Cystadane works by preventing the build-up of an amino acid called homocysteine. This amino acid can harm blood vessels and contribute to heart disease, stroke, or circulation problems.

Cystadane is used to reduce homocysteine levels in people with a genetic condition called homocystinuria, in which the amino acid builds up in the body. This medicine is not a cure for homocysteinuria.

Cystadane 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. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Cystadane is a powder medicine that must be mixed with a liquid before using it.

Gently shake the powder medicine bottle before measuring your dose. To get the correct dose, use the measuring scoop provided with Cystadane.

Mix Cystadane powder with 4 to 6 ounces of water, juice, milk, infant formula, or soft food. Swallow the mixture right away without chewing. Do not save for later use.

Cystadane doses are based on weight in young children. Your child's dose needs may change if the child gains or loses weight.

You may need frequent blood tests.

Cystadane is only part of a complete program of treatment that may also include other vitamin and mineral supplements and a special diet. Follow your diet and medication routines very closely.

Store Cystadane powder at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

To make sure you can safely take Cystadane, tell your doctor about all of your medical conditions.

Tell your doctor if you are pregnant or breast-feeding.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

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

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

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

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

• muscle weakness;

• memory problems;

• changes in your mental state;

• problems with speech, balance, or walking;

• vision changes; or

• unusual or unpleasant body or breath odor.

Common side effects of Cystadane may include:

• nausea; or

• upset stomach.

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.