Författare: Dipa Kamdar Senior Lecturer in Pharmacy Practice Kingston Un

One of the most popular new year’s resolutions is making a commitment to healthier eating. Whether that’s eating more fruits and vegetables, cutting down on meat consumption or even becoming a vegetarian or vegan a few days a week.

While there are many benefits that can come from following a healthier diet, it’s important that any diet changes are made carefully. This is especially true if you’re someone who takes a prescription drug, as many health food staples can negatively interact with them.

Here are some common foods and drinks interactions you should know about:

1. Grapefruit juice:

To break down some prescription drugs in the body, the liver uses enzymes called cytochrome P450. But grapefruit juice contains chemical compounds called furanocoumarins which can block the action of these enzymes. If this happens, some drugs can accumulate in the body.

This includes ciclosporin, a drug that’s commonly used to prevent organ transplant rejection and manage symptoms of rheumatoid arthritis and skin conditions such as psoriasis. A build-up of ciclosporin can cause many side-effects, ranging from mild nausea and vomiting to kidney and liver damage.

Statins, often used to treat high cholesterol levels and prevent heart attacks and strokes, can also be affected by grapefruit juice through the same mechanism. Increased statin levels in the body can raise the risk of side-effects, including muscle breakdown, which is rare but serious.

Many other drugs can potentially interact with grapefruit juice as well – including amlodipine (a common high blood pressure drug) and sildenafil (an erectile dysfunction drug). If you take any of these prescriptions drugs, it’s best to talk to your doctor or pharmacist before drinking even small amounts of grapefruit juice. It may even be best to avoid it altogether.

2. Pomegranate and cranberry juice:

Many fruits and fruit juices – especially from the citrus family – can affect the breakdown of drugs in the liver.

Pomegranate juice is also shown to block the liver enzymes which break down the anticoagulant drug warfarin. The drug is used to prevent blood clots from forming in people with heart arrhythmias such as atrial fibrillation or deep vein thrombosis.

Some reported cases suggest that pomegranate juice might increase the international normalised ratio (INR – the time taken for blood to clot) in patients taking warfarin. This means patients may be at higher risk of bleeding.

Pomegranate juice may also affect other drugs, such as tacrolimus, an anti-rejection drug used in organ transplants.

Similarly, a number of case reports suggest cranberry juice can also affect warfarin. There has been one reported death of a patient from bleeding after they had drunk cranberry juice for two weeks prior while taking warfarin.

But results from various studies are mixed – with some showing cranberry affects warfarin in the body while others don’t show any effect. Because of this, it may be worth checking the INR more often if you drink these juices or consider that any fluctuations in INR may be due to fruit juices.

3. Green leafy vegetables:

Spinach, broccoli and kale are often hailed as healthy foods because they’re filled with nutrients while being low in calories. However, they’re also high in vitamin K, which is needed to activate certain clotting factors (proteins in the blood which help it clot).

This may be problematic for patients taking warfarin. Warfarin works by blocking vitamin K in order to prevent blood clots from forming. But eating foods rich in vitamin K can lower your INR and increase the risk of developing a blood clot.

The vitamin K in leafy green vegetables, such as kale, may counteract warfarin.
masa44/ Shutterstock

It’s important to have a healthy diet – but be sure to monitor your INR levels or speak to your doctor if you do introduce more vitamin K-rich foods into your diet.

4. Milk:

Milk and dairy-rich foods such as cheese and yoghurt are all good sources of protein and calcium – a mineral required for healthy bones.

But these foods can affect the absorption of some drugs in the gut. This includes antibiotics such as some tetracyclines and ciprofloxacin. The calcium in the milk can bind to the antibiotic, meaning it cannot be absorbed into the bloodstream. This means the body will not get the full dose of antibiotic – making it harder for it to fight the infection.

Other drugs affected by dairy include levothyroxine, a drug used for patients with low thyroid levels.

But as these interactions happen in the gut, this means you can still have dairy even if you take these drugs. In most cases, you just need to leave at least a two-hour gap either before or after taking the drug before consuming dairy.

5. Beans:

Beans are considered healthy as they’re high in fibre and vitamins and minerals. Beans are also a great source of plant-based protein.

But soybeans, broad beans (fava beans) and snow peas may be high in tyramine. While tyramine is a substance naturally found in the body and in certain foods (such as aged cheeses, cured meats and fermented foods), it can interact with the antidepressant phenelzine.

Phenelzine is a monoamine oxidase inhibitor antidepressant (MAOI), which is less commonly used nowadays. The drug blocks enzymes which break down tyramine in the body. If patients eat tyramine-rich foods, this may result in high levels of tyramine, potentially leading to a dangerous rise in blood pressure. Only MAOI antidepressants, such as phenelzine, isocarboxazid, tranylcypromine, are affected by tyramine.

