Adverse effect to formoterol (LABA)

Well done! The mild tremor Amy describes is most likely an adverse effect of formoterol, the long-acting beta-2 agonist (LABA) in her inhaler.

Formoterol stimulates beta-2 adrenergic receptors in the airway smooth muscle, causing bronchodilation. However, when LABAs like formoterol are absorbed systemically, they can also activate beta-2 receptors in skeletal muscle, leading to transient tremor. Tremor is one of the most common side effects of beta-2 agonists, especially at higher doses or during frequent usage.

Other common side effects of beta-2 agonists include palpitations, tachycardia, headache, and anxiety. Thus, Amy’s headaches may also be related to formoterol use.

Further Progress

Amy returns for another follow-up appointment after two months. She reports that her symptoms are now worsening. She reports increased wheezing during her on-site work, particularly when exposed to paint fumes and construction dust. Night-time coughing has returned, disrupting her sleep twice in the past week. With spring well on its way, she now also complains of nasal congestion, sneezing, and watery eyes, which exacerbate her breathing difficulties. Amy also reports that she cannot exercise anymore since her asthma symptoms worsen during exercise.

Amy voices concern that her asthma may be deteriorating. Dr. Christou explains that she will prescribe another drug for Amy as add-on therapy to avoid increasing the dosage of her current medication, which is also known to be effective in patients with Amy’s symptoms and triggers.

What is the most likely drug prescribed?