Wednesday, March 26, 2008

Asthma drugs made EZ

Pharmacology is often considered a dirty word in nursing and medical school, and unfortunately the NCLEX and the USMLE loves to test you on this. One subject we recently tackled in our NCLEX review course was the treatment of Asthma. Here is a summary of what we talked about...

Obstructive Pulmonary Disease (Asthma, COPD)Medications: Site of Action
1.Adrenergic Agonists (Albuterol, etc)
2.Anticholinergics (Ipratroprium Bromide)
3.Xanthines (Theophylline)
4.Corticosteroids (Beclomethasone, etc)
5.Mast Cell Stabilizers (Cromolyn)
6.Leukotriene Antagonists (Montelukast-Singulair)

key to above figure: Allergen+IGE causes Mast cell to release histamine and leukotrienes which then seep out of blood stream and cause immune cells to inflame bronchioles. Various drugs work at different steps of this process. Some stop mast cells from releasing their products, some stop the products from leaving the blood stream, and some stop the products from causing the inflammation in the bronchioles. All three of these work directly on the immune system. On the other side of that, some drugs directly open the airway, not effecting the immunity at all. See below for the most critical details on these drugs and when we use them...

Obstructive Pulmonary Disease: Bronchodilators
1.Adrenergic Agonists (Albuterol, etc)
•Selective B2 agonists directly dilate airway; DOC for acute attack
Albuterol: PO, inhaled via MDI; NOT for maintenance therapy
Levalbuterol (Xopenex): Possibly less cardiac SE
Salmeterol: Long acting (12hrs) for night s/s
Terbutaline: Also relaxes uterus, tocolytic for premature labor

2.Anticholinergics (Ipratroprium Bromide) *technically not a dilator
Atrovent is often combined with Adrenergics to tx COPD, as scarred airways need extra help dilating
•Slow onset, long acting best used for prevention, not acutely
•SE: Dry mouth, GI distress

3.Xanthines (Theophylline)
•Similar to Caffeine, causes bronchodilation, CNS stimulation of the respiratory center, Inotropy/chronotropy → renal perfusion → urine
•Used in cases where overuse of other bronchodilators has caused decreased effectiveness, especially used with COPD
•Slow onset, long acting best used for prevention, not acutely
•Stimulant C/I with arrhythmias, SZ, hyperthyroid, PUD
•Monitor therapeutic levels (10-20)
Aminophylline is IV form of Theophylline

Obstructive Pulmonary Disease: Inflammation Modulators
1.Corticosteroids (Beclomethasone, etc)
•Steroids prevent further inflammation of constricted airways
•Available IV, PO or inhaled; Inhaled have benefit of being used at site of constriction without systemic effects (Rinse after!)
DOC for asthma prevention•Beclomethasone excellent antiinflammatory with few SE
•Patients have died from not being tapered off of systemic steroids when switching to inhaled forms
•Can be used WITH albuterol for acute attacks and is given IV (Solu-Medrol)

2.Mast Cell Stabilizers (Cromolyn)
•Used to prevent the release of inflammatory mediators
•Most effective for exercise or allergen induced bronchospasm
•Also useful to control perennial allergic rhinitis
•Available PO, inhaled, and opthalmic

3.Leukotriene Antagonists (Montelukast-Singulair)
•Leukotriene receptor blockade prevents inflammatory migration into bronchiole tissue
•Used for maintenance, with effects taking up to a week
•SE: Dyspepsia, insomnia, diarrhea, and liver dysfunction
•Other ex. Zafirlukast (Accolate), Zileuton (Zyflo)

Asthma Treatment Protocol (med first introduced)
  • Step 1, Mild Intermittent S/S: Short acting B2 agonists prn
  • Step 2, Mild Persistent: Inh steroid + short B2 ag prn; Cromolyn + B2 ag prn for children; Theophylline or Montelukast alternative agents if above protocol ineffective
  • Step 3, Moderate Persistent: Med dose inh steroid + Salmeterol (long acting B2) + short B2ag prn
  • Step 4, Severe Persistent: High dose inh steroid + Salmeterol + Systemic steroid + short B2 ag prn


Anonymous said...

Great review of the meds. Thanks a lot for the organization and explanation.

Philip Smith said...

Excellent blog very nice and unique information related to NCLEX Review. Thanks for sharing this information.