II. Indications

III. Pharmacokinetics

  1. Agents are highly protein bound (>90%)

IV. Mechanism: General and Antihypertensive Effects

  1. See Alpha Adrenergic Receptor (Alpha-1 antagonist)
  2. Peripheral Alpha-1 Adrenergic Antagonists
    1. Arterial and Venous Vasodilation

V. Mechanism: Benign Prostatic Hypertrophy

  1. Preparations used in Benign Prostatic Hypertrophy
    1. See Selective Alpha-1a Antagonist (Tamsulosin, Alfuzosin, Silodosin)
    2. Terazosin (Hytrin)
    3. Doxazosin (Cardura)
    4. Prazosin (Minipress)
  2. Rapid relaxation of smooth muscle tone
    1. Bladder neck
    2. Prostate Capsule
    3. Prostatic Urethra
  3. Relieves symptoms of urinary obstruction
    1. May see full effect within 2 weeks
  4. Does not effect size of Prostate (unlike Proscar)

VI. Preparations: Non-Selective Agents

  1. Terazosin (Hytrin)
    1. Dose: 1 mg orally at bedtime (Maximum 20 mg/day)
  2. Doxazosin (Cardura)
    1. Dose: 1 mg orally at bedtime (Maximum 16 mg/day)
  3. Prazosin (Minipress)
    1. Dose: 1 mg PO bid-tid (Maximum 40 mg/day)
    2. Terazosin and Doxazosin are preferred instead (once daily dosing at similar cost)
  4. Phenoxybenzamine (Dibenzyline)
    1. Dose: 10 mg PO bid (Maximum 120 mg/day)
    2. Terazosin and Doxazosin are preferred instead (once daily dosing at similar cost)

VII. Preparations: Selective Alpha-1a Antagonists (Prostate specific agents)

VIII. Preparations: Combination Alpha-Beta Antagonists

IX. Adverse Effects (Incidence: 7 to 9%)

  1. Dose at bedtime
    1. Slowly titrate to reduce side effects (esp. Orthostatic Hypotension)
  2. Cardiovascular adverse effects (also occurs with selective agents, albeit less often)
    1. Postural or Orthostatic Hypotension
      1. Common with first dose (may be severe)
      2. Exacerbated by Hyponatremia
    2. Dizziness
    3. Associated with fall risk and secondary Fracture risk
  3. Other adverse effects
    1. Fatigue
    2. Asthenia
    3. Xerostomia
    4. Headache
    5. Nightmares
    6. Sexual Dysfunction

X. Precautions

  1. Avoid using as monotherapy for Hypertension
    1. Higher risk of CVA and CHF compared with other agents
    2. (2000) JAMA 283:1967-75 [PubMed]

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Related Studies

Cost: Medications

Terazosin (on 6/18/2017 at Walmart.com)
Terazosin 10mg #30 capsules for $4.00 $0.13 each
Terazosin 10mg #90 capsules for $10.00 $0.11 each
Terazosin 1mg #30 capsules for $4.00 $0.13 each
Terazosin 1mg #90 capsules for $10.00 $0.11 each
Terazosin 2mg #30 capsules for $4.00 $0.13 each
Terazosin 2mg #90 capsules for $10.00 $0.11 each
Terazosin 5mg #30 capsules for $4.00 $0.13 each
Terazosin 5mg #90 capsules for $10.00 $0.11 each
prazosin (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
PRAZOSIN 1 MG CAPSULE Generic $0.42 each
PRAZOSIN 2 MG CAPSULE Generic $0.67 each
PRAZOSIN 5 MG CAPSULE Generic $1.04 each
terazosin (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
TERAZOSIN 1 MG CAPSULE Generic $0.06 each
TERAZOSIN 10 MG CAPSULE Generic $0.06 each
TERAZOSIN 2 MG CAPSULE Generic $0.06 each
TERAZOSIN 5 MG CAPSULE Generic $0.06 each
doxazosin (on 5/17/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
DOXAZOSIN MESYLATE 1 MG TAB Generic $0.29 each
DOXAZOSIN MESYLATE 2 MG TAB Generic $0.26 each
DOXAZOSIN MESYLATE 4 MG TAB Generic $0.28 each
DOXAZOSIN MESYLATE 8 MG TAB Generic $0.27 each
cardura (on 6/1/2017 at Medicaid.Gov Survey of pharmacy drug pricing)
CARDURA 2 MG TABLET Generic $0.26 each
CARDURA 4 MG TABLET Generic $0.28 each
CARDURA XL 4 MG TABLET $4.69 each

Ontology: Prazosin (C0032912)

