Abstract
BackgroundIt has been observed that acetaminophen potentiates the analgesic effect of morphine and tramadol in postoperative pain management. Its capacity as an analgesic drug or in combinations thereof to reduce the minimum alveolar concentration (MAC) of inhalational anesthetics represents an objective measure of this effect during general anesthesia. In this study, the effect of acetaminophen with and without morphine or tramadol was evaluated on the isoflurane MAC.MethodsForty-eight male Wistar rats were anesthetized with isoflurane in oxygen. MACISO was determined from alveolar gas samples at the time of tail clamping without the drug, after administering acetaminophen (300 mg/kg), morphine (3 mg/kg), tramadol (10 mg/kg), acetaminophen (300 mg/kg) + morphine (3 mg/kg), and acetaminophen (300 mg/kg) + tramadol (10 mg/kg).ResultsThe control and acetaminophen groups did not present statistically significant differences (p = 0.98). The values determined for MACISO after treatment with acetaminophen + morphine, acetaminophen + tramadol, morphine, and tramadol were 0.98% ± 0.04%, 0.99% ± 0.009%, 0.97% ± 0.02%, and 0.99% ± 0.01%, respectively.ConclusionsThe administration of acetaminophen did not reduce the MAC of isoflurane and did not potentiate the reduction in MACISO by morphine and tramadol in rats, and therefore does not present a sparing effect of morphine or tramadol in rats anesthetized with isoflurane.
Highlights
Acetaminophen, known as paracetamol, has analgesic and antipyretic properties like NSAIDs
Acetaminophen Alone or with Opioids on minimum alveolar concentration (MAC) of Isoflurane in Rats does not present a sparing effect of morphine or tramadol in rats anesthetized with isoflurane
Acetaminophen has constantly been compared with NSAIDs, starting with Vane et al [3] who demonstrated that the mechanism of action for aspirin-like drugs is the inhibition of prostaglandin synthesis
Summary
Acetaminophen, known as paracetamol, has analgesic and antipyretic properties like NSAIDs. Acetaminophen has constantly been compared with NSAIDs, starting with Vane et al [3] who demonstrated that the mechanism of action for aspirin-like drugs is the inhibition of prostaglandin synthesis. Flower et al [4] reported that the inhibition of brain cyclooxygenase is responsible for the antipyretic effect of paracetamol, generating the concept of a central mechanism of action. Chandrasekharan et al [5] reported the existence of a variant of COX-1 in dogs This enzyme, named COX-3 was identified in the central nervous system and was found to be selectively inhibited by antipyretic-analgesic drugs such as acetaminophen, suggesting a mechanism for pain and possibly fever reduction. It is known that the mechanism of action of acetaminophen is complex because it involves the inhibition of cyclooxygenases both centrally and peripherally depending on the concentration of circulating peroxides. The effect of acetaminophen with and without morphine or tramadol was evaluated on the isoflurane MAC.
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