Medication Interactions

Could you accidentally poison yourself by taking over-the-counter (OTC) products? 

Hundreds of senior citizens in Tennessee call Tennessee Poison Center after taking herbal medications, dietary supplements, vitamins, pain relievers, antihistamines, cough/cold therapies or gastrointestinal remedies. Why did those people call? Reasons included:

  • Feeling ill after taking OTC products with prescription medicine
  • Taking an extra dose
  • Taking someone else’s medicine
  • Discontinuing prescription medicine and substituting OTC medicine
  • Taking higher-than-recommended doses of OTC medicine

Information about Interactions
An interaction refers to a problem that occurs when a medication is combined with another medication, food or alcohol. That doesn’t just refer to combinations taken at the exact same time. Some interactions can occur even if the two items are spaced many hours apart.

Grapefruit and medication interactions
Avoid grapefruit or grapefruit juice unless approved by your pharmacist. Grapefruit juice interferes with enzymes that break down certain drugs in your digestive system. If components of your medicines build up, you may have abnormally high blood levels of these drugs and an increased risk of serious side effects. The exact chemical or chemicals in grapefruit juice that cause this interaction can be in the pulp, peel and juice of grapefruit as well as in dietary supplements that contain grapefruit bioflavonoids. Until proven safe, do not take grapefruit if you are on the following medications:

  • Carbamazepine (Carbatrol, Tegretol)
  • Buspirone (BuSpar) clomipramine (Anafranil) and sertraline (Zoloft)
  • Diazepam (Valium), triazolam (Halcion)
  • Felodipine (Plendil), nifedipine (Adalat, Procardia), nimodipine (Nimotop), nisoldipine (Sular) and possibly verapamil (Isoptin, Verelan)
  • Saquinavir (Fortovase, Invirase) and indinavir (Crixivan)
  • Simvastatin (Zocor), lovastatin (Mevacor) and atorvastatin (Lipitor), simvastatin-ezetimibe (Vytorin)
  • Cyclosporine (Neoral, Sandimmune), tacrolimus (Prograf) and sirolimus (Rapamune)
  • Amiodarone (Cordarone)
  • Sildenafil (Viagra)

Herbal and Prescription Medicine Interactions

Herbal Products and Prescription Medicine shows combinations of herbal products and prescription drugs and the medical problems that could result.

If you take these combinations, this could happen:

Aloe + digoxin heart medicine: Lowers potassium in the blood

Aloe + steroids or blood pressure medicine: Lowers potassium in the blood

Cats Claw + blood pressure medicine: Dangerously low blood pressure

Cats Claw + immunosuppressants: Immunosuppressant doesn’t work well

Chondroitin + blood-thinners: Risk of bleeding

Echinacea + immunosuppressants: Immunosuppressant doesn’t work well

Fish oil capsules + blood thinners: Risk of bleeding

Garlic pills + blood-thinners, aspirin: Risk of bleeding

Garlic pills + Diabetes medicine: Dangerously low blood sugar

Garlic pills + cyclosporine: Organ rejection

Gingko Biloba + blood-thinners: Risk of bleeding

Gingko + diuretic blood pressure pills: Higher blood pressure

Gingko + anticonvulsants: Risk of seizures

Ginseng + blood-thinners: Risk of bleeding

Glucosamine + Diabetes medicine: May raise blood sugar

Glucosamine + cancer medicine: Cancer medicine doesn’t work well

Hawthorn + digoxin heart medicine: Irregular heartbeat

St. John’s Wort + Digoxin: Digoxin doesn’t work well

St. John’s Wort + psychiatric medicine: Toxic side effects

St. John’s Wort + Cyclosporine: Organ rejection

St. John’s Wort + blood thinners: Blood thinners don't work well

Resources for more information about medicine interactions
There are many, many more interactions than can be listed here. Get in the habit of asking your pharmacist or physician before starting a new OTC product. Or you can look on-line at reputable medical websites such as WebMD or

Tennessee Poison Center (1-800-222-1222) is a free source of information just a phone call away. Nurses, pharmacists and physicians answer questions on the hotline 24 hours a day. If someone feels unwell after mixing medications, Tennessee Poison Center can help in a matter of minutes. In most cases, the caller can be taken care of in their own home while following the poison centers advice. The statewide toll-free Poison Help hotline number is 1-800-222-1222.

* Reprinted original article by JoAnn Chambers-Emerson, RN, BSN, CSPI Certified Specialist in Poison Information Florida Poison Information Center Tampa