ELI5. Grapefruit juice and the effects on mental health medication?


To me it’s interesting that grapefruit juice is listed as a “no no” while taking antidepressants/anti-anxiety medication.

I’ve looked into it and I still don’t understand. Can someone explain why you aren’t supposed to mix them? I’m only asking because I like a good Ruby Grapefruit White Claw once and a while…

In: 20

Anticoagulants are medicines that help to prevent blood clots. They’re given to people at high risk of getting clots, to reduce their chances of serious conditions such as strokes and heart attacks.

Do not drink grapefruit juice if you’re taking warfarin. It can increase the effect of warfarin on your blood, making you bleed more easily.

It’s safer to drink grapefruit juice if you’re taking the newer anticoagulants rivaroxaban, dabigatran, apixaban or edoxaban.

Antiplatelet medicines
Antiplatelet medicines prevent platelets (a type of blood cell) from sticking together and forming blood clots. They help to prevent heart attacks and strokes.

Do not drink grapefruit juice if you’re taking the antiplatelet medicine clopidogrel, as it may mean your medicine works less effectively.

If you’re taking ticagrelor, grapefruit may increase the effects of your medicine and make you bleed more easily.

You do not need to avoid grapefruit if you’re taking dipyridamole or low-dose aspirin.

Ciclosporin and immunosuppressants
Ciclosporin, sirolimus and tacrolimus are medicines that moderate your immune system (the body’s natural defence system).

If you’re taking any of these medicines, do not drink grapefruit juice without consulting your doctor.

Entocort is a medicine that contains budesonide and is used to treat Crohn’s disease, a condition that affects the digestive system.

Do not eat grapefruit or drink grapefruit juice while you’re taking this medicine, as the level of budesonide in your blood will increase.

Cytotoxic medicines
Some medicines used in the treatment of cancers may interact with grapefruit juice. You should check with your doctor before drinking grapefruit juice.

Other medicines
This list is not exhaustive and there are a number of other drugs that may interact with grapefruit. The risk of experiencing the effect of a drug interaction as a result of grapefruit can vary a lot from person to person.

For more information check the patient information leaflet that comes with your medicine, or you can ask your pharmacist

Something about how grapefruit juice interacts with the body causes the body to absorb chemicals more quickly, loosely speaking, than otherwise. It’s not a steady effect, or well understood, but it seems likely we’ll eventually figure out how to control it so you can take less medication and amplify it with grapefruit juice. For now, combining them can make your drugs hit you much harder than they should, with the accompanying negative effects.

Edit its lots of drugs, not just psychological medicine

Eating grapefruit or drinking grapefruit juice can affect some medicines. In most cases, it increases the level of the medicine in your blood. This can increase the risk of side effects or alter the effect the medicine has.

If your usual diet includes grapefruit or grapefruit juice and you’ve been prescribed a medicine that’s affected by grapefruit, speak to your GP or pharmacist. Do not stop taking your medicine without advice.

Medicines affected by grapefruit
Statins are medicines that lower your cholesterol. Grapefruit or grapefruit juice affects some statins.

Do not drink grapefruit juice if you’re taking simvastatin. Grapefruit juice increases the level of simvastatin in your blood and makes side effects more likely.

Atorvastatin interacts with grapefruit juice if you drink large quantities (more than 1.2 litres daily), but an occasional glass is thought to be safe.

Currently, healthcare professionals advise it is safe to drink grapefruit juice and eat grapefruit if you’re taking other types of statins.

Calcium channel blockers
Calcium channel blockers are medicines that relax the muscles that make up the walls of your arteries. They’re used as part of the treatment of conditions such as high blood pressure (hypertension) and coronary heart disease.

Grapefruit juice interacts with some calcium channel blockers and increases the level of the medicine in your blood. If you’re taking any of the medicines below, seek advice from your pharmacist or doctor if you wish to include grapefruit or grapefruit juice in your diet.

Grapefruit juice does not affect diltiazem.

Your liver has an enzyme called cytochrome P450 enzyme 3A4. This enzyme is important in modifying and breaking down a lot of chemicals and is taken into account when determining dosage of some drugs.

Graprefruit juice has a chemical in it that inactivates this enzyme.

So, if you drink grapefruit juice, you might overdose or take the wrong dose of some drugs because the dose is planned with the enzyme activity taken into account.

So, you have to avoid grapefruit juice when on some specific drugs.

Medications are dosed assuming a certain percentage of them flat out won’t work – your body will process some of them and kick them out prior to them entering the bloodstream. One of the ways it does this is with the use of certain enzymes. The problem is that grapefruit juice interacts with the enzyme, and if its tying up all the enzyme when you take a pill, it can’t intercept part of the medicine. Since the dosage is made assuming the enzyme will block some of it and it no longer does, you end up with a far higher dose than intended. For mental health medication, this is a REALLY big problem – these drugs tend to have a narrow effective range vs. the range where they start having too many negative effects, and even if they don’t, your doctor needs to know how much you are actually getting so they can adjust your dosage.

Weirdly enough, there are some other drugs where grapefruit juice has the *opposite* effect for other reasons. In these cases, the grapefruit juice is affecting proteins which transport the drug into your bloodstream. Disrupt those, and you end up with *not enough* drug.

Grapefruit juice is not the only food/drink that can cause these problems, but it’s certainly one of the more notable ones.