:Cysteamine
{{Short description|Chemical compound}}
{{Distinguish|cystamine}}
{{Use dmy dates|date=April 2020}}
{{cs1 config |name-list-style=vanc |display-authors=6}}
{{Infobox drug
| INN = mercaptamine
| IUPAC_name = 2-Aminoethane-1-thiol
| image = Cysteamine-2D-skeletal.png
| width =
| alt =
| image2 = Cysteamine 3D ball.png
| width2 =
| alt2 =
| caption = Skeletal formula (top)
Ball-and-stick model of the cysteamine
| INN_EMA = mercaptamine
| USAN = cysteamine
| tradename = Cystagon, Procysbi, Cystaran, others
| Drugs.com = {{drugs.com|cons|cysteamine}}
| DailyMedID = Cysteamine
| pregnancy_AU = B3
| pregnancy_AU_comment =
| pregnancy_category=
| routes_of_administration = By mouth, eye drops
| class =
| ATC_prefix = A16
| ATC_suffix = AA04
| ATC_supplemental = {{ATC|S01|XA21}}
| legal_AU =
| legal_AU_comment =
| legal_BR =
| legal_BR_comment =
| legal_CA = Rx-only
| legal_CA_comment = {{cite web|url=https://pdf.hres.ca/dpd_pm/00049612.PDF|title=Cystadrops : Cysteamine Ophthalmic Solution|website=Pdf.hres.ca|access-date=8 June 2022|archive-date=10 June 2022|archive-url=https://web.archive.org/web/20220610034106/https://pdf.hres.ca/dpd_pm/00049612.PDF|url-status=live}}{{cite web | title=Genetic disorders | website=Health Canada | date=9 May 2018 | url=https://www.canada.ca/en/services/health/drug-health-products/drug-medical-device-highlights-2017/approved-drugs/genetic-disorders.html | access-date=13 April 2024}}
| legal_DE =
| legal_DE_comment =
| legal_NZ =
| legal_NZ_comment =
| legal_UK = POM
| legal_UK_comment = {{cite web | title=Cystagon 150 mg hard capsules - Summary of Product Characteristics (SmPC) | website=Medicines.org.uk | date=19 June 2019 | url=https://www.medicines.org.uk/emc/product/6237/smpc | access-date=28 April 2020 | archive-date=9 June 2021 | archive-url=https://web.archive.org/web/20210609150203/https://www.medicines.org.uk/emc/product/6237/smpc | url-status=live }}{{cite web | title=Cystadrops 3.8 mg/mL eye drops solution - Summary of Product Characteristics (SmPC) | website=(emc) | date=19 June 2019 | url=https://www.medicines.org.uk/emc/product/8505/smpc | access-date=9 June 2020 | archive-date=9 June 2020 | archive-url=https://web.archive.org/web/20200609160936/https://www.medicines.org.uk/emc/product/8505/smpc | url-status=live }}{{cite web | title=Procysbi 25 mg gastro-resistant hard capsules - Summary of Product Characteristics (SmPC) | website=Medicines.org.uk | date=17 September 2019 | url=https://www.medicines.org.uk/emc/product/2079/smpc | access-date=9 June 2020 | archive-date=22 January 2021 | archive-url=https://web.archive.org/web/20210122225837/https://www.medicines.org.uk/emc/product/2079/smpc | url-status=live }}
| legal_US = Rx-only
| legal_EU = Rx-only
| legal_UN =
| legal_UN_comment =
| legal_status = Rx-only
| bioavailability =
| protein_bound =
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| index2_label = as salt
| CAS_number = 60-23-1
| CAS_supplemental = {{cascite|correct|CAS}}
| PubChem = 6058
| IUPHAR_ligand = 7440
| DrugBank = DB00847
| ChemSpiderID = 5834
| UNII = 5UX2SD1KE2
| KEGG = D03634
| KEGG2 = D10468
| ChEBI = 17141
| ChEMBL = 602
| NIAID_ChemDB =
| PDB_ligand = DHL
| synonyms = 2-Aminoethanethiol, β-Mercaptoethylamine, 2-Mercaptoethylamine, decarboxycysteine, thioethanolamine, mercaptamine bitartrate
| C=2 | H=7 | N=1 | S=1
| SMILES = C(CS)N
| StdInChI = 1S/C2H7NS/c3-1-2-4/h4H,1-3H2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI_comment =
| StdInChIKey = UFULAYFCSOUIOV-UHFFFAOYSA-N
| density =
| density_notes =
| melting_point = 95 to 97
| melting_high =
