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Doxazosin oral modified release


Modified release formulations of doxazosin.

Drugs List

  • CARDURA XL 4mg modified release tablet
  • CARDURA XL 8mg modified release tablet
  • DOXADURA XL 4mg tablets
  • doxazosin 4mg modified release tablet
  • doxazosin 8mg modified release tablet
  • LARBEX XL 4mg prolonged release tablet
  • RAPORSIN XL 4mg prolonged release tablet
  • Therapeutic Indications


    Benign prostatic hyperplasia

    Unlicensed Uses

    Dysfunctional voiding of urine



    4mg once daily. If necessary, the dose may be increased after four weeks to 8mg once daily.

    Benign prostatic hyperplasia
    4mg once daily. If necessary, the dose may be increased after four weeks to 8mg once daily.


    Urine voiding dysfunction (unlicensed)
    Children aged 12 to 18 years may be converted to modified release doxazosin once stabilised on standard release, if a suitable strength is available.

    Hypertension (unlicensed)
    Children aged 6 to 18 years may be converted to modified release doxazosin once stabilised on standard release, if a suitable strength is available.

    Patients with Renal Impairment

    Doxazosin is not dialysable.


    Children under 6 years
    Chronic urinary tract infections - if treating benign prostatic hyperplasia
    History of gastrointestinal obstruction
    History of gastrointestinal stenosis
    History of oesophageal obstruction
    History of postural hypotension
    Urolithiasis - if treating benign prostatic hyperplasia

    Precautions and Warnings

    Children aged 6 to 18 years
    Cardiac failure
    Hepatic impairment
    Hypotension - if treating benign prostatic hyperplasia
    Left ventricular failure with low filling pressure
    Pulmonary oedema

    Advise ability to drive/operate machinery may be affected by side effects
    Benign prostatic hyperplasia: Exclude prostate carcinoma before treatment
    Advise patient that postural hypotension may occur
    Intraoperative Floppy Iris Syndrome has been reported in cataract surgery
    May affect urine test results
    Advise patient not to take NSAIDs unless advised by clinician
    Hypotensive effects may be potentiated by alcohol
    Advise patients that empty tablet/capsule may be observed in stools

    Use with care in patients with diabetic autonomic neuropathy.

    Abnormally short transient times through the gastrointestinal tract (e.g. following surgical resection) could result in incomplete absorption. The clinical significance, given the long half life of doxazosin, is unclear.

    Pregnancy and Lactation


    Doxazosin is contraindicated for use during pregnancy.

    In animal studies doxazosin crosses the placenta. Doxazosin has demonstrated no teratogenic effects in animal testing, but at extremely high doses (300 times the maximum recommended human dose) reduced foetal survival was observed. Briggs (2011) states that reduced foetal survival has been observed in rabbits at 20 times therapeutic dose and delayed postnatal development in rat pups at 8 times the therapeutic dose during perinatal and postnatal periods.

    As there are no adequate or well-controlled studies in pregnant women, the safety of doxazosin during pregnancy has not been established. Schaefer (2007) comments that inadvertent use of the doxazosin is no reason for termination of pregnancy or for invasive procedures.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Doxazosin is contraindicated during breastfeeding.

    Animal studies have shown that doxazosin accumulates via a possible concentration mechanism in breast milk to 20 times that of the maternal blood plasma.

    Although no human reports to date are catalogued, presence and accumulation in human milk should be anticipated due to the animal study outcomes. The manufacturers recommend to stop breastfeeding when treatment with doxazosin is necessary and advice from LactMed, via TOXNET states that an alternative drug may be preferred especially whilst nursing a newborn or preterm infant. Information on LactMed also states that the pharmacological similar drug prazosin does not affect serum prolactin concentration in patients with hypertension. The prolactin level in a mother with established lactation may not affect her ability to breastfeed. Schaefer (2007) comments that doxazosin should not be taken during breastfeeding. If treatment has begun weaning is not necessary, however therapy should be changed to an antihypertensive of choice, including an acceptable calcium antagonist or, if really indicated, an ACE inhibitor with a low transfer dosage via breast milk. Hale recommends doxazosin is used with extreme caution and no paediatrics concerns have been reported via the milk.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    Advise patient that doxazosin therapy may impair ability to drive or operate machinery, especially when initiating treatment.

    Advise patients on the measures they should take to avoid postural hypotension which may occur particularly when initiating treatment. The hypotensive effects may be exaggerated by alcohol ingestion.

    Advise patient to swallow the tablet whole - the tablets should not be chewed, divided or crushed.

    Advise patients that empty tablet may occasionally be observed in stools.

    Advise patients not to purchase NSAIDs unless on medical advice if being treated for hypertension.

    Advise patients the initial dose may be taken at bedtime to minimise first dose postural hypotension.

    Side Effects

    Abdominal pain
    Abnormal ejaculation
    Abnormal liver function tests
    Allergic reaction
    Angina pectoris
    Back pain
    Blurred vision
    Cerebrovascular disorders
    Chest pain
    Dry mouth
    Gastrointestinal obstruction
    Increased appetite
    Influenza-like symptoms
    Intraoperative floppy iris syndrome
    Micturition disorders
    Muscle cramps
    Muscle weakness
    Myocardial infarction
    Peripheral oedema
    Postural hypotension
    Respiratory tract infection
    Sleep disturbances
    Taste disturbances
    Urinary incontinence
    Urinary tract infections
    Weight changes

    Effects on Laboratory Tests

    Doxazosin may influence plasma renin activity and the urinary excretion of vanillylmandelic acid.


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: June 2013

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    Martindale: The Complete Drug Reference, 37th edition (2011) ed. Sweetman, S. Pharmaceutical Press, London.

    Medications and Mothers' Milk, 14th Edition (2010) Hale, T. Hale Publishing, Amarillo, Texas.

    The Renal Drug Handbook. 3rd edition. (2009) ed. Ashley, C and Currie, Radcliffe Publishing Ltd, Abingdon.

    Summary of Product Characteristics: Cardozin XL 4mg prolonged release tablets (doxazosin)(Arrow). Actavis UK Ltd. March 2012.

    Summary of Product Characteristics: Cardura XL 4mg tablets. Pfizer Ltd. Revised November 2016.

    Summary of Product Characteristics: Cardura XL 8mg tablets. Pfizer Ltd. Revised November 2016.

    Summary of Product Characteristics: Colixil XL 4mg prolonged release tablets. Sandoz Ltd. Revised October 2012.

    Summary of Product Characteristics: Doxadura XL 4mg prolonged release XL tablets. Discovery Pharmaceuticals Ltd. Revised April 2010.

    Summary of Product Characteristics: Doxzogen XL 4mg prolonged release tablets. Generics UK Ltd. Revised November 2009.

    Summary of Product Characteristics: Larbex XL 4mg prolonged release tablets. Teva UK Ltd. Revised November 2009.

    Summary of Product Characteristics: Raporsin XL 4mg prolonged release tablets. Actavis. Revised September 2012.

    Summary of Product Characteristics: Slocinx XL 4mg prolonged release tablets. Zentiva. Revised July 2012.

    NICE Evidence Services Available at: Last accessed: 28 June 2017

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Doxazosin. Last revised: September 29, 2009
    Last accessed: June 26, 2013

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