Grapefruit–drug interactions

grapefruit interacts with the effects of some drugs

The grapefruit, a popular citrus fruit, and its juice, have long been noted for their potential to interact with a wide array of drugs, resulting in either diminished or enhanced effects of the medications. The count of drugs known to interact adversely with grapefruit has been steadily growing, with 85 identified interactions as of May 2014. Understanding these interactions is vital to both the pharmaceutical industry and healthcare providers.

Mechanism of Interaction

The primary culprits behind grapefruit's ability to modulate drug effects are organic compounds known as furanocoumarin derivatives. These compounds inhibit the action of the cytochrome P450 enzyme isoform CYP3A4, which is found in the hepatic and intestinal systems. This enzyme plays a pivotal role in drug metabolism, and its inhibition can significantly alter the bioavailability and clinical effect of various drugs.

Furthermore, bioactive compounds present in grapefruit juice can interfere with other transport proteins like P-glycoprotein and organic anion transporting polypeptides (OATPs). Such interference can either enhance or diminish the absorption and consequent effects of numerous drugs.

Of interest is the pomelo, the Asian fruit crossed with an orange to give rise to the grapefruit. It also contains substantial amounts of furanocoumarin derivatives. However, some hybrid varieties of grapefruit-pomelo have been developed with minimal to non-existent furanocoumarin content. There is even a commercially viable seedless type of this hybrid.

Drugs Affected by Grapefruit

The following drugs have been identified to interact with grapefruit due to the inhibition of CYP3A4:

Benzodiazepines: triazolam (Halcion), orally administered midazolam (Versed), orally administered nitrazepam (Mogodon), diazepam (Valium), alprazolam (Xanax) and quazepam (Doral, Dormalin).

Amphetamines: certain varieties such as dextroamphetamine and levoamphetamine have been noted to interact with grapefruit.

Antiretroviral drugs: ritonavir (Norvir) is particularly affected due to CYP3A4 inhibition which prevents its metabolism.

Antidepressants: sertraline (Zoloft and Lustral) can have altered effects in the presence of grapefruit juice.

Further in-depth information is provided on Amphetamines:

Amphetamines and Grapefruit

Amphetamines are a class of stimulants that can interact with the Cytochrome P450 CYP2D6 enzyme, which is affected by grapefruit. In particular, dextroamphetamine and levoamphetamine have interactions related to this enzyme.

The primary mechanism involves the fact that grapefruit and its juice inhibit the action of CYP2D6, leading to a potential increase in the plasma concentrations of these amphetamines when they are consumed with grapefruit or grapefruit juice. An increase in plasma concentration may intensify the therapeutic effects of these amphetamines but can also increase the risk of side effects.

Patients who are on amphetamines or are considering starting them should consult with their healthcare provider regarding potential interactions and the consumption of grapefruit or grapefruit juice.

See Also

• List of foods that may interact with medications
• Drug interaction

External Links

• FDA: Grapefruit Juice and Some Drugs Don't Mix
• Grapefruit-Drug Interactions Can Be Deadly, Study Suggests
• Hybrid grapefruit safe for prescription meds

Grapefruit–drug interactions Resources
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