Beware of grapefruit juice with your medications (includes list)

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Beware of grapefruit juice with your medications

18 Jan 2005

Grapefruit juice can be deadly for people on certain medications, nurse

researchers remind doctors, nurses, and everyone who takes medicine and enjoys

grapefruit juice, in a paper in the American Journal of Nursing, a journal of

the American Nurses Association.

Amy Karch, R.N., M.S., of the School of Nursing at the University of Rochester

Medical Center reported on a man from a northern climate who moved to Florida

for the winter - one of tens of thousands of " snowbirds " who head south each

winter - and began drinking two to three glasses of grapefruit juice each day.

Two months later the man died, the victim of a deadly interaction between

grapefruit juice and his cholesterol-lowering medication.

Karch's paper, " The Grapefruit Challenge: The juice inhibits a crucial enzyme,

with possibly fatal consequences, " appears in the December 2004 issue of the

journal.

Interactions between grapefruit juice and medications have long been recognized.

Last year, the Medical Letter on Drugs and Therapeutics devoted an entire issue

to grapefruit juice and the dangerous drug interactions that can result. The

U.S. Food & Drug Administration requires all prospective new drugs to be tested

for interactions with grapefruit juice. And a warning about grapefruit juice is

included in the " food-drug interactions " that come with dozens of medications.

Nevertheless, Karch says many health-care professionals and patients don't know

about the risk.

" The potential of drug interactions with grapefruit juice has been out there a

long time, but most people just aren't aware of it, " says Karch, a clinical

associate professor of nursing. " There is so much information bombarding people

all the time, that a lot of people may have heard this but forgotten it. But the

problems can be life-threatening. "

The patient profiled in Karch's article had high cholesterol and other risk

factors for cardiac disease. The doctor put the patient on atorvastatin

(Lipitor), and the patient began dieting and exercising. Two months after the

patient went to Florida for the winter, he suddenly had muscle pain, fatigue and

fever, and went to the emergency room. The patient ended up going into kidney

failure and ultimately died.

The only major change in the person's lifestyle had been that, upon arriving in

Florida, he began picking grapefruit off a tree on the patio and drinking two or

three glasses of fresh grapefruit juice every day.

Karch, an expert on drug interactions, explains that grapefruit juice is one of

the foods most likely to cause problems with drugs, because it is metabolized by

the same enzyme in the liver that breaks down many drugs. The cytochrome P-450

3A4 enzyme breaks down grapefruit juice into useful components for body, just

like it breaks down dozens of medications. Karch says when the system is

overloaded, the grapefruit juice can " swamp " the system, keeping the liver busy

and blocking it from breaking down drugs and other substances.

Drugs that use the same pathway and interact with grapefruit juice target some

of the most common health problems doctors see today. The list consists of more

than 50 medications, including some drugs used to treat high cholesterol,

depression, high blood pressure, cancer, depression, pain, impotence, and

allergies.

Karch notes that interactions with grapefruit juice are well known and

documented among drug researchers, and that an appropriate warning label is

included with each prescription. Nevertheless, she says that many patients,

nurses and doctors aren't aware of the interactions or the potential serious

consequences, and that many people fail to read the warning labels about

drug-food interactions.

The consequences of an interaction depend on the drug involved. A woman on

birth-control pills who drinks a lot of grapefruit juice might find herself

pregnant because the juice blocks the action of the medication. A person on an

anti-depressant might have too much or too little energy, depending on the

specific medication. Someone on antibiotics might end up with diarrhea or could

be ill longer than usual because the drug won't work as well as it should. A

heart patient might not get the lowered blood pressure that a medication should

deliver, or the heart's rhythms might become irregular if an anti-arrhythmia

drug can't do its job.

The most severe effects are likely with some cholesterol-lowering medications,

Karch says. While the liver devotes its resources to grapefruit juice, the

medication can build up to dangerous levels, causing a breakdown of the body's

muscles and even kidney failure. This is what happened to the patient discussed

in the article.

To prevent such problems, Karch repeats what doctors and nurses tell their

patients every day: Read a medication's warning label carefully. If an

interaction with grapefruit juice is possible, the patient should stop drinking

the juice until speaking with his or her doctor. In some cases it might be

possible to switch a patient to a different drug without the risk; in other

cases the patient might simply have to give up grapefruit juice.

She says that more people than usual are vulnerable at this time of year,

because losing weight is among the most popular New Year resolutions, and some

diets are built around drinking lots of grapefruit juice.

Karch's paper is the latest in a column the journal devotes to " practice

errors, " where nurses report unusual clinical problems and Karch looks into how

widespread the problem might be. Last year she also reported that nurses had

found that some types of skin patches could catch on fire when patients receive

magnetic resonance imaging (MRI) scans.

Drugs that Interact with Grapefruit Juice:

(from the December 2004 issue of the American Journal of Nursing)

Antibiotics: clarithromycin, erythromycin, troleandomycin

Anxiolytics: alprazolam, buspirone, midazolam, triazolam

Antiarrhythmics: amiodarone, quinidine

Anticoagulant: warfarin

Antiepileptic: carbamazepine

Antifungal: itraconazole

Anthelmintic: albendazole

Antihistamine: fexofenadine

Antineoplastics: cyclophosphamide, etoposide, ifosfamide, tamoxifen,

vinblastine, vincristine

Antitussive: dextromethorphan

Antivirals: amprenavir, indinavir, nelfinavir, ritonavir, saquinavir

Benign prostatic hyperplasia treatment: finasteride

â-blockers: carvedilol

Calcium channel blockers: diltiazem, felodipine, nicardipine, nifedipine,

nimodipine, nisoldipine, verapamil

Erectile dysfunction drugs: sildenafil, tadalafil

Hormone replacement: cortisol, estradiol, methylprednisolone, progesterone,

testosterone

Immunosuppressants: cyclosporine, sirolimus, tacrolimus

HMG-CoA reductase inhibitors: atorvastatin, fluvastatin, lovastatin, simvastatin

Opioids: alfentanil, fentanyl, sufentanil

Selective serotonin reuptake inhibitors: fluvoxamine, sertraline

Xanthine: theophylline

Tom Rickey

University of Rochester Medical Center