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Cysteamine is an organosulfur compound with the formula {{chem2|HSCH2CH2NH2}}. A white, water-soluble solid, it contains both an amine and a thiol functional group. It is often used as the salt of the ammonium derivative [HSCH2CH2NH3]+,{{cite book | vauthors = Reid EE |title= Organic Chemistry of Bivalent Sulfur |volume= 1|year=1958 |publisher=Chemical Publishing Company, Inc. |location= New York|pages=398–399}} including the hydrochloride, phosphocysteamine, and the bitartrate. The intermediate pantetheine is broken down into cysteamine and pantothenic acid.{{cite journal | vauthors = Besouw M, Masereeuw R, van den Heuvel L, Levtchenko E | title = Cysteamine: an old drug with new potential | journal = Drug Discovery Today | volume = 18 | issue = 15–16 | pages = 785–792 | date = August 2013 | pmid = 23416144 | doi = 10.1016/j.drudis.2013.02.003}}
It is biosynthesized in mammals, including humans, by the degradation of coenzyme A. It is the biosynthetic precursor to the neurotransmitter hypotaurine.{{cite book |vauthors=Singer TP |veditors=Greenberg DM |title=Metabolic pathways: Metabolism of sulfur compounds |volume=7 |date=1975 |publisher=Academic Press |location=New York |isbn=9780323162081 |edition=3rd |chapter-url=https://books.google.com/books?id=2h-CyZzkPAwC&pg=PA545 |chapter=Oxidative Metabolism of Cysteine and Cystine |page=545 |access-date=11 January 2017 |archive-date=7 June 2021 |archive-url=https://web.archive.org/web/20210607203433/https://books.google.com/books?id=2h-CyZzkPAwC&pg=PA545 |url-status=live }}
Medical uses
As a medication sold under the brand names Procysbi or Cystagon, among others, cysteamine is indicated to treat cystinosis, a lysosomal storage disease characterized by the abnormal accumulation of cystine, the oxidized dimer of the amino acid cysteine.{{cite web | title=Procysbi- cysteamine bitartrate capsule, delayed release pellets Procysbi- cysteamine bitartrate granule, delayed release | work = DailyMed | publisher = U.S. National Library of Medicine | date=9 April 2025 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d3a3ec28-f746-463a-bb92-3bc8826db09e | access-date=25 May 2025}}{{cite web | title=Procysbi EPAR | website=European Medicines Agency (EMA) | date=22 September 2023 | url=https://www.ema.europa.eu/en/medicines/human/EPAR/procysbi | access-date=25 May 2025}} It removes the excessive cystine that builds up in cells of people with the disease. It is available by mouth (capsule and extended release capsule) and in eye drops.{{cite web | title=Cystagon- cysteamine bitartrate capsule | website=DailyMed | date=29 January 2019 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f495b76d-96c6-48e5-8fa3-30a4336628eb | access-date=27 April 2020 | archive-date=25 March 2021 | archive-url=https://web.archive.org/web/20210325054850/https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f495b76d-96c6-48e5-8fa3-30a4336628eb | url-status=live }}{{cite web | title=Cystaran- cysteamine hydrochloride solution | website=DailyMed | date=22 November 2019 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b98ee838-ed23-42a9-93b5-72579e490fba | access-date=27 April 2020 | archive-date=24 March 2021 | archive-url=https://web.archive.org/web/20210324215617/https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b98ee838-ed23-42a9-93b5-72579e490fba | url-status=live }}{{cite web | title=Cystadrops EPAR | website=European Medicines Agency | date=22 February 2017 | url=https://www.ema.europa.eu/en/medicines/human/EPAR/cystadrops | access-date=27 April 2020 | archive-date=4 August 2020 | archive-url=https://web.archive.org/web/20200804152527/https://www.ema.europa.eu/en/medicines/human/EPAR/cystadrops | url-status=live}}
