Do not mix grapefruit juice and Viagra pills!
Everyone knows that the natural juices are very helpful. But one of them hit the doctors in the "black list" - namely grapefruit. In the U.S. even started to check all medications for compatibility with it. Especially dangerous to combine grapefruit juice with Viagra.
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 medications affected by grapefruit juice include the following:
– beta blockers — Cardizem (diltiazem)
– sedatives/sleeping pills — Halcion (triazolam), Versed (midazolam)
– transplant drug — cyclosporine (Neoral, Sandimune)
Now it appears that grapefruit juice can also affect the absorption of the popular erectile dysfunction drug Sildenafil (Viagra). Because erectile dysfunction is common in some males with HIV/AIDS, we report on the interaction between grapefruit juice and Viagra pills.
Study details
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.
Results
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 more than 40% of world production. About 60% of grapefruit crop is used for the production of juices and canned, and the remainder grapefruit is sold fresh.
Safety
It is not recommended to take grapefruit juice with drugs, because it increases the concentration of active substance in the blood stream and thus cause the effect of overdose. In addition, people who are allergic to citrus react to grapefruits, too. The sensitivity may be to the fruit itself or to an oil in the peel.
Everyone knows that the natural juices are very helpful. But one of them hit the doctors in the "black list" - namely grapefruit. In the U.S. even started to check all medications for compatibility with it. Especially dangerous to combine grapefruit juice with Viagra.
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 medications affected by grapefruit juice include the following:
– beta blockers — Cardizem (diltiazem)
– sedatives/sleeping pills — Halcion (triazolam), Versed (midazolam)
– transplant drug — cyclosporine (Neoral, Sandimune)
Now it appears that grapefruit juice can also affect the absorption of the popular erectile dysfunction drug Sildenafil (Viagra). Because erectile dysfunction is common in some males with HIV/AIDS, we report on the interaction between grapefruit juice and Viagra pills.
Study details
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.
Results
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 more than 40% of world production. About 60% of grapefruit crop is used for the production of juices and canned, and the remainder grapefruit is sold fresh.
Safety
It is not recommended to take grapefruit juice with drugs, because it increases the concentration of active substance in the blood stream and thus cause the effect of overdose. In addition, people who are allergic to citrus react to grapefruits, too. The sensitivity may be to the fruit itself or to an oil in the peel.
