Approximately **one billion people** worldwide live with obstructive sleep apnea. Most of them don't know it.
For those who do get diagnosed, the current gold-standard treatment is a **CPAP machine** — a device that pumps continuous pressurised air through a mask worn over the face during sleep, physically holding the airway open. CPAP works. But wearing a mask connected to a machine every night for the rest of your life is a significant commitment, and adherence rates are poor: studies consistently find that a third to a half of patients either don't use their CPAP consistently or abandon it entirely. The discomfort, noise, and inconvenience are real.
For decades, the search for a simpler treatment — ideally a pill — has been ongoing. The **FLOW trial**, published in ***The Lancet*** in early 2026, represents the most compelling answer yet.
**What the FLOW Trial Found**
The FLOW trial was a multicentre, randomised, double-blind, placebo-controlled, dose-finding study. **298 adults** with moderate to severe obstructive sleep apnea were enrolled at **28 medical institutions** across five European countries: Belgium, Czechia, France, Germany, and Spain. They received either placebo or one of three daily doses of sulthiame (100 mg, 200 mg, or 300 mg) for **15 weeks**.
The primary measure was the **apnea-hypopnea index (AHI)** — the number of breathing interruptions (complete or partial airway collapses) per hour of sleep. For moderate-to-severe sleep apnea, this number is typically 15–30 or more per hour. The higher the number, the more disrupted the sleep, and the worse the downstream health consequences.
Results at the two highest doses were striking:
😴 At **200 mg**, participants experienced approximately **30–40% fewer breathing interruptions** compared to placebo 😴 At **300 mg**, the reduction reached up to **47–50%** in apnea-hypopnea events 😴 **Overnight oxygenation improved** significantly in the treatment groups 😴 **Excessive daytime sleepiness** — one of sleep apnea's most disabling symptoms — was meaningfully reduced
The **200 mg dose** emerged as the likely clinical sweet spot: strong efficacy with fewer side effects than the 300 mg dose. The reported side effects — pins and needles, headache, fatigue, and occasional nausea — were generally mild to moderate and decreased over time.
**What Is Sulthiame?**
Sulthiame is not a new molecule. It was first synthesised in the **1950s** and has been used for decades in Europe as a treatment for certain types of epilepsy, particularly in children. It works by inhibiting an enzyme called **carbonic anhydrase**, which plays a key role in regulating blood chemistry and, it turns out, breathing.
The carbonic anhydrase connection to breathing is what makes sulthiame an interesting candidate for sleep apnea. The drug appears to work through a different mechanism than CPAP — rather than physically keeping the airway open with air pressure, sulthiame seems to:
🧠 **Improve upper airway muscle tone** — reducing the tendency of throat muscles to collapse during sleep 🫁 **Stabilise respiratory control** — helping the brain's breathing regulation centres maintain more consistent respiratory drive ⚗️ **Reduce central apnea events** — where the brain briefly stops sending the signal to breathe, contributing to mixed apnea episodes
This mechanism is fundamentally different from CPAP — which is why the two treatments might eventually complement each other rather than simply substituting.
**Why This Matters**
Sleep apnea is one of the most underdiagnosed conditions in medicine. Its symptoms — snoring, fatigue, poor concentration, morning headaches — are often attributed to stress, lifestyle, or ageing. The diagnosis requires an overnight sleep study, which is inaccessible or inconvenient for many patients.
Untreated sleep apnea is not benign. It is strongly associated with:
❤️ **Cardiovascular disease** — hypertension, heart attack, stroke 🧠 **Cognitive decline** — including increased dementia risk over time ⚡ **Type 2 diabetes** — through its effects on glucose metabolism and stress hormones 😔 **Depression and anxiety** — sleep fragmentation directly affects mood regulation 🚗 **Road accidents** — drowsy driving from sleep apnea causes thousands of fatalities annually
For a billion people globally, a pill that reduces breathing interruptions by half would be transformative — not just in symptom relief, but in cardiovascular and cognitive protection across decades of treatment.
**What Comes Next**
The FLOW trial was a Phase 2 dose-finding study — designed to establish that the drug works and to identify the right dose. Lead researcher **Professor Jan Hedner** from the University of Gothenburg in Sweden described the results as a breakthrough that now clears the path for larger, longer Phase 3 trials to confirm sustained efficacy and safety in broader patient groups.
If Phase 3 confirms what Phase 2 has shown, sulthiame would become the **first pharmacological therapy approved specifically for obstructive sleep apnea** — a treatment category that currently has no approved pill-form option anywhere in the world.
For the hundreds of millions of people whose CPAP machine sits collecting dust on the bedside table, that would be genuinely life-changing news. 💤
*Sources: The Lancet (2025/2026) · ScienceAlert · ScienceDaily (March 11, 2026) · European Respiratory Society · Gizmodo · New Atlas · University of Gothenburg · Drugs.com*
