Nefopam

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Nefopam
Nefopam enantiomers labelled.svg
Nefopam enantiomers ball-and-stick models from xtal labelled.png
Clinical data
Trade names nefopam medisol
AHFS/Drugs.com International Drug Names
Routes of
administration 		intramuscular, intravenous, oral
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • UK: POM (Prescription only)
Pharmacokinetic data
Bioavailability Low [1]
Protein binding 70–75% (mean 73%) [1] [2]
Metabolism Liver (N-demethylation, others) [1]
Metabolites Desmethylnefopam, others [1]
Elimination half-life Nefopam: 3–8 hours [1]
Desmethylnefopam: 10–15 hours [1]
Excretion Urine: 79.3% [1]
Feces: 13.4% [1]
Identifiers
  • (RS)-5-methyl-1-phenyl-1,3,4,6-tetrahydro-2,5-benzoxazocine
CAS Number
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
ChEBI
CompTox Dashboard (EPA)
ECHA InfoCard 100.033.757 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula C17H19NO
Molar mass 253.345 g·mol−1
3D model (JSmol)
  • CN1CCOC(C2=CC=CC=C2C1)C3=CC=CC=C3
  • InChI=1S/C17H19NO/c1-18-11-12-19-17(14-7-3-2-4-8-14)16-10-6-5-9-15(16)13-18/h2-10,17H,11-13H2,1H3 X mark.svgN
  • Key:RGPDEAGGEXEMMM-UHFFFAOYSA-N X mark.svgN
 X mark.svgNYes check.svgY  (what is this?)    (verify)

Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid painkilling medication, with central stimulant and sympathomimetic properties that is primarily used to treat moderate to severe pain. [3]

Contents

History

Nefopam is based on a benzoxazocine compound. It was developed in the 1960s and marketed under the name fenazocine. [4] It was initially used in shivering, as a muscle relaxant and as an antidepressant, but then increasingly as an analgesic. [4]

Medical uses

Analgesic

Nefopam was significantly more effective than aspirin as an analgesic in one clinical trial, [5] although with a greater incidence of side effects such as sweating, dizziness and nausea, especially at higher doses. [6] [7]

The estimated relative potency of nefopam to morphine indicates that 20 mg of nefopam HCl is the approximate analgesic equal of 12 mg of morphine with comparable analgesic efficacy to morphine, [8] [9] [10] or oxycodone. [11] Nefopam tends to produce fewer side effects, does not produce respiratory depression, [12] and has much less abuse potential, and so is useful either as an alternative to opioid analgesics, or as an adjunctive treatment for use alongside opioids or other types of analgesics. [10] [13]

Postoperative pain

A 2025 review, covering 17 studies, found that nefopam was an effective adjunctive postoperative analgesic with benefits in pain management, and correlated with a mean decrease in opioid consumption across the studies of 38%. Adverse effects were not discussed in detail in the included studies. [14]

Chronic pain

For chronic pain nefopam may sometimes be used when common alternatives are contraindicated or ineffective, or as an add-on therapy. [15]

Other Medical Uses

Nefopam is used to treat severe hiccups. [16]

Nefopam is thought to have some efficacy for treating (off-label) Parkinson's disease, in a similar fashion to those of Bupropion and Methylphenidate. [17]

Nefopam is effective for prevention of shivering during surgery or recovery from surgery. [18] [19]

Contraindications

Nefopam is contraindicated in people with convulsive disorders, those that have received treatment with irreversible monoamine oxidase inhibitors such as phenelzine, tranylcypromine or isocarboxazid within the past 30 days and those with myocardial infarction pain, mostly due to a lack of safety data in these conditions. [20]

Side effects

Common side effects include nausea, nervousness, dry mouth, light-headedness and urinary retention. [20] Less common side effects include vomiting, blurred vision, drowsiness, sweating, insomnia, headache, confusion, hallucinations, tachycardia, aggravation of angina and rarely a temporary and benign pink discolouration of the skin or erythema multiforme. [20]

CNS side effects

Some side effects, such as feeling confused or hallucinating, are more likely in patients over 65 years old. [21] [20]

Nefopam has been shown to have anticholinergic properties [20] and has a score of 2 on the anticholinergic burden (ACB) [22] scale. [23] Anticholinergic drugs have caused concerns about cognitive decline in older people. [24]

