Doxazosin

Doxazosin is a prescription drug indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes, including this drug.

• Doxazosin is available under the following different brand names: Cardura, Cardura XL, and Doxadura.

Adult and Pediatric Dosages Dosage Forms and Strengths

Tablets

• 1 mg
• 2 mg
• 4 mg
• 8 mg

Tablet, extended-release (adult dosage only)

• 4 mg
• 8 mg

Dosage Considerations – Should be Given as Follows:

Hypertension

Adult Dosage:

• Immediate release: 1-16 mg orally once daily in the morning or at night
• Extended-release: not indicated for hypertension

Geriatric Dosage:

• Avoid use for hypertension; high risk of orthostatic hypotension (Beers criteria); if used, lower initial dosages and gradual adjustments are recommended
• Immediate release: 0.5-16 mg orally once daily in the morning or at night
• Extended-release: not indicated for hypertension

Pediatric Dosage: (off-label)

• Immediate release: 1-4 mg orally once daily in the morning or at night

Benign Prostatic Hyperplasia

Adult and Geriatric Dosage:

• Immediate release: 1-8 mg/day orally
• Extended-release: 4 mg/day orally initially at breakfast; may be increased to no more than 8 mg/day orally

Dosing Modifications

• Liver (hepatic) impairment: Use with caution in mild-to-moderate hepatic dysfunction; do not use in severe impairment

Dosing Considerations

• Give the first dose and increase at bedtime to avoid fainting

Side effects of doxazosin include:

• dizziness
• fatigue
• headache
• spinning sensation (vertigo)
• upper respiratory tract infection
• swelling (edema)
• runny nose
• shortness of breath
• abdominal pain
• low blood pressure
• nausea
• dizziness upon standing (dose-related)
• anxiety
• irregular heartbeat or fluttering (palpitations)
• lightheadedness
• tired feeling
• drowsiness
• weight gain
• fainting
• weakness
• swelling of hands or feet
• dark urine
• easy bleeding or bruising
• fever
• persistent sore throat

Postmarketing side effects of Doxazosin reported include:

• Autonomic Nervous System: persistent and painful erection of the penis (priapism)
• Cardiovascular System: stroke, dizziness upon standing, heart attack (myocardial infarction)
• Central and Peripheral Nervous System: a reduced sense of touch (hypoesthesia), numbness, and tingling
• Endocrine System: enlarged breast in men (gynecomastia)
• Gastrointestinal System: gastrointestinal obstruction, vomiting
• General Body System: fatigue, hot flushes, feeling unwell (malaise)
• Heart Rate/Rhythm: slow heart rate, irregular heartbeats (cardiac arrhythmias)
• Hematopoietic: low white blood cell count, a rash with purple spots, low platelet count (thrombocytopenia)
• Liver/Biliary System: abnormal liver function tests, inflammation of the liver (hepatitis), obstruction of bile secretion leading to liver failure (hepatitis cholestatic), yellow skin and eyes (jaundice)
• Musculoskeletal System: muscle cramps, muscle weakness
• Psychiatric: agitation, loss of appetite, nervousness
• Respiratory System: difficulty breathing (bronchospasm) aggravated
• Skin Disorders: hair loss, hives, skin rash, severe itching
• Special Senses: blurred vision, intraoperative Floppy Iris Syndrome
• Urinary System: blood in the urine, urinary disorder, urinary frequency, nighttime urination, excessive urination
• Immune System: allergic reaction
• Eye Disorders: Intraoperative Floppy Iris Syndrome (prolapsed iris during surgery)

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Severe interactions of doxazosin include:
  • boceprevir
• Serious interactions of doxazosin include:
  • sildenafil
  • tamsulosin
  • vardenafil
  • yohimbe
• Mild interactions of doxazosin include:
  • brimonidine
  • butcher's broom
  • ethanol
  • lofexidine
  • phenylephrine
  • phenylephrine po
  • tizanidine
  • treprostinil

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

Warnings

• This medication contains doxazosin. Do not take Cardura, Cardura XL, or Doxadura if you are allergic to doxazosin or any ingredients contained in this drug.
• Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.

Contraindications

• Hypersensitivity to doxazosin or other quinazolines.

Effects of Drug Abuse

• No information was provided.

Short-Term Effects

• See "What Are Side Effects Associated with Using Doxazosin?"

Long-Term Effects

• See "What Are Side Effects Associated with Using Doxazosin?"

Cautions

• Use with caution in liver disease or recent stroke (cerebrovascular accident [CVA])
• Rule out prostate cancer before initiating therapy
• May cause first-dose fainting or sudden loss of consciousness
• Risk of dizziness upon standing (dose-dependent)
• Potential for low blood pressure, dry mouth, and urinary complications in elderly
• Priapism (painful penile erection, sustained for hours and unrelieved by sexual intercourse or masturbation) rarely reported (probably less frequently than once in every several thousand patients), with alpha-1 antagonists, including doxazosin; because the condition can lead to permanent impotence if not promptly treated, patients must be advised about seriousness of the condition
• Concomitant use of other antihypertensives (additive hypotensive effects)
• Extended-release form not indicated for high blood pressure
• Concomitant administration of immediate-release form with a phosphodiesterase-5 (PDE-5) inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension
• May increase the risk of heart failure by exacerbating underlying myocardial dysfunction by beta-1Receptor stimulation with increases in renin and aldosterone

Pregnancy and Lactation

• Doxazosin is not indicated for use in females or for the treatment of hypertension. The limited available data in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage
• No adverse developmental outcomes were observed in animal reproduction studies with oral administration to pregnant rats and rabbits at doses of up to 10 and 4 times, respectively, the 12 mg/day recommended dose; postnatal development was delayed in rats at a dose of 8 times the 12 mg/day recommended dose
• Doxazosin is present in human milk; there is no information on effects on breastfed infants or effects on milk production when breastfeeding