Definition (MSH) A selective adrenergic alpha-1 antagonist used in the treatment of HEART FAILURE; HYPERTENSION; PHEOCHROMOCYTOMA; RAYNAUD DISEASE; PROSTATIC HYPERTROPHY; and URINARY RETENTION.
Definition (NCI) A synthetic piperazine derivative and an alpha-1 adrenergic receptor inhibitor used primarily as an anti-hypertensive. Prazosin's effects are most pronounced in the large resistance vessels (i.e. arterioles) and result in a decrease in total systemic vascular resistance (SVR) without a rebound or reflex tachycardia. To a lesser extent, this agent also decreases the tone of the bladder sphincter, thereby allowing the opening of the bladder into the urethra and thus relieving the urinary conditions associated with benign prostatic hypertrophy.
Definition (CSP) 1-(4-amino-6,7-dimethoxy- 2-quinazolinyl) -4-(2-furoyl) piperazine.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D011224
SnomedCT 367555002, 387283005, 387433003, 76058001, 51505001
LNC LP18588-1, MTHU004704
English Furazosin, Prazosin, Piperazine, 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-furanylcarbonyl)-, 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline, 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-furanylcarbonyl)piperazine, Prazosin [Chemical/Ingredient], PRAZOSIN, prazosin (medication), Furazosin (product), prazosin, Prazosin (product), Prazosin (substance), Furazosin (substance)
Swedish Prazosin
Czech prazosin
Finnish Pratsosiini
Russian PRAZOZIN, ADVERZUTEN, FURAZOZIN, PRATSIOL, АДВЕРЗУТЕН, ПРАЗОЗИН, ПРАТСИОЛ, ФУРАЗОЗИН
Japanese プラゾシン, 塩酸プラゾシン, フラゾシン
Italian Furazosina, Prazosina
Spanish prazosina (producto), prazosín (producto), furazosín, furazosina, furazosín (producto), furazosina (sustancia), prazosina (sustancia), prazosina, prazosín, Furazosina, Prazosina
Polish Prazosyna
French Prazosine
German Furazosin, Prazosin
Portuguese Furazosin, Prazosina

Ontology: Terazosin (C0076107)

Definition (NCI_NCI-GLOSS) A drug used to treat urinary problems caused by an enlarged prostate. It is also used to treat high blood pressure and is being studied in the treatment of other conditions. Terazosin relaxes muscle tissue in blood vessels and in the prostate. It is a type of alpha blocker.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH C041226
SnomedCT 349914007, 129484001, 387068008
LNC LP101133-9, MTHU036183
English terazosin, Terazosin, Terazosin [Chemical/Ingredient], terazosine, TERAZOSIN, Terazosin (product), Terazosin (substance)
Spanish terazosina (producto), terazosina (sustancia), terazosina

Ontology: Doxazosin (C0114873)

Definition (MSH) A prazosin-related compound that is a selective alpha-1-adrenergic blocker.
Definition (NCI) A quinazoline with antihypertensive and antineoplastic properties. Doxazosin is an alpha-adrenergic antagonist that selectively inhibits alpha-1 adrenergic receptors. Blockages of the alpha-1 adrenergic action on the vascular smooth muscles lead to a decrease in vascular resistance and antihypertensive activity. This agent also shows high affinity to alpha-1c adrenoceptor, the predominant functional type in the prostate, which may partially attribute to its effect in treatment of benign prostatic hyperplasia. Furthermore, doxazosin induces apoptosis in prostate cancer cells mediated through inhibition of protein kinase B (PKB)/Akt-signaling death receptor regulatory pathway.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D017292
SnomedCT 108556006, 372508002
LNC LP171393-4
English Doxazosin, Piperazine, 1-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-((2,3-dihydro-1,4-benzodioxin-2-yl)carbonyl)-, Doxazosin [Chemical/Ingredient], doxazosin (medication), alpha blockers doxazosin, doxazosin, DOXAZOSIN, Doxazosin (product), Doxazosin (substance)
Swedish Doxazosin
Czech doxazosin
Finnish Doksatsosiini
Russian DOKSAZOZIN, ДОКСАЗОЗИН
Japanese ドキサゾシン, ドキサゾシンメシレート, メシル酸ドキサゾシン
Spanish Doxazosina, Doxazosin, doxazosina (producto), doxazosina (sustancia), doxazosina
Portuguese Doxazossina, Doxazosin, Doxazosina
Polish Doksazosyna, Metylosulfonian doksazosyny
French Doxazosine
German Doxazosin
Italian Dossazosina

Ontology: Minipress (C0242447)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D011224
English Pfizer Brand of Prazosin Hydrochloride, minipress, Minipress

Ontology: Hytrin (C0591628)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH C041226
English Abbott Brand of Terazosin Hydrochloride, hytrin, hytrin bph, Hytrin, Hytrin BPH, Deflox, Flotrin, Heitrin, Hytrine

Ontology: Cardura (C0678136)

Definition (MSH) Trade name in United States.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D017292
English Carduran, cardura, carduran, Cardura, Cardular, Pfizer Brand of Doxazosin Mesylate, Zoxan