II. Indications
- Non-selective agents
- Hypertension (non-selective agents)
- Not first-line antihypertensives, and avoid using as monotherapy (higher risk of CVA and CHF)
- Pheochromocytoma Hypertensive Crisis (Phentolamine, Phenoxybenzamine)
- Hypertension (non-selective agents)
-
Selective Alpha-1a Antagonists (e.g. Tamsulosin)
- Benign Prostatic Hypertrophy (Selective )
- Medical Expulsive Therapy for Ureteral Stone
III. Pharmacokinetics
- Agents are highly Protein bound (>90%)
IV. Mechanism: General and Antihypertensive Effects
- See Alpha Adrenergic Receptor (Alpha-1 Antagonist)
- Peripheral Alpha-1 Adrenergic Antagonists
- Arterial and Venous Vasodilation
V. Mechanism: Benign Prostatic Hypertrophy
- Preparations used in Benign Prostatic Hypertrophy
- See Selective Alpha-1a Antagonist (Tamsulosin, Alfuzosin, Silodosin)
- Terazosin (Hytrin)
- Doxazosin (Cardura)
- Prazosin (Minipress)
- Rapid relaxation of Smooth Muscle tone
- Relieves symptoms of urinary obstruction
- May see full effect within 2 weeks
- Does not effect size of Prostate (unlike Proscar)
VI. Preparations: Non-Selective Agents
- Terazosin (Hytrin)
- Hypertension
- Start 1 mg orally at bedtime
- Titrate to effective dose 1 to 5 mg daily or in divided doses (Maximum 20 mg/day)
- Benign Prostatic Hypertrophy (replaced by Selective Alpha-1a Antagonists)
- Start 1 mg orally at bedtime
- Titrate to effect by doubling dose every 1-2 weeks (to 2, 5 and 10 mg, maximum of 20 mg/day)
- Observe for effects after 4 to 6 weeks on optimal dose (typically 10 mg)
- Hypertension
- Doxazosin (Cardura)
- Hypertension
- Start: 1 mg orally at bedtime and titrate dose (Maximum 16 mg/day)
- Benign Prostatic Hypertrophy (replaced by Selective Alpha-1a Antagonists)
- Start: 1 mg orally at bedtime and titrate every 1-2 weeks doubling dose, to a maximum of 8 mg at bedtime
- Extended release formulation (e.g. Cardura XL) 4 mg in am daily (may increase to 8 mg daily after 3-4 weeks)
- Medical Expulsive Therapy for Ureteral Stone (replaced by Selective Alpha-1a Antagonists)
- Extended release formulation (e.g. Cardura XL) 4 mg orally daily (not FDA approved)
- Hypertension
- Prazosin (Minipress)
- Terazosin and Doxazosin are preferred instead (once daily dosing at similar cost)
- Hypertension
- Start 1 mg orally twice daily to three times daily
- Titrate to usual daily total dose 20 mg divided two to three times daily
- 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
- Phenoxybenzamine (Dibenzyline)
- Indicated in the Hypertensive Crisis of Pheochromocytoma
- Terazosin and Doxazosin are preferred as routine antihypertensive agents instead (once daily dosing at similar cost)
- Irreversible alkylation of the Alpha Adrenergic Receptor
- Start 10 mg orally twice daily
- Titrate to typical dose 20 to 40 mg orally twice daily
- Maximum daily dose: 120 mg/day
- Indicated in the Hypertensive Crisis of Pheochromocytoma
- Phentolamine (Rogatine)
- Hypertensive Crisis in Pheochromocytoma
- Dose: 5 mg IV/IM for one dose (results in profound drop in BP, e.g. 60/25 mmHg decrease in BP)
- IV extravasation of Catecholamines (e.g. Norepinephrine)
- Prepare 5-10 mg in 10 ml Normal Saline, and inject 1 ml around extravasation site
- In adults may repeat dose up to a total of 5 ml injected around extravasation site
- Hypertensive Crisis in Pheochromocytoma
VIII. Preparations: Selective Alpha-1a Antagonists (Prostate specific agents)
- See Selective Alpha-1a Antagonists
- Alfuzosin (Uroxatral, generic)
- Silodosin (Rapaflo)
- Tamsulosin (Flomax, generic)
IX. Preparations: Combination Alpha-Beta Antagonists
X. Adverse Effects (Incidence: 7 to 9%)
- Dose at bedtime
- Slowly titrate to reduce side effects (esp. Orthostatic Hypotension, Dizziness, drowsiness)
- Cardiovascular adverse effects (also occurs with selective agents, albeit less often)
- Postural or Orthostatic Hypotension
- Common with first dose (may be severe)
- Exacerbated by Hyponatremia
- Dizziness or light headedness
- Associated with Fall Risk and secondary Fracture risk
- Postural or Orthostatic Hypotension
- Other adverse effects
XI. Precautions
- Pregnancy Category C
- Avoid using as monotherapy for Hypertension
- Higher risk of CVA and CHF compared with other agents
- (2000) JAMA 283:1967-75 [PubMed]
XII. References
- Aldridge (1996) Lancet 348:602
- Hamilton (2010) Tarascon Pocket Pharmacopeia, p. 76-7
- (1994) Med Lett Drugs Ther 36: 15 [PubMed]
- (1997) Med Lett Drugs Ther 39: 1011 [PubMed]
- Grimm (2011) J Clin Hypertens 13(9):654-7 +PMID: 21896145 [PubMed]
- Lee (2000) Ann Pharmacother 34:188-99 [PubMed]
Images: Related links to external sites (from Bing)
Related Studies
| 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 |