Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (747 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Morphia; Morphine Chloride; Chloride, Morphine; Morphine Sulfate; Sulfate, Morphine; Morphine Sulfate (2:1), Pentahydrate; Morphine Sulfate (2:1), Anhydrous; SDZ 202-250.
Where it fits in the MeSH classification
- Broader topics
- Morphine Derivatives
- See also
- Receptors, Opioid
Research landscape
PubMed indexes 41,894 records tagged with the MeSH heading “Morphine” (counts retrieved 2026-10-31). 3,741 of them (8.9%) were published from 2020 onward, and the busiest period so far is through 1999 with 23,281 records.
Reviews account for 1,977 records (4.7%) and meta-analyses for 293. Randomized controlled trials number 4,465 (10.7%) as a share of all records on the topic. Randomized trials make up a comparatively large share of this literature, which means many treatment questions have been tested directly.
Show the data
| Period | Records |
|---|---|
| through 1999 | 23,281 |
| 2000-2009 | 7,943 |
| 2010-2019 | 6,929 |
| 2020 onward | 3,741 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 1,977 | 4.7% |
| Meta-analyses | 293 | 0.7% |
| Randomized controlled trials | 4,465 | 10.7% |
Method: PubMed query "Morphine"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| MRGPRX2 and Adverse Drug Reactions | 2021 | Review article Design not recorded in structured metadata | 85 | cc by PMID 34421893 · DOI · PMC8377365 |
| CRHCeA→VTA inputs inhibit the positive ensembles to induce negative effect of opiate withdrawal | 2021 | Research article Design not recorded in structured metadata | 45 | cc by PMID 34642456 · DOI · PMC8760059 |
| Morphine-responsive neurons that regulate mechanical antinociception | 2024 | Research article Design not recorded in structured metadata | 35 | cc by PMID 39208104 · DOI · PMC7616448 |
| Intrathecal Morphine for Enhanced Recovery After Laparoscopic Colorectal Surgery: A Randomized Clinical Trial | 2026 | Randomized controlled trial Design not recorded in structured metadata | 3 | cc by PMID 41433024 · DOI · PMC12728733 |
MRGPRX2 and Adverse Drug Reactions [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Many adverse reactions to therapeutic drugs appear to be allergic in nature, and are thought to be triggered by patient-specific Immunoglobulin E (IgE) antibodies that recognize the drug molecules and form complexes with them that activate mast cells.
- Closing excerpt
- For some of these drugs, then, MRGPRX2 activation may be considered a regular and predictable feature after administration of high doses.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (166 words)
Many adverse reactions to therapeutic drugs appear to be allergic in nature, and are thought to be triggered by patient-specific Immunoglobulin E (IgE) antibodies that recognize the drug molecules and form complexes with them that activate mast cells. However, in recent years another mechanism has been proposed, in which some drugs closely associated with allergic-type events can bypass the antibody-mediated pathway and trigger mast cell degranulation directly by activating a mast cell-specific receptor called Mas-related G protein-coupled receptor X2 (MRGPRX2). This would result in symptoms similar to IgE-mediated events, but would not require immune priming. This review will cover the frequency, severity, and dose-responsiveness of allergic-type events for several drugs shown to have MRGPRX2 agonist activity. Surprisingly, the analysis shows that mild-to-moderate events are far more common than currently appreciated. A comparison with plasma drug levels suggests that MRGPRX2 mediates many of these mild-to-moderate events. For some of these drugs, then, MRGPRX2 activation may be considered a regular and predictable feature after administration of high doses.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 34421893 · DOI · PMC8377365
CRHCeA→VTA inputs inhibit the positive ensembles to induce negative effect of opiate withdrawal [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Plasticity of neurons in the ventral tegmental area (VTA) is critical for establishment of drug dependence.
