Asthma drugs Flashcards
What is asthma?
Reversible airway obstruction as a result of bronchial hyper-reactivity, airway inflammation, mucous plugging and smooth muscle hypertrophy
What are the endogenous products that play important role in pathophysiology of lung?
Prostaglandins Acetylcholine Beta Adrenergics Histamine Adenosine ACE: inactivates bradykinin, which is enhanced by ACEI that cause cough and angioedema
How does Bradykinin and Substance P lead to a cough?
Bradykinin:
–Increases release of prostaglandins, Leukotrienes and Histamine leads to type J receptors at peripheral vagal afferents ending/non myelinated or C- fibers
Substance P:
—type J receptors at peripheral vagal afferent ending/non-myelinated or C-fibers
What is the role of methacholine in asthma?
Muscarinic Receptor (M3) agonist --used in bronchial challenge test to help diagnose asthma
Describe the role of inadequate surfactant in infants that leads to RDS.
Can be prevented if mothers who are about to deliver prematurely by dexamethasone administration
–test: lecithin to sphingolyelin ratio greater than 2.0m in amniotic fluid, indicated fetal lung maturity.
What factors precipitate an asthma attack?
Allergens: induce mast cell release of inflammatory mediators
Infections: viral URI or even bacterial/fungal
Pharmacological Factors: Beta Blockers, cholinergics
Exercise and Stress: Vagal and Adrenergic Influence
Moving on to the drugs used in asthma treatment, first are the bronchodilators (Beta receptor agonists, antimuscarinic drugs, methylxanthines). First lets start with the beta 2 receptor agonists, what are these drugs?
Albuterol Pirbuterol Terbutaline Salmeterol Formoterol
What is the MOA of beta 2 agonists?
Increasing intracellular concentrations of cAMP
–this leads to relaxation of bronchial smooth muscle and therefore bronchodilation
What are your short acting vs long acting beta 2 agonists?
SABA: albuterol, pirbuterol and terbutaline
LABAs: salmeterol and formoterol
–most of these drugs are inhaled, which minimizes their systemic side effects
–LABAs available in combination with ICS (inhalational corticosteriod) for long term control and prevention of symptoms in moderate to severe persistent asthma
What is a concern regarding long acting beta agonists?
Genetic Polymorphism in Beta 2 receptors
–causes slight worsening of asthma, exacerbations or even death
What are some clinical concerns of asthma?
Do not use LABAs inhaler for rescue medication!
LABAs should only be used in conjunction with an inhaled steroid
What drugs are used for exercise induced bronchoconstriction?
SABAs used just before exercise will prevent EIB for 2-4 hours after inhalation
LABAs will prevent up to 12 hours
What are the adverse effects of inhaled Beta 2 adrenergic agonists bronchodilators?
Tremors, Tachycardia, arrhythmias and hyperglycemia
–high doses of Beta 2 agonist can get into the systemic circulation and therefore into the blood stream
Next set of drugs for asthma are Anticholinergics as bronchodilators, Ipratropium and Tiotropium. What are their uses?
Ipratropium: a short acting inhaled anticholinergic can be used in asthma, QID
Tiotropium: a long acting anticholinergic used SID in COPD
What is the MOA of anticholinergics?
Parasympathetic stimulation causes bronchial constriction and mucous secretion.
–anticholinergics are used to block the muscarinic receptors in the smooth muscles and maintain bronchial dilation of the airway