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Alpha Blockers
Alpha Adrenergic Blocking Agents
13
Pharmacology
Graduate
10/22/2011

Additional Pharmacology Flashcards

 


 

Cards

Term
PheNoxybenzamine, PheNtolamine
Definition
Nonselective (a1 and a2 blockers)
Term
PrazoSin, TerazoSin, DoxazoSin, TamsuloSin, AlfuzoSin, SilodoSin
Definition
Selective a1 blockers
Term
Mechanism of Action of a-Blockers
Definition

*Inhibition of Peripheral a-receptors

1. Non-compet inhibition (long acting phenoxybenzamine). not immediate but lasts long bc receptors are PERMANENTLY inactivated by drug. IRREVERSIBLE. Synthesis of new receptors can restore functions.

2. Compet inhib (all drugs except phenoxy) short in onset and reversible

3. Dec BP by dec peripheral arterial resistance bc block a1 vasoconstriction

Term
Common Side Effects for a-Blockers
Definition

Too much loss of a-receptor functions in body

-ex: nasal congestion, difficulty ejaculating, reflex tachycardia, systemic fluid retention, orthostatic hypotensive symptoms

Term
(Side) Effects of Phenoxybenzamine (Irreversible)
Definition

Long acting, blocks a1 and a2

-Used in preventing severe hypertension from pheochromocytoma prior to surgery

- better than other drugs bc massive release of catechol from tumor cant overcome drug's irreversible blockade

-blocks extrasynaptic a2 receptors

-*Remember: a2 rec are first to face high circulating NE and E levels in pheo patients

Term

(Additional Side) Effects of Phenoxybenzamine (Irreversible)

Definition

1. may inhibit histamine, serotonin, Ach receptors

2. Miosis, sedation, drowsiness, vomiting, lethargy (CNS)

3. Shock and circulatory failure

Term

Effects of:

Phentolamine 

Definition

- short acting, blocks a1 and a2, reversible

- used to DIAGNOSE pheochromocytoma (phentolamine test), also used during surgery to prevent rise in bp from catech released from tumor

- used to reverse excessive systemic vasoconstriction and hypertension from I.V. overdose with non-spec a-agonists like NE

- prevent local dermal tissue necrosis at sites of injection of a-agonists (ex if accidently inject in skin and not vein)

- ORAVERSE: reverses oral soft-tissue anesthesia from local anesthetics with vasoconstrictor (like Epi). <dental anesthetic reversal agent>

Term
Additional Side Effects of:
Phentolamine 
Definition

1. Nausea, vomiting, diarrhea

2. Increased GI motility, bad for ULCERS

3. May stimulate or block various non-adrenergic receptors

Term

Effects of: 

Prazosin

Definition

-Prototype of selective a1 blockers

-useful in LONG TERM treatment of mild to moderate primary hypertension, esp when given with diuretic (offsets fluid retention)

- Relaxes smooth muscle of bladder sphincter, to inc urinary flow when u have dec urinary flow (BPH)

- Used for Raynaud's

- Maybe for nightmares/PTSD, likely to inhibit central a1 rec (CNS effects)

Term
Additional Side Effects of:
Prazosin 
Definition

1. Orthostatic HYPOtension, but only severe during 1st day (first dose phenomenon)

2. Salt and water retention (so take diuretic)

3. Tachycardia but not as much as with non-selective drugs

Term
Effects of: 
Doxazosin and Terazosin 
Definition

- dont get into CNS (remember, prazosin does)

- newer a1 blockers than prazosin

-half lives are much longer so might be better for long term control of chronic hypertension bc need fewer doses

Term

Effects of:
Tamsulosin and Silodosin

(FlowMax and RapaFlow) 

Definition

- Block subtype alpha-1A, found in smooth muscle of bladder sphincter and prostate

- treat BPH (by inc urination) bc more specific w/less systemic vascular actions/side effects 

-can still cause abnormal ejaculation due to a-1a in vas deferens

Term

Effects of: 

Alfuzosin

Definition

-a1 blocker, treats BPH, not subtype selective

- has UROselectivity (accumulation in prostatic tissue), won't interfere w/ejaculation

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