Beta Adrenergic Bronchodilators PDF 2021

9/22/21, 8:02 AM Beta Adrenergic Bronchodilators Beta Adrenergic Bronchodilators Overview These drugs, as the name implies, all act via the adrenergic receptors of the sympathetic nervous system. Adrenergic receptors in the lungs are Be...

9/22/21, 8:02 AM Beta Adrenergic Bronchodilators Beta Adrenergic Bronchodilators Overview These drugs, as the name implies, all act via the adrenergic receptors of the sympathetic nervous system. Adrenergic receptors in the lungs are Beta-2 sympathetic receptors. For this reason, this class of drugs is also commonly known as the beta-adrenergics or sympathomimetics (mimicing the action of the sympathetic system). Beta adrenergics cause bronchodilation through stimulation of the Beta-2 receptors of bronchial smoth muscle. In addition, there is some evidence that these drugs also inhibit the release of histamine from mast cells. Finally, there seems to be some evidence that these drugs enhance the mucocilliary clearance Key properties of these drugs, including duration of action, depend on their chemical category. There are three chemical categories of beta adrenergic bronchodilators: 1. catecholamines 2. resorcinols 3. saligenins In general, the catecholamines (e.g., epinephrine) have shorter onsets and durations of action than the resorcinols (e.g., metaproterenol) or saliginens (e.g., salmeterol). Due to their shorter onsets and durations of action, the catecholamines and resorcinols are referred to as short-acting beta-agonists (SABAs) and considered 'rescue' agents (to be used in acute bronchospasm), while the saliginens are classified as long-acting beta-agonists (LABAs) and considered 'controllers' (to be used for control of bronchospasm). Indications Beta adrenergic bronchodilators are indicated for: I. acute or chronic pulmonary obstructive disease with bronchospasm A. as evidenced by diagnosis 1. asthma 2. chronic bronchitis 3. emphysema 4. bronchiectasis 5. cystic fibrosis B. as evidenced by symptoms 1. severe, harsh cough that is associated with allergic triggers 2. wheezing on breath sounds C. as evidenced by pulmonary function testing 1. obstructive pattern to flow-volume loop with response to bronchodilator demonstrated II. inhalational injury A. mechanical (like a foreign body aspiration) B. chemical (like aspiration of stomach acid) C. thermal (an inhalational burn) III. retained secretions A. as evidenced by breath sound or chest x-ray abnormality 1. because of the relative controversy regarding this indication, treatment with a beta adrenergic may be initiated to treat retained secretions, but sputum production should be closely monitored and assessed for efficacy. If there is no significant https://s3.amazonaws.com/RTBoardReview/contents/tables_lists/adrenergic_bronchodilators.htm 1/3 9/22/21, 8:02 AM Beta Adrenergic Bronchodilators increase in secretion mobilization after 1-2 days of therapy, the drug can be reasonably discontinued. IV. prevention of exercise-induced bronchospasm A. beta agonists have been shown most effective to prevent bronchospasm associated with physical activity. The drug should be taken typically 10-20 minutes prior to exercise. Contraindications Contraindications are relative, because the potential of an undesired effect must be weighed against the benefit of administration. Contraindications include: I. hypersensitivity to the drug A. this is often a result, not from hypersensitivity to the drug itself, but to preservatives commonly added to the medication. A patient who demonstrates a reaction to one form of a beta adrenergic may not demonstrate the same reaction with another, or to a different manufacturer of the same medication. Check the package insert or Physician's Desk Reference (PDR) for information regarding the specific additives used for a given medication. II. cardiac arrhythmias associated with tachycardia A. Most beta agonists have some undesired cardiac (beta-1) effect, generally an increased heart rate, in addition to the desired pulmonary effects. Certain patients do not well tolerate the increase in heart rate that can occur as a result of administration of beta agonists. The cardiac effect is certainly dose-related (increasing the more drug is given over time). B. Strategies to decrease these unwanted effects with patients for whom tachycardia presents severe problems include: 1. decreasing the dose of the drug 2. decreasing the frequency 3. changing to a different, more specific beta agonist (e.g., Levalbuterol) 4. discontinuing use of the beta adrenergic and relying on a non-adrenergic bronchodilators Precautions 1. excessive use of beta adrenergics can lead to the development of paradoxical bronchospasm and an increase in work of breathing. Tolerance and tachyphylaxis an also occur. 2. concomitant use with adrenergic beta-blockers antagonizes the effects of bronchodilators. Such concomitant use may lead to systemic vasoconstriction and reflex bradycardia. 3. beta adrenergics should be used cautiously in patients with known cardiovascular disease, including coronary insufficiency, cardiac arrhythmias, history of stroke and hypertension (because of possible toxic symptoms) 4. Any inhaled aerosol has the potential for causing bronchoconstriction 5. these drugs may cross the placental barrier: use cautiously in pregnancy 6. if bronchial irritation, nervousness, or restlessness occur, reduce dosage 7. use cautiously in children under 1 year old, as the safety and and efficacy of these drugs has not yet been established in this population 8. co-administered adrenergics have additive effects 9. if an adrenergic/sympathomimetic crisis should occur, the effects can be counteracted by injection of a beta adrenergic-blocker 10. catecholamines are much less effective or ineffective when taken orally, as the gut has increased levels of Monoamine Oxidase (MAO) which inactivates adrenergics 11. catecholamines must also be stored out of direct light--many are supplied in brown bottles. Exposure to light metabolizes the adrenergics into inert adrenochromes. If there is a pink or reddish tinge to the medication, it has been inactivated and should be discarded. Adverse Reactions https://s3.amazonaws.com/RTBoardReview/contents/tables_lists/adrenergic_bronchodilators.htm 2/3 9/22/21, 8:02 AM Beta Adrenergic Bronchodilators 1. CNS effects: anxiety, fear/apprehension, tremors, irritability, lightheadedness, headache, flushing, pallor, sweating, insomnia 2. Cardiovascular effects: hypertension, arrhythmias, palpitations, reflex tachycardia from peripheral vasoconstriction. Overdose may also cause angina and hypotension. 3. Pulmonary effects: coughing, bronchospasm, pulmonary edema (IV use) 4. GI effects: nausea, vomiting, heartburn https://s3.amazonaws.com/RTBoardReview/contents/tables_lists/adrenergic_bronchodilators.htm 3/3