Term
| Alpha-adrenergic receptor antagonists |
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Definition
Example: Phenoxybenzamine
Clinical Applications:
HTN Crisis from:
-pheochromacytoma
-excess Rx (amphet.) for ADHD
-tyramine crisis (MAO-I induced)
Benign Prostate Hypertrophy
Chronic HTN -- (not frontline Rx)
Side Effect/toxicity: Postural Hypotension common; reflex tachycardia (except in Prazosin), lower vascular return, headache, dizziness, nausea, drowsiness, impotence (phenoxybenzamine), decr. plasma lipids |
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Term
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Definition
Incidence: relatively rare
Cause: tumor (usually benign, solid, unilateral, and located on adrenal gland) that increases synthesis and increases release of NE and EPI into circulation
Result: incr BP, incr HR --> leads to intermittent HTN crisis(es)
Txt: surgical removal of tumor (if solid) after stabilizing BP;
- alpha- / beta- blocker, e.g., Labetalol (only use beta blocker after alpha blockade)
- alpha 1-blocker, (i.e., phenoxybenzamine or phentolamine)
- inhibitor or tyrosine hydroxylase (i.e., alpha-methyl-p-tyrosine)
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Term
| Benign Prostate Hypertrophy |
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Definition
Enlarged (but non-malignant) prostrate leads to difficulty in urination
Alpha1-receptor blocker (ie Prazosin) cause prostrate relaxation
Relaxed prostrate improves urination
High incidence in males over 50 years old (may be as high as 50%) |
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Term
| Postural (orthostatic) hypotension |
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Definition
Venous return falls, blood pressure falls (>20mmHg SBP, >10mmHg DBP)
Sympathetic activity increases -> reflex mediated
ÄConstriction of great veins
ÄConstriction of arteries ( ↑ TPR)
ÄIncrease in heart rate (> 20bpm)
Major side effect of alpha-1 antagonists (and other alpha receptor blockers)
Sudden pooling of blood in feet and extremities --> not enough for brain vaso-motor reflex centers |
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Term
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Definition
- irreversible non-compet. alpha1-blocker (5-10 fold)
- also block Ach, histamine, serotonin (side effects)
- also inhibit Uptake I & II (side effects)
- ¯blood pressure, postural hypotension, tachycardia
- useful in long-term & acute pheochromocytoma**
- side effect: impotence |
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Term
Phentolamine & Tolazoline |
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Definition
- non selective a1 = a2 antagonist activity
- cardiovascular: vasodilation, reflex HR
- enhance NE release (alpha2-blockade)
- toxicity: hypotension (esp. orthostatic), tachycardia, arrhythmias, myocardial infarction |
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Term
| Prazosin, Tamsulosin, Doxazosin (-azosin; competitive) |
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Definition
- selective for a1- > a2-receptors (1000 fold)
- cardiovascular effects: reduced peripheral resistance, lowered vascular return, no reflex tachycardia
•Therapy:
- treat primary hypertension,
- benign prostrate hypertrophy
Toxicity: postural hypotension, headache, nausea ¯plasma lipids, dizziness, drowsiness
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Term
| Beta Blocking agents characteristics variability |
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Definition
Relative Affinity: for beta1 and beta2 receptors : propanolol (B1 and B2) |
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Term
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Definition
•Hypertension: Common agents (previous frontline)
- gradual ¯TPR in spite of long-term ¯cardiac output
- non-selective and b1-selective drugs are effective
- not effective for Acute HTN crisis
•Mechanism of action: Multiple sites
- CNS action to reduce sympathetic tone
- block of cardiac b-ARs
- block of presynaptic b-ARs to ¯NE release
- decrease in renin release |
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Term
| Norepinephrine (Levarterenol) |
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Definition
Therapeutic Use: Hypotension, txt of shock, acts as a pressor agent
Target: alpha1, beta 1/3/(2?) neuronal, non-circulating
Interactions: MAOIs, TCAs
Other Notes: |
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Term
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Definition
Therapeutic Use: Allergic rxns, shock, CPR
Target: alpha 1, beta 1/2/(3) adrenal medulla, circulating
Notes: MAOI, TCA |
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Term
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Definition
Therapeutic Use: decr. shock (Renal vasodilation -> D1 receptor)
Target: alpha 1/ beta 1/ DA receptors; precursor to NE
Interactions: MAOI
Notes: |
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Term
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Definition
Therapeutic Use: Asthma, cardiac stimulant
Target: Beta (1,2,3)
Interactions:
Side-Effects: BP (decr. or no-effect); incr. heart rate
Notes: Synthetic, not endogenous |
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Term
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Definition
Therapeutic Use: Hypertension (esp. in pregnant women b/c safety profile is good), opioid withdrawal
Target: CNS alpha 2 (decr. CNS sympathetic outflow, inhibit NE release)
Interactions: ...
Side Effects: dry mouth, sedation, impotence
Notes: Rebound HTN on abrupt withdrawal of clonidine txt (need to taper off) |
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Term
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Definition
Therapeutic Use: CHF* (frontline agent), cardiac stimulant (minimal change in HR or O2 demande --> incr CO)
Target: selective Beta 1 agonist
Interactions:
Side Effects:
Notes: exhibits tolerance and sensitization; administered via IV infusion |
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