Tetracycline belongs to the class of medications called antibiotics. It is used to treat certain types of infections that are caused by bacteria (antibiotics are not useful for viruses like the ones that cause the common cold).

Tetracycline is most commonly used to treat infections of the skin (including acne), Lyme disease, and certain 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.

The recommended adult dose of tetracycline is 250 mg to 500 mg 4 times daily on an empty stomach. For 2 hours before and after taking the medication, avoid dairy products as well as antacids that contain aluminum, calcium, or magnesium. Tetracycline should be taken with a full glass of water while standing or sitting upright and should not be taken at bedtime (to avoid irritation of the lining of the throat and the tube leading to the stomach, known as the esophagus).

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 the doctor. Finish all this medication, even if you have started 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 take this medication if you:

• are allergic to tetracycline or any ingredients of this medication
• are allergic to related medications such as doxycycline or minocycline
• are pregnant or breast-feeding (unless the benefits outweigh the risks)
• have severe reduction in kidney or liver function

Do not give this medication to children under 8 years of age who have a common infection that may be treated with a different antibiotic.

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.

• abdominal pain
• diarrhea
• fingernail or toenail changes
• increased skin sensitivity to sunlight
• nausea
• tongue discolouration
• vaginal yeast infections
• vomiting

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

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

• symptoms ofhepatic cholestasis, or blockage of bile flow (a digestive fluid) from the liver; symptoms may include yellowing of the skin or eyes, intense itching and/or dark coloured urine
• symptoms of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen)

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

severe diarrhea with mucus or blood in the stool

signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and 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.

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.

Antibiotic-related diarrhea: As with other antibiotics, tetracycline can cause a severe form of diarrhea associated with a condition known as pseudomembranous colitis. If you develop severe diarrhea while taking (or within a few weeks of taking) this medication, contact your doctor.

Bacterial resistance: Misuse of an antibiotic such as tetracycline may lead to the growth of resistant bacteria that will not be killed by the antibiotic. If this happens, the antibiotic may not work for you in the future. Although you may begin to feel better early in your course of treatment with tetracycline, you need to take the full course exactly as directed. Do not take tetracycline or other antibiotics to treat a viral infection such as the common cold; antibiotics do not kill viruses, and using them to treat viral infections can lead to the growth of resistant bacteria.

Liver function:Although not common, tetracycline can cause liver problems when taken for long periods of time or at high doses. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Overgrowth of organisms: The use of antibiotics may allow organisms not killed by the antibiotic to overgrow. This may cause unwanted conditions such as yeast infections.

Sensitivity to sunlight: An exaggerated sunburn reaction may occur for some people who take this medication. Watch for this if you spend time in direct sunlight or ultraviolet light and ensure that sun protection measures are taken (e.g., wear sunscreen, a hat, and long sleeve shirts). At the first sign of skin redness, stop taking the medication and see your doctor about changing your prescription.

Tooth discolouration: The use of tetracycline during tooth development (from the second 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. Tetracycline should therefore not be used by children 8 years old or younger unless other medications are unlikely to be effective or can't be used.

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 in small amounts into breast milk. Tetracycline is not recommended for nursing women unless potential benefits outweigh the risks.

There may be an interaction between tetracycline and any of the following:

• acetylsalicylic acid (ASA)
• antacids that contain aluminum, calcium, or magnesium
• birth control medications
• bismuth subsalicylate
• calcium supplements
• cholestyramine
• colestipol
• digoxin
• iron supplements
• lithium
• methotrexate
• multivitamin and mineral supplements
• penicillin antibiotics (e.g., amoxicillin, ampicillin, cloxacillin, penicillin)
• quinapril
• sodium bicarbonate
• sodium picosulfate
• sucralfate
• sulfonylurea diabetes medications (e.g., gliclazide, glyburide)
• vaccines
• vitamin A derivatives (e.g., isotretinoin, tretinoin)
• warfarin
• zinc sulfate or gluconate

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.