4 days ago
Coffee warning: Just one cup could trigger alarming effects for millions on common medication
A pharmacist has warned that drinking coffee can be harmful for thousands of people who take common medications.
This includes those on thyroid medication, SSRI antidepressants, drugs for ADHD and even over-the-counter decongestants for cold and flu.
The energy-boosting drink can also make life-saving heart medication less effective, increasing the risk of a deadly irregular heartbeat, according to pharmacy expert at Kingston University, Dipa Kamda.
While in other cases, caffeine can interact with prescription drugs, causing a range of debilitating symptoms such as insomnia, headaches, fast heart rate, raised blood drowsiness, confusion, and even stomach bleeding.
'While your morning brew might feel harmless, it can interact with certain medicines in ways that reduce their effectiveness, or increase the risk of side-effects,' warned Dipa Kamda, writing for The Conversation.
'From common cold tablets to antidepressants, caffeine's impact on the body goes far beyond a quick energy boost.
'Coffee may be part of your daily routine, but it's also a potent chemical compound that can influence how your body processes medicine.'
Caffeine is a stimulant that speeds up activity in your brain and nervous system, she explained.
Popular cold and flu medicines, like Sudafed, contain a decongestant called pseudoephedrine, which also has stimulant properties.
If you combine this with the caffeine in coffee, the effects can be amplified, causing jitters, restlessness, headaches, fast heart rate and insomnia.
Combining caffeine with pseudoephedrine can also raise blood sugar and body temperature, particularly important for people with diabetes, studies have found.
With many cold medications already containing added caffeine, drinking coffee can increase the risks further.
The risk also applies to those taking stimulant medications to treat ADHD, like amphetamines, or asthma drugs such as theophylline, which has stimulant properties.
The pharmacist warned: 'Using them together may increase the risk of side-effects such as a rapid heartbeat and sleep disruption.'
There is also added caffeine in some branded over-the-counter painkillers, such as those containing paracetamol or aspirin.
Drinking coffee can speed up how quickly the drugs are absorbed and while this helps them work faster, it can be dangerous.
Pseudoephedrine is a decongestant found in dozens of cold and flu medicines on the shelves
'It could raise the risk of side effects like stomach irritation, or bleeding,' said Ms Kamda.
'[Although] no serious cases have been reported, caution is still advised.
Drinking coffee while taking some types of medicines to control irregular heart rhythms (arrhythmias) or blood pressure is known to make them less effective.
However, Ms Kamda added those with heart conditions don't have to stop drinking coffee entirely, but may want to 'consider limiting intake or switching to decaf'.
If you drink coffee immediately before or after taking thyroid medication like levothyroxine, studies have found absorption of the drug can fall by up to 50 per cent.
This can cause symptoms of hypothyroidism, such as fatigue, weight gain and constipation, to return 'even if you're taking your medicine correctly,' she explained.
It is recommended those taking the medication should wait 30 to 60 minutes before eating or drinking coffee.
However, this is most common with tablet forms of levothyroxine, and less likely with liquid forms, Ms Kamda pointed out.
This timing rule also applies to a class of medications used to treat osteoporosis and other bone conditions called bisphosphonates, including alendronate and risedronate.
It can also make the most commonly prescribed type of antidepressant, selective serotonin inhibitors, for example sertraline and citalopram, less effective, lab studies have found.
And drinking coffee with the older and less commonly used tricyclic antidepressants (TCAs), such amitriptyline or imipramine, can tirgger side effects.
The pharmacist, with 17 years experience, explained: 'TCAs are broken down by the liver enzyme CYP1A2, which also metabolises caffeine.
'The competition between the two can slow drug breakdown, increasing side-effects, or delay caffeine clearance, making you feel jittery or wired longer than usual.'
The problematic ingredient in coffee, caffeine, can also be found in a cup of tea, a can of Coca Cola, and even in green tea.
The pharmacist added: 'Everyone metabolises caffeine differently. Some people feel fine after three cups, while others get side-effects after just one.
'Pay attention to how your body responds and talk to your pharmacist or GP if anything feels off.
'If you're ever unsure whether your medicine and your coffee are a good match, ask your pharmacist or doctor.
'A short conversation might save you weeks of side-effects or reduced treatment effectiveness, and help you enjoy your brew with peace of mind.'
