Obstructive sleep apnea (OSA) usually gets worse with weight gain, and better with weight loss. A new, combination medication, Phentermine + Topiramate, has been shown to help in weight reduction. This study evaluated the safety and efficacy of Phentermine + Topiramate compared to placebo for treatment of obese patients with moderate to severe OSA that were unwilling or unable to use CPAP. Both groups received a standardized weight reduction counseling program and the study lasted for 28 weeks.
The results showed that the Phentermine + Topiramate treatment showed significant improvements in sleep apnea severity, subjective sleep quality, weight loss, and systolic blood pressure when compared to placebo. Of note, the placebo group also had a reduction in OSA severity and weight reduction, just not as much as the treatment arm. There were no serious adverse events reported, except one case of kidney stones in a patient who already had a history of them. Topiramate typically causes fatigue, but this was not present, probably due to the stimulating effects of the Phentermine.
Phentermine is an appetite suppressant, and was once used in the combination weight loss medication Fen-Phen. The Fen part, or fenfluramine, was taken off the market because it was associated with heart valve damage. Topiramate is an anti-seizure medication, but has been shown to reduce weight through an unknown mechanism. It's not clear from this study if the combination of the two would be better than Phentermine alone. Also, this study was for 7 months, but what would happen when the medications were discontinued? Or would this have to be a life-long treatment?