Precision Pharmacotherapy in OSA: Targeting the Endotypes

This primary cause involves a narrow collapsible pharyngeal airway often exacerbated by obesity-related fat deposition and soft tissue enlargement. It is present in all patients with OSA but varies in magnitude, measured by critical closing pressure.

Pharmacological target: Reduce anatomical collapsibility

Noteworthy drug: Tirzepatide, a dual GIP/GLP-1 receptor agonist, has been associated with substantial reductions in apnea-hypopnea index among adults with obesity-related OSA and has received regulatory approval. Notable adverse effects are primarily gastrointestinal, including nausea, vomiting, diarrhea, and constipation.

This is a failure of the pharyngeal dilator muscles to reflexively activate and oppose airway collapse during sleep. More than a third of patients with OSA cannot adequately activate their upper airway muscles in response to narrowing.

Pharmacological target: Improve muscle responsiveness

Noteworthy drug: AD109 (atomoxetine + aroxybutynin), an investigational oral neuromuscular modulator, has been shown to increase upper airway muscle activity and reduce OSA severity. Notable adverse effects are insomnia, dry mouth, and modest increases in BP.

Premature arousal in response to modest upper airway narrowing prevents the timely accumulation of ventilatory drive and recruitment of upper airway dilator muscles. Patients awaken before the airway can reopen, perpetuating sleep fragmentation and recurrent respiratory events.

Pharmacological target: Increase arousal threshold

Noteworthy drugs: Hypnotics (eg, eszopiclone, trazodone) may increase the respiratory arousal threshold, promoting greater breathing stability during sleep. Effects on OSA severity are variable and generally modest. They are not recommended as monotherapy. In carefully selected patients, hypnotics may serve as adjunctive therapy. Notable adverse effects are residual sedation, respiratory depression, and cognitive impairment.

An oversensitive system generates exaggerated breathing responses to minor disturbances, leading to cyclical patterns of hyperventilation and apnea. High loop gain leads to an overcorrection of CO₂, driving levels too low, suppressing respiratory drive, and reducing upper airway dilator muscle activity.

Pharmacological target: Reduce respiratory control instability

Noteworthy drugs: Carbonic anhydrase inhibitors (eg, acetazolamide, sultiame) reduce loop gain and can improve OSA severity. They are not recommended as monotherapy but have a promising future role as adjunct or combination therapy. Notable adverse effects are electrolyte abnormalities, metabolic acidosis, paresthesia, and gastrointestinal symptoms.