Katzung 12th ed - Chapter 20 - Respiratory, Asthma (1.5)

Question 1

There are three broad categories of drugs that directly trigger bronchodilation. Name these three categories, with one example each.

Answer 1

• Sympathomimetics (beta-agonists)
• Methylxanthines (e.g. theophylline)
• Anti-muscarinics (e.g. ipratropium, atropine)

Question 2

List three beta-agonists used (rarely) in asthma that are NOT beta-2 selective.

Answer 2

Adrenaline, Isoprenaline, Ephedrine.

Question 3

List two beta-2-selective agents that are used in asthma.

Answer 3

Salbutamol, Terbutaline

Question 4

How do beta-agonists cause bronchodilation?

Answer 4

Binding to beta-adrenoceptors activates adenylyl cyclase to produce cAMP, which relaxes smooth muscle.

Question 5

How do methylxanthines cause bronchodilation? (and is there a second way?)

Answer 5

Methylxanthines (such as theophylline) inhibit the breakdown of cAMP by inhibiting phosphodiesterase (PDE). The increased levels of cAMP cause bronchodilation. (Another way they contribute to bronchodilation is by competitive inhibition of adenosine, which would otherwise cause bronchoconstriction.)

Question 6

How do anti-muscarinic agents cause bronchodilation?

Answer 6

Anti-muscarinics such as ipratropium antagonise the effects of acetylcholine. Without ipratropium, vagal stimulation would result in acetylcholine release, which causes bronchoconstriction and mucus secretion.

Question 7

Apart from theophylline, what is another methylxanthine that is worth knowing about?

Answer 7

Caffeine.

Question 8

Name some of the minor and major toxicities of theophylline. Which electrolytes can it affect?

Answer 8

Minor: headache, nausea, vomiting, insomnia
Major: seizures, arrhythmia, death
Electrolytes: hypoMg, hypoPO4, hypokalaemia

Question 9

How can theophylline be administered?

Answer 9

Oral or IV.

Question 10

What is the Vd for theophylline?

Answer 10

0.3 - 0.7 L/kg

Question 11

What is another name for isoprenaline?

Answer 11

Isoproterenol

Question 12

What are the effects of methylxanthines on:

• inotropy
• chronotropy
• diuresis
• skeletal muscle

Answer 12

• Positive inotrope
• Positive chronotrope
• Weak diuretic
• Causes increased strength of skeletal muscle contraction

Question 13

How can salbutamol initially cause transiently decreased PaO2?

Answer 13

Because it has vasodilator activity, and it thereby increases perfusion to poorly ventilated lung units.

Question 14

What does ketamine do to the airways?

Answer 14

It is a bronchodilator.

Question 15

Explain how corticosteroids are useful in preventing asthma exacerbations.

Answer 15

Corticosteroids are NOT bronchodilators. They reduce bronchial reactivity, by reducing the infiltration with lymphocytes, eosinophils and mast cells.

Question 16

What does disodium cromoglycate do?

Answer 16

Inhibits mast cell degranulation.