Xanthine derivatives - Amylophyllin



Mechanism of action:

[A]Amynophyllin→Inhibits Phosphodiesterase enzyme→No conversion of cAMP to 5-AMP→↑cAMP→Relaxation of bronchial smooth mucle→Bronchodilation→Relief of asthma.

[B]Amynophyllin→Inhibits presynaptic adenosine receptor of brochus→↑Catecholamine release→Bronchodilation.

Advantages:

1)      Rapid onset of action.
2)      Suitable for acute asthma(IV).

Disadvantages:

1)      Tachycardia.
2)      Palpitation.
3)      Headache.
4)      Dizziness.
5)      Medullary stimulation.
6)      Nervousness.
7)      Hypokalaemia.
8)      Seziure.

Difference between Salbutamole and Aminophylline:


Traits
Salbutamole
Aminophylline/Theophylline
1.Group
Adrenergic drug
Xanthine derivative
2.M/A

It stimulates  receptor→activates adenyl cyclase→Convert ATP to cAMP →Relaxation of bronchial smooth muscle→Bronchodilatation.
Inhibits enzyme phosphodiesterase (PDE)→Prevents conversion of cAMP to 5’cAMP→↑conc of cAMP→relaxation of bronchial smooth muscle→Bronchodilation.
3.Onset of action
Slow
Rapid(IV)
4.Duration of action
Longer
shorter
5.TI
High
Narrow
6.Usualy form of drug/Route
Inhalation
IV,oral
7.Caution during administration
Not needed
Close observation
8.Cardiot oxicity
Absent because Salbutamole has no effect.
Present
9.CNS toxicity
Less
More(Insomnia,Tremor,Restlessness)
10.Action onGFR
No action
GFR.

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