5. All these agents are active by oral as well
as the parenteral route, although
phentolamine is rarely give orally.
6. DURATION OF ACTION:
PHENOXYBENZAMINE: about 48
hours.
PHENTOLAMINE: 2-4 hours (Orally)
20-40 mins (Parenterally)
PRAZOCIN: 8-24 hours.
7. EFFECTS ON CARDIOVASCULAR
SYSTEM:
These agents cause lowering of
peripheral vascular resistance and blood
pressure.
They may cause orthostatic hypotension
and reflex tachycardia.
8. OTHER EFFECTS:
Alpha antagonists may cause Miosis and
nasal stiffness.
These agents are used for the treatment
of urinary retention due to prostatic
hyperplasia.
10. ORTHOSTATIC HYPOTENSION.
TACHYCARDIA.
MYOCARDIAL ISCHEMIA.
ANGINA may be precipitated by tachycardia
in pts with coronary disease.
The alpha-blockers are associated with an
exaggerated orthostatic hypotensive response
to the first dose in some patients. Therefore the
first dose is usually small and taken just before
going to bed.
11. It irreversibly blocks alpha1 and alpha 2
receptors.
It lowers blood pressure and cause
tachycardia due to baroreflex activation.
It is used in pheochromocytoma.
ADVERSE EFFECTS:
Orthstatic hypotension, tachycardia,
myocardial ischemia.
12. It blocks alpha1 and alpha2 receptors.
It reduces peripheral resistance and has
cardiac stimulation effect.
It is used in treatment of
pheochromocytoma.
Adverse effects: Tachycardia,
Arrhythmias and myocardial ischemia.
13. They selectively blocks Alpha1 receptors.
Decreases blood pressure.
These agents are used in hypertension
and beningn prostatic hyperplasia.
Adverse Effects: Orthostatic
Hypotension.
14. It selectively blocks alpha2 receptors that
leads to increase in sympathetic activity
and in turn increases norepinepherine
release.
Increases blood pressure and heart rate.
It is used in : Hypotension.
