Phentermine and Topiramate Side Effects

In clinical studies on phentermine and topiramate, some people reported side effects such as constipation, upper respiratory tract infections, and headaches. Fortunately, most reactions to this drug are not serious and can be treated easily. Some side effects, however, are serious and may need immediate treatment. Seek immediate medical care if you are taking this drug and experience difficulty breathing, problems concentrating, or thoughts of suicide.

An Introduction to Side Effects of Phentermine and Topiramate

As with any medicine, phentermine and topiramate (Qsymia®) can cause side effects. However, not everyone who takes the medication will have problems. In fact, most people tolerate it quite well. If side effects do occur, in many cases, they are minor and either require no treatment or are treated easily by you or your healthcare provider.
(This article covers many, but not all, of the possible side effects with phentermine and topiramate. Your healthcare provider can discuss a more complete list with you.)

Serious Phentermine and Topiramate Side Effects

Some side effects of this drug are potentially serious and should be reported immediately to your healthcare provider. These include but are not limited to:
  • Changes in mood or behavior, such as feeling depressed, anxious, agitated, irritable, or restless
  • Thoughts about death, suicide, or harming yourself
  • Attempts of suicide
  • Aggressive, violent, or dangerous acts or impulses
  • Feeling hyperactive or talking more than usual
  • Difficulty breathing or shortness of breath
  • Changes in vision, with or without eye pain and redness
  • A rapid, forceful, or otherwise abnormal heartbeat
  • Difficulty sleeping
  • Problems concentrating, speaking, or remembering things
  • Signs of metabolic acidosis, a problem that occurs when there is too much acid in the blood, such as:
    • Feeling tired
    • Not wanting to eat (loss of appetite)
    • Problems thinking
    • An abnormal heartbeat
  • Low blood sugar or signs of low blood sugar, such as:
    • Confusion or abnormal behavior
    • Blurred vision
    • Shakiness
    • Anxiety
    • Sweating
    • Fainting
  • Seizures
  • Signs of kidney stones, including severe side or back pain or blood in the urine
  • Signs of an allergic reaction, such as:
    • An unexplained rash
    • Hives
    • Itching
    • Swelling of the mouth or throat
    • Wheezing
    • Difficulty breathing.

More Headlines in Phentermine and Topiramate Side Effects

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Last reviewed by: Kristi Monson, PharmD
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