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Generic name: cysteamine
Brand names: Cystagon, Procysbi
Drug class: Miscellaneous uncategorized agents

Medically reviewed by  A Ras MD.

What is Procysbi used for?

Procysbi is a prescription medicine that is used to treat nephropathic cystinosis.

Before taking Procysbi, tell your doctor:

  • If you are allergic to Procysbi; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you are breast-feeding or plan to breast-feed.

This medicine may interact with other drugs or health problems.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Procysbi with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.


PROCYSBI, for oral administration, is a cystine-depleting agent that lowers the cystine content of cells in patients with nephropathic cystinosis, an inherited defect of lysosomal transport.

PROCYSBI contains the bitartrate salt of cysteamine. The chemical name for cysteamine bitartrate is ethanethiol, 2-amino, (2R,3R)-2,3-dihydroxybutanedioate (1:1) (salt). Cysteamine bitartrate is a highly water soluble white powder with a molecular weight of 227.24 and the molecular formula C2H7NS ∙ C4H6O6. It has the following chemical structure:

Chemical Structure

Each PROCYSBI delayed-release capsule contains either 25 mg cysteamine (equivalent to 74 mg cysteamine bitartrate) or 75 mg cysteamine (equivalent to 221 mg cysteamine bitartrate).

Each packet of PROCYSBI delayed-release oral granules contains either 75 mg cysteamine (equivalent to 221 mg cysteamine bitartrate) or 300 mg cysteamine (equivalent to 884 mg cysteamine bitartrate).

PROCYSBI delayed release granules contain the following inactive ingredients: Eudragit® L 30 D-55 (methacrylic acid-ethyl acrylate copolymer), hypromellose, microcrystalline cellulose, purified water, sodium lauryl sulfate, talc, and triethyl citrate. Additionally the capsule shell contains the following inactive ingredients: gelatin, ink (blue and white), and titanium dioxide.

 Mechanism of Action

Cysteamine is an aminothiol that participates within lysosomes in a thiol-disulfide interchange reaction converting cystine into cysteine and cysteine-cysteamine mixed disulfide, both of which can exit the lysosome in patients with cystinosis.

What are some things I need to know or do while I take Procysbi?

For all patients taking Procysbi:

  • Tell all of your health care providers that you take Procysbi. This includes your doctors, nurses, pharmacists, and dentists.
  • Avoid driving and doing other tasks or actions that call for you to be alert until you see how Procysbi affects you.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • Follow up with the doctor as you have been told.
  • Avoid drinking alcohol while taking Procysbi.
  • This medicine may raise the chance of ulcers or bleeding from the stomach or bowel. Talk with the doctor.
  • Low white blood cell counts have happened with Procysbi. This may lead to a higher chance of getting an infection. Call your doctor right away if you have signs of infection like fever, chills, or sore throat.
  • Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using Procysbi while you are pregnant.


  • If your child’s weight changes, talk with the doctor. The dose of Procysbi may need to be changed.

How is Procysbi best taken?

Use Procysbi as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • Swallow whole. Do not chew or crush.
  • Keep taking Procysbi as you have been told by your doctor or other health care provider, even if you feel well.
  • Take Procysbi with fruit juice (not grapefruit juice) or water.
  • Take at least 30 minutes before or 2 hours after a meal.
  • If you cannot take Procysbi without eating, you can eat a little bit of food (about 1/2 cup) within 1 hour before taking Procysbi through 1 hour after taking it.
  • Always take with a little bit of food or always take on an empty stomach.
  • Avoid high-fat food close to when you take Procysbi.
  • You may sprinkle contents of capsule on up to 1/2 cup (4 ounces/120 mL) of applesauce or berry jelly. The contents may also be mixed in 1/2 cup (4 ounces/120 mL) of fruit juice (not grapefruit juice) or water. Do not chew. Take within 30 minutes of mixing.
  • After mixing, take your dose right away. Do not store for future use.
  • Those who have feeding tubes may use Procysbi. Use as you have been told. Flush the feeding tube after Procysbi is given.
  • Some other drugs may need to be taken at some other time than Procysbi. If you take other drugs, check with your doctor or pharmacist to see if you need to take them at some other time than Procysbi.

What do I do if I miss a dose?

  • Take a missed dose as soon as you think about it.
  • If the next dose is less than 4 hours away, skip the missed dose and go back to your normal time.
  • Do not take 2 doses at the same time or extra doses.

What are the side effects of Procysbi that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of fluid and electrolyte problems like mood changes, confusion, muscle pain or weakness, a heartbeat that does not feel normal, very bad dizziness or passing out, fast heartbeat, more thirst, seizures, feeling very tired or weak, not hungry, unable to pass urine or change in the amount of urine produced, dry mouth, dry eyes, or very bad upset stomach or throwing up.
  • Ringing in ears.
  • Dizziness or passing out.
  • Feeling sleepy.
  • Eye pain.
  • Black, tarry, or bloody stools.
  • Throwing up blood or throw up that looks like coffee grounds.
  • Stomach pain.
  • Upset stomach or throwing up.
  • Not hungry.
  • Low mood (depression).
  • A very bad skin reaction (toxic epidermal necrolysis) may happen. It can cause very bad health problems that may not go away, and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.
  • Raised pressure in the brain has happened with Procysbi. Most of the time, this will go back to normal after Procysbi is stopped. Sometimes, loss of eyesight may happen and may not go away even after Procysbi is stopped. Call your doctor right away if you have a headache or eyesight problems like blurred eyesight, seeing double, or loss of eyesight.
  • Very bad skin problems like stretch marks, joint problems, and bone problems like broken bones and deformed bones have happened with Procysbi. Call your doctor right away if you have any skin changes or bone or joint pain.

What are some other side effects of Procysbi?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Diarrhea.
  • Feeling tired or weak.
  • Change in body odor.
  • Bad breath.
  • Eye irritation.
  • Flu-like signs.
  • Nose or throat irritation.
  • Ear pain.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out Procysbi?

  • Store at room temperature.
  • Store in the original container. Do not take out the antimoisture cube or packet.
  • Protect from light.
  • Keep lid tightly closed.
  • Store in a dry place. Do not store in a bathroom.
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.



  • NDC # 75987-100-04
  • Dispense only in
    original packaging
  • 25 mg
    (cysteamine bitartrate)
    delayed-release capsules
  • 60 capsules
  • Rx Only
  • Distributed by:
    Horizon Therapeutics USA, Inc.
    Deerfield, IL 60015
    Country of origin: Italy
  • Discard after:


  • NDC # 75987-101-08
  • Dispense only in
    original packaging
  • 75 mg
    (cysteamine bitartrate)
    delayed-release capsules
  • Rx Only
  • 250 capsules
  • Distributed by:
    Horizon Therapeutics USA, Inc.
    Deerfield, IL 60015
    Country of origin: Italy
PRINCIPAL DISPLAY PANEL - 75 mg Capsule Bottle Label


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