Respiratory Pharmacology Flashcards
What are the major classes of bronchodilator drugs?
1) βeta2 agonists (short and long acting)
2) Anticholinergics
3) Anti-inflammatory
What are examples of short and long acting Beta2 agonist bronchodilators?
1) Short acting => Albuterol (rescue)
2) Long acting => Salmeterol (used for maintenance)
What is an example of an anticholinergic bronchodilator?
Ipratropium bromide/Tiotropium br.
What is an example of an anti-inflammatory bronchodilator?
Glucorticosteroids
Give the brief summary of Beta 2 agonist action on smooth muscle
βeta2 agonist binds to beta2 receptor which via G protein stimulates adenylyl cyclase —> increases cAMP–> protein kinases -> reduces [Ca 2+]i —> relaxes smooth muscle
What are the additional actions of Beta 2 agonists a part from bronchodilation/relaxation?
- Enhance mucociliary clearance
- Decrease microvascular permeability
- Suppress mediator release from inflammatory cells
Describe the systemic pharmacokinetics of beta 2 agonists.
Systemic:
1) Reasonable oral absorption (especially in children/elderly –> liquid/tablet)
- Variable- presystemic metabolism
2) Metabolism COMT/MAO
3) Bioavailability 15-70%
4) T1/2 –> 6-8h
Describe the inhaled pharmacokinetics of beta 2 agonists (i.e. albuterol).
- 8-15% of dose reaches systemic circulation
- Low systemic concentrations (MDI - 90 mcg Alb = Cmax 1-2 mcg/L)
Describe the oral pharmacodynamics of beta 2 agonists.
Onset 30-60 min: peak 1-3 h., duration 6-8h
Describe the inhaled pharmacodynamics of beta 2 agonists (albuterol).
- Onset: 15-30 min duration 4-6 h
- Metabolism COMT/MAO
- βeta2 selectivity reduced at high doses
- Tolerance/tachyphylaxis => tendency to become desensitized (increase dosage)
What are the cardiovascular adverse effects of beta 2 agonists?
- Tachycardia, palpitations, flushing
- Exacerbation of angina/arrhythmias
- Vasodilates Pulm Art -> V/Q mismatch
What are the CNS adverse effects of beta 2 agonists?
- Tremor/Anxiety
- Headache
- Insomnia
What are the metabolic adverse effects of beta 2 agonists?
- Hypokalemia => especially important in patients with cardiac/arrhythmia issues
- Hyperglycemia
When do most adverse effects of beta 2 agonists occur?
Toxicity/adverse effects generally happen when given at milligram dosages (in contrast to microgram)
What is the mechanism of action of salmeterol?
lipophilic arm of salmeterol binds more readily and longer (at multiple sites that can alternate)
-> binds at an active and exosite
Why should long acting beta 2 agonist be used with glucosteroids?
Maintenance beta 2 agonist should be used with steroids to reduce the chance/number of sudden death syndrome.
Describe the pharmacodynamics of anti-cholinergics (ipatromium).
Slower rate of onset
Not as much bronchodilation as albuterol
Describe the pharmacokinetics of inhaled ipatromium.
- 8-15 % of dose reaches bronchi
- < 1% of dose reaches systemic circulation
- Inactive metabolites in urine
- Duration of action 6-8 h
What are the adverse effects associated with ipatromium?
- Bitter taste –> compliance (adherence) issues
- ACh effects: rare and mainly at high doses
- Drying of secretions does not occur
What is the major pro/con of tiotropium?
Tiotropium pro => longer acting (~ 24h) dry powder
con => ACh effects seen in patients with severe renal impairment
What is an example of inhaled corticosteroid?
Fluticasone
What are some examples of systemic inhaled corticosteroids?
Hydrocortisone; Prednisone; Methylprednisolone
What are the indications for systemic use of corticosteroids in asthma?
1) Acute severe asthma
2) Chronic maintenance therapy