Leukotriene Receptor Antagonists, Xanthines Flashcards
How do LTRA work?
They work by blocking the effects of leukotrienes C4, D4 and E4. The drug antagonizes the cysteinyl Leukotriene receptors found on smooth muscle and infiltrating immune cells. This prevents bronchoconstriction and infiltration of eosinophils.
When are LTRAs usually used in treatment?
As an alternative to ICS in young children (due to side effects of long-term steroid use in children).
Add on therapy to LABA+ICS (medium dose)
What is the usual dose of Montelukast?
One 10mg dose to be taken in the evening (either chewable tablet or granules).
What are some of the side effects of LTRAs to be aware of?
GI disturbances are normal at first
Neurophychiatric reactions (Depression, obsessive compulsive disorders, speech impairment, stuttering)
Churg-Strauss syndrome (inflammation of the blood vessels).
How does theophyllines work?
Reduce pro inflammatory response by reducing the pro-inflammatory cells and cause bronchodilation.
What is the interaction between xanthines and SABAs?
Both induce hypokalemia
How is use of theophylline monitored?
Concentration is measured 5 days after starting the and plasma concentration is measured 4-6 hours after administration.
How would you adjust theophylline doses for smokers?
Plasma concentration of theophylline is decreased in smokers and by alcohol consumption due to increasing the clearance and decreasing its half life, possible increase in dose however must be cautious due to narrow therapeutic window if an increased dose was provided.
How would you adjust theophylline doses for the elderly?
The elderly may be more sensitive to the effects of theophylline and are more likely to experience heart failure and therefore it is better to prescribe a reduced dose.
