Doxycycline is an antibiotic in the tetracycline family that works by inhibiting bacterial growth in the body 3. Doctors prescribe doxycycline to fight bacterial infections, such as pneumonia, respiratory or urinary tract infections, Chlamydia, gonorrhea and other serious infections 3. Low dosage doxycycline is used to treat acne and periodontal disease 3. According to DrugWatch.com, before taking doxycycline, patients should tell their doctors about any pre-existing medical conditions 13. If patients experience side effects or something just does not feel right while using doxycycline, they should contact their doctors immediately so the problem can be diagnosed 123.

Pregnancy and Nursing

Women who are pregnant or nursing should not use doxycycline because it might harm an unborn baby or cause eventual permanent tooth discoloration 3. As a tetracycline drug, doxycycline may have toxic effects on fetal bone development 123. According to SideEffects.org, doxycycline is secreted into breast milk, but the extent of absorption by the breastfed infant is not known 23. Since doxycycline may cause toxic effects on bones, the use of tetracycline drugs in nursing mothers is of concern 123. Women trying not to get pregnant should know that doxycycline might make birth control pills less effective, warns Drugs.com 3.

Gastrointestinal

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Some common side effects caused by doxycycline are gastrointestinal and include diarrhea, nausea, vomiting, indigestion and appetite reduction 123. Some patients may experience severe upper stomach pain that spreads to their back. If a patient has watery or bloody diarrhea, she should contact her doctor immediately and not take another medication to control diarrhea until advised by her physician.

Flu Symptoms, Headache, Dizziness

Patients taking doxycycline may experience fever, chills, body aches, joint pain and other flu symptoms 3. Other side effects may include weakness, severe headaches, dizziness or blurred vision.

Genital or Urinary

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Side effects from doxycycline may involve rectal and genital sores or swelling, vaginal discharge and itching, reduced urination or dark-colored urine 123.

Mouth and Throat Symptoms

Someone taking doxycycline may notice a swollen tongue, or sores and white patches in the mouth or on the lips 3. Difficulty swallowing and severe throat pain are rare but serious side effects and those affected should report these side effects to their doctors immediately.

Sunlight Sensitivity

Doxycycline may make skin more sensitive to sunlight and sunburn, so people should avoid exposure to the sun or UV rays from sunlamps or tanning beds 3. If patients taking doxycycline must spend time outdoors, they should use sunscreen and wear a hat 3.

Bruising or Skin Changes

Skin blistering, peeling or red skin rash may occur when someone takes doxycycline 3. Bruising or bleeding, or jaundice symptoms with yellowing skin or eyes might be other side effects.

Dairy Products

Dairy products can make it harder for the body to absorb doxycycline, so patients should not take this medication with milk or other dairy products, unless their doctor has instructed them to do so 3.

Side Effects in Children

Children younger than 8 years old should not be given doxycycline 3. It can cause permanent yellowing or graying of their teeth, and because tetracycline may negatively affect bones, a child's growth could be impacted.

Allergy-related Side Effects

Expired Prescriptions

Unused and expired doxycycline tablets or capsules should be thrown away, and patients should never take doxycycline after the bottle’s expiration date 3. According to MedLibrary.org, expired doxycycline can cause a dangerous syndrome resulting in damage to the kidneys 234.