sleeppillA study published in the journal SLEEP found that patients with moderate to severe obstructive sleep apnea (OSA) taking phentermine and topiramate extended-release capsules achieved significant improvements in key measures of OSA and cardiovascular risk factors along with weight loss during the 28-week trial.

A safe and effective pharmacologic treatment for OSA could be useful and more acceptable to some patients than positive airway pressure (PAP) therapy, but no drug is currently approved to treat OSA.

In the study recently reported in SLEEP, 45 obese adults who were not using PAP were randomized to placebo or treatment with phentermine and topiramate extended-release capsules for 28 weeks. Both groups received intensive lifestyle modification counseling. The primary endpoint was change in the apnea-hypopnea index (AHI), a measure of the average number of breathing interruptions per hour during sleep. An AHI of 5-15 is considered mild, 15-30 moderate, and severe if >30. The average AHI at baseline in both treatment groups was about 45, indicating that, on average, subjects had severe OSA at the beginning of the study.

By the end of the study, the number of apnea-hypopnea events in the phentermine and topiramate extended-release capsules group was reduced from an average of 44 events per hour (severe) to 14 events per hour (mild) at week 28. The placebo-adjusted LS mean change week 28 was -14.9 (p=0.0084).

Cardiovascular and metabolic risk factors, such as systolic blood pressure and mean overnight oxygen saturation, were also improved during the study.

At week 28, the LS mean percent change in weight from baseline was -10.3% in the phentermine and topiramate extended-release capsules group and -4.2% in the placebo group (p=0.0006) in which subjects received only lifestyle modification counseling. More subjects in the phentermine and topiramate extended-release capsules group (54.5%) achieved at least 10% weight loss compared with 13.0% in the placebo group (p=0.0044).

The most common adverse events reported during the study included dry mouth, altered taste, sinusitis, and upper airway infection.

“Obstructive sleep apnea is a serious condition associated with potentially deadly cardiovascular and metabolic events for the more than 15 million patients living with the disease. Unfortunately, there are no drug treatments available for the condition, and because current treatment options are limited to devices or surgery, patient compliance is low,” stated David Winslow, MD, the principal investigator of the study and lead author of the paper. “These positive data, from what is considered a sizable study for OSA, are exciting for those of us in the medical community treating obese patients with this condition.”

This randomized, placebo-controlled, proof-of-concept study suggests that phentermine and topiramate extended-release capsules combined with lifestyle modification may be useful in the treatment of patients with obstructive sleep apnea who are unable to use PAP therapy. Additional and larger studies are required to explore these results more thoroughly.

Phentermine and topiramate extended-release capsule is not approved for the treatment of obstructive sleep apnea. This study was funded by VIVUS Inc.