Pharmacology Flashcards
How was Salbutamol derived?
Chinese herb Ma Huang to Ephedrine and then to short acting beta agonist salbutamol
Why is oral Salbutamol not used?
Because of unacceptable systemic side effects
How does inhaled Salbutamol get absorbed?
Majority of inhaled Salbutamol gets absorbed by the buccal mucosa where it undergoes first pass metabolism in the liver.
When is peak plasma concentration reached after a single dose of inhaled salbutamol is given?
Peak plasma concentration is reached in 10 minutes
When does maximum bronchodilatation occur after a single inhaled Salbutamol dose?
12-15 minutes
Why is the use of a spacer device especially important in children?
It minimises the risk of poor technique.
It also slows down drug delivery and also allows a more uniform distribution of the aerosol particles.
It reduces the deposition within the buccal mucosa and results in increased drug delivery by around 20 to 30 percentage.
How does abnormal physiology affect drug delivery?
The speed of absorption of inhaled salbutamol is reduced and maximum serum concentrations are reached more slowly.
This is because of the different regional ventilation seen during an acute asthma attack. Increased secretions and bronchospasm will lead to reduced zones of ventilation. This leads to ventilation perfusion mismatch and hypoxia. In this instance inhaled salbutamol will be delivered maximally to areas of ventilated lung and intravenous salbutamol may be required to open up perfused but unventilated lungs.
What are the indications and benefits of the nebulised Salbutamol?
A large range of particles are produced. Larger particles are filtered by the nose and are absorbed and recirculated via blood stream to lungs. Hence, nebulisers are recommended for severe asthma attacks where there is hypoxia and hence oxygen requirement- because they have the biggest VP mismatch and would benefit with maximal Salbutamol blood levels.
Why are home nebulisers discouraged?
Salbutamol will transiently increase ventilation profusion mismatch and thus lead to worsening hypoxia.
How does age affect drug delivery?
Children less than 5 yrs have smaller lungs and so absorb lesser proportion of the drug.
What are the other actions of Salbutamol?
Inhibits mast cell mediator release and TNF-alpha release from monocytes.
Increases mucus secretion and mucociliary clearance.
Hypokalemia
Hyperglycaemia
Dose dependent tachycardia
Salbutamol shakes (tremors)
What is Salbutamol tachyphylaxis?
This is seen as early as one week after starting regular treatment.
More pronounced with mono therapy.
Over use or over reliance on short acting bronchodilators is discouraged.
Children on regular Salbutamol May find it significantly less effective during an aggravation.
What is poor control of asthma?
If short acting bronchodilators are needed more than twice a week.
What is the half life of Salbutamol?
4 hrs
What are the other side effects of Salbutamol?
Headache, hyperactivity and muscle cramps.
