Do NOT use Doxycycline if:

• you are allergic to any ingredient in Doxycycline, or to similar medicines such as demeclocycline (Declomycin), minocycline (Dynacin, Minocin, Solodyn, Vectrin), or tetracycline (Brodspec, Panmycin, Sumycin, Tetracap)
• you are taking acitretin, isotretinoin, or a penicillin (eg, amoxicillin)
• you have recently received or will be receiving a live oral typhoid vaccine.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Doxycycline. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have diarrhea, a stomach or intestinal infection, a history of lupus, or the blood disease porphyria

• if you have liver or kidney disease, you may need a dose adjustment or special tests to safely take Doxycycline.

Some medicines may interact with Doxycycline. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Barbiturates (eg, phenobarbital), carbamazepine, or hydantoins (eg, phenytoin) because they may decrease Doxycycline's effectiveness
• Acitretin or isotretinoin because side effects, such as increased pressure inside the skull (resulting in severe headaches and vision problems) may occur
• Anticoagulants (eg, warfarin), digoxin, methotrexate, or methoxyflurane because the risk of their side effects may be increased by Doxycycline
• Live oral typhoid vaccine, hormonal birth control (eg, birth control pills), or penicillins (eg, amoxicillin) because their effectiveness may be decreased by Doxycycline.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Doxycycline may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Be sure to use Doxycycline for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
• Long-term or repeated use of Doxycycline may cause a second infection. Tell your doctor if signs of a second infection occur. Your medicine may need to be changed to treat this.
• Mild diarrhea is common with antibiotic use. However, a more serious form of diarrhea (pseudomembranous colitis) may rarely occur. This may develop while you use the antibiotic or within several months after you stop using it. Contact your doctor right away if stomach pain or cramps, severe diarrhea, or blood stools occur. Do not treat diarrhea without first checking with your doctor.
• Doxycycline may cause you to become sunburned more easily. Avoid the sun, sunlamps, or tanning booths until you know how you react to Doxycycline. Use a sunscreen or wear protective clothing if you must be outside for more than a short time.
• Tell your doctor or dentist that you take Doxycycline before you receive any medical or dental care, emergency care, or surgery.
• Hormonal birth control (eg, birth control pills) may not work as well while you are using Doxycycline. To prevent pregnancy, use an extra form of birth control (eg, condoms).
• Doxycycline may interfere with certain lab tests. Be sure your doctor and lab personnel know you are using Doxycycline.
• Pregnancy and breast-feeding: Doxycycline has been shown to cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Doxycycline while you are pregnant. Doxycycline is found in breast milk. Do not breastfeed while taking Doxycycline.

All medicines may cause side effects, but many people have no, or minor, side effects.

Check with your doctor if any of these most common side effects persist or become bothersome:

Loss of appetite; nausea; sensitivity to sunlight; vomiting.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); bloody stools; chest pain; dark urine; decreased urination; fever, chills, or sore throat; moderate to severe sunburn; severe diarrhea; severe or persistent headache; stomach pain or cramps; throat irritation; trouble swallowing; unusual bruising or bleeding; unusual joint pain; unusual tiredness; vaginal irritation or discharge; vision changes; yellowing of the skin or eyes.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.