Salbutamol

[PHW2:p199-200]

 

 

Pharmacodynamics

Mechanism of action

[PHW2:p199]

Main action at beta2 receptors

Some action at beta1 receptor at high doses

Effects

[PHW2:p200]

CVS

IV or high dose
--> Stimulation of beta1 receptors
--> Tachycardia

Lower doses
--> Stimulation of beta2 receptors
--> Vasodilation
--> Decreased BP

Precipitation of arrhythmia
* Especially in presence of hypokalaemia

 

Respiratory

Relaxation of bronchial smooth muscles

Reversal of hypoxic pulmonary vasoconstriction

Increased shunt
--> Possible hypoxaemia

 

Metabolism

Stimulation of Na/K ATPase pump
--> Increased K+ uptake
--> Hypokalaemia

Increased blood glucose level

 

Uterus

Relaxes gravid uterus

 

Others

Direct effects on skeletal muslces
--> Tremour

Pharmacokinetics

[PHW2:p200]

Incomplete oral absorption

Significant hepatic first-pass metabolism

 

10% protein-bound

Halflife = 4-6 hours

 

Metabolised in liver

Inactive metabolite

 

Pharmaceutics

Clear solution 50-500 microgram/mL for IV use

Metered dose inhaler (100microgram)

Dry powder (200-400 microgram) for inhalation

2.5-5mg/mL solution for nebulisation

Oral preparation (syrup 0.4mg/mL, 2/4/8 mg tablets)

 

 

Clinical

Usage

[PHW2:p200]

Used in treatment of reversible lower airway obstruction

Premature labour (? as a tocolytic)