Tetracyclines are medicines that kill certain infection-causing microorganisms. Tetracyclines are called broad-spectrum antibiotics, because they can be used to treat a wide variety of infections. Physicians may prescribe these drugs to treat eye infections, pneumonia, gonorrhea, Rocky Mountain spotted fever, urinary tract infections, and other infections caused by bacteria. The medicine is also used to treat acne. The tetracyclines will not work forcolds, flu, and other infections caused by viruses.

Tetracyclines are available only with a physician's prescription. They are sold in capsule, tablet, liquid, and injectable forms. Some commonly used medicines in this group are tetracycline (Achromycin V, Sumycin) and doxycycline (Doryx, Vibramycin). The recommended dosage depends on the type of tetracycline, its strength, and the type and severity of infection for which it is beingtaken. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage. To make sure the infectionclears up completely, take the medicine for as long as it has been prescribed. Do not stop taking the drug just because symptoms begin to improve. Tetracycline works best when at a constant level in the blood. To help keep levels constant, take the medicine in doses spaced evenly through the day and night.Do not miss any doses.

This medicine works best when taken on an empty stomach, with a full glass ofwater. The water will help prevent irritation of the stomach and esophagus (the tube-like structure that runs from the throat to the stomach). If the medicine still causes stomach upset, it may be necessary to take it with food. However, tetracyclines should never be taken with milk or milk products, as these may prevent the medicine from working properly. Do not drink or eat milk or dairy products within 1-2 hours of taking tetracyclines (except doxycycline and minocycline). Do not take antacids, calcium supplements, salicylates such as Magan or Trilisate, magnesium-containing laxatives, or sodium bicarbonate (baking soda) within 1-2 hours of taking tetracyclines. Do not takeany medicines that contain iron (including multivitamin and mineral supplements) within 2-3 hours of taking tetracyclines.

The most common side effects are stomach cramps or a burning sensation in thestomach, mild diarrhea, nausea, or vomiting. These problems usually go awayas the body adjusts to the drug and do not require medical treatment. Less common side effects, such as sore mouth or tongue and itching of the rectal orgenital areas also may occur and do not need medical attention unless they donot go away or they are bothersome. Some people feel dizzy when taking thesedrugs. The medicine may also cause blurred vision. Because of these possibleeffects, anyone who takes these drugs should not drive, use machines or do anything else that might be dangerous until they have found out how the drugsaffect them.

This medicine may increase sensitivity to sunlight. Even brief exposure to sun can cause a severe sunburn or a rash. While being treated with this medicine, avoid being in direct sunlight, especially between 10 a.m. and 3 p.m.; wear a hat and tightly woven clothing that covers the arms and legs; use a sunscreen with a skin protection factor (SPF) of at least 15; protect the lips with a sun block lipstick; and do not use tanning beds, tanning booths, or sunlamps. The sensitivity to sunlight and sunlamps may continue for 2 weeks to several months after stopping the medicine, so continue to be careful about sunexposure.

Tetracyclines may permanently discolor the teeth of people who took the medicine in childhood. The drugs may also slow down the growth of children's bones. Do not give tetracyclines to infants or children under 8 years of age unless directed to do so by the child's physician. Pregnant women should not taketetracyclines during the last half of pregnancy. These drugs can prevent thebaby's bones and teeth from developing properly and can cause the baby's adult teeth to be permanently discolored. The medicine can also cause liver problems in pregnant women. Women who are breastfeeding should not take tetracyclines. The drugs pass into breast milk and can affect the nursing baby's teethand bones. They may also make the baby more sensitive to sunlight and may increase its risk of fungal infections. Birth control pills may not work properly when taken while tetracyclines are being taken. To prevent pregnancy, use additional methods of birth control while taking tetracyclines.

Taking outdated tetracyclines can cause serious side effects. Do not take this medicine if its color, appearance, or taste have changed or if the expiration date on its label has passed. Flush any such medicine down the toilet. Ifthere is any question about whether the medicine is still good, check with aphysician or pharmacist. Anyone who has had unusual reactions to tetracyclines in the past should let his or her physician know before taking the drugs again. Before using tetracyclines, people with diabetes, or diseases of the liver or kidneys should make sure their physicians are aware of their conditions.

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