When applied topically, it can lighten skin darkened by post-inflammatory hyperpigmentation, sun exposure or melasma.{{cite journal| vauthors = Hsu C, Mahdi H, Pourahmadi M, Ahmadi S |date=April 2013|title=Cysteamine cream as a new skin depigmenting product | journal = Journal of the American Academy of Dermatology |volume=68 |issue=4 |pages=AB189 |doi=10.1016/j.jaad.2012.12.781|url=https://www.jaad.org/article/S0190-9622(12)02060-9/fulltext|access-date=2021-10-10|url-access=subscription}}{{Cite web |title=Cysteamine cream |work=DermNet NZ |url=https://dermnetnz.org/topics/cysteamine-cream/ |access-date=2021-06-29 |archive-date=29 June 2021 |archive-url=https://web.archive.org/web/20210629033843/https://dermnetnz.org/topics/cysteamine-cream/ |url-status=live }}{{cite journal | vauthors = Grimes PE, Ijaz S, Nashawati R, Kwak D | title = New oral and topical approaches for the treatment of melasma | journal = International Journal of Women's Dermatology | volume = 5 | issue = 1 | pages = 30–36 | date = February 2019 | pmid = 30809577 | pmc = 6374710 | doi = 10.1016/j.ijwd.2018.09.004 }}
Adverse effects
The label for oral formulations of cysteamine carry warnings about symptoms similar to Ehlers-Danlos syndrome, severe skin rashes, ulcers or bleeding in the stomach and intestines, central nervous symptoms including seizures, lethargy, somnolence, depression, and encephalopathy, low white blood cell levels, elevated alkaline phosphatase, and idiopathic intracranial hypertension that can cause headache, tinnitus, dizziness, nausea, double or blurry vision, loss of vision, and pain behind the eye or pain with eye movement.
Additional adverse effects of oral cysteamine include bad breath, skin odor, vomiting, nausea, stomach pain, diarrhea, and loss of appetite.
For eye drops, the most common adverse effects are sensitivity to light, redness, and eye pain, headache, and visual field defects.
Interactions
There are no drug interactions for normal capsules or eye drops, but the extended release capsules should not be taken with drugs that affect stomach acid like proton pump inhibitors or with alcohol, as they can cause the drug to be released too quickly. It does not inhibit any cytochrome P450 enzymes.
Pharmacology
People with cystinosis lack a functioning transporter (cystinosin) which transports cystine from the lysosome to the cytosol. This ultimately leads to buildup of cystine in lysosomes, where it crystallizes and damages cells.{{cite book | vauthors = Nesterova G, Gahl WA | veditors = Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJ, Stephens K, Amemiya A | chapter = Cystinosis | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK1400/ | title = GeneReviews | publisher = University of Washington | location = Seattle WA | pmid = 20301574 | date = October 6, 2016 | access-date = 11 January 2017 | archive-date = 5 April 2011 | archive-url = https://web.archive.org/web/20110405074013/https://www.ncbi.nlm.nih.gov/books/NBK1400/ | url-status = live }} Cysteamine enters lysosomes and converts cystine into cysteine and cysteine-cysteamine mixed disulfide, both of which can exit the lysosome. Cysteamine also promotes the transport of L-cysteine into cells.
History
The therapeutic effect of cysteamine on cystinosis was reported in the 1950s. Cysteamine was approved as a drug for cystinosis in the US in 1994. An extended release form was approved in 2013.{{cite news| vauthors = Pollack A |title=F.D.A. Approves Raptor Drug for Form of Cystinosis|url=https://www.nytimes.com/2013/05/01/business/fda-approves-raptor-drug-for-form-of-cystinosis.html|work=The New York Times|date=30 April 2013|access-date=26 February 2017|archive-date=10 September 2021|archive-url=https://web.archive.org/web/20210910154630/https://www.nytimes.com/2013/05/01/business/fda-approves-raptor-drug-for-form-of-cystinosis.html|url-status=live}}
References
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