Drugs Affecting the Respiratory System
Bronchodilators:
Beta 2 Receptor Agonists (B2RA): Short and long acting beta agonists
• B2RA widely used
... [Show More] in all ages to treat reversible bronchoconstriction caused by reactive airway disease (RAD) or COPD
• Bronchodilators
• Short-acting beta agonists: Albuterol (ProAir, Ventolin, Proventil) , metaproterenol (Alupent), terbutaline (Brethine, Brethaire), bitolterol (Tornalate), pirbuterol (Maxair), and levalbuterol (Xopenex)
• Long-acting beta agonists: arformoterol (Brovana), salmeterol (Serevent), formoterol (Foradil), and indacaterol (Arcapta Neohaler)
• Drug of choice during pregnancy for asthma
Pharmacodynamics
• Act on smooth muscle to reverse bronchospasm, decreases airway resistance and residual volume and increasing VC and airflow
• Stimulate beta 2 adrenergic receptors in the lungs to increase cAMP production which relaxes bronchial smooth muscle and inhibits mediators from hypersensitivity cells (mast cells)
• All beta agonists stimulate beta 1 activity (increased HR, tremor)f
Short Acting Beta Agonists
• Albuterol
o Selective beta2 agonist with minor beta1 activity
o Often first-line drug r/t less ADRs than the other drugs in this class
o Increases HR by stimulating beta 2 receptors in the heart and vascular smooth muscle
• Levalbuterol: (similar to albuterol), where the (S)-isomer from racemic albuterol is removed
• Pirbuterol: selective beta 2 agonist, similar to albuterol
• Terbutaline: similar to albuterol, selective beta 2 with minor beta 1 activity
o Known to inhibit uterine contractions
• Metaproterenol: beta 2 selective with some beta 1 activity, less selective than albuterol or terbutaline
• Bitolterol: hydrolyzed by esterase in the lung to colterol, or terbutylnorepinephrine, selective beta 2
Long Acting Beta Agonists (Salmeterol, formoterol, indacaterol, and aformoterol)
• Salmeterol is more selective for beta2 receptors than albuterol and has minor beta1 activity.
o 12 hour half-life
o Formoterol: 200-fold greater agonist activity at B2 than albuterol and has minor B1 activity
o Aformoterol (R,R)-enantiomer of formoterol, twice as potent as formoterol
o Indacaterol: 24 fold greater B2 activity than B1
o Salmeterol and formoterol exert long-lasting broncho protection against allergen, exercise, histamine, and methacholine caused bronchospasm
Pharmacokinetics
• Contraindications: Cardiac arrhythmias (tachycardia or heart block caused by digitalis intoxication, angina, narrow-angle glaucoma, organic brain damage (epi only), and shock during general anesthesia with halogenated agents
• Monitor closely: HTN, ischemic heart disease, coronary insufficiency, CGH, and Hx of stroke and/or cardiac arrhythmias
• Diabetics: potential drug-induced hyperglycemia, insulin dose may need increased
• Hyperthyroidism: ADRs are more likely to occur with use of bronchodilators
• Digoxin: require close monitoring, albuterol increases the volume of distribution of dig and can cause decreased dig blood levels
• Pheochromocytoma: avoid, severe HTN may occur
• Older adults: Lower doses r/t increased sympathomimetic sensitivity
• Black Box warning for LABAs: The risks of salmeterol (Serevent) and formoterol (Foradil) outweighed the benefits and should not be used singly in asthma for all ages
o Two-fold increase in catastrophic events (asthma-related intubations and death)
o The use of LABAs is contraindicated without the use of an asthma controller medication such as an inhaled corticosteroid
o Only use long-term in patients who asthma cannot be adequately controlled on asthma controller medications
o Use for the shortest duration of time required to achieve control, then maintain on an asthma controller medication
o Pediatric and adolescent patient who require addition of a LABA to an inhaled corticosteroid should be a combination product containing both an inhaled ICS and a LABA, to ensure compliance with both medications
• Terbutaline pregnancy category B (prevent contractions) (others category C)
• Albuterol safe for all age children
• Metaproterenol can be used in young children
• Levalbuterol, as young as 2 (drug insert says 6)
• Salmeterol should not be used in children less than age 4 years and never singly.
• Formoterol age 5 and older
• Indacaterol and aformoterol are used for COPD, not for use in children or adolescents
Drug and Food Interactions
o Many drug interactions
o Digitalis glycosides: increased risk of dysrhythmia
o Beta adrenergic blocking agents (Beta Blockers): direct competition for beta sites resulting in mutual inhibition of therapeutic effects
o Including beta blocker eye drops
o Tricyclic antidepressants and MAOIs potentiate effects of beta agonist on vascular system
ADRs
o Usually transient
o Stopping the med is not usually needed, reduce dose then slowly increase
o Supraventricular and ventricular ectopic beats have occurred
o Tachycardia and palpitations
o Some central nervous system (CNS) excitation effects
o Tremors, dizziness, shakiness, nervousness, and restlessness
o Headaches, rarely insomnia, post inhalation cough
o Salmeterol has an increased risk of exacerbation of severe asthma symptoms if the patient is deteriorating
o Overuse can lead to seizures, hypokalemia, anginal pain and HTN
o Stimulant like effects
o GI upset, take po meds with food
Clinical Use and Dosing
Bronchospasm
• Bronchodilators are used primarily in the treatment of bronchospasm associated with asthma, bronchitis (acute or chronic), and chronic obstructive pulmonary disease (COPD)
o Albuterol
MDI dose children over 4 and adults is 2 puffs every 4 to 6 hours
o Nebulizer dose children over age 12 and adults is 2.5 mg/dose
For younger children over 15 kg, dose is 0.1 to 0.15 mg/kg/dose
o Dose may be repeated once after 5 to 10 minutes, up to 2 times, three doses total during exacerbations
o Oral dose in adults is 2 to 4 mg 3 or 4 times a day
For children 6 to 12, 2 mg albuterol 3 to 4 times a day (PO form rarely used in children)
Oral syrup: children under age 6, 0.1 mg/kg 3 times a day (rarely used)
o May combine with ipratropium
o Aformoterol (Brovana): nebulizer 15 mcg/ by inhalation BID (not approved for use in children)
o Indacaterol (Arcapta Neohaler): powder via a Neohaler device
adults with COPD, one capsule one daily with a Neohaler device
o Levalbuterol (Xopenex): inhalation solution (nebulizer) in adolescents over age 12 and adults is 0.63 mg TID (every 6 to 8 hours) [Show Less]