Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Periostat. If you are concerned about side effects, discuss the risks and benefits of Periostat with your doctor.

The following side effects have been reported by at least 1% of people taking Periostat. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• common cold (e.g., runny nose, nasal congestion, sneezing, cough, sore throat)
• flu-like symptoms (e.g., Fever, body aches, headache, cough, sore throat)
• Diarrhea
• headache
• heartburn or indigestion
• joint pain
• nausea
• rash
• tooth ache or other tooth problems

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• persistent heartburn or indigestion
• signs of bowel inflammation (e.g., fever that appears after starting the medication and watery and severe diarrhea, which may also be bloody)
• sinus infection
• Sunburn
• symptoms of a gum abscess (e.g., swollen or painful gums, tooth sensitivity, discharge with pus)
• symptoms of a vaginal yeast infection (vaginal itching and thick white discharge)
• symptoms of thrush (yeast infection in the mouth; white, curd-like patches in the mouth or on the tongue)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of increased blood pressure in the brain (e.g., severe headache, migraine, or dizziness)
• symptoms of a Anaphylaxis (severe allergic reaction) (e.g., Hives; difficulty breathing; swelling of the face, mouth, tongue, or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Periostat.

Each white capsule imprinted with "TM Periostat 20 mg" contains 20 mg of doxycycline. Nonmedicinal ingredients: hard gelatin capsules, magnesium stearate, microcrystalline cellulose, and titanium dioxide.

Do not take Periostat if you:

• are allergic to doxycycline or any ingredients of Periostat
• are allergic to other tetracyclines (e.g., Minocycline, Tetracycline)
• are in the second half of pregnancy
• have Myasthenia Gravis (a condition associated with muscle weakness)

Do not give Periostat to infants and children less than 8 years old.

There may be an interaction between doxycycline 20 mg and any of the following:

• alcohol
• antacids containing aluminum, calcium, or magnesium
• Asa (e.g., Aspirin®)
• barbiturates (e.g., Phenobarbital, butalbital, pentobarbital)
• BCG
• birth control pills
• Bismuth Subsalicylate
• calcium supplements
• Carbamazepine
• Cholestyramine
• Colesevelam
• Colestipol
• iron and iron-containing products
• magnesium supplements
• Methotrexate
• multivitamins/minerals with vitamins A, D, and E
• pancuronium
• penicillins (e.g., Penicillin V, amoxicillin, ampicillin)
• Phenytoin
• Porfimer
• proton pump inhibitors (e.g., Lansoprazole, Omeprazole, Pantoprazole)
• Quinapril
• retinoic acid derivatives (e.g., Alitretinoin, Isotretinoin, tretinoin)
• rifampin
• rocuronium
• sodium picosulfate
• Sucralfate
• typhoid vaccine (oral)
• Warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Periostat. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use Periostat.

Birth control: Some antibiotics may decrease the effectiveness of birth control pills. Ask your doctor if you should be using more than one method of birth control while you are taking Periostat.

High blood pressure in the brain: Doxycycline may increase the risk of high blood pressure in the brain. Contact your doctor right away if you experience blurred vision, double vision, and headache.

Esophagus problems: People taking doxycycline have experienced ulcers and injury to their esophagus. To help prevent this, take doxycycline with a full glass of water while standing or sitting upright. Do not lie down for at least 1 to 2 hours after taking the medication.

Infection: Periostat may cause an overgrowth of certain bacteria and fungi. If you experience frequent yeast infections in the mouth (thrush), discuss with your doctor how Periostat may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Periostat, and whether any special monitoring is needed.

The safety and effectiveness of using Periostat for people with oral Candidiasis (thrush) have not been established. If you develop symptoms of infection (e.g., fever, chills) while taking Periostat, contact your doctor.

Stomach problems: People taking Periostat may develop diarrhea caused by an infection with C. difficile bacteria. Get medical attention as soon as possible if you have loose, watery, and bloody bowel movements, with or without fever or stomach cramps, after taking doxycycline. Diarrhea caused by C. difficile infection can lead to serious health problems if it is not properly treated.

Sun sensitivity: Periostat may make your skin more sensitive to the sun. Avoid excessive sun exposure, including sun beds and sun lamps, while taking Periostat. If you cannot avoid sun exposure, use sunscreen and protective clothing. Stop taking Periostat and contact your doctor if you get a sunburn.

Tooth development: Using Periostat during tooth development (e.g., the last half of pregnancy, infancy, or childhood up to age 8) may cause a permanent yellow-grey-brown discoloration of the teeth. Periostat should not be used during pregnancy, breast-feeding, or for infants and children under 8 years old unless the benefits outweigh the risks.

Pregnancy: Doxycycline can cause birth defects to the unborn baby if it is taken during pregnancy. It should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Periostat, contact your doctor immediately.

Breast-feeding: Periostat should not be used by breast-feeding women unless the benefits outweigh the risks. If you are a breast-feeding mother and are taking doxycycline, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using Periostat have not been established for children under 8 years old.