Does Grapefruit Affect Blood Pressure Medications?

Normally, consuming grapefruit is good for the body, as this fruit is rich in vitamins and helps fortify the immune system. It contains both vitamin C and potassium, which are great for the optimal functioning of your body. If you have taken a liking to grapefruit, you'd normally be right in concluding that it's a great addition to a very healthy and balanced diet. 

Grapefruit and the human body

Grapefruit juice actually indirectly amplifies the effect of many medications. This poses a risk, as doctors prescribe specific daily doses to meet your medical needs. When a drug is present in the body in a quantity higher than the recommended dose, it also causes more intense side effects.

The human body produces an enzyme called CYP3A4, located in the small intestine. This enzyme helps the body to break down (metabolize) many different kinds of medications. Consuming grapefruit, whether the whole fruit, its juice, or any product that contains it, the normal functioning of the CYP3A4 enzyme is blocked, causing a lower metabolization of the drugs. Consequently, a drug metabolized with the help of CYP3A4 will stay in your body for longer, in stronger quantities.

Scientists have discovered that the quantity of CYP3A4 in the body varies from person to person, so the effects of grapefruit juice will also vary from one person to another. There have been a lot of studies conducted on the interaction between grapefruit and medicines. While the fruit causes some drugs to stay in the body for a longer period of time, it has an opposite effect on some other drugs.

For instance, if you’re taking medication that contains fexofenadine, grapefruit juice will prevent the required amount of drug from entering the blood stream, thus minimizing its efficiency. This happens because grapefruit juice can also interfere with drug transporters, which are proteins that help our bodies absorb the drugs by moving them to the cells.

What kinds of medication negatively interact with grapefruit?

Grapefruit doesn’t interact with just every type of medication out there. However, the FDA has required that medical companies specify any potential interactions on their labels, especially for over the counter drugs.

Some of the following drugs are known to interact negatively with grapefruit:

• Some medications prescribed for arrythmias, such as amiodarone
• Certain (but not all) anti-anxiety medications, with buspirone being the prime example
• Drugs to prevent organ rejection after a transplant.
• Corticosteroids that are prescribed to treat ulcerative colitis, Crohn’s disease, and many other conditions
• Calcium channel blockers or angiotensin inhibitors which are used as high blood pressure treatment.
• Antihistamines, used for allergies.
• Medication prescribed to lower cholesterol levels, specifically statins.

Medication for lowering blood pressure and grapefruit: What do you need to know?

Some of the most common blood pressure meds include:

• Calcium channel blockers, to prevent calcium buildup in the heart and artery cells.
• Renin inhibitors, which are meant to block the production of renin (a kidney enzyme that is linked to an increase in blood pressure).
• ACE inhibitors, pills that cause the blood vessels to relax and prevent the release of angiotensin (a hormone that is known for narrowing blood vessels and preventing blood from circulating normally).
• Beta blockers, which block the effects of epinephrine (adrenaline), causing the heart to beat at a slower rate.
• Angiotensin II receptor blockers which, unlike ACE inhibitors, don’t prevent angiotensin formation, but rather block it from acting upon the blood vessels by narrowing them.
• Diuretics, which are often referred to as water pills, and remove excess sodium and water from your organism, as fluid build-up is a threat to your blood pressure.
• Aldosterone antagonists, which prevent a hormone called norepinephrine from narrowing your arteries.
• Central-acting agents that act on your brain to make sure that it doesn’t tell your heart to beat faster.
• Vasodilators that, such as the name hints, will cause your blood vessels to dilated, facilitating blood flow.

As far as the calcium channel blockers are concerned, these meds are prescribed to high blood pressure patients who need to have their artery muscles relaxed, as constriction of these vessels prevents blood from circulating normally. Calcium channel blockers are among the most frequently-prescribed hypertension drugs.

Losartan and eplerenone are prescribed for patients that have too much angiotensin in their bodies, causing high blood pressure. Losartan interacts with grapefruit juice by diminishing its effects and rendering it useless.

On the other hand, eplerenone levels will greatly increase when it interacts with grapefruit juice. It causes your potassium levels to rise as well, thus interfering with your heart’s rhythm. Alternatively, doctors may choose to prescribe spironolactone, which is a drug that acts similarly to eplerenone and losartan, without any grapefruit juice interactions.

As far as calcium channel blockers are concerned, an alternative is amlodipine, which is just as efficient as felodipine and nifedipine, but without grapefruit juice interactions.

Conclusion

One of the lifestyle changes recommended by doctors is to eat healthy food that increases your potassium levels, and grapefruit is very rich in potassium, making it an excellent dietary choice for many people. If you like to consume grapefruit or its juice, but you have been prescribed a medicine that interacts with it, consult with your doctor to see if they can prescribe a safer alternative. Of this is not possible, you do need to stay away from grapefruit for the sake of your health. 

If you are currently taking a regular prescription medication and you aren't sure whether grapefruit is safe for you, you can always ask your doctor.