Preferred IUPAC name
Other names
fampridine (INN)
dalfampridine (USAN)
3D model (JSmol)
ECHA InfoCard 100.007.262 Edit this at Wikidata
EC Number
  • 207-987-9
MeSH 4-Aminopyridine
  • InChI=1S/C5H6N2/c6-5-1-3-7-4-2-5/h1-4H,(H2,6,7) checkY
  • InChI=1/C5H6N2/c6-5-1-3-7-4-2-5/h1-4H,(H2,6,7)
  • n1ccc(N)cc1
Molar mass 94.1146 g/mol
Appearance colourless solid
Melting point 155 to 158 °C (311 to 316 °F; 428 to 431 K)
Boiling point 273 °C (523 °F; 546 K)
polar organic solvents
Basicity (pKb) 4.83[1]
N07XX07 (WHO)
License data
Legal status
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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4-Aminopyridine (4-AP, fampridine, dalfampridine) is an organic compound with the chemical formula C5H4N–NH2. The molecule is one of the three isomeric amines of pyridine. It is used as a research tool in characterizing subtypes of the potassium channel. It has also been used as a drug, to manage some of the symptoms of multiple sclerosis,[6][7] and is indicated for symptomatic improvement of walking in adults with several variations of the disease.[8] It was undergoing Phase III clinical trials as of 2008,[9] and the U.S. Food and Drug Administration (FDA) approved the compound on January 22, 2010.[10] Fampridine is also marketed as Ampyra (pronounced "am-PEER-ah," according to the maker's website) in the United States by Acorda Therapeutics[10][11] and as Fampyra in the European Union, Canada, and Australia. In Canada, the medication has been approved for use by Health Canada since February 10, 2012.[12]


In the laboratory, 4-AP is a useful pharmacological tool in studying various potassium conductances in physiology and biophysics.[citation needed] It is a relatively selective blocker of members of Kv1 (Shaker, KCNA) family of voltage-activated K+ channels. However, 4-AP has been shown to potentiate voltage-gated Ca2+ channel currents independent of effects on voltage-activated K+ channels.[13]

Convulsant activity

4-Aminopyridine is a potent convulsant and is used to generate seizures in animal models for the evaluation of antiseizure agents.[14]

Vertebrate pesticide

4-Aminopyridine is also used under the trade name Avitrol as 0.5% or 1% in bird control bait. It causes convulsions and, infrequently, death, depending on dosage.[15] The manufacturer says the proper dose should cause epileptic-like convulsions which cause the poisoned birds to emit distress calls resulting in the flock leaving the site; if the dose was sub-lethal, the birds will recover after 4 or more hours without long-term ill effect.[16] The amount of bait should be limited so that relatively few birds are poisoned, causing the remainder of the flock to be frightened away with a minimum of mortality. A lethal dose will usually cause death within an hour.[16] The use of 4-aminopyridine in bird control has been criticized by the Humane Society of the United States.[17]

Medical use

Clinical data
Trade namesAmpyra, Fampyra, others
License data
  • 1,4-dihydropyridin-4-imine
CompTox Dashboard (EPA)
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Fampridine has been used clinically in Lambert–Eaton myasthenic syndrome and multiple sclerosis. It acts by blocking voltage-gated potassium channels, prolonging action potentials and thereby increasing neurotransmitter release at the neuromuscular junction.[18] The drug has been shown to reverse saxitoxin and tetrodotoxin toxicity in tissue and animal experiments.[19][20][21][22] In calcium entry blocker overdose in humans, 4-aminopyridine can increase the cytosolic Ca2+ concentration very efficiently independent of the calcium channels.[19]

Multiple sclerosis

Fampridine has been shown to improve visual function and motor skills and relieve fatigue in patients with multiple sclerosis (MS). However, the effect of the drug is strongly established for walking capacity only.[23] Common side effects include dizziness, nervousness and nausea, and the incidence of adverse effects was shown to be less than 5% in all studies.[24][4]

4-AP works as a potassium channel blocker. Strong potassium currents decrease action potential duration and amplitude, which increases the probability of conduction failure − a well documented characteristic of demyelinated axons. Potassium channel blockade has the effect of increasing axonal action potential propagation and improving the probability of synaptic vesicle release. A study has shown that 4-AP is a potent calcium channel activator and can improve synaptic and neuromuscular function by directly acting on the calcium channel beta subunit.[25]

MS patients treated with 4-AP exhibited a response rate of 29.5% to 80%. A long-term study (32 months) indicated that 80-90% of patients who initially responded to 4-AP exhibited long-term benefits. Although improving symptoms, 4-AP does not inhibit progression of MS. Another study, conducted in Brazil, showed that treatment based on fampridine was considered efficient in 70% of the patients.[26]

Spinal cord injury

Spinal cord injury patients have also seen improvement with 4-AP therapy. These improvements include sensory, motor and pulmonary function, with a decrease in spasticity and pain.[27]

Tetrodotoxin poisoning

Clinical studies have shown that 4-AP is capable of reversing the effects of tetrodotoxin poisoning in animals, however, its effectiveness as an antidote in humans has not yet been determined.[19][20][21]


Case reports have shown that overdoses with 4-AP can lead to paresthesias, seizures,[28] and atrial fibrillation.[29]


4-aminopyridine is excreted by the kidneys. 4-AP should not be given to people with significant kidney disease (e.g., acute kidney injury or advanced chronic kidney disease) due to the higher risk of seizures with increased circulating levels of 4-AP.


