A health expert has warned anyone taking one of a number of common medications - some available without prescription - should avoid drinking coffee. Coffee can interact with certain

medicines in ways that reduce their effectiveness or increase the risk of side-effects, according to Dipa Kamdar, Senior Lecturer in Pharmacy Practice at Kingston University. Even common

drugs like over-the-counter painkillers or pills for a cold can react badly with coffee and potentially cause serious problems. Dipa said: "From common cold tablets to antidepressants,

caffeine’s impact on the body goes far beyond a quick energy boost. Tea also contains caffeine but not in the same concentrations as coffee, and doesn’t seem to affect people in the same

asthma treatments and ADHD medications, as caffeine can amplify side-effects. "If you’re on antidepressants, antipsychotics, or blood pressure drugs, discuss your caffeine habits with

your doctor. Consider reducing intake or choosing a decaffeinated option if you experience side-effects like restlessness, insomnia or heart palpitations. "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." Dipa listed the drugs that could interact with coffee in a potentially dangerous way, including rapid

heartbeat, sleeplessness, drowsiness, confusion, stomach irritation and bleeding. 1. COLD AND FLU MEDICINES Caffeine is a stimulant, which means it speeds up the central nervous system.

Pseudoephedrine, a decongestant found in cold and flu remedies such as Sudafed, is also a stimulant. When taken together, the effects can be amplified – potentially leading to jitters or

restlessness, headaches, fast heart rate and insomnia. Many cold medications already contain added caffeine, increasing these risks further. Some studies also suggest that combining caffeine

with pseudoephedrine can raise blood sugar and body temperature – particularly important for people with diabetes. Stimulant effects are also a concern when combining caffeine with ADHD

medications such as amphetamines, or with asthma drugs such as theophylline, which shares a similar chemical structure to caffeine. Using them together may increase the risk of side-effects

such as a rapid heartbeat and sleep disruption. 2. THYROID MEDICATION Levothyroxine, the standard treatment for an underactive thyroid, is highly sensitive to timing – and your morning

coffee can get in the way. Studies show that drinking coffee too soon after taking levothyroxine can reduce its absorption by up to 50%. Caffeine speeds up gut motility (the movement of food

and waste through the digestive tract), giving the drug less time to be absorbed – and may also bind to it in the stomach, making it harder for the body to take in. These effects reduce the

drug’s bioavailability, meaning less of it reaches your bloodstream where it’s needed. This interaction is more common with tablet forms of levothyroxine, and less likely with liquid

formulations. If absorption is impaired, symptoms of hypothyroidism – including fatigue, weight gain and constipation – can return, even if you’re taking your medicine correctly. The same

timing rule applies to a class of osteoporosis medications called bisphosphonates, including alendronate and risedronate, which also require an empty stomach and around 30-60 minutes before

food or drink is taken. 3. ANTIDEPRESSANTS AND ANTIPSYCHOTICS The interaction between caffeine and mental health medications can be more complex. Selective serotonin reuptake inhibitors

(SSRIs), such as sertraline and citalopram, are a type of antidepressant medication widely used to treat depression, anxiety and other psychiatric conditions. Lab studies suggest caffeine

can bind to these drugs in the stomach, reducing absorption and potentially making them less effective. Tricyclic antidepressants (TCAs), such as amitriptyline and imipramine, are a class of

older antidepressants that work by affecting the levels of neurotransmitters in the brain. They were among the first antidepressants developed and are less commonly used today, compared

with newer antidepressants such as SSRIs, due to their potential for more side-effects and higher risk of overdose. 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. Clozapine, an

antipsychotic, is also processed by CYP1A2. One study showed that drinking two-to-three cups of coffee could increase blood levels of clozapine by up to 97%, potentially increasing risks

such as drowsiness, confusion, or more serious complications. 4. PAINKILLERS Some over-the-counter painkillers, such as those containing aspirin or paracetamol, include added caffeine.

Coffee can speed up how quickly these drugs are absorbed by accelerating how fast the stomach empties and making the stomach more acidic, which improves absorption for some medications such

as aspirin. While this may help painkillers work faster, it could also raise the risk of side-effects like stomach irritation or bleeding, especially when combined with other sources of

caffeine. Though no serious cases have been reported, caution is still advised. 5. HEART MEDICATIONS Caffeine can temporarily raise blood pressure and heart rate, typically lasting

three-to-four hours after consumption. For people taking blood pressure medication or drugs that control irregular heart rhythms (arrhythmias), this may counteract the intended effects of

the medication. This doesn’t mean people with heart conditions must avoid coffee altogether – but they should monitor how it affects their symptoms, and consider limiting intake or switching

to decaf if needed.