DIREC ACTING BETA SELECTIVE AGONISTS
These drugs are stimulating selectively at beta receptors of the postganglionic adrenergic nervous system.
Beta-1 receptors are mostly situated on the postsynaptic membrane and beta-2 receptors are found both in pre and postsynaptic membrane.
Beta receptors are present in heart muscle and their stimulation may cause an increase in heartbeat, rate, and rhythm by an increase in both inotropic and chronotropic effects.
Beta-1stimulation leads to increased lipolysis.
Beta-2 receptor stimulation works through adenylate cyclase to dilate the vasculature in bronchial as well as skeletal muscles.
The uterus, ciliary and detrusor muscles are relaxed.
Glucagon release is increased.
Both b-1 and b-2 receptor stimulation leads to reduced intestinal tone and motility.
1.Dobutamine
It is a dopamine derivative
Primarily act on the beta-1 receptor with a secondary effect on beta-2 receptor
The physiological effects of dobutamine are increased heart rate, and contractility(beta-1);
Smooth muscle relaxation (beta-2)
Use
Treatment of unstable CHF and shock.
Route
Intra venously
Side effects
1.Arrhythmias
2.Hypertension
3.Headaches
4.Palpitations
5.Angina
6.Nausea.
2.Isoproterenol
It acts equally on both b-1 and b-2.
Physiological effects
1.Increases both cardiac inotropic and chronotropic effects(b-1)
2.Increases peripheral vascular resistance(b-2)
3.Relaxes smooth muscles(b-2)
Use
It is appropriate to use isoproterenol in
1.Stimulate heart rate in heart block and bradycardia
2. To treat asthma but now it becomes older.
I.V route is preferable
Side effects
1.Arrhythmias
2.Palpitation
3.Tachycardia
4.Headache
3.Albuterol, Metaproterenol, and Terbutaline
Mainly on b-2 receptors causes smooth muscle relaxations
But on concentration may affect b-1
Albuterol and metaproterenol can be given by inhalation
Terbutaline by oral or s.c
Uses
1.Asthma
2.Chronic Obstructive Pulmonary Disease
3.Bronchitis
4.Uterine relaxation in premature labour-Terbutaline and ritodrine
Side effects
Similar to the above
No comments:
Post a Comment