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Cysteamine Side Effects

In Summary

Commonly reported side effects of cysteamine include: lethargy, vomiting, and anorexia. Other side effects include: skin rash. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to cysteamine: oral capsule, oral capsule delayed release

In addition to its needed effects, some unwanted effects may be caused by cysteamine. In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking cysteamine:

More common:
  • Abdominal or stomach pain
  • diarrhea
  • drowsiness
  • fever
  • loss of appetite
  • nausea or vomiting
  • skin rash
Less common:
  • Confusion
  • dizziness
  • headache
  • mental depression
  • sore throat
  • trembling
  • Convulsions
  • increased thirst
  • unusual tiredness or weakness
Incidence not known:
  • Blistering, peeling, or loosening of the skin
  • blurred or double vision
  • bone lesions
  • bulging soft spot on head of an infant
  • change in the ability to see colors, especially blue or yellow
  • chills
  • continuing ringing or buzzing or other unexplained noise in the ears
  • cough
  • eye pain
  • hearing loss
  • itching
  • joint or muscle pain
  • loss of appetite
  • loss of vision
  • pain behind the eyes
  • pain in the legs
  • pain with eye movement
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • reddish purple lines on the arms, face, legs, trunk, or groin
  • severe headache
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips

Minor Side Effects

Some of the side effects that can occur with cysteamine may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common:
  • Breath odor
  • constipation
  • hives or welts
  • redness of the skin
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  • weight loss

For Healthcare Professionals

Applies to cysteamine: oral capsule, oral delayed release capsule


The most common adverse events were vomiting, abdominal pain, nausea, anorexia, fever, diarrhea, lethargy, headache, and rash.[Ref]


Very common (10% or more): Vomiting (35%), diarrhea (16%)
Common (1% to 10%): Nausea, bad breath, abdominal pain, dyspepsia
Uncommon (0.1% to 1%): Gastrointestinal ulceration and bleeding, constipation, gastroenteritis, duodenitis[Ref]


Very common (10% or more): Anorexia (31%)
Uncommon (0.1% to 1%): Dehydration[Ref]

Nervous system

Very common (10% or more): Lethargy (11%)
Common (1% to 10%): Dizziness, headache, encephalopathy
Uncommon (0.1% to 1%): Somnolence, seizures, convulsions, ataxia, confusion, tremor, hyperkinesia, jitteriness
Postmarketing reports: Benign intracranial hypertension with papilledema[Ref]


Very common (10% or more): Fever (22%)
Common (1% to 10%): Fatigue, asthenia
Uncommon (0.1% to 1%): Decreasing hearing[Ref]


Common (1% to 10%): Rash, skin odor
Uncommon (0.1% to 1%): Hair color changes, skin fragility (molluscoid pseudomotor on elbows)
Frequency not reported: Urticaria
Postmarketing reports: Skin lesions, skin striae, skin fragility[Ref]

Cases of Ehlers-Danlos like syndrome and vascular disorders on elbows have been reported in children chronically treated with high doses of different cysteamine preparations. In cases where histopathological examination of the skin was performed, the results suggested angioendotheliomatosis.[Ref]


Common (1% to 10%): Abnormal liver function
Frequency not reported: Elevated alkaline phosphatase[Ref]


Uncommon (0.1% to 1%): Hypertension[Ref]


Uncommon (0.1% to 1%): Abnormal urine odor[Ref]


Uncommon (0.1% to 1%): Leukopenia, anemia[Ref]


Uncommon (0.1% to 1%): Anaphylactic reaction[Ref]


Uncommon (0.1% to 1%): Joint hyperextension, leg pain, genu valgum, osteopenia, compression fracture, scoliosis
Postmarketing reports: Molluscoid pseudotumors[Ref]


Uncommon (0.1% to 1%): Nervousness, abnormal thinking, depression, emotional lability, hallucinations, nightmares[Ref]


Uncommon (0.1% to 1%): Nephrotic syndrome, interstitial nephritis, renal failure[Ref]

Cases of nephrotic syndrome have been reported within 6 months of starting therapy with progressive recovery after treatment discontinuation. In some cases, histology showed a membranous glomerulonephritis of the renal allograft and hypersensitivity interstitial nephritis.[Ref]


1. "Product Information. Procysbi (cysteamine)." Raptor Pharmaceutical Corporation, Novato, CA.

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. "Product Information. Cystagon (cysteamine)." Mylan Pharmaceuticals, Morgantown, WV.

4. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Not all side effects for cysteamine may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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