• you are allergic to any ingredient in Sumycin or other tetracycline antibiotics (eg, doxycycline)
• you are taking acitretin or methoxyflurane.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Sumycin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have diarrhea, a stomach infection, or kidney problems.

Some medicines may interact with Sumycin. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Acitretin or isotretinoin because side effects, such as increased pressure in the fluid surrounding the brain, may occur
• Digoxin, methotrexate, methoxyflurane, or oral anticoagulants (eg, warfarin) because the risk of their side effects may be increased by Sumycin
• Atovaquone, lithium, oral contraceptives (birth control pills), or penicillins (eg, amoxicillin) because their effectiveness may be decreased by Sumycin.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Sumycin may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Sumycin may cause dizziness or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Sumycin with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Contact your doctor right away if stomach pain or cramps, severe diarrhea, or bloody stools occur. Do not treat diarrhea without first checking with your doctor.
• Be sure to use Sumycin for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
• Sumycin may cause you to become sunburned more easily. Avoid the sun, sunlamps, or tanning booths until you know how you react to Sumycin. Use a sunscreen or wear protective clothing if you must be outside for more than a short time.
• Do not use after expiration date. Outdated medicine is highly toxic to the kidneys.
• Long-term or repeated use of Sumycin may cause a second infection. Tell your doctor if signs of a second infection occur. Your medicine may need to be changed to treat this.
• Hormonal birth control (eg, birth control pills) may not work as well while you are using Sumycin. To prevent pregnancy, use an extra form of birth control (eg, condoms).
• Lab tests may be performed while you use Sumycin. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Use of Sumycin in children may cause permanent discoloring of the teeth.
• Sumycin should be used with extreme caution in children younger 8 years; safety and effectiveness in these children have not been confirmed.
• Pregnancy and beast-feeding: Sumycin has been shown to cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Sumycin while you are pregnant. Sumycin is found in breast milk. Do not breast-feed while taking Sumycin.

Check with your doctor if any of these most common side effects persist or become bothersome:

Black hairy tongue; blurred vision; bulky loose stools; diarrhea; difficulty swallowing; fever; headache; hives; hoarseness; indigestion; inflammation or redness of tongue; joint pain; loss of appetite; mouth sores; nausea; rash; sensitivity to sunlight; sore throat; stomach pain; swelling and itching of the rectum.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); infection (fever, chills, sore throat); itching; nausea; severe skin reaction to the sun; vaginal irritation or discharge; vomiting.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.