Grapefruit Juice & Viagra. Please, do not mix!
While this article draws attention to Viagra and grapefruit juice together, there is also reference to the numerous benefits of grapefruit.
The original formulation of the protease inhibitor saquinavir -- Invirase -- became available in North America around the mid-1990s. However, Invirase was poorly absorbed. The manufacturer suggested that taking Invirase with concentrated grapefruit juice would enhance the absorption of this drug. This effect occurs because grapefruit juice contains compounds that impair the activity of certain enzymes in the intestine -- enzymes that help break down Invirase.
A few years later, doctors began to use another protease inhibitor, ritonavir (Norvir) , in combination with Invirase. Ritonavir is much more effective than grapefruit juice at inhibiting enzymes in the intestine and liver. Examples of other drugs affected by grapefruit juice include the following:
beta blockers – Cardizem (diltiazem)
sedatives/sleeping pills – Halcion (triazolam), Versed (midazolam)
transplant drug – cyclosporine (Neoral, Sandimune)
It appears that grapefruit juice can also affect the absorption of the popular erectile dysfunction drug Viagra (Sildenafil). Because erectile dysfunction is common in some males with HIV/AIDS.
Researchers in Koln, Germany, conducted a study using 24 healthy, HIV negative male subjects whose average age was 29 years. The men received a glass of grapefruit juice on an empty stomach and then one hour later another glass of grapefruit juice with Viagra 50 mg. Blood samples were collected over the next 24 hours. A week later the experiment was repeated with water being substituted for grapefruit juice.
Researchers found that the absorption of Viagra increased by 23% when taken with grapefruit juice instead of water. Grapefruit juice also delayed the absorption of Viagra. This latter point is important because Viagra is supposed to be taken one hour before sex, and taking the drug with grapefruit juice may result in disappointment for some users of Viagra.
The grapefruit juice used in this study was white juice and supplied by Dohler-Euro Citrus NBI, GmbH. Other brands, types and doses of grapefruit juice may have different effects. The researchers suggest that the combination of Viagra and grapefruit juice be "avoided."
Men who use protease inhibitors are usually prescribed less-than-normal doses of Viagra because protease inhibitors can raise levels of Viagra several times greater than normal, which can cause dangerous side effects. Therefore, men who use protease inhibitors and Viagra may wish to also avoid taking Viagra with grapefruit juice.
The United States is the largest producer of grapefruit, accounting for over 40% of global production. Approximately 60% of the grapefruit crop is used for the manufacture of juice and canned grapefruit, while the rest is sold fresh.
High in vitamin C and potassium and a good source of folate, iron, calcium, and other minerals. Pink and red varieties are high in beta carotene, a precursor of vitamin A. High in fiber, low in calories. Grapefruit contain bioflavonoids and other plant chemicals that protect against cancer and heart disease.
Nutritional information per 100 g
Water - 91%
Protein - 0.6 g
Fat - 0.1 g
Carbohydrates - 8g
Fiber - 0.6 g
Calories - 30 to 33
The nutritional value of the grapefruit varies with the color (white, pink, or red). Red and pink grapefruits have a higher amount of vitamin A. Half a grapefruit provides more than 50 percent of the adult Recommended Dietary Allowance (RDA) of vitamin C; it also has 325mg of potassium, 25mcg (micrograms) of folate, 40mg of calcium, and l mg of iron. The pink and red varieties are high in beta carotene, an antioxidant that the body converts to vitamin A.
A cup of unsweetened grapefruit juice has 95mg of vitamin C, more than 150 percent of the RDA, and most of the other nutrients found in the fresh fruit.
Grapefruit stimulates the appetite and is used for its digestive, stomachic, antiseptic, tonic, and diuretic qualities.
Grapefruit and Weight Loss Diets
Over the years a number of people have promoted the grapefruit as possessing a unique ability to burn away fat. People following grapefruit diets lose weight because they eat little else-a practice that can lead to nutritional deficiencies.
