Pharmacology for Dentistry

152 Section 3/ Drugs Acting on ANS

BETA BLOCKERS WITH ADDITIONAL ALPHA

BLOCKING ACTIVITY

LABETALOL

It is a adrenergic antagonist which can
block both alpha and beta receptors. It is
non-selective (β 1 +β 2 ) and selective (α 1 )
receptor blocker. Labetalol is five times more
potent in blocking beta than alpha receptors.
Both alpha and beta blocking actions of
labetalol contribute to a decrease in blood
pressure in hypertensive patients. It is
effective in mild to moderate hypertension,
pheochromocytoma and clonidine with-
drawal hypertension. The most serious side
effect is postural hypotension because of
alpha blocking activity. Other side effects
include sexual dysfunction, failure of
ejaculation, depression etc.

CARVEDILOL

It is beta (βββββ 1 +βββββ 2 ) and alpha (ααααα 1 ) blocking
agent with additional antioxidant property.
It is mainly used in hypertension and in CHF
as cardioprotective agent.

Carvedilol significantly reduces
systemic blood pressure, pulmonary artery
pressure, right atrial pressure, systemic
vascular resistance, and heart rate, while
stroke volume index is increased.

Carvedilol is a dualaction cardiovascular
agent with non selective beta blocking, α 1
antagonistic vasodilating properties and is
devoid of intrinsic sympathomimetic activity.

Carvedilol is well absorbed after oral
administration with peak serum levels
occurring after one hour. Excretion is
primarily in bile and significant accumulation

of carvedilol or its active metabolites is

unlikely in patients with renal impairment.

Carvedilol is indicated for the management

of essential hypertension. It can be used alone

or in combination with other anti-hypertensive

agents. It is effective also in CHF.

Carvedilol may be used in patients unable

to tolerate an ACE inhibitor. Carvedilol may

be used in patients who are not receiving

digitalis, hydralazine and nitrate therapy.

Adverse effects include symptomatic pos-

tural hypotension, dizziness, headache, fa-

tigue, gastrointestinal upset and bradycardia.

CARDIOSELECTIVE/βββββ 1 BLOCKERS

METOPROLOL

It is cardioselective beta blocking agent

and is devoid of intrinsic sympathomimetic

activity. It reduces plasma renin activity in

hypertensive patients. Metoprolol may be

preferred to a nonselective agent in

asthmatics and patients prone to develop

hypoglycemia. Its antianginal action is

comparable to that of propranolol. It is

metabolised by hydroxylation and excreted.

ATENOLOL

It is cardioselective beta 1 blocking agent

with low lipid solubility, generally

administered once daily because of its longer

duration of action. Most commonly used in

hypertension and angina pectoris.

BISOPROLOL

Another cardioselective beta 1 blocking

agent devoid of intrinsic sympathomimetic

activity given once daily in the treatment of

hypertension and angina pectoris.