August 2, 2022
Albuterol and levalbuterol are short-acting beta-2 agonists (SABAs) that are used to manage acute breathlessness associated with asthma, COPD, or bronchospasm.1-3 Both drugs exert their primary effects by binding to beta-2 receptors in the lungs, which causes smooth muscle relaxation and bronchodilation.1-3 So, what’s the difference between the two?
Albuterol is a racemic mixture, meaning it contains equal parts of (R)-albuterol and (S)-albuterol stereoisomers (mirror image molecules). Drugs and endogenous ligands bind to receptors like a key in a lock, so the specific three dimensional shape of the key matters tremendously because a mirror image of the key would not open the lock. Gloves/mittens are another way of describing stereoisomers – each has the same makeup, size and general shape, but one fits the left hand and the other the right.
Accordingly, despite having virtually identical physical properties, albuterol’s stereoisomers have different biological effects. (R)-albuterol causes bronchodilation.3,4 (S)-albuterol does not, and it has even been speculated that it may have detrimental effects, including blunting the benefits of the other isomer and propensity towards bronchospasm / bronchial reactivity.3-7
Concerns about (S)-albuterol’s negative effects led to the development of levalbuterol, which only contains (R)-albuterol.2 Levalbuterol was initially marketed as more effective and better tolerated (e.g., cause less tachycardia) than albuterol, despite data suggesting that both have similar effects on heart rate.2,4,8,9 Some studies comparing the two have demonstrated modestly lower heart rates in patients using levalbuterol, while others have shown no difference.1,2,8 Ultimately, both drugs are similarly effective and levalbuterol has yet to demonstrate a consistent advantage in terms of tolerability or clinical outcomes.1-9
Levalbuterol typically costs more than albuterol and the price difference tends to be more significant for nebulized formulations than for inhalers.10 Considering the price difference and the lack of confirmed clinical differences, albuterol should be used as first-line therapy when a SABA is indicated and levalbuterol should be reserved for patients who have a documented intolerance or poor response to albuterol.
If you’re curious, follow these links for additional information about albuterol and levalbuterol and stereoisomeric drugs.
John Corrigan, PharmD
Clinical Pharmacist, OnePoint Patient Care
John’s primary responsibilities as a clinical pharmacist at OnePoint Patient Care are staff and partner education, medication utilization reviews, and assisting with formulary development and maintenance. He attended the University of Iowa for both undergraduate studies and pharmacy school. He earned a PharmD from the University of Iowa College of Pharmacy in 2013. He was first introduced to hospice and OnePoint Patient Care as a 4th year pharmacy student, completing a 5-week elective clinical hospice pharmacy rotation. He started his employment with OnePoint Patient Care as a staff pharmacist in 2014. He transitioned to his current role, as a clinical pharmacist, in the spring of 2019.