The FDA has more recently approved Qsymia (a branded drug) as a weight loss medication for individuals who are struggling with obesity. Qsymia contains two drugs one of which is phentermine and the other is topiramate.
Qsymia is made by the pharmaceutical company Vivus, Inc. and was formerly known as Qnexa. Adipex is a branded drug that is made by Gate Pharmaceuticals and contains Phentermine hydrochloride only. Adipex is also a weight loss medication. Both Qsymia and Adipex require a prescription.
Phentermine as an appetite suppressant is thought to activate a release of a class of neurotransmitters known as catecholamines which include dopamine, epinephrine and norepinephrine. The catecholamines are also known to increase blood concentrations of leptin which is a hormone that tells the brain you are full which suppresses your appetite. On the other hand, Topiramate (Topamax) is an anticonvulsant and migraine drug which also acts as a weight loss medication by making you feel full which also suppresses appetite. It also can make foods taste less appealing and increase metabolism thereby burning more calories.
Besides the obvious difference in Adipex ad Qsymia in that Adipex contains only Phentermine and Qsymia contains Phentermine and Topiramate, these two prescription drugs have different phentermine concentrations. Adipex comes in 37.5 mg caps that contain 31 mg of phentermine. Qsymia contains 3.75 mg of phentermine and 23 mg of topiramate. Other Qsymia caps come in 7.5 mg/46 mg, 11.25 mg/69 mg and 15mg/92 mg options (Phentermine to Topiramate).
A clinical trial in 2014 that ran for 56 weeks, found that Qsymia helped patients lose 10 percent of their weight (24 pounds) on average. Researchers found that dosage greatly affected the amount of weight loss and that the highest dosages gave twice the amount of weight loss.
As you can see, Qsymia can be used long term. On the other hand, Adipex (designed to be used short term, 3 to 5 weeks) produces a 3.5 percent weight loss according to Adipex clinical trials. Looks like Qsymia wins out on most pounds lost on the average.
Now, if you look at these two drugs from a cost perspective, it looks like Adipex wins out by far.
According to WebMD, a one month supply of Qsymia runs about $135, whereas Adipex runs about $59 for one month.
So, it looks like Adipex is more than two times cheaper but then consider you would only take it for 2 months or less whereas you would be on Qsymia for over a year.
That really adds up. Another issue with Qsymia is that it has more side effects and in particular depression and suicidal thoughts independent of the dosage used. Qsymia may also produce acute myopia that comes with individuals who have secondary angle closure glaucoma.
Clearly Adipex doesn’t have these side effects to contend with. The major side effect of Adipex is insomnia, however that is why it is recommended to take it in the morning which essentially takes care of the insomnia issue.