SIDE EFFECTS: Nausea, vomiting, diarrhea, stomach pain/cramping, and loss of appetite may occur. Taking this medication with food may lessen these symptoms. Headache and dizziness may also occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: mouth sores, sun sensitivity (sunburn), hearing problems (e.g., hearing loss), joint pain/aches, new lump/growth in the neck (goiter), change in the amount of urine, mental/mood changes (e.g., confusion), numbness or tingling of the hands/feet, muscle weakness.

This medication may rarely cause serious (possibly fatal) allergic reactions and other side effects such as a severe peeling skin rash (e.g., Stevens-Johnson syndrome), blood disorders (e.g., agranulocytosis, aplastic anemia), liver damage, lung injury, or heart problems. Seek immediate medical attention if you notice any of the following symptoms: severe dizziness, fainting, fast/irregular heartbeat, skin rash/blisters, itching/swelling (especially of the face/tongue/throat), persistent sore throat/fever, paleness, persistent cough, trouble breathing, easy bleeding/bruising, yellowing eyes/skin, persistent nausea/vomiting, seizures, stomach/abdominal pain, unusual tiredness, dark urine.

This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have the following symptoms because these products may make them worse. Tell your doctor immediately if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new vaginal yeast infection (oral or vaginal fungal infection). Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge or other new symptoms.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Pediazole (erythromycin and sulfisoxazole) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before taking erythromycin with sulfisoxazole, tell your doctor or pharmacist if you are allergic to it; or to other macrolide antibiotics (e.g., azithromycin, clarithromycin) or sulfa medications; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: severe allergies, asthma, blood disorders, decreased bone marrow function (bone marrow suppression), diabetes, a certain genetic condition (glucose-6-phosphate dehydrogenase/G6PD deficiency), kidney disease, liver disease, a certain type of muscle disease (myasthenia gravis).

Erythromycin/sulfisoxazole may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can infrequently result in serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that require immediate medical attention. The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may affect the heart rhythm (see also Drug Interactions section). Before using erythromycin/sulfisoxazole, tell your doctor or pharmacist if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using erythromycin/sulfisoxazole safely.

This medication may make you more sensitive to the sun. Avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective clothing when outdoors.

Before having surgery, tell your doctor or dentist that you are taking this medication.

Caution is advised when using this drug in the elderly because they may be more sensitive to its side effects, especially hearing loss and irregular heartbeat.

This medication should not be used in children younger than 2 months of age due to the risk of serious side effects.

Caution is advised when erythromycin is used in infants. Although very unlikely, a stomach problem called IHPS (infantile hypertrophic pyloric stenosis) has sometimes occurred. Contact your child's doctor immediately if your child has persistent vomiting or increased irritability with feeding.

This medication should be used only when clearly needed during pregnancy. This medication should not be used near the time of delivery because of possible harm to the unborn baby. Discuss the risks and benefits with your doctor.

This medication passes into breast milk and may have undesirable effects on a nursing infant. Therefore, breast-feeding while using this medication is not recommended. Consult your doctor before breast-feeding.