Services & Amenities

Facts from Ask a Pharmacist

Warning: Do Not Take with Grapefruit—What Does it Mean?

Grapefruit’s sweet and sour taste is refreshing and it is a healthy food choice; a natural source of vitamin C and potassium, but it may not be a safe choice with certain medications.

Can grapefruit really cause problems when taken with certain medications?
An interaction is when the effects of a drug are changed by the presence of another drug, food or drink. Grapefruit juice and fresh grapefruit can interact with more than eighty-five prescription and over-the-counter drugs used to treat common medical conditions. Although grapefruit juice tends to get all the attention in the media, it is important to remember that the whole fruit can cause the same problems as the juice.
How does grapefruit change the way my medication works?
When the drug is swallowed, it dissolves and some of the drug is broken down or metabolized to an inactive form in the intestine by proteins called enzymes. Grapefruit can interfere or block the action of these enzymes, causing an increased amount or too much active drug to be absorbed by the body resulting in dangerous drug levels and increased side effects.
Why grapefruit juice and not all citrus juices?
Studies have found that the furanocoumarins found in grapefruit most likely cause this interaction. These compounds are not found in apple or other citrus fruits such as lemons which is why you do not have to worry as much about other fruits.
How much grapefruit? Does it matter when I eat or drink the grapefruit?
One cup of grapefruit juice or a whole grapefruit can produce a major interaction, however as few as two wedges may produce some amount of interaction. The effects of grapefruit may last for up to three days, therefore taking your medications and grapefruit at different times is not enough; you may need to avoid eating grapefruit to prevent this interaction.
Who is at the greatest risk and why?
Older people seem to be at the greatest risk; they eat the most grapefruit, take the most medications, and they have a decreased ability to counteract the effects of dangerous drug levels in the body. Also, everyone is unique; some people have more enzymes than others, so grapefruit may affect people differently when they take the same drug.
What do the medications affected by grapefruit have in common?
The drugs that are affected by grapefruit have two common characteristics:
  1. Taken by mouth (oral medications)
  2. Amount of drug absorbed by the body is small
The table at the end of this article includes the common drugs affected by grapefruit. The interaction with grapefruit is drug specific. Other drugs in the same class may not interaction with grapefruit.
Is there a different kind of interaction causing the opposite effect?
Grapefruit and sweet oranges can cause the opposite effect with other medications by blocking the action of another protein called transporters. Transporters move the drug into the body’s cells where it is absorbed. If this is blocked, drug absorption will be decreased and the effectiveness of the medicine is reduced. To avoid this interaction you can separate the fruit and medication by four hours.
What are some tips to avoid these problems in the future?
  • Ask your healthcare provider or pharmacist if you can have grapefruit while using your medications
  • Carefully read the Medication Guide that comes with your prescription medications and drug warning labels or stickers on your prescription bottles
  • Carefully read the Drug Facts label on your over-the-counter medications
  • Check the ingredients label of all fruit juices and flavored drinks to make sure they do not contain grapefruit
  • Avoid Seville oranges (found in marmalade) and tangelos (cross of tangerine and grapefruit)

Danielle Kilmer
PharmD Candidate 2014
Drug Information, Strong Memorial Hospital

Drugs that Interact with Grapefruit and May Cause an Increase in Side Effects*

Generic Name Brand Name Effect
amiodarone Cordarone Irregular heartbeat
apixaban Eliquis Increased risk for bleeding; Avoid in elderly
atorvastatin Lipitor Muscle tissue breakdown/acute kidney failure
budesonide Entocort EC Increased cortisol hormone in the blood
buspirone BuSpar Increased adverse effects such as dizziness; Avoid in elderly
carbamazepine Tegretol Increased adverse effects
cilostazol Pletal Increased adverse effects
clomipramine Anafranil Increased side effects such as dry mouth/dizziness/fatigue
colchicine Colcrys Increased adverse effects
crizotinib Xalkori A serious effect on the heart called torsade’s/bone marrow suppression
cyclosporine Sandimmune/Neoral Structural kidney damage/liver injury/bone marrow suppression
darifenacin Enablex Urinary retention/constipation
dasatinib Sprycel A serious effect on the heart called torsade’s/bone marrow suppression
dextromethorphan Robitussin DM Drowsiness/hallucinations; Avoid in elderly
diazepam Valium Drowsiness
dronedarone Multaq Potential for a serious effect on the heart called torsade’s
eplerenone Inspra ncreased potassium in the blood, may cause irregular heartbeat; Avoid in elderly
erlotinib Tarceva Bone marrow suppression; Avoid in elderly
erythromycin   Potential for a serious effect on the heart called torsade’s; Avoid in elderly
everolimus Afinitor Bone marrow suppression/kidney damage
felodipine Plendil Low blood pressure/increased heart rate
fesoterodine Toviaz Urinary retention/constipation
lapatinib Tykerb A serious effect on the heart called torsade’s/bone marrow suppression
lovastatin Mevacor Muscle tissue breakdown/acute kidney failure
maraviroc Selzentry Low blood pressure that happens when you stand up from a seated position causing dizziness; Avoid in elderly
nifedipine Adalat CC Low blood pressure/increased heart rate
nilotinib Tasigna A serious effect on the heart called torsade’s/bone marrow suppression
nisoldipine Sular Low blood pressure/increased heart rate
oxycodone   Slowed breathing rate; Avoid in elderly
pazopanib Votrient A serious effect on the heart called torsade’s/bone marrow suppression
pimozide Orap Potential for a serious effect on the heart called torsade’s
primaquine   Bone marrow suppression
quetiapine Seroquel Dizziness/drowsiness; Avoid in elderly
quinidine   Potential for a serious effect on the heart called torsade’s
quinine Qualaquin Potential for a serious effect on the heart called torsade’s; Avoid in elderly
rivaroxaban Xarelto Increased risk for bleeding
simvastatin Zocor Muscle tissue breakdown/acute kidney failure
sirolimus Rapamune Bone marrow suppression/kidney damage
solifenacin Vesicare Potential for a serious effect on the heart called torsade’s
sunitinib Sutent A serious effect on the heart called torsade’s/bone marrow suppression
tacrolimus Prograf Kidney damage; symptoms include tremor, headache, and insomnia
tamsulosin Flomax Low blood pressure that happens when you stand up from a seated position causing dizziness
ticagrelor Brilinta Increased risk for bleeding
verapamil Isoptin/Calan/Verelan Low blood pressure/increased heart rate
ziprasidone Geodon Potential for a serious effect on the heart called torsade’s; Avoid in elderly

