Sulbutamol

General pharmacology of salbutamol:

► The chemical name of salbutamol is 1-(4-hydroxy-3-hydroxymethylphenyl)-2-(t-butylamino)-ethanol sulfate, molecular formula is (C13H21NO3)2 • H2SO4 and molecular weight is 576.7.

► After oral administration, approximately 50% of salbutamol is absorbed from the intestinal tract with a slower onset of action, reaching a peak at about 2 hours after intake. After inhalation, salbutamol reaches the lungs directly and acts within 3-5 minutes with a peak at 15-20 minutes. Overall duration of action of salbutamol is 4-6 hours. It is metabolized in the intestinal tract and in the liver and is excreted via the urine.

Mechainsm of action:

[A]  agonist (Salbutamole)→Bronchus→(+)  receptor→(+) Adenyl cyclase→

↑cAMP→Bronchodilation→Relief of asthma.

[B] agonist(Salbutamole)→Mast cell→(+)  receptor→(+) Adenyl cyclase→

↑cAMP→Stabilizes mast cell→No histamin release→No bronchosecretion→Relief of astham.

Advantages:

1)      It is directly delivered to the site of action.So minimum systemic absorption.

2)      Selctive stimulation of pulmonary receptor.

3)      Rapid onset of action.i.e within 15 min.

4)      Long duration of action(4-6 hour)

5)      Minimum toxic effects & unwanted CVS effects are less.

6)      Less dose required.

7)      Suitable for acute asthma.

Disadvantage:

[A]Chronic use of inhaler:

·         Dryness of airways.

·         Irritation of airways.

·         Orophrayngeal candidiasis.

[B]Due to systemic use(oral):

·         Tremor.

·         Tachycardia.

·         Arrythmia.

·         Palpitation.

·         Hypokalaemia.

Adverse effects of salbutamol:

[A]Chronic use of inhaler:

·         Dryness of airways.

·         Irritation of airways.

·         Oropharyngeal candidiasis.

[B]Due to systemic use:

·         Tremor.

·         Tachycardia.

·         Arrythmia.

·         Palpitation.

·         Hypokalaemia.