Respiratory: Pharmacology - Sympathomimetics in respiratory disease Flashcards
Time to maximal bronchodilation with epinephrine
15 mins
What is ephedrine? What is it used for? How does it compare to epinephrine in terms of duration of action, potency and central effects?
Non-selective sympathomimetic
Used infrequently in asthma
Longer duration of action, more central effects, and less potency than epinephrine
What is isoproterenol? Why is it no longer used for the treatment of asthma?
Non-selective B agonist
Responsible for increased mortality in asthma due to cardiac arrhythmia
Time to maximal bronchodilation and duration of effect of salbutamol
15mins to maximal bronchodilation
3-4hrs duration
Describe the pharmacokinetics (distribution, metabolism, excretion) of salbutamol
Distribution: 10-30% reaches bronchial smooth muscle with inhalation (80-90% deposited in mouth or pharynx)
Metabolism: significant first pass
Excretion: renal
Seven adverse effects seen with salbutamol
- Transient decreased PaO2
- Tremor
- Tachycardia
- Hypokalaemia (increased K+ uptake by skeletal muscle)
- Cramps
- Hypotension (peripheral vasodilation)
- Anaphylaxis
What is the mechanism of the transient decrease in PaO2 seen with salbutamol?
Vasodilation increases perfusion of poorly ventilated lung units
Duration of action of salmeterol
12hrs
Uses of salmeterol
As “preventer” in asthma
Should not be used for monotherapy as no anti-inflammatory effect
Pharmacodynamics of indacaterol
Ultra long acting B agonist (once daily dosing)
Can indacaterol be used for monotherapy in asthma and COPD? Why/why not?
Should be used in combination with ICS in asthma, as prolonged bronchodilation masks bronchial inflammation
Can be used as monotherapy in COPD
How is terbutaline administered?
Subcut
Clinical indications for terbutaline
Severe asthma where aerosolised therapy is not available or has failed
Tocolytic in premature labour (uterine smooth muscle relaxation)
