Related Experiment Video
Updated: May 27, 2026
09:38
Determining Pain Detection and Tolerance Thresholds Using an Integrated, Multi-Modal Pain Task Battery
Published on: April 14, 2016
Paracetamol and opioid pathways: a pilot randomized clinical trial
Gisèle Pickering1, Fares Moustafa, Stephanie Desbrandes
1CHU Clermont-Ferrand, Centre de Pharmacologie Clinique, F-63003 Clermont-Ferrand, France. gisele.pickering@u-clermont1.fr
Fundamental & Clinical Pharmacology
|November 19, 2011
Summary
This study found that naloxone, an opioid antagonist, did not block the pain-relieving effects of paracetamol (acetaminophen) in healthy volunteers. This suggests the opioid system is not significantly involved in how paracetamol works.
Area of Science:
- Pharmacology
- Neuroscience
- Pain Management
Background:
- Paracetamol (acetaminophen) is a widely used analgesic.
- Its pain-relieving mechanism may involve descending inhibitory pain pathways and the opioid system.
Purpose of the Study:
- To investigate the role of the opioid system in paracetamol's antinociceptive effects in humans.
- To determine if naloxone, an opioid antagonist, can inhibit paracetamol's pain-relieving action.
Main Methods:
- A randomized, controlled, double-blind, crossover study in 12 healthy male volunteers.
- Intravenous administration of paracetamol (1g) or placebo, followed by naloxone (8mg) or placebo.
- Recording of cerebral potentials evoked by painful thermal stimuli to assess pain integration.
Main Results:
- Paracetamol significantly reduced pain perception compared to placebo.
- Naloxone did not inhibit the antinociceptive effect of paracetamol.
- Area under the curve analysis showed no significant difference between paracetamol/placebo and paracetamol/naloxone treatments.
Conclusions:
- This pilot study suggests that the opioid system is not significantly implicated in the mechanism of action of paracetamol.
- Further confirmation in a larger cohort is warranted to validate these findings.
Related Concept Videos
01:25Analgesia and Pain Management
Pain is critical to various clinical pathologies, provoking an urgent need for effective management. Pain, whether acute or chronic, is a complex neurochemical process. Its alleviation depends on the type, with nonopioid analgesics effective for mild to moderate pain, such as musculoskeletal or inflammatory pain, while neuropathic pain responds best to anticonvulsants, tricyclic antidepressants, or serotonin/norepinephrine reuptake inhibitors. For severe acute or chronic pain, opioids may be...
01:15Opioid Analgesics: Synthetic and Semisynthetic Opioids
Synthetic and semisynthetic opioids are pivotal in pain management and tackling opioid addiction. Semisynthetic opioids, including morphinans (morphine derivatives), oxycodone, oxymorphone, hydrocodone, and hydromorphone, have improved pharmacokinetic profiles compared to morphine. Additionally, heroin and 6-MAM (6-Monoacetylmorphine) show better CNS penetration than morphine due to heightened lipid solubility. Hydromorphone, a potent opioid, undergoes hepatic metabolism to form the active...
01:20Opioid Analgesics: Morphine and Other Natural Cogeners
Opioids are a class of drugs that mimic endogenous opioid peptides and act on opioid receptors, and help in pain relief. These compounds are classified as natural, synthetic, or semi-synthetic. Natural opioids, like morphine, codeine, and thebaine, are derived from the opium poppy plant (Papaver somniferum or Papaver album) and are termed opiates. Synthetic opioids are artificial, while semi-synthetic opioids combine natural and synthetic compounds. Morphine, a prototypical opioid, possesses a...
01:22Opioid Receptors: Overview
Opioid receptors, including the mu (μ, MOR), delta (δ, DOR), and kappa (κ, KOR) types, belong to the rhodopsin family of G protein-coupled receptors. These receptors are located throughout the central and peripheral nervous systems and in non-neuronal tissues such as macrophages and astrocytes. Opioid receptor ligands can be categorized into agonists or antagonists. Highly selective agonists include [d-Ala2, MePhe4, Gly(ol)5]-enkephalin or DAMGO for MOR, [D-Pen2, D-Pen5]-enkephalin or DPDPE for...
01:21Chemotherapy-Induced Nausea and Vomiting: Cannabinoids
Tetrahydrocannabinol (THC) is a phytocannabinoid that primarily interacts with the CB1 receptor, a type of G protein-coupled receptor (GPCR) predominantly in and around the chemoreceptor trigger zone (CTZ) and emetic center. THC also blocks the serotonin receptor activity in the dorsal vagal complex (DVC) by inhibiting serotonin release. THC exerts its anti-emetic effects through these interactions, which are beneficial for patients undergoing chemotherapy.
Two synthetic agonists of THC,...
Two synthetic agonists of THC,...
01:29Local Anesthetics: Clinical Application as Epidural Anesthesia
Epidural anesthetics are administered in the fat-filled epidural space, the outermost part of the spinal canal. This technique is commonly employed for pain management and anesthesia during lower abdomen and pelvis surgeries or labor and delivery.
Since epidural anesthetics can be infused through an epidural catheter, all types of drugs, including short-acting ones, can be administered. Chloroprocaine and lidocaine are examples of short and long-duration anesthetics, respectively. Bupivacaine...
Since epidural anesthetics can be infused through an epidural catheter, all types of drugs, including short-acting ones, can be administered. Chloroprocaine and lidocaine are examples of short and long-duration anesthetics, respectively. Bupivacaine...