Overdose

Overdose and death have been reported with nefopam. [25] Overdose usually manifests with convulsions, hallucinations, tachycardia, and hyperdynamic circulation. [20] Treatment is usually supportive, managing cardiovascular complications with beta blockers and limiting absorption with activated charcoal. [20]

Interactions

Nefopam has additive anticholinergic and sympathomimetic effects with other agents with these properties. [20] Its use should be avoided in people receiving some types of antidepressants (tricyclic antidepressants or monoamine oxidase inhibitors) as there is the potential for serotonin syndrome or hypertensive crises to result. [20]

Mechanisms of action

The mechanism of action of nefopam and its analgesic effects are not well understood.

Analgesic mechanisms of action

Nefopam may have three analgesic mechanisms in the brain and spinal cord;

Pharmacology

A 2025 review noted a significant literature gap on the pharmacokinetic and pharmacodynamic properties of nefopam. [14]

Nefopam [28] [29]
SiteKi (nM)
SERT Tooltip Serotonin transporter29
NET Tooltip Norepinephrine transporter33
DAT Tooltip Dopamine transporter531
5-HT2A 1,685
5-HT2B 330
5-HT2C 56

Pharmacokinetics

The absolute bioavailability of nefopam is low. [1] It is reported to achieve therapeutic plasma concentrations between 49 and 183 nM. [29] The drug is approximately 73% protein-bound across a plasma range of 7 to 226 ng/mL (28–892 nM). [1] The metabolism of nefopam is hepatic, by N-demethylation and via other routes. [1] Its terminal half-life is 3 to 8 hours, while that of its active metabolite, desmethylnefopam, is 10 to 15 hours. [1] It is eliminated mostly in urine, and to a lesser extent in feces. [1]

Chemistry

Nefopam is a cyclized analogue of orphenadrine, diphenhydramine, and tofenacin, with each of these compounds different from one another only by the presence of one or two carbons. [30] [31] [32] The ring system of nefopam is a benzoxazocine system. [30] [33]

Use by country

Nefopam is used in the UK [34] although some UK regions do not advise initiation of use, it is currently a prescription only medication. [35] [36] It is used in France, [37] although some concerns have been raised. [38]

As of 2014 Nefopam was not FDA-approved in the US. [39]

Society and culture

Recreational use

Recreational use of nefopam has rarely been reported, [25] and is far less common than with opioid analgesics. [40]

