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Drug Interactions between hydrochlorothiazide and Qsymia

This report displays the potential drug interactions for the following 2 drugs:

  • hydrochlorothiazide
  • Qsymia (phentermine/topiramate)

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Interactions between your drugs


hydroCHLOROthiazide topiramate

Applies to: hydrochlorothiazide and Qsymia (phentermine / topiramate)

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with thiazide-like diuretics, such as hydrochlorothiazide, may enhance the hypokalemic effects and increase the serum concentrations of topiramate. The mechanism for this interaction has not been delineated. The results of a clinical study involving healthy subjects showed that following administration of hydrochlorothiazide, the Cmax and AUC of topiramate increased by 27% and 29%, respectively. In addition, decreases in serum potassium were greater when hydrochlorothiazide and topiramate were given concomitantly compared to when either was given alone.

MANAGEMENT: Until more information is available, caution is advised if topiramate is administered with a thiazide-like diuretic, such as hydrochlorothiazide. Dosage adjustments as well as clinical and laboratory monitoring of topiramate should be considered whenever a thiazide-like diuretic is added to or withdrawn from therapy. Serum potassium levels should also be monitored during concomitant therapy. Patients should be observed for the development of topiramate adverse effects.


  1. "Product Information. Topamax (topiramate)." Ortho Pharmaceutical Corporation, Raritan, NJ.
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. Cerner Multum, Inc. "Australian Product Information." O 0
  4. "Product Information. Topiramate (topiramate)." Cipla USA Inc., Miami, FL.
View all 4 references

Drug and food interactions


phentermine food

Applies to: Qsymia (phentermine / topiramate)

Using phentermine with alcohol can increase the risk of cardiovascular side effects such as increased heart rate, chest pain, or blood pressure changes. In addition, you may also be more likely to experience nervous system side effects such as dizziness, drowsiness, depression, and difficulty concentrating. You should avoid or limit the use of alcohol while being treated with phentermine. Do not use more than the recommended dose of phentermine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medication without first talking to your doctor.

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.