O coffee It is a drink present in many people's routine. Despite offering benefits, such as promoting more energy and energy for the day, caffeine can have some side effects when consumed in excess or when mixed with other substances. In fact, that's why medicines should not be taken with coffee .
One study published in 2020 in the scientific journal BioMed Research International showed that taking certain medicines with coffee It can affect how they work in the body. According to research, the drink can improve the therapeutic response of some medications, but may inhibit the action of other drugs . But how does this happen, exactly?
According to Moacyr Luiz Aizenstein, professor at the Department of Pharmacology at ICB-USP (Institute of Biological Sciences at the University of São Paulo), a medicine administered orally goes through several stages in the body until it enters the bloodstream and reaches its target. “Caffeine can interfere with all these processes when taken together with the medication and, most of the time, the effect is not positive, that is, it is harmful”, he says to CNN .
Which path does the medicine take through the body?
To understand how caffeine can impair the functioning of a medication, it is necessary to understand how the drug acts in the body. In general, a medicine can be administered in different ways: oral, intravenous, subcutaneous and intramuscular, for example. The most common way is oral, through tablets or drops.
When ingested, the medicine goes through different stages in the body. The first of them is the absorption process , which starts in the stomach, moving to the upper part of the small intestine. At this point, it is disintegrated from the pharmaceutical form (tablet) and the active ingredient dissolves, so that it is released to move on to the next stage. It then goes to the liver until it reaches the bloodstream.
“This absorption is partial, not everything that is absorbed is used. Normally, in the case of oral medicines, the bioavailability [o que é aproveitado do fármaco] It varies from 30%, 50% and 70%, depending on the characteristics of the medicines”, explains Aizenstein.
Once in the bloodstream, the medicine is distributed throughout the body, including its target (such as receptors, ion channels or enzymes), where it will have a therapeutic effect. The drug then goes back to the liver, where it is metabolized, that is, transformed into another compound (metabolite), facilitating its excretion through the kidneys.
In a didactic way, the last phases are called pharmacodynamics (when the drug-target interaction occurs) and pharmacokinetic phase (characterized by the path that the drug takes in the body), as explained by Michelle Fidelis Correa, professor of the pharmacy course at Universidade Cruzeiro do South, to CNN .
“It is worth highlighting that there are factors that can influence and/or change all of these phases, such as routes of administration, pharmaceutical forms, particular characteristics of each organism, as well as drug interactions”, he states.
What happens to the medicine when it is taken with coffee?
When the medicine is taken with coffee, caffeine can positively or negatively influence the entire route that the drug takes in the body . This can enhance or minimize its effect, causing variable consequences.
“Caffeine, like any other molecule, can interact with other substances. This interaction can lead to changes in the processes mentioned above and significantly affect the effect of the medicines”, says Correa.
The professor exemplifies that caffeine can modify the absorption of drugs, by altering the dissolution profile and gastrointestinal pH. Consequently, she impairs the absorption of certain medications It is reduces its therapeutic effects .
Another negative effect can be observed in the metabolization stage by the liver. According to Aizenstein, some types of drugs are metabolized by the same enzymes that act on caffeine. “This causes competition between them, because, often, there are not enough enzymes to metabolize both substances. As a result, drugs or caffeine will inhibit metabolism”, he explains.
The main risk in this scenario is the increased concentration of the drug in the bloodstream which can enhance its effect to levels that are not foreseen in the leaflet . “Caffeine can increase, for example, the concentration of warfarin in the body, which is an anticoagulant, increasing the risk of bleeding”, says the professor. “This happens with other substances too, such as methotrexate, which is an anti-inflammatory, and some types of antipsychotics used to treat schizophrenia”, he adds.
What medicines should not be taken with coffee?
According to experts consulted by CNN , there are several medications that interact with caffeine and, therefore, it is important to be aware of which medication you use. “In general, medications that are metabolized by cytochrome P450 (CYP450) enzymes have important interactions that must be considered,” says Correa.
“Caffeine is mainly metabolized by these enzymes, and can play a competitive role with other drugs and impact the rate of metabolism. The induction or inhibition of these metabolizing enzymes can result in a failed therapeutic response, intensification of side effects or even toxicity”, adds the professor.
Furthermore, some other types of medicines have their effect impaired by the action of caffeine and can pose health risks. This is the case of:
- Antidepressants : medications for depression may have their absorption in the stomach and small intestine impaired by caffeine;
- Anxiolytics : caffeine, as it has a stimulating action and promotes the action of neurotransmitters such as dopamine and adrenaline, reduces the therapeutic effect of medications used to treat anxiety;
- Antipsychotics: reduces the therapeutic effect of medications used to treat schizophrenia by affecting absorption by the stomach and intestine, in addition to impairing the drug's metabolism in the liver;
- Levothyroxine : medicine used to treat hypothyroidism whose absorption is affected by caffeine and, therefore, must be taken on an empty stomach.
Furthermore, some vitamins and minerals may have their absorption affected by caffeine. The study published in BioMed Research Internationalfor example, mentions that “iron absorption is reduced between 39% and 90% when drinking a cup of coffee or other caffeinated drinks” and, therefore, the drink should not be ingested together with foods rich in iron or vitamin supplements.
According to Aizenstein, the absorption of vitamin D can also be impaired by caffeine. “This is very serious, as vitamin D deficiency is one of the causes of osteoporosis and the literature has already shown that elderly people who drink a lot of coffee may be at greater risk of this disease,” he says.
What medications can have the effect enhanced by caffeine?
On the other hand, there are some medications that can have their effect enhanced by caffeine. This happens mainly because the substance can increase the absorption and bioavailability of drugs, increasing their concentration in the body.
According to experts consulted by CNN among the medications whose effects are enhanced by caffeine are analgesics, non-steroidal anti-inflammatory drugs, muscle relaxants, diuretics and central nervous system stimulants.
Source: CNN Brasil
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