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Mercaptamine

Cystadrops, Procysbi · ATC code S01XA21

Also known as: Merkaptamin

Key facts
Active substance
Mercaptamine
ATC code
S01XA21
Authorisation
centrally authorised across the EU (EMA)
Dosage forms
Cystadrops 3.8 mg/mL eye drops solution · PROCYSBI 25 mg gastro-resistant hard capsules / PROCYSBI 75 mg gastro-resistant hard capsules
Marketing authorisation holder
Recordati Rare Diseases, Chiesi Farmaceutici S.p.A
Information as of
2026-10-28

Key facts

Mercaptamine (cysteamine) reduces cystine accumulation in cystinosis; it is authorised as eye drops (Cystadrops) for corneal cystine crystals and as gastro-resistant capsules (Procysbi) for nephropathic cystinosis.

What it is used for

  • Cystadrops: corneal cystine crystal deposits in adults and children from 6 months of age with cystinosis.
  • Procysbi: proven nephropathic cystinosis; when started early it delays the development of renal failure.

Dosing

  • Cystadrops: one drop in each eye 4 times a day during waking hours, about 4 hours apart; may be reduced progressively to a minimum of 1 drop daily per eye according to eye examination; no more than 4 drops a day per eye. Do not stop, as crystals re-accumulate. Discard the bottle after 7 days.
  • Procysbi: given every 12 hours. When transferring from immediate-release cysteamine bitartrate, use the same total daily dose split into two doses; check WBC cystine after 2 weeks and then every 3 months.
  • Procysbi in newly diagnosed adults: start at 1/6 to 1/4 of the target maintenance dose of 1.3 g/m²/day; in children dose by weight (see the full text). Doses above 1.95 g/m²/day are not recommended.
  • Procysbi: intact capsules should not be given to children under about 6 years (aspiration risk).

Contraindications

  • Cystadrops: hypersensitivity to the active substance or any excipient.
  • Procysbi: hypersensitivity to any form of cysteamine, to penicillamine or to any excipient; breast-feeding.

Important warnings

  • Cystadrops: contains benzalkonium chloride (eye irritation, keratopathy, discolours soft contact lenses); remove lenses and wait at least 15 minutes before re-inserting.
  • Procysbi: oral cysteamine does not prevent corneal crystal deposits – continue the eye drops.
  • Procysbi: serious skin lesions and bone abnormalities at high doses; monitor skin and bones; do not re-administer after severe rash (e.g. toxic epidermal necrolysis).
  • Procysbi: GI ulceration and bleeding, benign intracranial hypertension, reversible leukopenia and abnormal liver function; monitor blood counts and liver function.

Side effects

  • Cystadrops: very common eye pain, blurred vision, eye irritation, ocular hyperaemia, eye pruritus, increased lacrimation, eye deposits; mostly transient and mild to moderate.
  • Procysbi: very common anorexia, vomiting, nausea and diarrhoea; common headache, encephalopathy, abdominal pain, breath and skin odour, rash.

Interactions

  • Cystadrops: no interactions with oral medicines expected; allow ten minutes between eye medicines.
  • Procysbi: give bicarbonate at least one hour before or after; electrolytes, minerals, vitamin D and thyroid hormone can be co-administered.

Pregnancy and breastfeeding

  • Teratogenic in animals; Procysbi should not be used in pregnancy, particularly the first trimester, unless clearly necessary. Negative pregnancy test and contraception before starting.
  • With Cystadrops systemic exposure is negligible; take care with concomitant oral cysteamine.

Summary of the official product information, written with AI on 2026-10-29. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

Full official text →

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For patients

Package leaflet, verbatim

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

EU – centrally authorised (all member states)

  • CystadropsRecordati Rare Diseases · EMEA/H/C/003769
  • ProcysbiChiesi Farmaceutici S.p.A · EMEA/H/C/002465

Source: European Medicines Agency (EMA), product information

Brand names in 3 more European countries
Iceland
Cystadrops, Cystagon, Procysbi
Liechtenstein
Cystadrops, Cystagon, Procysbi
Norway
Cystadrops, Cystagon, Procysbi

EMA – Article 57 product data (EU/EEA), 2026-10-29

Medelix receives no money from pharmaceutical companies. Brand names are listed alphabetically and without ranking.

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Sources

  1. European Medicines Agency. Cystadrops – EPAR, Product Information. 2026-10-28. https://www.ema.europa.eu/en/documents/product-information/cystadrops-epar-product-information_en.pdf
  2. European Medicines Agency. Procysbi – EPAR, Product Information. 2026-10-28. https://www.ema.europa.eu/en/documents/product-information/procysbi-epar-product-information_en.pdf

Editorial: Medelix editorial team · last updated 2026-10-28 · How these pages are made · Report an error

Source: European Medicines Agency (EMA), product information. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.