- Closing excerpt
- These data suggest that neurons encoding opioid reward experience are inhibited by enhanced CRHCeA→VTA inputs induced by chronic morphine exposure, leading to negative effect during opiate withdrawal, and provide new insight into the pathological changes in VTA plasticity after drug abuse and mechanism of opiate dependence.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (172 words)
Plasticity of neurons in the ventral tegmental area (VTA) is critical for establishment of drug dependence. However, the remodeling of the circuits mediating the transition between positive and negative effect remains unclear. Here, we used neuronal activity-dependent labeling technique to characterize and temporarily control the VTA neuronal ensembles recruited by the initial morphine exposure (morphine-positive ensembles, Mor-Ens). Mor-Ens preferentially projected to NAc, and induced dopamine-dependent positive reinforcement. Electrophysiology and rabies viral tracing revealed the preferential connections between the VTA-projective corticotrophin-releasing hormone (CRH) neurons of central amygdala (CRHCeA→VTA) and Mor-Ens, which was enhanced after escalating morphine exposure and mediated the negative effect during opiate withdrawal. Pharmacologic intervention or CRISPR-mediated repression of CRHR1 in Mor-Ens weakened the inhibitory CRHCeA→VTA inputs, and alleviated the negative effect during opiate withdrawal. These data suggest that neurons encoding opioid reward experience are inhibited by enhanced CRHCeA→VTA inputs induced by chronic morphine exposure, leading to negative effect during opiate withdrawal, and provide new insight into the pathological changes in VTA plasticity after drug abuse and mechanism of opiate dependence.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 34642456 · DOI · PMC8760059
Morphine-responsive neurons that regulate mechanical antinociception [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Opioids are widely used, effective analgesics to manage severe acute and chronic pain, although they have recently come under scrutiny because of epidemic levels of abuse.
- Closing excerpt
- Our results reveal a specific RVM-spinal circuit that scales mechanical nociception whose function confers the antinociceptive properties of morphine.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (132 words)
Opioids are widely used, effective analgesics to manage severe acute and chronic pain, although they have recently come under scrutiny because of epidemic levels of abuse. While these compounds act on numerous central and peripheral pain pathways, the neuroanatomical substrate for opioid analgesia is not fully understood. By means of single-cell transcriptomics and manipulation of morphine-responsive neurons, we have identified an ensemble of neurons in the rostral ventromedial medulla (RVM) that regulates mechanical nociception in mice. Among these, forced activation or silencing of excitatory RVMBDNF projection neurons mimicked or completely reversed morphine-induced mechanical antinociception, respectively, via a brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)-dependent mechanism and activation of inhibitory spinal galanin-positive neurons. Our results reveal a specific RVM-spinal circuit that scales mechanical nociception whose function confers the antinociceptive properties of morphine.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 39208104 · DOI · PMC7616448
Intrathecal Morphine for Enhanced Recovery After Laparoscopic Colorectal Surgery: A Randomized Clinical Trial [4]
Abstract reading summary — source excerpts
- Opening excerpt
- ImportanceDespite the recovery advantages of minimally invasive surgical techniques, moderate to severe pain after laparoscopic colorectal surgery is a common barrier to improving postoperative recovery quality.
- Closing excerpt
- gov Identifier: NCT06636864.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (277 words)
