Do NOT use Doxazosin if:

• you are allergic to any ingredient of Doxazosin or to similar medicines (eg, prazosin).

Some medical conditions may interact with Doxazosin. Tell your health care provider 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 a history of prostate cancer, kidney or liver problems, or high or low blood pressure
• if you will be having eye surgery.

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

• Phosphodiesterase type 5 inhibitors (eg, sildenafil, vardenafil) because severe low blood pressure may occur
• Clarithromycin, HIV protease inhibitors (eg, ritonavir), itraconazole, ketoconazole, nefazodone, telithromycin, or voriconazole because they may increase the risk of Doxazosin's side effects.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Doxazosin 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:

• Doxazosin may cause drowsiness, dizziness, lightheadedness, or fainting. These effects may be worse if you take it with alcohol or certain medicines. Use Doxazosin with caution. Do not drive or perform other possible unsafe tasks until you know how you react to it.
• Doxazosin may cause a sudden drop in blood pressure after the first dose. Take your first dose at bedtime. If you get up during the night, sit up slowly, then stand slowly. This will help to reduce your lightheadedness or dizziness. These effects will more likely occur after the first few doses or if your dose has increased, but can occur at any time while you are taking the medicine. It can also occur if you stop taking the medicine and then restart treatment.
• Doxazosin may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects.
• Do NOT take more than the recommended dose without checking with your doctor.
• Tell your doctor or dentist that you take Doxazosin before you receive any medical or dental care, emergency care, or surgery (including eye surgery).
• Doxazosin may rarely cause a prolonged, painful erection. This could happen even when you are not having sex. If this is not treated right away, it could lead to permanent sexual problems such as impotence. Contact your doctor right away if this happens.
• Patients who take medicine for high blood pressure often feel tired or run down for a few weeks after starting treatment. Be sure to take your medicine even if you may not feel "normal." Tell your doctor if you develop any new symptoms.
• Lab tests, including blood pressure, may be performed while you use Doxazosin. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Use Doxazosin with caution in the elderly; they may be more sensitive to its effects, especially low blood pressure.
• Doxazosin should not be used in children; safety and effectiveness in children have not been confirmed.
• Pregnancy and breast-feeding: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Doxazosin while you are pregnant. It is not known if Doxazosin is found in breast milk. If you are or will be breast-feeding while you use Doxazosin, check with your doctor. Discuss any possible risks to your baby.

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:

Dizziness; drowsiness; lightheadedness; nasal congestion; tiredness; weakness.

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); chest pain; fainting; irregular heartbeat; prolonged, painful erection; severe or prolonged dizziness or headache; shortness of breath; swelling of the ankles, feet, or hands; vision changes.

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.