There are approximately one billion people worldwide living with obstructive sleep apnea. Most of them don't know it. Of those who do, many refuse or cannot tolerate the gold-standard treatment — a CPAP machine, which delivers pressurised air through a mask worn every night. The device works, but many people find it claustrophobic, uncomfortable, or simply too disruptive to their sleep and their relationships to persist with.
For this enormous group of people, a clinical trial published today in *The Lancet* offers the most promising news in years: a pill — sulthiame — may soon be a viable alternative.
**What the Trial Found**
The Phase 2 FLOW trial was a double-blind, randomised, placebo-controlled study involving 298 people with moderate to severe obstructive sleep apnea, conducted across 28 centres in five European countries. It is the most rigorous test yet of sulthiame's efficacy for OSA.
The results were striking. Participants taking the highest dose of sulthiame (300 mg) experienced a **39.9% decrease** in their apnea-hypopnea index (AHI) — the standard clinical measure of how many times per hour breathing is interrupted during sleep. At the same dose, participants taking higher doses saw up to a **47% reduction** in breathing pauses using a slightly broader measurement.
Oxygen levels overnight improved. Sleep quality scores improved. Daytime sleepiness — measured on the validated Epworth Sleepiness Scale — improved significantly. The drug was well-tolerated, with most reported side effects mild to moderate: pins and needles, headaches, and fatigue.
**How Does It Work?**
Sulthiame has been used as an anti-epilepsy drug for decades. It works by inhibiting carbonic anhydrase, an enzyme involved in regulating the body's carbon dioxide levels. In the context of sleep apnea, this mechanism has an unexpected benefit: it stabilises the breathing control system and increases respiratory drive, reducing the likelihood that the upper airway will collapse during sleep — which is what causes the characteristic gasping, choking, and silence-pause-gasp cycle of OSA.
This mechanism is distinct from other investigational drugs for sleep apnea, which have largely focused on muscle tone in the upper airway. Sulthiame targets the neurological control of breathing itself.
**Why This Matters**
Sleep apnea is not just a nuisance. Untreated OSA significantly raises the risk of hypertension, heart attack, stroke, type 2 diabetes, and premature death. It impairs cognitive function, reaction times, and mood. Drivers with untreated sleep apnea are up to seven times more likely to have a road traffic accident.
CPAP works when people use it. The problem is adherence: studies consistently show that 30–50% of patients prescribed CPAP either never start using it or abandon it within a year. The number of people living with untreated or inadequately treated sleep apnea — and all the health consequences that come with it — is staggeringly large.
A pill changes the equation entirely. It doesn't require fitting, calibration, or nightly equipment setup. It doesn't require sleeping next to a machine. It doesn't affect your partner's sleep. If a daily tablet can provide meaningful, sustained reduction in apnea events, it has the potential to reach millions of patients who currently go untreated.
**What Comes Next**
The FLOW trial is a Phase 2 result — it demonstrates efficacy and safety in a controlled population, but Phase 3 trials in larger, more diverse populations are required before regulatory approval. Those trials are expected to begin later in 2026.
For the researchers, clinicians, and — most importantly — the billion people living with sleep apnea, today's publication is a significant step. The era of the only treatment being a mask may be coming to an end. 😴
*Sources: The Lancet (March 11, 2026) · University of Gothenburg · ScienceDaily (March 11, 2026) · ApniMed · Healio Pulmonology*
