Medication and tablets that won’t work properly if you take them with coffee

We have become a nation of coffee drinkers, sipping our way through 500 cups each year.

But when reaching for that first one in the morning, many of us also see it as a good time to take our medications — and that’s not always a good thing.

Researchers have found that coffee can affect how some medicines are absorbed, broken down and removed from the body, sometimes with serious consequences.

BLOOD PRESSURE PILLS

If you are one of the quarter of UK adults with high blood pressure, you might also rethink taking your anti-blood pressure medication alongside your morning coffee.

‘’Caffeine narrows blood vessels by blocking adenosine receptors, which are responsible for causing them to widen, which can raise blood pressure,’’ explains Professor Parastou Donyai, chief scientist at the Royal Pharmaceutical Society.

‘’This can work against medicines prescribed for high blood pressure.’’

The effect is short-lived, but it can also distort blood pressure readings. Dr Natalie Rout, a GP based in London, adds: ‘’I’d recommend avoiding coffee completely with blood pressure medications. and [if you do drink it, wait one to two hours after having coffee before measuring your blood pressure, to ensure an accurate reading.’’

THYROID DRUGS

Caffeine increases the contraction of muscles that move food through the gut, which means drugs can move too quickly before they can be absorbed.

This is a problem for people taking the thyroid hormone drug levothyroxine, prescribed to treat an underactive thyroid (hypothyroidism) — the drug is absorbed through the layer of barrier cells lining the gut.

Taking it with coffee can reduce the amount of levothyroxine taken up, because of the increased rate at which it passes through the gut.

‘‘Take your thyroid drugs in the morning on an empty stomach and wait an hour before you drink coffee,’’ Dr Rout says.

Taking it at night is also an option — a 2022 study found that levothyroxine was just as effective when taken at bedtime, hours after eating.

HEARTBURN MEDICATION

Millions of Britons take omeprazole for indigestion, heartburn and acid reflux — but caffeine cancels the desired effects of the medication, says Dr Rout.

Omeprazole is a proton pump inhibitor, meaning it stops cells in the stomach lining from producing too much acid.

Reducing the amount of acid in turn reduces acid reflux symptoms and can also prevent stomach ulcers.

Caffeine on the other hand stimulates the secretion of hydrochloric acid.

‘’Take the omeprazole on an empty stomach, and consider stopping the coffee altogether because hopefully then you don’t need to go on the medication at all,” advises Dr Rout.

However, she adds, caffeine may not be the culprit: ‘‘As well as caffeine, several things can make acid reflux worse: smoking, alcohol, spicy food, fruit juice and fizzy drinks. Sometimes it takes trials of elimination to determine what the causative factors are.’’

BLOOD THINNERS

One medication that people should be extra wary of taking with coffee is the blood thinner warfarin, especially for older people. as Dr Rout explains: ‘’Every drug is metabolised by the body in a particular way, and many are metabolised in the liver by something called the P450 system enzymes in the body involved in drug metabolism.

Drugs either induce or ‘inhibit’ the P450 system.

‘’Caffeine is also metabolised by the P450 system so interacts with certain medications, such as warfarin, causing an increase in the availability of the drug.’’

Increased levels of the blood thinner mean it takes blood longer to clot, which raises the risk of bleeding.

‘‘I advise taking warfarin with water — not coffee — to avoid increasing the risk of bleeding,’ says Dr Rout.

DEPRESSION PILLS

The P450 process is also why you might want to rethink taking antidepressants such as fluvoxamine (a type of selective serotonin reuptake inhibitor, or SSRI) with your coffee (The effect has not been well studied with other SSRIs, such as Prozac.)

Fluvoxamine blocks the P450 enzyme, which lengthens the amount of time it takes to clear caffeine from the body.

The same process can also counteract the desired effects of ADHD medications, and lead to agitation. As Professor Donyai explains: ‘‘Caffeine is a stimulant so speeds up the central nervous system, increasing your heart rate and blood pressure, and combining it with stimulant drugs used for aDhD can increase the side effects of the medication.’’

These also include irritability and anxiety.

SUPPLEMENTS

It’s not just prescription drugs that people should think about — some over-the-counter medications can also interact with coffee.

Caffeine prevents the release of a compound called antidiuretic hormone, which, in turn, leads to more urine being produced.

This is because antidiuretic hormone controls the amount of water released by the kidneys. Caffeine prevents the release of this compound, resulting in a greater production of urine.

As a result, important minerals and vitamins, including B vitamins, magnesium and calcium, can be expelled in urine. Coffee can also reduce the absorption of iron (by forming a compound with it that is insoluble, so iron cannot be absorbed by the gut) — so doctors recommend having a gap before tea or coffee after taking iron supplements.

SOME DRUGS WORK BETTER WITH IT

HEADACHES: Combining the painkillers aspirin and paracetamol with caffeine

can make them more effective.

In a study in 1986, scientists in Thai land found that drinking the equivalent of two cups of coffee alongside aspirin led to more of the drug being absorbed. and, in 2019, researchers in Malaysia discovered that caffeine interacted through the P450 system to increase levels of paracetamol in the body.

Debbie Shipley, Head of Information and Support Services at The Migraine Trust, says: ‘‘Caffeine acts by inhibiting an enzyme called cyclooxygenase which mediates inflammation and pain at some sites and works by blocking certain receptors in the brain called adenosine receptors, which may help to relieve migraines.’’

Ms Shipley adds that it is important to be consistent with your caffeine consumption, as caffeine can be a trigger for migraines.

So if you are taking extra caffeine via your painkillers, you should adjust your coffee and tea intake, by drinking less.

MOVEMENT DISORDERS: Surprisingly, coffee may reduce dyskinesia, a movement disorder that is characterised by uncontrolled shakes, tics or tremors, caused as a side-effect of the Parkinson’s drug levodopa.

Studies have shown that the effect can be produced by one and a half cups of coffee a day.

Michael Schwarzschild, a professor of neurology at Harvard Medical School, said: ‘‘Evidence in people and mice shows that caffeine can block act ion at brain receptors called adenosine a2a receptors, which can prevent dyskinesia.’’

‘’This means caffeine may reduce the risk of developing dyskinesia in Parkinson’s if paired with levodopa from the start — but this needs to be tested in a clinical trial’.’

The bottom line?

‘‘Generally, take medication with a glass of water and wait an hour before any caffeinated drink,’ advises Dr ROut.