Cysteamine

Cysteamine
INN: mercaptamine
Skeletal formula (top)
Ball-and-stick model of the cysteamine
Clinical data
Trade namesCystagon, Procysbi, Cystaran, others
Other names2-Aminoethanethiol, β-Mercaptoethylamine, 2-Mercaptoethylamine, decarboxycysteine, thioethanolamine, mercaptamine bitartrate, cysteamine (USAN US)
AHFS/Drugs.comMicromedex Detailed Consumer Information
License data
Pregnancy
category
  • AU: B3
Routes of
administration		By mouth, eye drops
ATC code
Legal status
Legal status
  • CA: ℞-only
  • UK: POM (Prescription only)
  • US: ℞-only
  • EU: Rx-only
  • In general: ℞ (Prescription only)
Identifiers
  • 2-Aminoethane-1-thiol
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
PDB ligand
CompTox Dashboard (EPA)
ECHA InfoCard100.000.421 Edit this at Wikidata
Chemical and physical data
FormulaC2H7NS
Molar mass77.15 g·mol−1
3D model (JSmol)
Melting point95 to 97 °C (203 to 207 °F)
  • C(CS)N
  • InChI=1S/C2H7NS/c3-1-2-4/h4H,1-3H2 checkY
  • Key:UFULAYFCSOUIOV-UHFFFAOYSA-N

Cysteamine is an organosulfur compound with the formula 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]+, including the hydrochloride, and the bitartrate. Another derivative is phosphocysteamine, H3NCH2CH2SPO3Na. The intermediate pantetheine is broken down into cysteamine and pantothenic acid.

It is biosynthesized in mammals, including humans, by the degradation of coenzyme A. It is the biosynthetic precursor to the neurotransmitter hypotaurine.

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. It removes the excessive cystine that builds up in cells of people with the disease. Cysteamine functions by the following chemical reaction converting the disulfide cystine to a more soluble mixed disulfide and cysteine, both of which are more soluble than cystine.

(SCH2CH(NH3)CO−2)2 + HSCH2CH2NH2 → H2NCH2CH2SSCH2CH(NH3)CO−2 + HSCH2CH(NH3)CO−2

It is available by mouth (capsule and extended release capsule) and in eye drops.

When applied topically, it can lighten skin darkened by post-inflammatory hyperpigmentation, sun exposure or melasma.

Adverse effects

The label for oral formulations of cysteamine carries 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 the buildup of cystine in lysosomes, where it crystallizes and damages cells. 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.

References

  1. ↑ "Cystadrops : Cysteamine Ophthalmic Solution" (PDF). Pdf.hres.ca. Archived (PDF) from the original on 10 June 2022. Retrieved 8 June 2022.
  2. ↑ "Genetic disorders". Health Canada. 9 May 2018. Retrieved 13 April 2024.
  3. ↑ "Cystagon 150 mg hard capsules - Summary of Product Characteristics (SmPC)". Medicines.org.uk. 19 June 2019. Archived from the original on 9 June 2021. Retrieved 28 April 2020.
  4. ↑ "Cystadrops 3.8 mg/mL eye drops solution - Summary of Product Characteristics (SmPC)". (emc). 19 June 2019. Archived from the original on 9 June 2020. Retrieved 9 June 2020.
  5. ↑ "Procysbi 25 mg gastro-resistant hard capsules - Summary of Product Characteristics (SmPC)". Medicines.org.uk. 17 September 2019. Archived from the original on 22 January 2021. Retrieved 9 June 2020.
  6. 1 2 3 "Cystagon- cysteamine bitartrate capsule". DailyMed. 29 January 2019. Archived from the original on 25 March 2021. Retrieved 27 April 2020.
  7. 1 2 3 4 "Cystaran- cysteamine hydrochloride solution". DailyMed. 22 November 2019. Archived from the original on 24 March 2021. Retrieved 27 April 2020.
  8. 1 2 3 4 5 6 7 8 9 10 "Procysbi- cysteamine bitartrate capsule, delayed release pellets Procysbi- cysteamine bitartrate granule, delayed release". DailyMed. U.S. National Library of Medicine. 9 April 2025. Retrieved 25 May 2025.
  9. 1 2 3 4 5 6 7 8 "Procysbi EPAR". European Medicines Agency (EMA). 22 September 2023. Retrieved 25 May 2025.
  10. 1 2 "Cystadrops EPAR". European Medicines Agency. 22 February 2017. Archived from the original on 4 August 2020. Retrieved 27 April 2020.
  11. ↑ Reid EE (1958). Organic Chemistry of Bivalent Sulfur. Vol. 1. New York: Chemical Publishing Company, Inc. pp. 398–399.
  12. 1 2 3 Besouw M, Masereeuw R, van den Heuvel L, Levtchenko E (August 2013). "Cysteamine: an old drug with new potential". Drug Discovery Today. 18 (15–16): 785–792. doi:10.1016/j.drudis.2013.02.003. PMID 23416144.
  13. ↑ Tennezé L, Daurat V, Tibi A, Chaumet-Riffaud P, Funck-Brentano C (1999). "A study of the relative bioavailability of cysteamine hydrochloride, cysteamine bitartrate and phosphocysteamine in healthy adult male volunteers". British Journal of Clinical Pharmacology. 47 (1): 49–52. doi:10.1046/j.1365-2125.1999.00844.x. PMC 2014194. PMID 10073739.
  14. ↑ Singer TP (1975). "Oxidative Metabolism of Cysteine and Cystine". In Greenberg DM (ed.). Metabolic pathways: Metabolism of sulfur compounds. Vol. 7 (3rd ed.). New York: Academic Press. p. 545. ISBN 9780323162081. Archived from the original on 7 June 2021. Retrieved 11 January 2017.
  15. ↑ Hsu C, Mahdi H, Pourahmadi M, Ahmadi S (April 2013). "Cysteamine cream as a new skin depigmenting product". Journal of the American Academy of Dermatology. 68 (4): AB189. doi:10.1016/j.jaad.2012.12.781. Retrieved 10 October 2021.
  16. ↑ "Cysteamine cream". DermNet NZ. Archived from the original on 29 June 2021. Retrieved 29 June 2021.
  17. ↑ Grimes PE, Ijaz S, Nashawati R, Kwak D (February 2019). "New oral and topical approaches for the treatment of melasma". International Journal of Women's Dermatology. 5 (1): 30–36. doi:10.1016/j.ijwd.2018.09.004. PMC 6374710. PMID 30809577.
  18. ↑ Nesterova G, Gahl WA (6 October 2016). "Cystinosis". In Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJ, Stephens K, Amemiya A (eds.). GeneReviews. Seattle WA: University of Washington. PMID 20301574. Archived from the original on 5 April 2011. Retrieved 11 January 2017.
  19. ↑ Pollack A (30 April 2013). "F.D.A. Approves Raptor Drug for Form of Cystinosis". The New York Times. Archived from the original on 10 September 2021. Retrieved 26 February 2017.