Mercaptamine (cysteamine)
Brand names: Cystagon, Cystadrops, Procysbi
Mercaptamine (cysteamine) is a cystine-depleting agent used to treat nephropathic cystinosis, reducing the accumulation of cystine in body tissues.
ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.
Clinical monograph
How it works
Within lysosomes, cysteamine reacts with cystine to form cysteine and a cysteine-cysteamine mixed disulphide, both of which can exit the lysosome via alternative transporters, thereby lowering intracellular cystine.
Prescribing in practice
- Lifelong, consistent dosing is essential and treatment should be started promptly after diagnosis to delay organ damage, with leucocyte cystine used to guide therapy.
- Gastrointestinal upset and a strong odour (breath and sweat) are common and can affect adherence.
- It can cause serious skin and bone lesions at high exposure, so the dose should not be exceeded.
Monitoring
Monitor leucocyte cystine concentrations to titrate dosing, alongside clinical review for adverse effects.
Counselling the patient
- Take the medicine regularly and exactly as prescribed; missing doses reduces its protective effect.
- A noticeable body or breath odour can occur and is expected.
- Report severe gastrointestinal symptoms, skin changes or bone pain.
Evidence & guidelines
Cysteamine is established as the cornerstone of treatment for nephropathic cystinosis, shown to delay progression of renal and extrarenal complications.
Reference: SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.