Last updated
IUPAC name
Systematic IUPAC name
(2-Sulfanylpropanamido)acetic acid
Other names
3D model (JSmol)
ECHA InfoCard 100.016.163 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 217-778-4
MeSH Tiopronin
PubChem CID
RTECS number
  • MC0596500
  • InChI=1S/C5H9NO3S/c1-3(10)5(9)6-2-4(7)8/h3,10H,2H2,1H3,(H,6,9)(H,7,8) Yes check.svgY
  • CC(S)C(=O)NCC(O)=O
Molar mass 163.19 g·mol−1
AppearanceWhite, opaque crystals
Melting point 93 to 98 °C (199 to 208 °F; 366 to 371 K)
log P −0.674
Acidity (pKa)3.356
Basicity (pKb)10.641
G04BX16 ( WHO ) QG04BX16 ( WHO )
By mouth
Legal status
GHS labelling:
Lethal dose or concentration (LD, LC):
1,300 mg kg−1(oral, rat)
Related compounds
Related alkanoic acids
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)
Clinical data
Trade names Thiola
License data
CompTox Dashboard (EPA)
ECHA InfoCard 100.016.163 OOjs UI icon edit-ltr-progressive.svg

Tiopronin, sold under the brand name Thiola, is a medication used to control the rate of cystine precipitation and excretion in the disease cystinuria. [3] [4]


It is available as a generic medication. [5] [6]

Medical uses

Tiopronin is indicated, in combination with high fluid intake, alkali, and diet modification, for the prevention of cystine stone formation in people 20 kilograms (44 lb) and greater with severe homozygous cystinuria, who are not responsive to these measures alone. [1] [2]

Side effects

Tiopronin may present a variety of side effects, which are broadly similar to those of D-penicillamine and other compounds containing active sulfhydryl groups. [7] Its pharmacokinetics have been studied. [8]


Mechanism of action

Tiopronin works by reacting with urinary cysteine to form a more soluble, disulfide linked, tiopronin-cysteine complex. [8]

Society and culture

In the U.S., the drug was marketed by Mission Pharmacal at $1.50 per pill, but in 2014 the rights were bought by Retrophin, owned by Martin Shkreli, and the price increased to $30 per pill for a 100 mg capsule. [9] [10]

In 2016 Imprimis Pharmaceuticals introduced a lower cost version marketed as a compounded drug. [11]


It may also be used for Wilson's disease (an overload of copper in the body), and has also been investigated for the treatment of arthritis, [12] [13] though tiopronin is not an anti-inflammatory.[ citation needed ]

Tiopronin is also sometimes used as a stabilizing agent for metal nanoparticles. The thiol group binds to the nanoparticles, preventing coagulation. [14]

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