Doxazosin Side Effects

Medically reviewed by Drugs.com. Last updated on Mar 31, 2025.

Applies to doxazosin: oral tablet, oral tablet extended release.

Precautions

It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly. This is especially important for elderly patients, who may be more sensitive to the effects of this medicine.

For patients taking this medicine for high blood pressure :

• Do not take other medicines unless they have been discussed with your doctor. This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.

Dizziness, lightheadedness, or sudden fainting may occur after you take this medicine, especially when you get up from a lying or sitting position. These effects are more likely to occur when you take the first dose of this medicine. Taking the first dose at bedtime may prevent problems. However, be especially careful if you need to get up during the night. These effects may also occur with any doses you take after the first dose. Getting up slowly may help lessen this problem. If you feel dizzy, lie down so that you do not faint. Then sit for a few moments before standing to prevent the dizziness from returning.

The dizziness, lightheadedness, or sudden fainting is more likely to occur if you drink alcohol, stand for a long time, exercise, or if the weather is hot. While you are taking this medicine, be careful to limit the amount of alcohol you drink. Also, use extra care during exercise or hot weather or if you must stand for a long time.

Doxazosin may cause some people to become drowsy or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy, drowsy, or are not alert. After you have taken several doses of this medicine, these effects should lessen.

The possibility of priapism, a painful or prolonged erection of the penis, is a rare side effect that can occur when taking doxazosin and must have immediate medical attention.

Serious side effects of doxazosin

Along with its needed effects, doxazosin may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur while taking doxazosin:

Other side effects of doxazosin

Some side effects of doxazosin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to doxazosin: oral tablet, oral tablet extended release.

General adverse events

The most common adverse reaction was dizziness.^[Ref]

Nervous system

• Very common (10% or more): Dizziness (up to 19%)
• Common (1% to 10%): Somnolence, headache, vertigo
• Uncommon (0.1% to 1%): Cerebrovascular accident, hypoesthesia, syncope, tremor, tinnitus
• Very rare (less than 0.01%): Dizziness postural, paresthesia
• Frequency not reported: Taste disturbance^[Ref]

Other

• Very common (10% or more): Fatigue/malaise (12%)
• Common (1% to 10%): Asthenia, chest pain, influenza-like symptoms
• Uncommon (0.1% to 1%): Pain, facial edema^[Ref]

Respiratory

• Common (1% to 10%): Dyspnea, rhinitis, respiratory tract infection, bronchitis, cough
• Uncommon (0.1% to 1%): Epistaxis
• Very rare (less than 0.01%): Bronchospasm
• Postmarketing reports: Bronchospasm aggravated^[Ref]

Gastrointestinal

• Common (1% to 10%): Dry mouth, abdominal pain, dyspepsia, nausea
• Uncommon (0.1% to 1%): Constipation, flatulence, vomiting, gastroenteritis, diarrhea
• Frequency not reported: Gastrointestinal obstruction^[Ref]

Genitourinary

• Common (1% to 10%): Polyuria, urinary tract infection, cystitis, urinary incontinence
• Uncommon (0.1% to 1%): Dysuria, micturition frequency, hematuria, impotence
• Very rare (less than 0.01%): Micturition disorder, nocturia, priapism
• Frequency not reported: Retrograde ejaculation^[Ref]

Cardiovascular

• Common (1% to 10%): Hypotension, postural hypotension, palpitation, tachycardia
• Uncommon (0.1% to 1%): Angina pectoris, myocardial infarction
• Very rare (less than 0.01%): Bradycardia, cardiac arrhythmias, hot flushes^[Ref]

Metabolic

• Common (1% to 10%): Edema, peripheral edema
• Uncommon (0.1% to 1%): Gout, appetite increased, anorexia, weight increased^[Ref]

Musculoskeletal

• Common (1% to 10%): Myalgia, back pain
• Uncommon (0.1% to 1%): Arthralgia
• Rare (less than 0.1%): Muscle cramps, muscle weakness^[Ref]

Dermatologic

• Common (1% to 10%): Pruritus
• Uncommon (0.1% to 1%): Skin rash
• Very rare (less than 0.01%): Urticaria, purpura, alopecia^[Ref]

Psychiatric

• Uncommon (0.1% to 1%): Agitation, depression, anxiety, insomnia, nervousness
• Frequency not reported: Libido decreased^[Ref]

Hepatic

• Uncommon (0.1% to 1%): Abnormal liver function tests
• Very rare (less than 0.01%): Cholestasis, hepatitis, jaundice
• Postmarketing reports: Hepatitis cholestatic^[Ref]

Immunologic

• Uncommon (0.1% to 1%): Allergic drug reaction
• Postmarketing reports: Allergic reaction^[Ref]

Hematologic

• Very rare (less than 0.01%): Leukopenia, thrombocytopenia
• Frequency not reported: White blood cell counts decreased, neutrophil count decreased^[Ref]

Ocular

• Very rare (less than 0.01%): Blurred vision
• Frequency not reported: Intraoperative Floppy Iris Syndrome (IFIS)^[Ref]

Endocrine

• Very rare (less than 0.01%): Gynecomastia^[Ref]

Renal

• Very rare (less than 0.01%): Diuresis increased^[Ref]

See also:

Further information

Doxazosin side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer