Each person reacts differently to drugs. Some people benefit significantly from a particular medication, while others experience side effects with symptoms that can range from mild to fatal. According to estimates, approximately 7% of patients suffer from severe adverse reactions and about 0.4% suffer fatal consequences. Adverse reactions to drugs are the fifth most frequent cause of death in the Western world. In most cases, these reactions are determined by inherited genetic variations or interactions between certain drugs.

The path of drugs through our body

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If a drug is taken or injected with a needle, it first enters the bloodstream, through which it reaches the target organ. The drug is recognized by certain enzymes that break it down and remove it from the bloodstream. This causes most drugs to lose their effect. The deactivated drug is then filtered out of the blood with the help of the kidney and finally excreted with urine.

Long-term Drug Treatment

Due to the fact that many drugs operate over a long period of time, they need to be taken in regular intervals to ensure that the amount of the drug in the bloodstream is kept in the correct range.


This is how the drug always remains at the right concentration and shows its intended effect.

Genetic defects inhibit the break down of the drug

pharmaco sensor Unfortunately, many people. enzyme-producing genes that are crucial in this process.

The drug still enters the blood circulation and has its effect, but enzymes do not break it down and it remains in the body for a significantly longer period of time. This is only a minor problem after only one dose, but when a person takes warfarin three times a day, the level of warfarin in the blood gradually increases until it leads to toxic side effects.

The problem with the regular administration of a drug when there is a genetic defect

In the case of blood thinners, drug action is at the right level at the beginning of therapy, but the concentration of the drug rises constantly with every administration until it reaches to the point of causing uncontrolled bleeding.

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This means that 20% of the population that carries a genetic defect needs a significantly lower dose of warfarin because the usual dose could lead to serious adverse reactions.

Prodrugs, the precursors of active drugs

Some drugs, so-called “prodrugs”, are taken in an inactive form and are only activated by the enzymes of the body. Examples for this kind of drugs include the cancer prevention drug tamoxifen and the painkiller codeine.
A prodrug enters the bloodstream in its inactive form. Enzymes in the blood transform it into its active form, and then it takes effect. For example, the painkiller, codeine is transformed into If morphine in this way and then relieves pain.

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In some people, the enzyme that converts a specific prodrug into a drug does not function, so that the drug never has an effect on the body, other than potential side effects.

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In the case of codeine, there is no pain relief after taking the drug and an alternative drug needs to be chosen. In the case of tamoxifen, a drug that prevents the emergence of breast cancer, the drug’s ineffectiveness will only be discovered if cancer develops.

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