Topamax & Phentermine for Weight Loss

Phentermine and Topamax may cause weight loss.

Phentermine and Topamax are two very different types of medications. Phentermine is intended to be used as a weight loss aid, while Topamax is intended to be used to treat certain seizure disorders or prevent migraines from occurring. Both medications, however, may cause weight loss. Talk to your doctor to determine if either of these medications are appropriate for you to take.


Phentermine, which is in a class of medications called anorectics, works by decreasing a person's appetite. Since it can be habit-forming, doctors typically limit the amount of time you can take the medication. Although the specific length of time you can take the medication will depend on how your body responds to it, most people take the medication for three to six weeks, according to the National Center for Biotechnology Information's PubMed Health website. This medication can cause side effects, including vomiting, constipation, diarrhea, unpleasant taste in the mouth or dry mouth. Serious side effects may also occur, including insomnia, tremors, dizziness, restlessness, heart palpitations, increased blood pressure, shortness of breath, swelling of the legs or ankles, chest pain or difficulty exercising. If you experience any of these serious side effects, call a doctor.


Topamax, which is in a class of medications called anti-convulsants, works by decreasing abnormal excitement in the brain. The medication is approved to treat to treat seizures in people who suffer from epilepsy or Lennox-Gastaut syndrome. It is also approved to prevent migraine headaches. This medication may cause numerous side effects, including weight loss, weakness, hair loss, difficulty urinating, pain with urination, swelling, insomnia, unusual hair growth, skin problems, changes in menstruation, back or muscle pain, bone pain, dry or teary eyes, nosebleeds, difficulty swallowing, dandruff, extreme thirst, uncontrollable shaking, excessive movement, uncontrollable eye movements, constipation, diarrhea, gas, heartburn, changes in the ability to taste food, overgrowth of the gums, increased saliva, swelling of the tongue, numbness or tingling in limbs, difficulty concentrating, memory problem, confusions, lack of coordination, aggressive behavior, headaches, depression, irritability, mood swings and slowed reactions. Serious side effects may also occur, including changes in vision, eye pain, worsening of seizures, chest pain, trouble breathing, inability to respond to the things around you, stomach pain, vomiting, fast or shallow breathing, pounding or irregular heartbeat, slow heartbeat, excessive tiredness, intense back or side pain, constant need to urinate, fever, chill, loss of appetite and bloody or foul-smelling urine. Call a doctor if you experience any of these serious side effects.

Topamax for Weight Loss

Although Topamax is not approved by the U.S. Food and Drug Administration for weight loss, weight loss is a common side effect of the medication. In clinical studies, approximately 16 percent of adults and 21 percent of children experienced weight loss. Because of this, some doctors prescribe this medication off-label to individuals for the purpose in helping them lose weight. Although this practice may be appropriate in certain circumstances, it has many potential risks. Topamax can cause numerous side effects, many with the potential to be quite serious. Always do your own research and discuss the latest studies with a doctor to determine if taking this medication for weight loss is safe or appropriate for you.


Phentermine and Topamax do not have any known drug interactions. However, this does not necessarily mean that no interactions exist or that it is safe to take the two medications together. Always review your medical history with a doctor. This includes notifying your doctor of all of the current medications and supplements you are taking. Do not take these two medications together unless you have permission from your doctor to do so.