Bronchodilatory Drugs

Question 1

Beta-agonists (SABA and LABA)

Answer 1

Act through antagonism of beta 2 adrenergic receptors. Promote activity of Gs protein. Increases cAMP, increases PKA activity, increases phosphorylation of MLCK.
Example: Short: Salbutamol. Long: Salmetarol
ADRs: Tremors, tachycardia, headache, muscle aches

Question 2

Corticosteroids

Answer 2

A cytoplasmic nuclear receptor. Acts through regulation of pro-inflammatory genes, inhibits expression and therefore decreases inflammation.
Example: Beclometasone, budesonide, dexamethasone
ADRs: Oral candidiasis, osteoporosis

Question 3

Muscarinic Antagonists

Answer 3

Anticholinergic. Bind to muscarinic receptors and inhibit the Gq protein cascade (prevents cleavage of PIP2 by PLC and subsequent increase in calcium).
Example: Ipratropium, tiotropium
ADRs: Headache, cough, dry mouth, urinary retention

Question 4

Xanthines

Answer 4

Act within the Gs protein pathway. Inhibit PDE (phosphodiesterase), preventing conversion of cAMP to AMP. Maintains levels of PKA and phosphorylation of MLCK
Metabolised by CytP450, many drug interactions
Example: Aminophylline, theophylline
ADRs: Tachycardia, hypokalaemia, rhabdomyolysis

Question 5

Leukotrienes Receptor Antagonists

Answer 5

Bind to the LTR1 preventing binding of leukotrienes and decreasing inflammatory effects.
Example: Montelukast
ADRs: URTI, pyrexia, GI disturbances

Question 6

Antihistamines

Answer 6

Bind to the H1 receptor, preventing binding of histamine and stimulation of inflammatory effects.
Examples: Cetirizine, chlorphenamine, loratidine
ADRs: Somnolence, headache, insomnia

Question 7

Cromones

Answer 7

May act to stabilise mast cells or sensory input
Example: Sodium cromoglicate
ADRs: Headache, rhinitis

Question 8

Stages of Asthma Treatment: Stage 1

Answer 8

Mild intermittent asthma:

Inhaled short acting beta agonist as required

Question 9

Stages of Asthma Treatment: Stage 2

Answer 9

Regular preventer therapy:

Add inhaled steroid

Question 10

Stages of Asthma Treatment: Stage 3

Answer 10

Initial add on therapy:
Add Long-acting Beta Agonist
Assess control with LABA:
- Benefit but control still needed: Increase corticosteroid
- No response: Stop LABA and increase corticosteroid.

Question 11

Stages of Asthma Treatment: Stage 4

Answer 11

Persistent Poor Control
Consider:
- Increasing inhaled corticosteroid
- Addition of medication: Leukotriene receptor antagonist (montelukast) or xanthine (theophylline)

Question 12

Stages of Asthma Treatment: Stage 5

Answer 12

Continuous or frequent use of oral steroids
Use daily steroid tablet - lowest possible dose.
Refer for specialist care.