adrenoceptor blockers Flashcards
All active by
Oral route
Parenteral route
alpha blocking drugs
IRREVERSIBLE LONG-ACTING
Prototype Only slightly alpha1 selective Short elimination half life Long duration of action (48 hours) Binds covalently to the alpha receptors
PHENOXYBENZAMINE
DoA of PHENOXYBENZAMINE
48 hours)
REVERSIBLE SHORT-ACTING
• Prototype • Nonselective (alpha1=alpha2) Duration of action Oral (2-4 hours) IV (20-40 minutes)
PHENTOLAMINE
ALPHA1 SELECTIVE
Prototype
Selective reversible alpha1 blocker
Duration of action 8-24 hours
Doxasozin, terazosin and tamsulosin
PRAZOSIN
- Prototype
- Selective alpha2 competitive blockers
- Used primarily in research application
YOHIMBINE, RAUWOLSCINE
NONSELECTIVE BLOCKERS
Most important effects are on the ??
CVS system
Predictable result of the use of an agonist in a patient who has received
an alpha-blocker
Reversal in the BP effect of large doses of epinephrine
From pressor response (alpha receptors) to a depressor response (beta receptors)
Not observed with phenylephrine or NE because they lack sufficient beta2 effects
EPINEPHRINE REVERSAL
Block alpha1 receptors much more effectively
Cause much less tachycardia than the nonselective blockers when reducing BP
SELECTIVE ALPHA1 BLOCKERS
• Tumor that secretes cathecolamines
pheochromocytoma
type of BLOCKERS
• Severe hypertension caused by overdose with drugs of abuse such as amphetamine, cocaine, or phenylpropanolamine
NONSELECTIVE ALPHA
type of BLOCKERS
Prazosin, doxazosin, and terazosin are used in hypertension
Used together with tamsulosin for urinary hesitancy and prevention of urinary retention with benign prostatic hyperplasia
SELECTIVE ALPHA
Prazosin, doxazosin, and terazosin Used together with ? for urinary hesitancy and prevention of urinary retention with benign prostatic hyperplasia
tamsulosin
• TOXICITY of alpha blockers
•
Main manifestation is orthostatic hypotension
Competitive pharmacologic antagonists
Propranolol is the prototype
Developed for chronic oral use
• Bioavailability and duration of action vary widely
BETA BLOCKING DRUGS
Beta1 receptor selectivity
Acebutolol
Atenolol
Esmolol
Metoprolol
Advantage when treating patients with asthma
Beta1 receptor selectivity
PARTIAL AGONIST ACTIVITY
Nonselective beta-blockers
Nadolol
Propranolol
Timolol
Pindolol
Combined alpha and beta-blockers
Optically active
Labetalol
Carvedilol
PARTIAL AGONIST ACTIVITY
”Intrinsic sympathomimetic activity”
May be an advantage in treating patients with asthma
At maximum dose, can cause some bronchodilatation
Pindolol
Acebutolol
Labetalol