Skip to Content


Generic Name: cysteamine (sis TEE a meen)
Brand Name: Cystagon, Procysbi

Medically reviewed by on Mar 11, 2019 – Written by Cerner Multum

What is Cystagon?

Cystagon works by reducing the amount of cystine (an amino acid) in the body.

Cystagon is used to treat nephropathic cystinosis (NEF-roe-PATH-ik SIS-tin-OH-sis), a rare genetic condition that causes a build-up of cystine in the kidneys and other organs. Too much cystine can cause kidney failure or other medical problems.

Cystagon is for use in adults and children, but Procysbi should not be given to a child younger than 1 year old.

Cystagon may also be used for purposes not listed in this medication guide.

Important Information

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

You should not use Cystagon if you are allergic to Cystagon or penicillamine.

Tell your doctor if you have ever had:

It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

You should not breast-feed while using this medicine.

How should I use Cystagon?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Swallow the capsule whole and do not crush or chew it.

If you cannot swallow a Cystagon capsule whole, carefully follow the patient instructions for opening the capsule and mixing the medicine with certain foods. These instructions may be different from one brand of cysteamine to another. Use the directions for the specific brand you are using. Procysbi also comes with instructions for giving the mixture through a gastronomy tube (12 French or larger).

Take Procysbi with water or fruit juice, but not grapefruit juice. You may take Procysbi with or without food, but take it the same way each time.

  • To take Procysbi with food, eat only a small amount (1/2 cup) of food within 1 hour before or 1 hour after you take the medicine.

  • To take Procysbi without food, take the medicine at least 30 minutes before or 2 hours after a meal.

A child may not be able to swallow a Cystagon capsule without choking. For children younger than 6 years old, you may open the capsule and mix the medicine with a soft food.

You will need frequent medical tests.

You should not stop using Cystagon without your doctor's advice. Stopping suddenly may make your condition worse.

Cystinosis is often treated with a combination of drugs, including vitamin and mineral supplements. Use all medications as directed and read all medication guides you receive. Do not change your dose or dosing schedule without your doctor's advice.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the missed dose as soon as you remember.

  • For Cystagon: Skip the missed dose if your next dose is due in less than 2 hours.

  • For Procysbi: If you are less than 8 hours late for the dose, use the medicine as soon as you can. Skip the missed dose if your next dose is due in less than 4 hours.

Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Cystagon?

Avoid driving or hazardous activity until you know how Cystagon will affect you. Your reactions could be impaired.

Avoid eating high-fat foods within 1 hour before or 1 hour after you take Procysbi.

Avoid drinking alcohol while taking Procysbi. Alcohol can make the medicine less effective or cause side effects.

Cystagon side effects

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Call your doctor at once if you have any of these side effects (some of these may be caused by your cystinosis disorder and not by this medicine):

  • depressed mood, extreme drowsiness;

  • a seizure;

  • unusual bruising or streaks on the skin;

  • bone pain, abnormal joint movement;

  • an electrolyte imbalance--increased thirst or urination, confusion, constipation, leg cramps, irregular heartbeats, tingly feeling;

  • increased pressure inside the skull--severe headaches, ringing in your ears, dizziness, vision problems, pain behind your eyes; or

  • stomach problems--pain, nausea, vomiting, loss of appetite, coughing up blood or vomit that looks like coffee grounds.

Common side effects may include:

  • drowsiness, feeling tired;

  • stomach pain, nausea, vomiting, loss of appetite, diarrhea;

  • unusual breath odor or skin odor;

  • rash;

  • fever; or

  • headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Cystagon?

Take Procysbi at least 1 hour before or 1 hour after taking any medicine that contains bicarbonate or carbonate.

Other drugs may affect Cystagon, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.