Chemistry:Orphenadrine
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| Trade names | Generic; many brand names[1] |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682162 |
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| Routes of administration | Oral, intravenous, intramuscular |
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| Bioavailability | 90% |
| Protein binding | 95% |
| Metabolism | Hepatic demethylation |
| Elimination half-life | 13–20 hours[2] |
| Excretion | Renal and biliary |
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| Chemical and physical data | |
| Formula | C18H23NO |
| Molar mass | 269.388 g·mol−1 |
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Orphenadrine (sold under many brand names)[1] is an anticholinergic drug of the ethanolamine antihistamine class; it is closely related to diphenhydramine. It is a muscle relaxant that is used to treat muscle pain and to help with motor control in Parkinson's disease, but has largely been superseded by newer drugs.[citation needed] It is considered a dirty drug due to its multiple mechanisms of action in different pathways.[citation needed] It was discovered and developed in the 1940s.
Medical use
Orphenadrine is a skeletal muscle relaxant.[1][3] It is used to relieve pain caused by muscle injuries such as strains and sprains, in combination with rest and physical therapy.[3] A 2004 review found fair evidence that orphenadrine is effective for acute back or neck pain, but found insufficient evidence to establish the relative efficacy of the drug in relation to other drugs in the study.[4]
Orphenadrine and other muscle relaxants are sometimes used to treat pain arising from rheumatoid arthritis but there is no evidence they are effective for that purpose.[5]
In 2003, a Cochrane Review of the use of anticholinergic drugs to improve motor function in Parkinson's disease found that as a class, the drugs are useful for that purpose; it identified one single-site randomised, cross-over study of orphenadrine vs placebo.[6] Although orphenadrine and other anticholinergics have largely been superseded by other drugs; they have a use in alleviating motor function symptoms, and appear to help about 20% of people with Parkinson's.[7]
Side effects
Orphenadrine has the side effects of the other common antihistamines in large part. Stimulation is somewhat more common than with other related antihistamines, and is especially common in the elderly. Common side effects include dry mouth, dizziness, drowsiness, constipation, urine retention, blurred vision, and headache.[3] Its use in Parkinson's is especially limited by these factors.[6]
Orphenadrine is contraindicated in patients with glaucoma, myasthenia gravis, sphincter relaxation disorders, digestive problems such as peptic ulcers, bowel obstruction, or with enlarged prostate, bladder disorders; that is, they should not consume this drug.[8]
Continuous and/or cumulative use of anticholinergic medications, including first-generation antihistamines, is associated with higher risk of cognitive decline and dementia in older people.[9][10]
Pharmacology
Orphenadrine is known to have these pharmacological properties:
- Nonselective mACh receptor antagonist (anticholinergic, 58% as potent as atropine)[11] Various monographs and package inserts, nursing manuals, journal articles and so forth have proposed the theory that this anticholinergic (atropine-like) activity, NMDA antagonism and possible local anaesthetic and miscellaneous analgesic effects may be the reason for orphenadrine's efficacy against muscle and other pain.[12] These reasons are behind the use of orphenadrine and other drugs of a number of types which are used with paracetamol, aspirin, naproxen, and similar agents with or without opioid analgesics to more effectively manage pain of various types.[13]
- H1 receptor antagonist (antihistamine)[13]
- NMDA receptor antagonist[14] (Ki value of 6.0 ± 0.7 μM, one hundred times less potent than phencyclidine, which binds with a Ki of 59 nM)[15][16]
- NDRI (norepinephrine and dopamine reuptake inhibitor)[17][18]
- Nav1.7, Nav1.8, and Nav1.9 sodium channel blocker[19]
- HERG potassium channel blocker[20]
History
George Rieveschl was a professor of chemistry at the University of Cincinnati and led a research program working on antihistamines. In 1943, one of his students, Fred Huber, synthesized diphenhydramine. Rieveschl worked with Parke-Davis to test the compound, and the company licensed the patent from him. In 1947 Parke-Davis hired him as their Director of Research. While he was there, he led the development of orphenadrine, an analog of diphenhydramine.[21]
Prior to the development of amantadine in the late 1960s and then other drugs, anticholinergics like orphenadrine were the mainstay of Parkinson's treatment.[7]
Formulation
Orphenadrine has been available as a citrate salt and a hydrochloride salt; in the US as of February 2016 the citrate form was available in tablets, extended release tablets, compounding powder and by injection for acute use in a hospital setting.[1][22]
Orphenadrine is often available mixed with aspirin, paracetamol/acetaminophen, ibuprofen, caffeine, and/or codeine.[1]
The brand names Norflex and Norgesic are formulations of the citrate salt of orphenadrine and Disipal is the hydrochloride salt.[23]
Chemistry
Orphenadrine is a derivative of diphenhydramine with a methyl group added to one of the phenyl rings.[24]
Stereochemistry
Orphenadrine has a chiral center and two enantiomers. When employed as a therapeutic agent, it is typically supplied as the racemate.[25]
| Enantiomers | |
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-Orphenadrin_Structural_Formula_V1.svg) (R)-orphenadrine CAS number: 33425-91-1 |
-Orphenadrin_Structural_Formula_V1.svg) (S)-orphenadrine CAS number: 33425-89-7 |
References
- ↑ 1.0 1.1 1.2 1.3 1.4 "Orphenadrine". Drugs.com international listings. https://www.drugs.com/international/orphenadrine.html.
- ↑ "Difference between single and multiple dose pharmacokinetics of orphenadrine hydrochloride in man". European Journal of Clinical Pharmacology 21 (4): 343–50. 1982. doi:10.1007/BF00637624. PMID 7056281.
