Doxazosin Mesylate

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Apr 15, 2024

Warnings

Doxazosin (Cardura) Risks, Warnings, and Complications

Doxazosin can cause serious health complications in certain high-risk individuals. Talk to your doctor or pharmacist about other treatment options for BPH or high blood pressure if you are at an increased drug-associated risk. Some of the risks of taking doxazosin include:

POSTURAL HYPOTENSION: Doxazosin can cause postural hypotension (low blood pressure when going from a lying or sitting position to standing). This can lead to dizziness and fainting. It typically happens within a few hours of taking a dose. The risk of a sudden drop in blood pressure is greater when you first start doxazosin or after a dose increase. Taking doxazosin with PDE5 inhibitors such as sildenafil (Viagra) and tadalafil (Cialis) can have an additive blood pressure-lowering effect. Tell your doctor if you develop persistent or severe dizziness. Be careful when getting out of bed. Rest your feet on the ground for a few minutes before standing up.
INTRAOPERATIVE EYE PROBLEMS: Doxazosin can cause a complication called intraoperative floppy iris syndrome during cataract surgery. Make sure your eye surgeon knows you are on an alpha blocker before any planned eye surgery. They may ask you to stop doxazosin temporarily and/or modify their surgical technique.
MASKED SYMPTOMS OF PROSTATE CANCER: BPH is a non-cancerous condition. However, it can cause many of the same symptoms as prostate cancer. Taking doxazosin can prevent a timely diagnosis of prostate cancer by treating the symptoms. Your doctor may order a blood test called prostate-specific antigen before starting you on doxazosin to rule out prostate cancer.
PRIAPISM: Doxazosin and other alpha-blockers can cause priapism, a painful or prolonged erection that lasts more than 4 hours and is unrelieved by masturbation or sexual intercourse. This condition requires immediate treatment to prevent permanent damage to the penis. Get emergency medical help if you develop a painful erection that does not go away.
GASTROINTESTINAL CONDITIONS: Doxazosin extended-release (Cardura XL) should be used with caution in people with preexisting severe narrowing in the gastrointestinal tract. There are rare reports of people with known strictures (narrowing) developing obstructive symptoms after taking extended-release formulations. A significant increase in GI retention time, for example, due to chronic constipation, can increase systemic exposure to doxazosin and the risk of severe adverse reactions.
HEPATIC IMPAIRMENT: Doxazosin is not safe for people with severe hepatic impairment (liver dysfunction). It should be used with caution in people with mild to moderate hepatic impairment. Before starting treatment with this medicine, tell your doctor if you have a history of liver problems.
HEART PROBLEMS: Doxazosin should be used with caution in people who have heart problems such as congestive heart failure, chest pain, or myocardial infarction (heart attack) within the last 6 months. Tell your doctor without delay if you develop new or worsening chest pain after starting doxazosin.

Precautions Before Starting Doxazosin (Cardura)

Tell your doctor if you have ever had allergic reactions to doxazosin, any of the active or inactive ingredients in doxazosin formulations, other alpha-blocker drugs, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, nutritional supplements, and herbal products. This can help avoid possible drug interactions.

Give your doctor a complete medical history. Doxazosin may carry an increased risk of adverse effects for people with certain medical conditions such as angina, low blood pressure, low blood pressure after taking medications, or liver disease. If you are taking the extended-release tablet, tell your doctor if you have constipation, short gut syndrome, or a narrowing or blockage in your gastrointestinal tract.

Elderly patients (65 years of age or above) should talk to their doctor about the risks versus benefits of taking doxazosin. There may be other safer medications available.

Tell your doctor if you are pregnant, could be pregnant, are planning a pregnancy, or are breast-feeding. The fetal risk associated with this medication (risk of major birth defects and miscarriage) is not known.

Precautions During Use of Doxazosin (Cardura)

Keep all your medical and lab appointments during treatment with doxazosin.

Doxazosin can cause drowsiness and dizziness. Be careful when driving and operating machinery until you know how this medicine affects you.

You may feel dizzy or lightheaded after taking doxazosin, especially with changes in position. Stand up slowly from a sitting or lying position. Rest your feet on the floor for a few minutes before standing up. If you feel dizzy, sit down and rest for a few minutes. These symptoms are more likely after the first dose and after a dose increase. Tell your doctor if the symptoms continue.

Tell all your health care providers that you are on doxazosin before any surgery, including eye surgery and dental procedures.

Doxazosin (Cardura) Drug Interactions

Certain other drugs can affect how doxazosin works. Possible interactions between doxazosin and other medicines can increase the risk of severe adverse reactions. The following medications can interact with doxazosin:

Antihistamines
Antibiotics such as clarithromycin (Biaxin, in Prevpac) and telithromycin (Ketek)
Respiratory medications such as ipratropium (Atrovent, in Combivent)
Antifungal medications such as itraconazole (Onmel, Sporanox), ketoconazole (Nizoral), and voriconazole (Vfend)
Drugs prescribed to treat erectile dysfunction (ED), such as sildenafil (Viagra, Revatio), tadalafil (Cialis, Adcirca), and vardenafil (Staxyn, Levitra)
Other medications used to treat high blood pressure
HIV/AIDS medications, including ritonavir (Norvir, in Kaletra), indinavir (Crixivan), atazanavir (Reyataz), nelfinavir (Viracept), and saquinavir (Invirase)
Medications prescribed for motion sickness, urinary problems, irritable bowel disease, ulcers, Parkinson's disease,
Antidepressants such as nefazodone

The above list may not describe all the potential interactions of doxazosin. Give your doctor or pharmacist a list of all the medicines you are taking, including prescription drugs, nonprescription drugs, dietary supplements, and herbal remedies. Also, tell your healthcare professional if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription and over-the-counter medications.

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