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

Doxycycline belongs to the class of medications known as tetracyclines. It is an antibiotic that is used to treat certain infections that are caused by bacteria. It is most commonly used to treat lung infections such as pneumonia and bronchitis, urinary tract infections such as cystitis, throat infections such as tonsillitis, skin infections, and sexually transmitted infections.

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 blue, hard gelatin capsule contains doxycycline 100 mg. Nonmedicinal ingredients: lactose monohydrate, croscarmellose sodium, stearic acid, and magnesium stearate; capsule shell: gelatin, titanium dioxide, and FD&C Blue No. 1.


Each round, biconvex, light orange, film-coated tablet, engraved "APO-DOXY 100" on one side, contains doxycycline 100 mg. Nonmedicinal ingredients: microcrystalline cellulose, croscarmellose sodium, magnesium stearate, colloidal silicon dioxide, hydroxypropyl methylcellulose, polyethylene glycol, titanium dioxide, FD&C Yellow No. 6, purified water, and carnauba wax.

How should I use this medication?

The dose and length of treatment with doxycycline varies with the condition being treated. The usual recommended adult dose of doxycycline is 200 mg for the first dose followed by 100 mg once daily at the same time each day, with or after a meal. For some types of infections, doxycycline may be give twice daily.

The medication should be taken with plenty of water while standing or sitting upright to reduce the risk of injury to the esophagus. Do not lie down for at least 1 to 2 hours after taking the medication. This medication should not be taken with antacids or iron preparations, as these may interfere with its effectiveness.

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. Finish all of this medication, even if you start to feel better. 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 doxycycline if you:

  • are allergic to doxycycline or any ingredients of the medication
  • are allergic to other tetracycline antibiotics
  • are a woman in the second or third trimester of pregnancy
  • are breastfeeding
  • have myasthenia gravis
  • Do not give this medication to children under 8 years of age.

    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 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.

    • abdominal pain
    • diarrhea (mild)
    • flushing
    • loss of appetite
    • nausea
    • pain or difficulty swallowing
    • stomach upset
    • tooth discolouration
    • vomiting

    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:

    • headache
    • increased sensitivity of the skin to sunlight
    • ringing or buzzing noise in the ears
    • signs of bowel inflammation (e.g., fever that appears after starting the medication and watery and severe diarrhea, which may also be bloody)
    • skin rash
    • sore mouth or tongue
    • vision changes
    • yellowing skin or eyes

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

    • signs of a severe allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
    • signs of an auto-immune reaction (swelling of the hands and feet, muscle and joint pain, and rash)

    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.

    Liver disease: People with liver disease may have a higher risk of side effects from this medication. If you have liver disease or reduced liver function, 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.

    Other infections: The use of antibiotics may occasionally result in organisms not killed by the antibiotic to overgrow, resulting in conditions such as yeast infections which may cause vaginal itching and irritation. Women may prevent yeast infections by eating yogurt daily while taking this antibiotic. Talk to your doctor if you have any concerns.

    Stomach problems: People taking this medication may develop diarrhea caused by an infection with the bacteria C. difficile. 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 doxcycyline. Diarrhea caused by C. difficile infection can lead to serious health problems if it is not properly treated.

    Sunburn: An exaggerated sunburn reaction may occur for some people taking tetracyclines, including doxycycline. Avoid exposure to excessive sunlight, including sunlamps and tanning beds, and use sunblock with minimum SPF 15. Stop taking doxycycline at the first sign of skin redness.

    Pregnancy: Like other tetracycline antibiotics, doxycycline may cause harm to the developing baby if this medication is taken during pregnancy. This medication 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 passes into breast milk and causes discoloration of the teeth and reduced bone growth in a breast-feeding infant if it is taken by the mother while still breast-feeding. Due to the adverse effects on the developing infant, this medication should not be used by women who are breast-feeding.

    Children: The use of doxycycline during tooth development (from the last trimester of pregnancy to the age of 8 years) may cause permanent discoloration of the teeth (yellow-grey-brown). Though more commonly associated with long-term use of tetracyclines, this effect has also been known to occur after taking the medication for a short time.

    The safety and effectiveness of using this medication have not been established for children under 8 years of age.

    What other drugs could interact with this medication?

    There may be an interaction between doxycycline 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.