The drug was originally intended, by Acorda Therapeutics, to have the brand name Amaya, however the name was changed to Ampyra to avoid potential confusion with other marketed pharmaceuticals.[30]

Four of Acorda's patents pertaining to Ampyra were invalidated in 2017 by the United States District Court for the District of Delaware and a fifth patent expired in 2018.[31] Since then, generic alternatives have been developed for the U.S. market.[32]

The drug is marketed by Biogen Idec in Canada as Fampyra[33] and as Dalstep in India by Sun Pharma.[34]


Parkinson's disease

Dalfampridine completed Phase II clinical trials for Parkinson's disease in July 2014.[35][needs update]

See also


  1. ^ Albert A, Goldacre R, Phillips J (1948). "455. The strength of heterocyclic bases". Journal of the Chemical Society (Resumed): 2240–2249. doi:10.1039/JR9480002240.
  2. ^ "Fampyra 10 mg prolonged-release tablets - Summary of Product Characteristics (SmPC)". (emc). 15 August 2018. Retrieved 24 August 2020.
  3. ^ "Ampyra- dalfampridine tablet, film coated, extended release". DailyMed. 20 December 2019. Retrieved 24 August 2020.
  4. ^ a b "Fampyra EPAR". European Medicines Agency (EMA). 17 September 2018. Retrieved 24 August 2020.
  5. ^ "Dalfampridine (Ampyra) Use During Pregnancy". Drugs.com. 22 June 2020. Retrieved 24 August 2020.
  6. ^ Solari A, Uitdehaag B, Giuliani G, Pucci E, Taus C (2002). Solari A (ed.). "Aminopyridines for symptomatic treatment in multiple sclerosis". The Cochrane Database of Systematic Reviews (4): CD001330. doi:10.1002/14651858.CD001330. PMC 7047571. PMID 12804404.
  7. ^ Korenke AR, Rivey MP, Allington DR (October 2008). "Sustained-release fampridine for symptomatic treatment of multiple sclerosis". The Annals of Pharmacotherapy. 42 (10): 1458–1465. doi:10.1345/aph.1L028. PMID 18780812. S2CID 207263182.
  8. ^ "New Drugs: Fampridine". Australian Prescriber (34): 119–123. August 2011. Archived from the original on 2012-02-27.
  9. ^ "Acorda Clinical Development and Product Pipeline". Acorda.
  10. ^ a b "FDA Approves Ampyra to Improve Walking in Adults with Multiple Sclerosis". U.S. Food and Drug Administration (FDA) (Press release). Archived from the original on Jan 12, 2017.
  11. ^ "Ampyra". National Multiple Sclerosis Society.
  12. ^ "Notice of Decision for FAMPYRA". hc-sc.gc.ca. Archived from the original on 2012-05-02. Retrieved 2012-04-21.
  13. ^ Wu ZZ, Li DP, Chen SR, Pan HL (December 2009). "Aminopyridines potentiate synaptic and neuromuscular transmission by targeting the voltage-activated calcium channel beta subunit". The Journal of Biological Chemistry. 284 (52): 36453–36461. doi:10.1074/jbc.M109.075523. PMC 2794761. PMID 19850918.
  14. ^ Yamaguchi S, Rogawski MA (March 1992). "Effects of anticonvulsant drugs on 4-aminopyridine-induced seizures in mice". Epilepsy Research. 11 (1): 9–16. doi:10.1016/0920-1211(92)90016-m. PMID 1563341. S2CID 5772125.
  15. ^ "EPA Reregistration Eligibility Decision for 4-aminopyridine" (PDF). U.S. Environmental Protection Agency. 27 September 2007. p. 23.
  16. ^ a b "What is Avitrol?". Avitrol Corporation, Tulsa, Oklahoma, US. Retrieved 15 August 2012.
  17. ^ Brasted M (May 13, 2008). "Poisonous Solution: The Avitrol Problem". Humane Society of the United States. Archived from the original on December 25, 2008. Retrieved December 23, 2008.
  18. ^ Judge SI, Bever CT (July 2006). "Potassium channel blockers in multiple sclerosis: neuronal Kv channels and effects of symptomatic treatment". Pharmacology & Therapeutics. 111 (1): 224–259. doi:10.1016/j.pharmthera.2005.10.006. PMID 16472864.