*In the future more drugs may be added to this list.

References:

  1. Dahan A, Altman H. Food-drug interaction: grapefruit juice augments drug bioavailability-mechanism, extent and relevance. Eur J Clin Nutr. 2004;58:1-9.
  2. Kiani J, Imam SZ. Medicinal importance of grapefruit juice and its interaction with various drugs. Nutrition Journal. 2007;6:33.
  3. Bailey DG, Dresser G, Arnold JMO. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences. CMAJ. 2013;185(4):309-316.
  4. Dolton MJ, Rougogalis BD, McLachlan. Fruit Juices as Perpetrators of Drug Interactions: The Role of Organic Anion-Transporting Polypeptides. Clin Pharmacol Ther. 2012;92(5):622-630.
  5. Don’t take this with that! Food and Drug Administration Web site. http://www.fda.gov/Drugs/ResourcesFRYou/SpecialFeatures/ucm341427.html. Accessed October 30, 2013.
  6. Grapefruit Juice and Medicine May Not Mix. Food and Drug Administration Web site. http://www.fda.gov/ForConsumers/ConsumerUpdates. Accessed October 30, 2013
  7. Avoiding Drug Interactions. Food and Drug Administration Web site. http://www.fda.gov/Consumer/Updates/interactions112808.html. Accessed October 30, 2013
  8. Grapefruit juice: Beware of dangerous medication interactions. Mayo Clinic Web site. http://www.mayoclinic.comm/health/ffoo-and-nutrition/AN00413. Accessed October 30, 2013.
  9. Pharmacists Letter. January 2013;29(1):1-1.

Calcium Supplements: What You Need to Know

Calcium is important in maintaining strong bones. Without enough calcium, your bones will weaken and you may be more at risk for fractures and osteoporosis. Throughout your life, your bones are constantly recycling themselves by breaking down old bone and building new bone. While young and still growing, ones’ bones do more building than breaking down. As the body ages, however, the balance shifts and bones begin to do more breaking down than building. So, this is the time to make sure you get adequate calcium in the diet and in order to maintain strong bones, supplementation may be necessary. Other groups at risk for low calcium include vegans and ovo-vegetarians, lactose intolerant individuals, and postmenopausal women.

Foods rich in calcium include dairy products such as milk, cheese, yogurt, and other foods such as tofu and some other soy products, sardines, eggs, orange juice, and green vegetables such as kale, broccoli, turnip greens and spinach. Some foods such as cereals and breads are often fortified with calcium. The Recommended Daily Allowance (RDA) of calcium set by the National Institutes of Health varies by age group and gender. If your physician recommends taking a calcium supplement, deciding on what product to take can be confusing. Ask your pharmacist for help before making a purchase. Or you can call the Drug Information Helpline and "Ask a Pharmacist" at (585) 275-3718.

Many calcium supplements include vitamin D. That is because vitamin D helps your body absorb calcium. Your body makes some vitamin D but is dependent upon exposure to sunlight. Very few foods are available that naturally contain vitamin D. Some of these foods include fatty fish such as tuna, salmon, and swordfish. Many dairy products are fortified with vitamin D. So adding foods to your diet that are rich in calcium and vitamin D can help to improve your bone health. Diet alone may not be enough for you and you may need supplementation.

How Much Acetaminophen is Too Much?

Taking more than a total of 4000 mg. of acetaminophen in a 24-hour period for an adult (less for a child) may cause liver damage and serious illness, especially if taken several days in a row. Since consumption of alcoholic beverages can increase your risk for liver damage, speak with your primary care physician regarding alcohol consumption if you take more than just an occasional dose of acetaminophen.

Follow these simple steps:

  • Keep a good record of the total daily amount of acetaminophen you take and DO NOT EXCEED 4000 mg. per day.
  • Read all your prescription and over-the-counter medication labels carefully so that you know whether or not they contain acetaminophen.

Acetaminophen is most commonly found in pain relievers. Prescription medications containing acetaminophen include Vicodin and Percocet, and is usually abbreviated APAP.

An early sign of illness related to taking too much acetaminophen is nausea, vomiting, and/or abdominal pain.

Call the Drug Information Helpline at (585) 275-3718.