Alpha Adrenergic Antagonist

Aka: Alpha Adrenergic Antagonist, Peripheral Alpha-1 Adrenergic Antagonist, Postsynaptic Alpha Adrenergic Antagonist, Alpha Adrenergic Receptor Blocker, Prazosin, Minipress, Terazosin, Hytrin, Doxazosin, Cardura, Phenoxybenzamine, Dibenzyline, Phentolamine, Rogatine

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II. Indications

  1. Non-selective agents
    1. Hypertension (non-selective agents)
      1. Not first-line antihypertensives, and avoid using as monotherapy (higher risk of CVA and CHF)
    2. Pheochromocytoma Hypertensive Crisis (Phentolamine, Phenoxybenzamine)
  2. Selective Alpha-1a Antagonists (e.g. Tamsulosin)
    1. Benign Prostatic Hypertrophy (Selective )
    2. Medical Expulsive Therapy for Ureteral Stone

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. Hypertension
      1. Start 1 mg orally at bedtime
      2. Titrate to effective dose 1 to 5 mg daily or in divided doses (Maximum 20 mg/day)
    2. Benign Prostatic Hypertrophy (replaced by Selective Alpha-1a Antagonists)
      1. Start 1 mg orally at bedtime
      2. Titrate to effect by doubling dose every 1-2 weeks (to 2, 5 and 10 mg, maximum of 20 mg/day)
      3. Observe for effects after 4 to 6 weeks on optimal dose (typically 10 mg)
  2. Doxazosin (Cardura)
    1. Hypertension
      1. Start: 1 mg orally at bedtime and titrate dose (Maximum 16 mg/day)
    2. Benign Prostatic Hypertrophy (replaced by Selective Alpha-1a Antagonists)
      1. Start: 1 mg orally at bedtime and titrate every 1-2 weeks doubling dose, to a maximum of 8 mg at bedtime
      2. Extended release formulation (e.g. Cardura XL) 4 mg in am daily (may increase to 8 mg daily after 3-4 weeks)
    3. Medical Expulsive Therapy for Ureteral Stone (replaced by Selective Alpha-1a Antagonists)
      1. Extended release formulation (e.g. Cardura XL) 4 mg orally daily (not FDA approved)
  3. Prazosin (Minipress)
    1. Terazosin and Doxazosin are preferred instead (once daily dosing at similar cost)
    2. Hypertension
      1. Start 1 mg orally twice daily to three times daily
      2. Titrate to usual daily total dose 20 mg divided two to three times daily
      3. Maximum total daily dose: 40 mg/day (but doses above 20 mg/day offer little additional benefit)

VII. Preparations: Unique Non-Selective Agents Indicated in Pheochromocytoma Hypertensive Crisis

  1. Phenoxybenzamine (Dibenzyline)
    1. Indicated in the Hypertensive Crisis of Pheochromocytoma
      1. Terazosin and Doxazosin are preferred as routine antihypertensive agents instead (once daily dosing at similar cost)
    2. Irreversible alkylation of the Alpha Adrenergic Receptor
    3. Start 10 mg orally twice daily
      1. Titrate to typical dose 20 to 40 mg orally twice daily
      2. Maximum daily dose: 120 mg/day
  2. Phentolamine (Rogatine)
    1. Hypertensive Crisis in Pheochromocytoma
      1. Dose: 5 mg IV/IM for one dose (results in profound drop in BP, e.g. 60/25 mmHg decrease in BP)
    2. IV extravasation of Catecholamines (e.g. Norepinephrine)
      1. Prepare 5-10 mg in 10 ml Normal Saline, and inject 1 ml around extravasation site
      2. In adults may repeat dose up to a total of 5 ml injected around extravasation site

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

  1. See Selective Alpha-1a Antagonists
  2. Alfuzosin (Uroxatral, generic)
  3. Silodosin (Rapaflo)
  4. Tamsulosin (Flomax, generic)

IX. Preparations: Combination Alpha-Beta Antagonists

  1. Labetalol (Trandate)
  2. Carvedilol (Coreg)

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

  1. Dose at bedtime
    1. Slowly titrate to reduce side effects (esp. Orthostatic Hypotension, Dizziness, drowsiness)
  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 or light headedness
    3. Associated with Fall Risk and secondary Fracture risk
  3. Other adverse effects
    1. Drowsiness
    2. Fatigue
    3. Asthenia
    4. Xerostomia
    5. Headache
    6. Nightmares
    7. Sexual Dysfunction

XI. Precautions

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

XII. References

  1. Aldridge (1996) Lancet 348:602
    1. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)64801-5/abstract
  2. Hamilton (2010) Tarascon Pocket Pharmacopeia, p. 76-7
  3. (1994) Med Lett Drugs Ther 36: 15 [PubMed]
  4. (1997) Med Lett Drugs Ther 39: 1011 [PubMed]
  5. Grimm (2011) J Clin Hypertens 13(9):654-7 +PMID: 21896145 [PubMed]
  6. Lee (2000) Ann Pharmacother 34:188-99 [PubMed]

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Related Studies

Cost: Medications

prazosin (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
PRAZOSIN 1 MG CAPSULE Generic $0.18 each
PRAZOSIN 2 MG CAPSULE Generic $0.26 each
PRAZOSIN 5 MG CAPSULE Generic $0.50 each
terazosin (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
TERAZOSIN 1 MG CAPSULE Generic $0.14 each
TERAZOSIN 10 MG CAPSULE Generic $0.16 each
TERAZOSIN 2 MG CAPSULE Generic $0.14 each
TERAZOSIN 5 MG CAPSULE Generic $0.16 each
doxazosin (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
DOXAZOSIN MESYLATE 1 MG TAB Generic $0.09 each
DOXAZOSIN MESYLATE 2 MG TAB Generic $0.07 each
DOXAZOSIN MESYLATE 4 MG TAB Generic $0.09 each
DOXAZOSIN MESYLATE 8 MG TAB Generic $0.11 each
FPNotebook does not benefit financially from showing this medication data or their pharmacy links. This information is provided only to help medical providers and their patients see relative costs. Insurance plans negotiate lower medication prices with suppliers. Prices shown here are out of pocket, non-negotiated rates. See Needy Meds for financial assistance information. GoodRx is another tool for finding lower drug prices.

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
Derived from the NIH UMLS (Unified Medical Language System)

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
Derived from the NIH UMLS (Unified Medical Language System)

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
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Minipress (C0242447)

Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D011224
English Pfizer Brand of Prazosin Hydrochloride, minipress, Minipress
Derived from the NIH UMLS (Unified Medical Language System)

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
Derived from the NIH UMLS (Unified Medical Language System)

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
Derived from the NIH UMLS (Unified Medical Language System)

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