Grapefruits, however, are a good food to include in a sensible weight-loss diet; a serving contains less than 100 calories, and its high-fiber content satisfies hunger. If you're trying to lose weight, make grapefruit your first course to help prevent overeating. It's also an ideal snack food.
Grapefruit and Cholesterol Control
Grapefruits are especially high in pectin, a soluble fiber that helps lower blood cholesterol.
Grapefruit for Cancer Control
Recent studies indicate that grapefruits contain substances that are useful in preventing several diseases. Pink and red grapefruits are high in lycopene, an antioxidant that appears to lower the risk of prostate cancer. Researchers have not yet identified lycopene's mechanism of action, but a 6-year Harvard study involving 48,000 doctors and other health professionals has linked 10 servings of lycopene-rich foods a week with a 50 percent reduction in prostate cancer.
Other protective plant chemicals found in grapefruits include phenolic acid, which inhibits the formation of cancer-causing nitrosamines; limonoids, terpenes, and monoterpenes, which induce the production of enzymes that help prevent cancer; and bioflavonoids, which inhibit the action of hormones that promote tumor growth.
Other Uses of Grapefruit
Some people with rheumatoid arthritis, lupus, and other inflammatory disorders find that eating grapefruit daily seems to alleviate their symptoms. This is thought to stem from plant chemicals that block Prostaglandins, substances that cause inflammation.
People who are allergic to citrus fruits are likely to react to grapefruits, too. The sensitivity may be to the fruit itself or to an oil in the peel.
Interactions With Drugs and Medicines
Grapefruit has serious interactions with many commonly prescribed medications. Grapefruit juice inhibits a special enzyme in the intestines that is responsible for the natural breakdown and absorption of many medications. When the action of this enzyme is blocked, the blood levels of these medications increase, which can lead to toxic side effects from the medications.
Grapefruit juice research has suggested that flavonoids and/or furanocoumarin compounds are the substances that act to block the enzyme in the intestines that normally metabolizes many drugs. The grapefruit juice-drug interaction can lead to unpredictable and hazardous levels of certain important drugs.
These medications should not be consumed with grapefruit juice unless advised by a doctor:
Statins (Cholesterol Lowering Drugs):- Baycol (Cerivastatin) - Mevacor (Lovastatin)
Lipitor (Atorvastatin) - Zocor (Simvastatin)
Antihistamines:- Ebastine - Seldane (Terfenadine, taken off the U.S. market)
Calcium Channel Blockers (Blood Pressure Drugs):- Nimotop (Nimodipine) - Nitrendipine -
Plendil (Felodipine) - Pranidipine - Sular (Nisoldipine)
Psychiatric Medications:- Buspar (Buspirone) - Halcion (Triazolam) - Tegretol (Carbamazepine) - Valium (Diazepam) - Versed (Midazolam)
Intestinal Medications:- Propulsid (Cisapride, taken off the U.S. market)
Immune Suppressants:- Neoral (Cyclosporine) - Prograf (Tacrolimus)
Pain Medications:- Methadone
Toxic blood levels of these medications can occur when patients taking them consume grapefruit juice. The high blood levels of the medications can cause damage to organs or impair their normal function, which can be dangerous. The following drugs may potentially have interactions with grapefruit juice, but this potential has not been scientifically studied. Use caution:-
Amiodarone (Cordarone) - Cilostazol (Pletal) - Donepezil (Aricept) - Losartan (Cozaar) - Montelukast (Singulair) - Pimozide (Orap) - Quetiapine (Seroquel)
Sildenafil (Viagra) - Tamoxifen (Nolvadex) - Tamsulosin (Flomax)
The information contained herein should not be construed as medical advice, nor is it intended as such. Any further information regarding your, or an individuals circumstances relating to any information herein should naturally be directed towards your general Practioner/pharmacist. This article is wholly provided for informational purposes only and is not a substitute for qualified medical advice from a medical professional.