Doxazosin

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Contents

[edit] BRAND NAMES

[edit] STRUCTURE

Doxazosin.jpg

[edit] MECHANISM OF ACTION

Doxazosin exerts a selective postsynaptic action, inhibiting the binding of norepinephrine to the α1 receptors.

Three α1 receptor subtypes have been identified, α1a, α1b and α1d:

  • α1a and α1d subtypes are predominant in the prostate, bladder, and detrusor muscle.
  • α1b subtypes are largely located on vascular smooth muscle.

Doxazosin antagonizes all three subtypes; blockade of α1a and α1d can lead to smooth muscle relaxation in the lower urinary tract resulting in improved urinary flow rates. At the same time blockade of α1b subtypes can cause relaxation in peripheral vascular resistance which results in a decrease in blood pressure.

[edit] INDICATIONS

  • Treatment of the signs and symptoms of benign prostatic hyperplasia (hesitation, intermittency, dribbling, weak urinary stream, incomplete emptying of the bladder, nocturia, daytime frequency, urgency and burning).
  • Treatment of hypertension, alone or in combination with diuretics, beta blockers, Calcium channel blockers, or ACE inhibitors

[edit] DOSAGE

The initial dosage of Doxazosin in patients with hypertension and/or BPH is 1 mg given once daily in the a.m. or p.m. This starting dose is intended to minimize the frequency of postural hypotension and first-dose syncope.

In hypertension, dosage may then be increased after 1-2 weeks to 2 mg and thereafter if necessary to 4 mg, 8 mg and 16 mg. The usual dose range is 2-4 mg daily. Increases in dose beyond 4 mg increase the likelihood of excessive postural effects.

In BPH the dosage may then be increased to 2 mg and thereafter to 4 mg and 8 mg once daily. The recommended titration interval is 1–2 weeks.

For the extended release tablets (Cardura XL) indicated for the treatment of the signs and symptoms of benign prostatic hyperplasia, the initial dose is 4 mg given once daily with breakfast. Depending on the patient’s symptomatic response and tolerability, the dose may be increased to 8 mg, the maximum recommended dose. The recommended titration interval is 3–4 weeks.

[edit] CONTRAINDICATIONS

  • Hypersensitivity to Doxazosin

[edit] WARNINGS AND PRECAUTIONS

  • Postural hypotension, dizziness, lightheadedness and syncope can occur, especially at initiation of therapy or at the time of dose increases. Treatment should be initiated with the 1 mg dose and should then be adjusted slowly to the recommended dose
  • Patients should be screened for the presence of prostate cancer prior to treatment and at regular intervals afterwards because prostate cancer causes many of the symptoms associated with BPH and the two disorders frequently co-exist.

[edit] INTERACTIONS

  • Concomitant administration of Doxazosin with a PDE5 inhibitor (Viagra, Levitra, Cialis, Stendra) can result in additive blood pressure lowering effects and symptomatic hypotension.

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category C (US). Doxazosin should be used during pregnancy only if clearly needed
  • Nursing mothers: It is not known whether Doxazosin is excreted in human milk, therefore, caution should be exercised if administered to a nursing mother.

[edit] SIDE EFFECTS

The most commonly adverse reactions are asthenia, headache, hypotension, and dizziness

[edit] RELATED LINKS

Benign Prostatic Hyperplasia (BPH) and Treatments (Video 1)
Benign Prostatic Hyperplasia (BPH) and Treatments (Video 2)

