How does this medication work? What will it do for me?

Doxycycline belongs to the group of medications called tetracyclines. It is used, in addition to dental treatment, to treat adults with periodontitis (inflammation and infection of the tissues, such as ligaments and bones, which support the teeth). Although doxycycline is typically used as an antibiotic, experts believe that doxycycline 20 mg helps periodontitis by slowing the breakdown of collagen, a protein that helps connect and support other tissues in the body.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

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

How should I use this medication?

The usual recommended dose of this medication is 20 mg twice a day.

Doxycycline should be taken at least one hour before the morning and evening meals. Take this medication with a full glass of water to ensure the medication does not stay in the esophagus (the tube that connects the mouth and the stomach) and cause irritation.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to doxycycline or any ingredients of this medication
  • 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 this medication to infants and children less than 8 years old.

What side effects are possible with this medication?

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 this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. 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.

  • diarrhea
  • heartburn or indigestion
  • joint pain
  • nausea
  • sore nose or throat

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
  • sunburn
  • 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
  • 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 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 this medication.

Are there any other precautions or warnings for this medication?

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 this medication.

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 this medication.

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

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

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

Tooth development: Using this medication during tooth development (e.g., the last half of pregnancy, infancy, or childhood up to the age of 8 years) may cause a permanent yellow-grey-brown discoloration of the teeth. This medication should not be used during pregnancy, breast-feeding, or for infants and children less than 8 years of age 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 this medication, contact your doctor immediately.

Breast-feeding: This medication 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 this medication have not been established for children less than 8 years of age.

What other drugs could interact with this medication?

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

  • alcohol
  • antacids containing aluminum, calcium, or magnesium
  • aripiprazole
  • ASA (e.g., Aspirin®)
  • barbiturates (e.g., phenobarbital, butalbital, pentobarbital)
  • BCG
  • birth control pills
  • bismuth subsalicylate
  • calcium supplements
  • carbamazepine
  • cholestyramine
  • 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
  • pimozide
  • porfimer
  • quinapril
  • retinoic acid derivatives (e.g., alitretinoin, isotretinoin, tretinoin)
  • rifampin
  • rocuronium
  • sodium picosulfate
  • sucralfate
  • typhoid vaccine
  • 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 this medication. 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.