Can a medicine become a poison?

It’s a winter night. You walk through snow-covered streets, accompanied by the satisfying crunch of each step. It is cold, but the joy of watching the snow masks the chill and you even dare to make a snow angel without fear of getting cold. After walking for a while, you start to feel like it is time to go back home. But who would go home without ending the day with a snowball fight? You throw a snowball right at your friend’s head without any warning and immediately hide behind the gray Jetta, it means a war! He throws one back but misses, Jetta is your shield! After ten minutes of relentless battle, you surrender after getting hit by cold, wet snowball under your shirt.

You are home now, mama is little angry, you walked outside in the cold and got a snowball under your shirt. She warns you with a firm tone, “You’ll wake up with a fever in the morning.”

Yes, it happened—Mama was right. You have a fever and can’t go to school now. Normally, that would be the good news, but today is the school trip to the car museum!

Mama says you need to take that orange syrup to get better and hands you a spoon. It tastes just like an orange juice. But how can an orange juice cure a fever? 

You ask, “if I drink the whole bottle, would I get completely better, and can go the car museum?”  

Mama laughs. “Would you like to get poisoned or what?” she says before heading to her room.

“Would you like to get poisoned or what!” you mimicked. “How mama could say something that silly, How can a medicine made to cure poison you and make you sick? If it’s meant to help, it can’t harm.” you thought…

But is that really true? Can something meant to help actually cause harm?

Before we answer that, let’s break it down: What exactly is a drug, and how does it work?

A drug is defined as a substance used for diagnosis, cure, treatment, or prevention of disease.¹ This means that any substance with these purposes can be considered a drug.

We have defined what a drug is. Now it’s time to talk about drugs’ action mechanisms. 

Every drug works differently, but we don’t need a full pharmacology lecture. Let’s focus on a few key concepts: half-life, plasma protein binding, drug-drug interaction, metabolism, elimination and bioavailability.

Half-life of a drug is the time it takes for its concentration in the body to decrease by half.  Longer the half-life, longer the drug stays in our body. There are several factors affecting the half-life of a drug; characteristics of drugs, plasma protein binding, efficiency of metabolizing organs and enzymes. Characteristic of drugs can be its size, charge, and affinity to bind plasma proteins. In a healthy person, half-life of a drug can be calculated, but if the patient has an enzyme deficiency, kidney or liver failure or using another drug, half-life would be affected and drug’s length of stay in the body will be changed which can render the drug less effective or make it toxic.²

Plasma protein binding is a factor that increases the half-life of a drug because plasma proteins are large and block filtration of drugs in kidneys and the drug stays longer in the blood.³

Drug-drug interaction happens when different drugs taken together and can potentially get each other’s metabolism altered by competing for the same enzyme or proteins leading failure of therapy and toxicity. Therefore, usage of multiple drugs should be done carefully.⁴

Bioavailability refers to the amount of a drug that reaches the bloodstream unchanged and ready to act. There are various mechanisms that can affect bioavailability such as route of administration, age, gender, protein binding etc. Drugs given intravenously, directly to the bloodstream via a needle, have a bioavailability of 100% as they reach to the blood without any interactions. However, it is not the case for the drugs taken orally such as pills. Oral drugs, however, must pass through the liver before reaching circulation, a process called the first-pass effect. Here, the liver’s CYP450 enzyme metabolizes portion of the drug, making it inactive, modifying its effect, or, even worse, turning it toxic.⁵ This is where things get tricky.

Now we know that even a drug designed to help can become toxic once interacted with our liver that is supposed to render harmful substances to harmless ones. Are we that defenseless against drug poisoning and is our liver backstabbing us? Of course not! Nothing has been overlooked in human body’s design. To address that, we have other enzymes that can detoxify those molecules. 

Let’s talk about one of the most commonly used drugs for headaches: Paracetamol. 

Paracetamol (aka acetaminophen) is first metabolised by the enzyme p450 in the liver that results in a molecule called  NAPQI which is toxic and should be detoxified. Toxic NAPQI is then, again in liver, conjugated to glutathione with the enzyme S-transferase and became a nontoxic compound. The final product is transformed into such a composition that it is no longer toxic and the kidneys can remove it easily in the urine.⁶

It shows us that it’s not just a single organ or an enzyme regulating the drugs, but rather a whole system together where each part relies on the others to maximize the benefits of drugs while preventing toxicity. The liver processes the drug, transforming it into a form that enzymes can further metabolize, and the kidneys can safely excrete, ensuring the body is free of toxins. 

So, main actors regulating and influencing the process of drug metabolism are the liver, enzymes, kidneys, plasma proteins and the drug’s characteristics. However, when these actors don’t play their role properly, a therapeutic drug can become toxic. People are all different and not everyone has a fully healthy liver or kidneys. Some individuals are born with enzyme deficiencies, while others experience age-related metabolic changes. In pediatric patients, certain enzymes are underdeveloped, whereas in geriatrics, enzyme activity may decline. Additionally, some people have to take multiple drugs which can interfere with each other’s metabolism and lead to toxicity.⁷

Now we know enough pharmacology to understand a real example.

