyl alone did not significantly alter isoflurane MAC in these cats.
- The combination of acepromazine and fentanyl significantly decreased isoflurane MAC.
- This decrease in isoflurane MAC was fully reversed by naltrexone administration.
Conclusions:
- Acepromazine facilitates fentanyl's MAC-sparing effect in cats that are otherwise resistant to fentanyl alone.
- Opioid-induced increases in brain catecholamine concentrations in cats may counteract the MAC-sparing effect of opioids.
- This interaction highlights the complex role of catecholamines in modulating opioid anesthetic requirements.
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