Leukotriene receptor antagonists

Question 1

Name the main two leukotriene receptor antagonists.

Answer 1

Montelukast and Zafirlukast.

Question 2

What do leukotriene receptor antagonists do?

Answer 2

Inhibit bronchoconstriction induced by cysteinyl leukotrienes by blocking CysLT1 receptors on bronchial smooth muscle.

Question 3

1) What do cysteinyl-leukotrienes do?

2) Where are cysteinyl-leukotrienes released from?

Answer 3

1) Contribute to airway oedema, enhanced secretion of mucous and airway eosinophilia.
2) Activated mast cells and eosinophils in response to several airway insults. Synthesis of cysteinyl-leukotrienes is increased by many mediators such as cytokines.

Question 4

1) What do LTRAs reduce?

2) In what 3 conditions might LTRAs be most useful?

Answer 4

1) Both the early and late bronchoconstrictor responses to inhaled antigens.
2) Mild to moderate asthma, exercise induced asthma and hypersensitivity reactions provoked by NSAIDs.

Question 5

1) Where are LTRAs absorbed from and metabolised in?
2) What is the half life of Montelukast and Zafirlukast?
3) Name 2 potential unwanted effects of LTRAs.

Answer 5

1) Absorbed from the gut and metabolised in the liver.
2) Montelukast = 3-5 hours, Zafirlukast = 10 hours.
3) Headaches and GI upset.