ImportanceDespite the recovery advantages of minimally invasive surgical techniques, moderate to severe pain after laparoscopic colorectal surgery is a common barrier to improving postoperative recovery quality.ObjectiveTo evaluate whether intrathecal morphine (ITM) combined with transversus abdominis plane block (TAPB) improves postoperative recovery quality after laparoscopic colorectal surgery.Design, setting, and participantsThis prospective, double-blind randomized clinical trial was conducted at Sun Yat-sen University Cancer Center between October 15, 2024, and February 15, 2025. Adults scheduled for elective laparoscopic colorectal surgery were randomized 1:1 to ITM or saline placebo. Data were analyzed from March 1, 2025, to March 31, 2025.InterventionsBoth groups received liposomal bupivacaine for TAPB as part of standard enhanced recovery after surgery (ERAS) protocol. The intervention group received ITM, 3 µg/kg, while the control group received intrathecal normal saline.Main outcomes and measuresThe primary outcome was the Quality of Recovery 15 (QoR-15) score at 24 hours postoperatively. Secondary outcomes included postoperative pain scores, cumulative opioid consumption (in morphine milligram equivalents [MME]), time to first flatus, time to first ambulation, incidence of adverse effects, and length of hospital stay.ResultsA total of 252 patients were included in the intention-to-treat analysis (mean [SD] age, 58.4 [11.1] years; 112 female patients [44.4%]). At 24 hours postoperatively, the intervention group had significantly higher mean (SE) QoR-15 scores compared to the control group (114.95 [1.04] vs 102.22 [0.76]; mean difference, 12.21; 95% CI, 9.91-14.51; P Conclusions and relevancePer the results of this randomized clinical trial, in laparoscopic colorectal surgery, ITM combined with TAPB can significantly enhance early postoperative recovery and analgesia, albeit with an increased risk of pruritus. This strategy may be a valuable component of multimodal analgesia regimens following laparoscopic colorectal surgery.Trial registrationClinicalTrials.gov Identifier: NCT06636864.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41433024 · DOI · PMC12728733
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Morphine and alternative opioids in cancer pain: the EAPC recommendations [5]
- Research article Strategies to manage the adverse effects of oral morphine: an evidence-based report [6]
- Research article Does multimodal analgesia with acetaminophen, nonsteroidal antiinflammatory drugs, or selective cyclooxygenase-2 inhibitors and patient-controlled analgesia morphine offer advantages over morphine alone? Meta-analyses of randomized trials [7]
- Research article Effect of perioperative systemic α2 agonists on postoperative morphine consumption and pain intensity: systematic review and meta-analysis of randomized controlled trials [8]
- Research article Effects of acetaminophen on morphine side-effects and consumption after major surgery: meta-analysis of randomized controlled trials [9]
- Research article The Role of Opioid Receptors in Immune System Function [10]
References
- McNeil BD. MRGPRX2 and Adverse Drug Reactions. . 2021. PMID 34421893 · DOI · PMC8377365
- Jiang C, Yang X, He G, Wang F, Wang Z, Xu W, et al.. CRHCeA→VTA inputs inhibit the positive ensembles to induce negative effect of opiate withdrawal. . 2021. PMID 34642456 · DOI · PMC8760059
- Fatt MP, Zhang MD, Kupari J, Altınkök M, Yang Y, Hu Y, et al.. Morphine-responsive neurons that regulate mechanical antinociception. . 2024. PMID 39208104 · DOI · PMC7616448
- Zheng L, Lu Y, Lu X, You L, Yu C, Lai J, et al.. Intrathecal Morphine for Enhanced Recovery After Laparoscopic Colorectal Surgery: A Randomized Clinical Trial. . 2026. PMID 41433024 · DOI · PMC12728733
- Hanks GW, Conno F, Cherny N, Hanna M, Kalso E, McQuay HJ, et al.. Morphine and alternative opioids in cancer pain: the EAPC recommendations. Br J Cancer. 2001. PMID 11237376 · DOI · PMC2363790
- Cherny N, Ripamonti C, Pereira J, Davis C, Fallon M, McQuay H, et al.. Strategies to manage the adverse effects of oral morphine: an evidence-based report. J Clin Oncol. 2001. PMID 11331334 · DOI
- Elia N, Lysakowski C, Tramèr MR. Does multimodal analgesia with acetaminophen, nonsteroidal antiinflammatory drugs, or selective cyclooxygenase-2 inhibitors and patient-controlled analgesia morphine offer advantages over morphine alone? Meta-analyses of randomized trials. Anesthesiology. 2005. PMID 16306743 · DOI
- Blaudszun G, Lysakowski C, Elia N, Tramèr MR. Effect of perioperative systemic α2 agonists on postoperative morphine consumption and pain intensity: systematic review and meta-analysis of randomized controlled trials. Anesthesiology. 2012. PMID 22546966 · DOI
- Remy C, Marret E, Bonnet F. Effects of acetaminophen on morphine side-effects and consumption after major surgery: meta-analysis of randomized controlled trials. Br J Anaesth. 2005. PMID 15681586 · DOI
- Eisenstein TK. The Role of Opioid Receptors in Immune System Function. Front Immunol. 2019. PMID 31921165 · DOI · PMC6934131
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.