  19. ^ a b c van der Voort PH, Wilffert B, van Roon EN, Uges DR (July 2016). "4-Aminopyridine as a life-saving treatment in calcium channel antagonist intoxication". The Netherlands Journal of Medicine. 74 (6): 276. PMID 27571731.
  20. ^ a b Chang FC, Spriggs DL, Benton BJ, Keller SA, Capacio BR (July 1997). "4-Aminopyridine reverses saxitoxin (STX)- and tetrodotoxin (TTX)-induced cardiorespiratory depression in chronically instrumented guinea pigs". Fundamental and Applied Toxicology. 38 (1): 75–88. doi:10.1006/faat.1997.2328. PMID 9268607. S2CID 17185707.
  21. ^ a b Chen HM, Lin CH, Wang TM (November 1996). "Effects of 4-aminopyridine on saxitoxin intoxication". Toxicology and Applied Pharmacology. 141 (1): 44–48. doi:10.1006/taap.1996.0258. PMID 8917674.
  22. ^ Octopus Envenomations at eMedicine.com
  23. ^ Valet M, Quoilin M, Lejeune T, Stoquart G, Van Pesch V, El Sankari S, et al. (November 2019). "Effects of Fampridine in People with Multiple Sclerosis: A Systematic Review and Meta-analysis". CNS Drugs. 33 (11): 1087–1099. doi:10.1007/s40263-019-00671-x. PMID 31612418. S2CID 204543081.
  24. ^ Fampyra: EPAR - Product Information (PDF), London: European Medicines Agency, 1 Jun 2017, retrieved 11 Feb 2018
  25. ^ Wu ZZ, Li DP, Chen SR, Pan HL (December 2009). "Aminopyridines potentiate synaptic and neuromuscular transmission by targeting the voltage-activated calcium channel beta subunit". The Journal of Biological Chemistry. 284 (52): 36453–36461. doi:10.1074/jbc.M109.075523. PMC 2794761. PMID 19850918.
  26. ^ "Real-life experience with fampridine (Fampyra) for patients with multiple sclerosis and gait disorders". NeuroRehabilitation. August 1, 2016.
  27. ^ Van Diemen HA, Polman CH, Koetsier JC, Van Loenen AC, Nauta JJ, Bertelsmann FW (June 1993). "4-Aminopyridine in patients with multiple sclerosis: dosage and serum level related to efficacy and safety". Clinical Neuropharmacology. 16 (3): 195–204. doi:10.1097/00002826-199306000-00002. PMID 8504436.
  28. ^ Pickett TA, Enns R (March 1996). "Atypical presentation of 4-aminopyridine overdose". Annals of Emergency Medicine. 27 (3): 382–385. doi:10.1016/S0196-0644(96)70277-9. PMID 8599505.
  29. ^ Johnson NC, Morgan MW (February 2006). "An unusual case of 4-aminopyridine toxicity". The Journal of Emergency Medicine. 30 (2): 175–177. doi:10.1016/j.jemermed.2005.04.020. PMID 16567254.
  30. ^ Jeffrey S (January 22, 2010). "FDA Approves Dalfampridine to Improve Walking in Multiple Sclerosis". Medscape.
  31. ^ "US courts invalidates Dalfampridine patents". Acorda.
  32. ^ House DW (7 October 2019). "Supreme Court declines to hear Acorda appeal of adverse Ampyra patent ruling". Seeking Alpha. Retrieved 8 October 2019.
  33. ^ "Fampyra Drug Monograph" (PDF). Health Canada Drug Product Database. Biogen Idec Canada Inc. 26 November 2014. Retrieved 10 October 2017.
  34. ^ "Dalstep 10mg Registration Details". Registrationwala. Archived from the original on 2020-09-15. Retrieved 2018-11-25.
  35. ^ Clinical trial number NCT01491022 for "A Randomized Trial to Evaluate Ampyra for Gait Impairment in Parkinson's Disease" at ClinicalTrials.gov
  36. ^ Shinkichi Shimizu, Nanao Watanabe, Toshiaki Kataoka, Takayuki Shoji, Nobuyuki Abe, Sinji Morishita, Hisao Ichimura "Pyridine and Pyridine Derivatives" in "Ullmann's Encyclopedia of Industrial Chemistry" 2007; John Wiley & Sons: New York.
  37. ^ Gardner TS, Wenis E, Lee J (1954). "The Synthesis of Compounds for the Chemotherapy of Tuberculosis. Iv. The Amide Function". The Journal of Organic Chemistry. 19 (5): 753. doi:10.1021/jo01370a009.