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Sanga M, Banach J, Ledvina A, Modi NB, Mittur A (November 2016). "Pharmacokinetics, metabolism, and excretion of nefopam, a dual reuptake inhibitor in healthy male volunteers". Xenobiotica; the Fate of Foreign Compounds in Biological Systems. 46 (11): 1001–1016. doi:10.3109/00498254.2015.1136989. PMID   26796604. S2CID   34603935.
  2. ↑ Seyffart G (6 December 2012). Drug Dosage in Renal Insufficiency. Springer Science & Business Media. pp. 407–. ISBN   978-94-011-3804-8.
  3. ↑ Brayfield A, ed. (27 October 2016). "Nefopam hydrochloride". MedicinesComplete. London, UK: Pharmaceutical Press. Retrieved 4 September 2017.
  4. 1 2 3 4 5 Kim KH, Abdi S (April 3, 2014). "Rediscovery of nefopam for the treatment of neuropathic pain". The Korean Journal of Pain. 27 (2): 103–111. doi:10.3344/kjp.2014.27.2.103. PMC   3990817 . PMID   24748937.
  5. ↑ Cohen A, Hernandez CM (1976). "Nefopam hydrochloride: new analgesic agent". The Journal of International Medical Research. 4 (2): 138–143. doi:10.1177/030006057600400211. PMID   799984. S2CID   41618926.
  6. ↑ Wang RI, Waite EM (July 1979). "The clinical analgesic efficacy of oral nefopam hydrochloride". Journal of Clinical Pharmacology. 19 (7): 395–402. doi:10.1002/j.1552-4604.1979.tb02498.x. PMID   479385. S2CID   25877487.
  7. ↑ Pillans PI, Woods DJ (September 1995). "Adverse reactions associated with nefopam". The New Zealand Medical Journal. 108 (1008): 382–384. PMID   7566787.
  8. ↑ Sunshine A, Laska E (November 1975). "Nefopam and morphine in man". Clinical Pharmacology and Therapeutics. 18 (5 Pt 1): 530–534. doi:10.1002/cpt1975185part1530. PMID   1102231. S2CID   19051105.
  9. ↑ Phillips G, Vickers MD (October 1979). "Nefopam in postoperative pain". British Journal of Anaesthesia. 51 (10): 961–965. doi: 10.1093/bja/51.10.961 . PMID   391253.
  10. 1 2 Heel RC, Brogden RN, Pakes GE, Speight TM, Avery GS (April 1980). "Nefopam: a review of its pharmacological properties and therapeutic efficacy". Drugs. 19 (4): 249–267. doi:10.2165/00003495-198019040-00001. PMID   6991238. S2CID   24713213.
  11. ↑ Tigerstedt I, Tammisto T, Leander P (December 1979). "Comparison of the analgesic dose-effect relationships of nefopam and oxycodone in postoperative pain". Acta Anaesthesiologica Scandinavica. 23 (6): 555–560. doi:10.1111/j.1399-6576.1979.tb01486.x. PMID   397711. S2CID   40976610.
  12. ↑ Gasser JC, Bellville JW (August 1975). "Respiratory effects of nefopam". Clinical Pharmacology and Therapeutics. 18 (2): 175–179. doi:10.1002/cpt1975182175. PMID   1097153. S2CID   22220503.
  13. ↑ Kapfer B, Alfonsi P, Guignard B, Sessler DI, Chauvin M (January 2005). "Nefopam and ketamine comparably enhance postoperative analgesia". Anesthesia and Analgesia. 100 (1): 169–174. doi:10.1213/01.ANE.0000138037.19757.ED. PMC   1283103 . PMID   15616073.
  14. 1 2 Bader NA, Al-Ahmad MM, Naeem WA, Amer MG (April 5, 2025). "Efficacy of nefopam in postoperative pain management: A systematic review of opioid consumption". Journal of Applied Pharmaceutical Science. 15 (5): 024–039. doi: 10.7324/JAPS.2025.203223 .
  15. ↑ "Use of nefopam for chronic pain". SPS - Specialist Pharmacy Service. January 5, 2024.
  16. ↑ Bilotta F, Rosa G (December 2000). "Nefopam for severe hiccups". The New England Journal of Medicine. 343 (26): 1973–1974. doi: 10.1056/nejm200012283432619 . PMID   11186682.
  17. ↑ Beśka M, Walawender I, Kasperski J, Skaba D, Nowak P, Reichman-Warmusz E, et al. (January 2010). "Biological Peculiarities of the Analgesic Drug Nefopam in Rats". Advances in Clinical and Experimental Medicine . 1 (19). Retrieved 18 December 2024– via ResearchGate.
  18. ↑ Kang P, Park SK, Yoo S, Hur M, Kim WH, Kim JT, et al. (January 2019). "Comparative effectiveness of pharmacologic interventions to prevent shivering after surgery: a network meta-analysis". Minerva Anestesiologica. 85 (1): 60–70. doi:10.23736/S0375-9393.18.12813-6. PMID   30226340. S2CID   52288008.
