B - 11. B-2 Agonists, Muscarinic M3 Antagonists And Methylxanthines

Question 1

B-2 agonists - mechanism of action

Answer 1

B-2 stimulation on bronchial smooth muscle -> cAMP increase -> bronchodialation

Question 2

SABA drugs; names, length of action

Answer 2

Salbutamol
Terbutaline
Fenterol

5 min to act, lasts 2-4h

Question 3

SABA drugs; indication and side effects

Answer 3

Indications: Acute asthma, exercise induced bronchospasm/exercise asthma

Side effects: Sympathetic stimulation effects

Question 4

LABA drugs; names, length of action

Answer 4

Salmetarol
Formoterol

Lasts over 12 hours

Question 5

LABA drugs; indication and side effects

Answer 5

Used 2x day as profylaxis against asthma

Side effects are sympathetic activation, but to a much higher degree than SABA, and can cause arrythmias. It is therefore virtually never used as monotherapy, but in combination with corticosteroids

Question 6

M3 antagonists mechanism of action

Answer 6

Binds to M3 receptor on respiratory smooth muscle -> Ach can’t bind -> bronchoconstriction inhibited

Question 7

M3 antagonists; names and length of action

Answer 7

Ipratropium - 4-6h (short acting)

Tiotropium - 24h (long acting)

Question 8

M3 antagonists; indications, SE, contraindication

Answer 8

More effective for COPD than asthma
Used in combo with LABA

Side effects: Tachycardia, dry mouth, pupil dialation, restlessness

Contraindication: Narrow angle glucoma

Question 9

Methylxanthines; name - mode of action

Answer 9

Theophylline

Taken orally - enters SmM of respiratory tract
Inhibits PDE -> cAMP increases -> SmM relaxation

Also blocks adenosine receptors, causing

• vasodialation
• decreased HR
• neurotransmitter release in brain
• increased contraction in SmM of respiratory tract (not epic)

Question 10

Methylxanthines; problems

Answer 10

• very narrow theurapeutic index - easy to OD
• metabolized by CYP450

Is rarely used anymore