A European epilepsy drug could be an effective treatment for sleep apnea, a new study suggests.

Patients who took sulthiame had few pauses in their breathing while asleep, as well as higher levels of blood oxygen, according to clinical trial results presented Tuesday at the European Respiratory Society annual meeting in Vienna.

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“This suggests that sulthiame could be an effective treatment for obstructive sleep apnea, especially for those who find they cannot use the existing mechanical treatments” like a CPAP machine, said researcher Jan Hedner from Sahlgrenska University Hospital and the University of Gothenburg in Sweden.

Sulthiame has never been approved for use in the United States, but it is used in Europe to treat epilepsy. It appears to quell seizures by increasing blood levels of an established anticonvulsant called phenytoin.

The drug also targets the respiratory system by inhibiting an enzyme called carbonic anhydrase, which stimulates upper airway muscles, researchers explained.

For the study, researchers recruited nearly 300 people being treated for sleep apnea at hospitals in Spain, France, Belgium, Germany and the Czech Republic. None of the patients were using CPAP machines or mouthpieces to keep their airways open during sleep.

Three-fourths of the participants were prescribed sulthiame at different dosage levels, and the remaining quarter took a placebo pill.

Those taking the highest dose of sulthiame had 40% to 50% better breathing at night than those on placebo, based on different measures of sleep apnea, researchers said.

Sulthaime patients also felt less sleepy during the daytime, researchers said.

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The drug produced mild to moderate side effects like pins and needles, headache, fatigue and nausea.

“People taking sulthiame in the trial had a reduction in obstructive sleep apnea symptoms such as stopping breathing during the night and feeling sleepy during the day,” Hedner said in a meeting news release. “Their average levels of oxygen in the blood were also improved with the treatment.”

However, Hedner said further clinical trials are needed to confirm these benefits before sulthaime can be widely adopted as a treatment for sleep apnea.

Head of the ERS meeting, Sophia Schiza, noted this is one of the first studies to suggest that a drug could help with sleep apnea. Schiza was not involved in the research.

“The results are promising,” Schiza, a professor of respiratory and sleep medicine at the University of Crete in Greece, said in a news release. “We need to continue testing sulthiame and other treatments to understand their long-term effects, including any side effects.”

Because these findings were presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.