This example will show us how a defective liver, kidney or lack of plasma proteins can turn a curative drug into a poison. Warfarin is an oral anticoagulant with a narrow theurapatic-index, meaning that small variations in dosage can cause toxicity—increased activity leads to excessive bleeding.⁸ Warfarin is found 97% bound to Albumin, a plasma protein produced by liver, which means that only 3% of the taken dose is active. In a patient with liver disease, albumin production decreases, resulting in less warfarin being bound to plasma proteins. Similarly, in kidney disease, excessive albumin loss through urine reduces the amount available in the bloodstream to bind drugs. As a result, the free (active) warfarin level increases, effectively doubling its anticoagulant activity for every 3% increase in free warfarin. Therefore, scientists concluded that low albumin levels increase the risk of major bleeding in patients on warfarin therapy.⁹

Have you ever thought about those key actors in your own life, do they play their roles right?

Is your liver functioning well? Are your kidneys efficiently removing drugs to avoid poisoning? Do you have enzyme deficiencies that puts you in danger against toxic substances?  Let’s find it out together.

You were watching the news together with your father when the reported said “The suspect is believed to be a foreign national.”

You commented “Why do they let foreigners in our country, they only cause harm to us!”

Your father, with an angry tone, replied, “How could you say such a thing! You cannot blame the whole foreigners because of a mistake of one! Would you like to be accounted for a crime someone else committed that you have nothing to with!”

You realized your mistake… Thank god your father was not like your friends at school, who are actively searching for foreigners’ mistakes just to use them as a tool for collective hatred—a poison for both themselves and the world.

After that day, you began to understand why your friends were so hateful toward foreigners, but you were not. Their parents were not showing them the right approach to such news! They were not playing their role correct! As a result, the news that was meant to inform people had become a toxic tool spreading hatred! 

Next day, you were at school, what a coincidence, teacher asked “Did anyone hear yesterday’s news?” 

Your classmate, sitting in the front row by the window, said “Yes, suspect was a foreigner. As always…”

Teacher was disappointed, she asked “Why would that matter? Would it be fair if someone in this class cheats in the exam and we punish you all?” 

Your classmate’s face turned red with shame. From that day on, he never spoke against foreigners again. You were grateful to have such a teacher, her simple explanation had prevented a future filled with hate. She was shaping the next generation, respected her position, and did what she was supposed to do.  

However, that wasn’t the case for the neighboring class… Their teacher was intolerant toward foreigners, and it was affecting the students negatively. Seeing the same news all day on every platform was like receiving a drug intravenously, making its bioavailability 100%. And their teacher, being the defective kidney, failed to filter out the news meant to inform. Instead, it became a poison for them. Things could have been different if the teacher had informed them about the risks of collective hatred.

All these events made you wonder “Do I, in any way, influence the ‘metabolism’ of those around me?”. The answer was yes. The neighbour’s kid next door, that friend on the school bus, your siblings, your football teammates—anyone you interact with.

We are all influencing each other without realizing it. We must constantly remind ourselves—and each other—to take the right path and make the right choices. That teacher could have remained silent to avoid potential conflict with the student, but that would have been a betrayal of her position. You can’t change every mistake or erase all flawed beliefs in a single day. But your courage and willingness to help others will make a difference over time.

To sum up, pharmacological principles apply not only to drugs but also to the ideas, ideologies, and news that we consume daily. And it is not only the liver, kidneys and enzymes that prevent drug poisoning but also our parents, teachers, neighbors, friends, and—ourselves. Some ideas are injected into us intravenously, reaching our minds at full strength through nonstop exposure on TV, radio, and social media. We must be vigilant and detect flaws in our own “metabolism” early to avoid getting poisoned. If our teacher or parents fail to protect us from harmful influences, we must seek out other protective sources such as safe online communities, books of trusted experts or open-minded friends and relatives who are willing to guide us with honesty and correct us when our ideas are wrongly shaped.

And finally, never forget: you have an influence on those around you, even if you don’t realize it. While it may not be an official duty, it’s your responsibility to help them avoid poisoning but benefit from things they are exposed to, just like a healthy liver does for the body...

REFERENCES

1. U.S. Food and Drug Administration. (2017). Drugs@FDA glossary of terms. U.S. Food and Drug Administration. Retrieved January 2025, from https://www.fda.gov/drugs/drug-approvals-and-databases/drugsfda-glossary-terms ↩︎
2. Brunton, L. L., Hilal-Dandan, R., & Knollmann, B. C. (Eds.). (2018). Goodman & Gilman’s The pharmacological basis of therapeutics (13th ed.). McGraw-Hill Education. ↩︎
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7. Brunton, L. L., Hilal-Dandan, R., & Knollmann, B. C. (Eds.). (2018). Goodman & Gilman’s The pharmacological basis of therapeutics (13th ed.). McGraw-Hill Education. ↩︎
8. Brunton, L. L., Hilal-Dandan, R., & Knollmann, B. C. (Eds.). (2018). Goodman & Gilman’s The pharmacological basis of therapeutics (13th ed.). McGraw-Hill Education. ↩︎
9. Kawai, M., Harada, M., Motoike, Y., Koshikawa, M., Ichikawa, T., Watanabe, E., & Ozaki, Y. (2019). Impact of serum albumin levels on supratherapeutic PT-INR control and bleeding risk in atrial fibrillation patients on warfarin: A prospective cohort study. International Journal of Cardiology: Heart & Vasculature, 22, 111-116. https://doi.org/10.1016/j.ijcha.2019.01.002 ↩︎