[edit] BIBLIOGRAPHY

[edit] REFERENCES

Benign Prostatic Hypertrophy
5α reductase inhibitors Dutasteride (Avodart)   Finasteride (Proscar)
Alpha 1 antagonists Alfuzosin (Uroxatral, Xatral)   Doxazosin (Cardura)   Prazosin   Silodosin (Silodyx, Rapaflo)   Tamsulosin (Omnic, Flomax, Secotex)   Terazosin (Hytrin)
Phytotherapy Pygeum africanum   Serenoa repens
PDE5 inhibitors Tadalafil (Cialis)
Combination products Dutasteride/Tamsulosin (Combodart, Jalyn, Duodart)
Other Mepartricin
Veterinary Osaterone (Ypozane)
Antihypertensives
ACE inhibitors Benazepril (Lotensin)   Captopril (Capoten)   Cilazapril   Delapril   Enalapril (Renitec, Vasotec)   Fosinopril (Monopril)  Lisinopril (Prinivil, Zestril)   Moexipril (Univasc)  Perindopril (Aceon)  Quinapril (Accupril)  Ramipril (Altace, Triatec)   Trandolapril (Mavik)  Zofenopril (Bifril, Zopranol)
Angiotensin II receptor antagonist Azilsartan (Edarbi)   Candesartan (Atacand)   Eprosartan (Teveten)   Irbesartan (Aprovel, Avapro, Karvea)   Losartan (Cozaar)   Olmesartan (Benicar, Olmetec)   Telmisartan (Micadis)   Valsartan (Diovan, Tareg)
Renin inhibitors Aliskiren (Rasilez, Tekturna)
Alpha-1 blockers Doxazosin (Cardura)   Prazosin (Minipress)   Terazosin (Hytrin)
Alpha-2 agonists (centrally acting) Clonidine (Oral route)   Clonidine (Transdermal) (Catapresan)   Guanfacine (Tenex)   Methyldopa (Aldomet)
Calcium channel blockers Dihydropyridines‎ Amlodipine (Norvasc)   Barnidipine (Vasexten)   Felodipine (Plendil)   Isradipine (Dynacirc)   Lacidipine (Lacipil, Motens)   Lercanidipine (Zanidip)   Manidipine   Nicardipine   Nifedipine (Adalat)   Nisoldipine   Nitrendipine
Benzothiazepine‎ Diltiazem (Cardizem, Taztia XT, Tiazac, Tildiem)
Phenylalkylamine‎ Gallopamil   Verapamil (Calan)
Beta blockers Beta1 selective (cardioselective) Acebutolol (Sectral)   Atenolol (Tenormin)   Betaxolol (Kerlon)   Bisoprolol (Concor)   Celiprolol (Cordiax)   Metoprolol (Betaloc, Lopressor, Toprol-XL)   Nebivolol (Bystolic, Lobivon, Nebilox)
Nonselective (Beta1 and Beta2 blockers) Oxprenolol (Trasitensin)   Propranolol (Inderal)   Timolol (Blocadren)
Nonselective (Beta1, Beta2 and Alpha1 blockers) Carvedilol (Dilatrend)   Labetalol (Trandate)
Beta blocker with intrinsic sympathomimetic activity (ISA) Acebutolol (Sectral)   Celiprolol (Cordiax)
Lipophilic Beta blockers Propranolol (Inderal)   Metoprolol (Betaloc, Lopressor, Toprol-XL)   Oxprenolol (Trasitensin)
Diuretics Carbonic anhydrase inhibitors Acetazolamide (Diamox)
Loop diuretics Bumetanide   Etacrynic acid   Furosemide (Lasix)   Piretanide   Torasemide (Demadex)
Thiazide diuretics Chlorothiazide (Diuril)   Hydrochlorothiazide (Esidrex)
Thiazide-like diuretics Chlortalidone (Hygroton)   Indapamide (Lozol, Lozide)   Metolazone
Potassium-sparing diuretics Epithelial sodium channel blockers: Amiloride (Midamor)   Triamterene (Dyrenium)
Aldosterone receptor antagonists: Potassium canrenoate   Eplerenone (Inspra)   Spironolactone (Aldactone)
Osmotic diuretics Mannitol
Combination therapy Amiloride/Hydrochlorothiazide (Moduretic)   Spironolactone/Hydrochlorothiazide (Aldactazide)