SIDE EFFECTS: Diarrhea, loss of appetite, nausea, vomiting, headache, dizziness, lightheadedness, or rectal discomfort may 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: sunburn-like skin reaction (sun sensitivity), darkening of the skin and other areas of the body (e.g., lips, inside of the mouth), difficult/painful swallowing, unusual increase in the amount of urine (except for the expected increase in urination if you are treating SIADH), unusual decrease in the amount of urine or no urine, unusual thirst, weakness, unusual tiredness, brown/gray tooth discoloration.

Tell your doctor immediately if any of these rare but very serious side effects occur: hearing changes (e.g., ringing in the ears, decreased hearing), persistent/severe headache, vision changes (e.g., blurred vision), easy bruising/bleeding, new signs of infection (e.g., persistent sore throat, fever, chills), stomach/abdominal pain, persistent nausea/vomiting, yellowing eyes/skin, dark urine.

This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a type of 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. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction, including: rash, skin sores/blisters, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, new or worsening swelling/pain in the joints, chest pain, fast/irregular heartbeat.

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 Declomycin (demeclocycline hcl) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before taking demeclocycline, tell your doctor or pharmacist if you are allergic to it; or to other tetracycline medication (e.g., doxycycline, minocycline, tetracycline); 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: kidney disease, liver disease, problems swallowing, esophagus problems (e.g., esophageal ulcers, hiatal hernia, acid reflux disease-GERD), lupus, a certain hormone imbalance called "water diabetes" (diabetes insipidus).

This drug may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.

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 using demeclocycline.

This medication should not be used in children younger than 8 years of age because it may cause permanent tooth discoloration and other problems. Tooth discoloration has also occurred in older children and young adults. Consult your doctor for more information.

This medication is not recommended for use during pregnancy. It may harm an unborn baby. Consult your doctor for more details and to discuss reliable forms of birth control.

This medication passes into breast milk in very small amounts. While there have been no reports of harm to nursing infants, consult your doctor before breast-feeding.