Qsymia can cause irregular vaginal bleeding while you are taking birth control pills. This should not make the pills less effective in preventing pregnancy.
Using this medicine with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.
Tell your doctor about all your other medicines, especially:
acetazolamide;
methazolamide;
zonisamide;
valproic acid or divalproex sodium (Depakene or Depakote)
birth control pills;
a diuretic or "water pill";
insulin or oral diabetes medicine; or
medicines that impair or decrease your thinking, concentration, or muscle coordination.
This list is not complete. Other drugs may interact with phentermine and topiramate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.
 Qsymia drug interactions (more detail)