- ↑ 3.0 3.1 3.2 "Orphenadrine". Medline Plus. 1 December 2010. https://www.nlm.nih.gov/medlineplus/druginfo/meds/a682162.html.
- ↑ "Comparative efficacy and safety of skeletal muscle relaxants for spasticity and musculoskeletal conditions: a systematic review". Journal of Pain and Symptom Management 28 (2): 140–75. August 2004. doi:10.1016/j.jpainsymman.2004.05.002. PMID 15276195.
- ↑ "Muscle relaxants for pain management in rheumatoid arthritis". The Cochrane Database of Systematic Reviews 1: CD008922. January 2012. doi:10.1002/14651858.CD008922.pub2. PMID 22258993. https://semanticscholar.org/paper/003c071b2e52403938b6a16031f1b6c93d95b8a3.
- ↑ 6.0 6.1 "Anticholinergics for symptomatic management of Parkinson's disease". The Cochrane Database of Systematic Reviews 2002 (2): CD003735. 2003. doi:10.1002/14651858.CD003735. PMID 12804486.
- ↑ 7.0 7.1 Marsden's Book of Movement Disorders. Oxford University Press. 2012. p. 281. ISBN 978-0-19-261911-2. https://books.google.com/books?id=g815isikVSAC&pg=PA281.
- ↑ "Orphenadrine Citrate Extended release label". October 1998. https://www.accessdata.fda.gov/drugsatfda_docs/anda/99/40249_Orphenadrine%20Citrate_Prntlbl.pdf.
- ↑ "Cumulative use of strong anticholinergics and incident dementia: a prospective cohort study". JAMA Internal Medicine 175 (3): 401–407. March 2015. doi:10.1001/jamainternmed.2014.7663. PMID 25621434.
- ↑ "Drugs with anticholinergic properties, cognitive decline, and dementia in an elderly general population: the 3-city study". Archives of Internal Medicine 169 (14): 1317–1324. July 2009. doi:10.1001/archinternmed.2009.229. PMID 19636034.
- ↑ "Effects of antiparkinsonian drugs on muscarinic receptor binding in rat brain, heart and lung". Pharmacology & Toxicology 62 (2): 90–4. February 1988. doi:10.1111/j.1600-0773.1988.tb01852.x. PMID 3353357.
- ↑ Nurses' Drug Guide 2010 [full citation needed]
- ↑ 13.0 13.1 "Analgesic effects of antihistaminics". Life Sciences 36 (5): 403–16. February 1985. doi:10.1016/0024-3205(85)90252-8. PMID 2578597.
- ↑ "Orphenadrine is an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist: binding and patch clamp studies". Journal of Neural Transmission. General Section 102 (3): 237–46. 1995. doi:10.1007/BF01281158. PMID 8788072.
- ↑ "Orphenadrine is an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist: binding and patch clamp studies". Journal of Neural Transmission. General Section 102 (3): 237–46. 1995. doi:10.1007/BF01281158. PMID 8788072.
- ↑ "NMDA receptor antagonists ketamine and PCP have direct effects on the dopamine D(2) and serotonin 5-HT(2)receptors-implications for models of schizophrenia". Molecular Psychiatry 7 (8): 837–44. 2002. doi:10.1038/sj.mp.4001093. PMID 12232776.
- ↑ "Assessment of the adrenergic effects of orphenadrine in rat vas deferens". The Journal of Pharmacy and Pharmacology 51 (3): 307–12. March 1999. doi:10.1211/0022357991772303. PMID 10344632.
- ↑ "Insights into the Modulation of Dopamine Transporter Function by Amphetamine, Orphenadrine, and Cocaine Binding". Frontiers in Neurology 6: 134. 2015. doi:10.3389/fneur.2015.00134. PMID 26106364.
- ↑ "Involvement of voltage-gated sodium channels blockade in the analgesic effects of orphenadrine". Pain 142 (3): 225–35. April 2009. doi:10.1016/j.pain.2009.01.010. PMID 19217209. https://zenodo.org/record/896063.
- ↑ "Anticholinergic antiparkinson drug orphenadrine inhibits HERG channels: block attenuation by mutations of the pore residues Y652 or F656". Naunyn-Schmiedeberg's Archives of Pharmacology 376 (4): 275–84. December 2007. doi:10.1007/s00210-007-0202-6. PMID 17965852.
- ↑ Drug Discovery: A History. John Wiley & Sons. 2005. p. 405. ISBN 978-0-471-89979-2. https://books.google.com/books?id=Cb6BOkj9fK4C&pg=PA405.
- ↑ "FDA listing of Orphenadrine citrate registrations". United States Food and Drug Administration. http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm?fuseaction=Search.Overview&DrugName=ORPHENADRINE%20CITRATE.
- ↑ "Disipal Brand of Orphenadrine HCl". Riker. http://www.decodog.com/inven/MD/md30554.jpg.
- ↑ "Ring Transformations. Chapter 9". The Practice of Medicinal Chemistry (4th ed.). Elsevier. 2015. pp. 250–251. ISBN 978-0-12-417213-5. https://books.google.com/books?id=dtScBAAAQBAJ&pg=PA251.
- ↑ Rote Liste Service GmbH (Hrsg.) (2017). Rote Liste 2017 Arzneimittelverzeichnis für Deutschland (einschließlich EU-Zulassungen und bestimmter Medizinprodukte). 57. Frankfurt/Main: Rote Liste Service GmbH. pp. 207. ISBN 978-3-946057-10-9.
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