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Precautions and Warnings With Phentermine and Topiramate

Specific Phentermine and Topiramate Precautions and Warnings

Some warnings and precautions to be aware of prior to taking this drug include the following:
 
  • Phentermine and topiramate can cause your heart to beat faster at rest. This could be a problem if you already have a fast heart rate or heart problems, or if you have recently had a heart attack or stroke. Your healthcare provider will check your heart rate periodically during phentermine and topiramate treatment. Let him or her know if you experience a racing, pounding, or otherwise abnormal heartbeat while at rest.
 
  • This medicine contains topiramate (Topamax®), which is a seizure medication. Seizure medications may increase the risk for suicidal thoughts and behaviors (see Seizure Medications and Suicide). Let your healthcare provider know if you have any unusual changes in your mood or behavior during treatment, including new or worsening depression, thoughts of dying or of suicide, or attempts at harming yourself.
 
  • This medication can cause potentially serious eye problems, including a decrease in vision and angle closure glaucoma, an eye condition associated with high eye pressure caused by a blockage of fluid in the eye. These problems could lead to a loss of vision if not treated right away. Let your healthcare provider know if you have any changes in vision, with or without eye pain and redness.
  • Phentermine and topiramate may cause changes in mood, including depression, anxiety, and insomnia. Let your healthcare provider know if you develop any of these problems during treatment.
 
  • This medication has been reported to cause thinking problems, such as difficulty with concentration, attention, memory, and speech (in particular, difficulty finding the right word). Your healthcare provider will slowly increase your dose at the beginning of treatment to help reduce your risk for developing these potential side effects. Let your healthcare provider know if you develop any of these problems.
 
  • Because phentermine and topiramate has the potential to cause problems with concentration and attention, you should use caution when driving or operating any potentially hazardous machinery until you know how the medication affects you.
 
  • Phentermine and topiramate has been reported to cause metabolic acidosis, which occurs when there is too much acid in the blood. If metabolic acidosis is not treated, it can lead to other problems, such as kidney stones, osteoporosis, and breaking a bone. Metabolic acidosis can stunt a child's growth, and can harm your baby if you develop the condition during pregnancy.

    Your healthcare provider will order blood tests to check the amount of acid in your blood before you start taking phentermine and topiramate, and during treatment. Let him or her know if you have symptoms of metabolic acidosis, which may include:
    • Rapid breathing
    • Feeling tired
    • Loss of appetite
    • An irregular heartbeat
    • Problems thinking clearly.
 
  • This medication may increase blood creatinine levels. Creatinine is a waste product in the body that is removed by the kidneys. High creatinine levels are often a sign of kidney problems. Your healthcare provider will get blood tests to measure the amount of creatinine in your blood before you start taking phentermine and topiramate, and periodically during treatment.
 
  • If you have diabetes, you may develop low blood sugar (hypoglycemia) as you start eating less and lose weight with phentermine and topiramate. As a result, you may need an adjustment in your diabetes medications. You should check your blood sugar levels before you start taking phentermine and topiramate, and during treatment.
 
  • If you have high blood pressure, the weight loss caused by phentermine and topiramate may lower your blood pressure. As a result, you may need a lower dose of your blood pressure medications. Your healthcare provider will check your blood pressure before you start taking phentermine and topiramate, and during treatment.
 
  • Combining phentermine and topiramate with alcohol or other medicines that can cause drowsiness could lead to serious side effects, such as dizziness, extreme drowsiness, lightheadedness, and problems with coordination (see Drug Interactions With Phentermine and Topiramate). In general, you should avoid using alcohol during phentermine and topiramate treatment.
 
  • Stopping this medication suddenly could cause seizures. If you need to stop taking phentermine and topiramate, your healthcare provider may need to gradually reduce your dose, especially if you are being treated with high doses.
 
  • Because phentermine and topiramate is removed from the body by the kidneys, people with moderate or severe kidney disease will be given lower doses. Phentermine and topiramate should generally not be used in people with end-stage kidney disease who are on dialysis.
 
  • People with moderate liver disease may also need lower phentermine and topiramate doses. This diet medicine should generally not be used in people with severe liver disease.
 
  • This medicine may increase your risk for developing kidney stones. The risk for kidney stones may be higher in people who follow a ketogenic diet (a high-fat, low-carbohydrate diet) and people who take medicines known as carbonic anhydrase inhibitors (see Drug Interactions With Phentermine and Topiramate). You can reduce your chances of getting kidney stones by drinking plenty of fluids during phentermine and topiramate treatment.
 
  • Phentermine and topiramate can cause decreased sweating and an increase in body temperature, which could be serious enough to lead to hospitalization. You should watch for these possible side effects when you exercise or are in hot weather.
 
  • This medicine may lower your blood potassium levels (known medically as hypokalemia). People who take certain diuretics ("water pills") have a higher risk for this side effect (see Drug Interactions With Phentermine and Topiramate). Your healthcare provider will monitor your blood potassium levels, with a simple blood test, during treatment.
 
  • It is very important that you keep all your healthcare and laboratory appointments while taking this medication. Your healthcare provider will need to do blood tests before you start treatment, and periodically during treatment, to make sure you are not developing potentially serious side effects.
 
  • Phentermine and topiramate is considered a pregnancy Category X medication. This means it should not be used by women who are pregnant (see Qsymia and Pregnancy).
 
  • Phentermine and topiramate passes through breast milk. Therefore, if you are breastfeeding or plan to start, be sure to talk with your healthcare provider before taking the medication (see Qsymia and Breastfeeding).
 

More Headlines in Precautions and Warnings With Phentermine and Topiramate

↶ What Should I Tell My Healthcare Provider?
‣ Who Should Not Take Phentermine and Topiramate?
‣ Final Thoughts
Last reviewed by: Kristi Monson, PharmD
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