  19. ↑ Alfonsi P, Adam F, Passard A, Guignard B, Sessler DI, Chauvin M (January 2004). "Nefopam, a nonsedative benzoxazocine analgesic, selectively reduces the shivering threshold in unanesthetized subjects". Anesthesiology. 100 (1): 37–43. doi:10.1097/00000542-200401000-00010. PMC   1283107 . PMID   14695722.
  20. 1 2 3 4 5 6 7 8 9 "Data Sheet ACUPAN™ Nefopam hydrochloride 30 mg tablets 20 mg intramuscular injection" (PDF). Medsafe New Zealand. iNova Pharmaceuticals (New Zealand) Limited. 3 September 2007. Retrieved 10 March 2014.
  21. ↑ "Side effects of nefopam". nhs.uk. April 25, 2024.
  22. ↑ "Anticholinergic Burden (ACB)". January 6, 2022.
  23. ↑ "ACB Calculator". www.acbcalc.com.
  24. ↑ Andre L, Gallini A, Montastruc F, Montastruc JL, Piau A, Lapeyre-Mestre M, et al. (December 2019). "Association between anticholinergic (atropinic) drug exposure and cognitive function in longitudinal studies among individuals over 50 years old: a systematic review". European Journal of Clinical Pharmacology. 75 (12): 1631–1644. doi:10.1007/s00228-019-02744-8. PMID   31468067. S2CID   201675824.
  25. 1 2 Bismuth C, Fournier PE, Bavoux E, Husson O, Lafon D (September 1987). "[Chronic abuse of the analgesic nefopam (Acupan)]". Journal de Toxicologie Clinique et Experimentale (in French). 7 (5): 343–346. PMID   3448182.
  26. 1 2 Girard P, Chauvin M, Verleye M (January 2016). "Nefopam analgesia and its role in multimodal analgesia: A review of preclinical and clinical studies". Clinical and Experimental Pharmacology & Physiology. 43 (1): 3–12. doi: 10.1111/1440-1681.12506 . PMID   26475417.
  27. ↑ "New Zealand Data Sheet Acupan(TM)" (PDF). Medsafe. New Zealand The Ministry of Health. 17 May 2017. Retrieved 4 September 2017.
  28. ↑ Roth BL, Driscol J. "PDSP Ki Database". Psychoactive Drug Screening Program (PDSP). University of North Carolina at Chapel Hill and the United States National Institute of Mental Health. Retrieved 14 August 2017.
  29. 1 2 Gregori-Puigjané E, Setola V, Hert J, Crews BA, Irwin JJ, Lounkine E, et al. (July 2012). "Identifying mechanism-of-action targets for drugs and probes" (PDF). Proceedings of the National Academy of Sciences of the United States of America. 109 (28): 11178–11183. Bibcode:2012PNAS..10911178G. doi: 10.1073/pnas.1204524109 . PMC   3396511 . PMID   22711801.
  30. 1 2 Wermuth CG, Aldous D, Raboisson P, Rognan D (1 July 2015). The Practice of Medicinal Chemistry. Elsevier Science. pp. 250–251. ISBN   978-0-12-417213-5.
  31. ↑ Sneader W (23 June 2005). Drug Discovery: A History. John Wiley & Sons. pp. 405–. ISBN   978-0-471-89979-2.
  32. ↑ Kubinyi H, Müller G (6 March 2006). Chemogenomics in Drug Discovery: A Medicinal Chemistry Perspective. John Wiley & Sons. pp. 54–. ISBN   978-3-527-60402-9.
  33. ↑ Cruz A (2014). Therapeutic Hypothermia. CRC Press. pp. 176–.
  34. ↑ "Nefopam: a painkiller taken to treat moderate pain". nhs.uk. April 25, 2024.
  35. ↑ "Medicines Safety Sub-Group Nefopam Bulletin" (PDF). NHS West Yorkshire ICS Area Prescribing Committee. November 2017.
  36. ↑ "Barnsley APC Position Statement on Nefopam" (PDF). best.barnsleyccg.nhs.uk. August 2023.
  37. ↑ Schulz T, Lalande L, Aubrun F, Dziadzko M (May 6, 2022). "Nefopam prescribing preferences in French hospitals: results of a survey". The Pan African Medical Journal. 41: 213. doi:10.11604/pamj.2022.41.213.33365. PMC   9167477 . PMID   35721644.
  38. ↑ Revol B, Delorme J, Jouanjus É, Spadari M, Djezzar S, Lepelley M, et al. (May 6, 2021). "[Thirty years of nefopam abuse in France]". Therapie. 76 (6): 527–537. doi: 10.1016/j.therap.2021.01.058 . PMID   33618914.
  39. ↑ "Public Notification: Pro ArthMax Contains Several Hidden Drug Ingredients". Center for Drug Evaluation and Research. U.S. Food and Drug Administration. August 16, 2021.
  40. ↑ Tracqui A, Berthelon L, Ludes B (May 2002). "Fatal overdosage with nefopam (Acupan)". Journal of Analytical Toxicology. 26 (4): 239–243. doi: 10.1093/jat/26.4.239 . PMID   12054367.
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