A healthy diet can improve your overall health in many ways. Just be sure to consult with a doctor of pharmacist before drastically changing your diet – particularly if you take prescription medications. Läs mer…

St John’s wort is an herbal supplement that has been used for centuries to boost mood. Even today, many people use it as a natural treatment for mild to moderate depression. St John’s wort contains several active compounds, such as hypericin and hyperforin, which are believed to influence mood.

Studies which have investigated the efficacy of St John’s wort have shown mixed results about its effectiveness for treating symptoms of depression. But while this treatment is not currently recommended by health authorities in the UK, many people still purchase the supplement from pharmacies and health food shops — seeing it as a more natural alternative to antidepressants.

But what people might not realise is that although it’s derived from a natural source, St John’s wort can have potentially serious interactions with other prescription drugs.

Here are six you should know about if you use this supplement:

1. Hormonal contraceptives

St John’s wort is known to have an effect on certain liver enzymes which break down drugs. The plant derivative can act as an enzyme inducer – increasing the clearance of hormonal contraceptives. This makes them less effective and increases the chance of pregnancy.

It’s recommended that people who use combined oral contraceptive pills, progestogen-only pills or the implant avoid using enzyme inducers – such as St John’s wort. The Medicines and Healthcare Products Regulatory Agency (MHRA) have also reported some cases of unplanned pregnancies in women using the implant and St John’s wort.

St John’s wort is not found to decrease the effectiveness of injectable progestogen contraceptives, the hormonal coil IUD and non-hormonal options, such as the copper coil.

2. Anti-depressants

There are different types of anti-depressants. The most commonly prescribed are selective serotonin reuptake inhibitors (SSRIs), such as citalopram and sertraline. Other anti-depressants include monoamine oxidase inhibitors (MAOIs) such as phenelzine, which are less commonly prescribed.

Both types of anti-depressants are thought to work by increasing the levels of chemicals in the brain called neurotransmitters. In particular, they’re thought to increase levels of the neurotransmitters serotonin and noradrenaline (norepinephrine), which are linked to mood.

It’s uncertain how St John’s wort works – but it’s thought it works in a similar fashion to anti-depressants by increasing levels of the same neurotransmitters.

Combining St John’s wort with these anti-depressant drugs may lead to excessive serotonin levels – increasing the risk of serotonin syndrome. This is a relatively uncommon but serious reaction. It can cause mild symptoms – such as confusion, muscle twitching and sweating – as well as life-threatening symptoms, including seizures and irregular heartbeat.

3. Anti-migraine drugs

Triptans, such as sumatriptan, are sometimes used as an alternative to painkillers in the treatment of migraines.

The exact cause of migraines is not fully understood but may be partly linked with temporary widening of blood vessels in the brain. Triptans target the serotonin receptors on these blood vessels, causing them to narrow. This may help alleviate migraine symptoms.

St John’s wort also mimics serotonin.
Shidlovski/ Shutterstock

As triptans work by mimicking serotonin, combining them with St John’s wort can lead to excessive serotonin levels, increasing the risk of serotonin syndrome.

4. Anti-epileptic drugs

Since St John’s wort is a liver enzyme inducer, theoretically this may cause it to breakdown anti-epileptic drugs – such as carbamazepine and phenytoin. This means they could be less effective, and put people at risk of seizures.

There has also been a reported case where a patient experienced more frequent, severe seizures when taking St John’s wort with a type of anti-epileptic that was not initially thought to interact with the herbal supplement. As such, the current advice from the MHRA is to avoid using St John’s wort if you take an anti-epileptic drug.

5. Warfarin

Warfarin is the most commonly prescribed anti-coagulant drug in the UK. It’s often used to prevent blood clots from forming in people with heart arrhythmias (such as atrial fibrillation or deep vein thrombosis).

But some clinical evidence suggests St John’s wort induces the same liver enzymes that break down warfarin. This could make warfarin less effective and raise the risk of clotting.

Preferably, patients should avoid using St John’s wort if they take warfarin. If they do take them together, they should have their INR (international normalised ratio – the time it takes for blood to clot) checked regularly to reduce risk of clots or bleeds.

6. Anti-retroviral drugs

Some anti-retroviral drugs used to treat HIV (such as lopinavir/ritonavir and efavirenz) are metabolised by liver enzymes. Many are also moved in and out of cells by pumps called P-glycoprotein. But St John’s wort can induce the same liver enzymes and pumps as these drugs, which reduces the amount of these anti-retroviral drugs in the body. This can raise the viral load in an infected person’s blood.

While a small study showed no significant interaction with St John’s wort and the liver enzymes involved in metabolising these drugs, this finding was based on a preparation of St John’s wort that contained low levels of hyperforin. Since some preparations have higher levels of hyperforin, it’s important future research investigates whether these types have any significant effect. If you take anti-retroviral drugs and do decide to use St John’s wort, it’s important you have your viral load levels checked regularly.

There are other drugs that can potentially interact with St John’s wort, too. These include erectile dysfunction drugs, some opioid painkillers and immunosuppressants. It’s important to consult a doctor or pharmacist before taking St John’s wort – especially if you take other prescription drugs. Läs mer…