Respiratory pharmacology Flashcards
Describe autonomic control bronchial tone
- No sympathetic innervation but is dilated by circulating adrenaline
- has B2 adrenoceptors (increase cAMP in bronchial SM causing relaxation)
Describe parasympathetic control of bronchial tone
- muscarinic acetlycholine receptors
- M3 (increase IP3 and intracellular Ca)
- Causes constriction of bronchial SM
How do PDE inhibitors cause relaxation of smooth muscle?
PDE inhibitors prevent PDE from decreasing the amounts of intracellular cAMP and gAMP. A build up of these will inhibit contraction and cause muscle relaxation.
How can bronchodilation be acheived pharmacologically?
Drug targets:
- B-adrenergic agonists
- anticholinergic drugs
- methylxanthines (PDE inhibitors)
Why do we need to target drug delivery to the lungs?
To avoid any unwanted side effects. i.e. smooth muscle relaxation in other parts of the body
What are the 2 main characteristics that a drug targeted to the lungs should have?
Poor lipid solubility and high water solubility
Give an example of a B-adrenoreceptor agonist and when it might be used
Adrenaline (epinephrine) - emergency treatment of life threatening bronchoconstriction
e.g. terbutaline, salbutamol, salmeterol, clenbuterol
What are the pharmacological properties of adrenaline?
- Stimulates adrenergic pathways
- Side effects - increased heart rate, palpatations; skeletal muscle tremors
- Tolerance - rapid tolerance will occur if used repeatedly, suitable for intermittent use
What are the properties of anticholinergic drugs, e.g. atropine?
- Mechanism - block endogenous parasympathetic tone
- Side effects - CNS stimulation, GI inhibition
- Administration - topical
What are the properties of methylxanthines?
e. g. theobromine, caffeine, theophylline, etamiphylline
- Mechanism - PDE inhibitors
- Decrease inflammatory mediators
- Side effects - GI; CVS stimulation; CNS agitation, nervousness, convulsions
