Respiratory Pharmacology Flashcards
Boothe - Clinical Pharmacology
Respiratory Pharmacology - Drugs Affecting the Respiratory System
What are bronchodilator?
Drugs that reverse smooth muscule contraction of the bronchioles. by increaseing cAMP and decreasing cGMP or decreasing Ca2+.
How do B-agonists result in bronchodilation?
Promote bronchodilation regardless of cause.
Activation of adenylyl cyclase and then production of cAMP –> protein kinases –> bronchodilation.
What are the additional effects of B agonists?
Increased mucocillary clearance (due to decreased fluid viscosity, due to increased movement of chloride and water into the lumen) and increased cilliary beat frequency.
enhance vascular integrity, inhibit MCT and basophil mediator release
What may occur with repeated doses of B agonists?
Desensitiation via reduced receptor number and receptor internalisation.
This may cause patients to increase dosage to confur desired clinical response which may mask worsening or severe disease
What may be the concern utilising non selective B agonists for bronchodilation?
May have adverse cardiac affects and may contribute to airway constriciton - this may be reduced by aerosolising these drugs as only B2 receptors appear to line the airways
What is the MOA of theophyiline
non-specific inhibition of phosphodiesterases and increased cAMP and therefore activation of phosphokinases –> not completely understood.
Likely to cause bronchodilation and anti-inflammatory
Is theophylline stronger or weaker than B agonists
Weaker - however also results in increased mucocilliary clearance and reduced MCT degranulation and reduced cytokine production
Importantly may increase respiratory muscle strenght
How can theophylline be give?
Oral or IV
What is the difficulty of dosing oral slow release theophylline?
Markedly differing bioavailability and absorption time making dosing very difficult
When should theophylline be dosed in cats
More bioavailable in the evening - weird
What are some adverse reactions to theophylline?
CNS aggitation, GI upset, diuresis, tachycardia
When given rapidly IV may result in hypotension, nausea, tremors, respiratory failure
What may drug interaction may incrase the risk of theophylline toxicity
Fluroquinalone administration. Reduce metabolism and clearance –> increase toxicity
How will atropine influence the respiratory tract
May cause bronchodilation –> however MAY also cause broncho-constriciton.
Decrease mucocilliary clearance and reduce fluid flux into secretion
Bad side effects pretty much outway any potential benefit
What is cromolyn
A calcium channel blocker that stops mast cell degranulation
Why are glucocorticoids the cornerstone of treating inflammatory lung disease?
Anti-inflammatory effects as well as permmisive effects on beta receptors mediating bronchodilation
How are glucocorticoids of often administered in respiratory disease and does increasing dose increase efficacy
Inhaled or oral and no
When should systemic and inhalaed steroids be used
in uncontrolled disease or disease so severe that steroids unlikely to get to the small airways
How do leukotrienes effect the respiratory system and what drugs may be used to inhibit this
potent causes of oedema, inflammation, bronchoconstriciton
Drugs: LT synthesis inhibitors or LT-receptor antagonists ( more effective)
When may leukotriene inhibition be utilised
none have ever been studied in dogs and cats
Used in humans in mild cases - in addition to steroids or as sole agents
Offer mild anti-inflammatory and mild bronchodilation
Discuss NSAIDs and asthma
Not a lot of evidence but may shunt AA towards the lipoxygenase pathway and make things worse. But no one knows with newer nsaids
What is the goal of anti-tussive therapy?
Decrease the frequency and severity of the cough without impairing mucocilliary defences
What causes a cough
chemoreceptors and stretch receptors, commonly caused by bronchoconstriciton
decreased airways size causes increased air velocity to irritate stretch receptors
Where can a cough be supressed
peripherally - removing secretion with expectorants or mucolytics
inducing bronchodilation
blocked centrally in the cough centre (medulla)
How do opioids function as antitussives?
depress the cough center.
What are common cough suppressant opioids
codiene and butorphanol