Cysteamine works by reducing the amount of cystine (an amino acid) in the body. Cysteamine is used in people with cystinosis (SIS-tin-OH-sis), a rare genetic condition that causes a build-up of cystine in the kidneys and other organs, including the eyes.

Cystadrops (for the eyes) is used to keep cystine crystals from building up in the cornea (surface of the eye).

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

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.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Do not take by mouth. Cystadrops is for use only in the eyes.

Cystaran is usually used once every hour while you are awake. Cystadrops are usually applied 4 times per day. Follow your doctor's dosing instructions very carefully.

Do not use while wearing soft contact lenses. A preservative in Cystadrops could permanently stain the lenses. Use the medicine at least 15 minutes before inserting your contact lenses.

Wash your hands before using eye medication.

To apply the eye drops: Tilt your head back slightly and pull down your lower eyelid to create a small pocket. Hold the dropper above the eye and squeeze a drop into this pocket. Close your eyes for 1 or 2 minutes.

Use only the number of drops your doctor has prescribed.

Do not touch the tip of the eye dropper or place it directly on your eye. A contaminated dropper can infect your eye, which could lead to serious vision problems.

Storing Cystadrops:

• Keep the bottle in the original carton.

• Store Cystaran in a freezer until you are ready to start using it. Thaw for 24 hours before your first use, then store the bottle tightly closed in a refrigerator or at room temperature. Do not refreeze after thawing.

• Store Cystadrops in a refrigerator. After first opening the bottle, store it in a refrigerator or at room temperature tightly closed and protected from light. Do not refrigerate after opening the bottle.

Throw the bottle away after 1 week of use, even if there is still medicine inside. If using Cystaran, remove a new bottle from the freezer in time to allow 24 hours for thawing so you will not miss a dose.

Tell your doctor if you are pregnant or breastfeeding.

Cysteamine is not approved for use by anyone younger than 18 years old.

Use the medicine as soon as you remember, and then go back to your regular schedule. Do not use two doses at one time.

An overdose of cysteamine is not expected to be dangerous. Seek emergency medical attention or call the Poison Help line at 1-800-222-1222 if anyone has accidentally swallowed the medication.

Your dose needs may change if you switch to a different brand or strength of Cystadrops. Avoid medication errors by using only the form and strength your doctor prescribes.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Cystadrops may cause serious side effects. Call your doctor at once if you have:

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

Common side effects of Cystadrops may include:

• eye pain, redness, itching, or irritation;

• vision problems;

• headache; or

• increased sensitivity to light.

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.