Side effects of medicinal products

In addition to their desired effect, medicinal products usually also have side effects. However, these do not always have to occur. Whether side effects occur depends on the properties of the medicinal product and patient-specific factors, for example.

At a glance

  • Side effects are harmful and unintended reactions to a medicinal product.
  • There are a number of factors that affect how well people tolerate a medicinal product.
  • Information about side effects can be found in the package insert.
  • If side effects occur, especially serious ones, it is best to seek medical advice. Such side effects should be reported to the relevant authorities.
  • Reporting side effects improves patient protection.
Part of a package insert with several tablets lying on it. The sentence “What side effects are possible?” is enlarged by a magnifying glass.

What are side effects?

Side effects are harmful and unintended reactions to a medicinal product or medication. Side effects can be known or unforeseen. If the type, severity or result of side effects deviates from the product information about the medicinal product, they are described as unexpected.

Differentiation is also made between non-serious and serious side effects. Serious side effects are side effects that

  • are fatal or life-threatening
  • result in a need for inpatient treatment or the prolongation of inpatient treatment
  • lead to permanent or serious disability
  • cause birth defects

Important: Most side effects are not classed as serious. They are usually minor issues, for example temporary gastrointestinal problems or reddened skin.

What causes side effects?

Medicinal products have certain effects on the body. The desired effect on a specific area or process in the body may be undesirable elsewhere. For example, cortisone suppresses the immune system thereby reducing allergic reactions or autoimmune reactions (desired effect). At the same time, however, it makes people more susceptible to infections with pathogens (undesired effect).

Different levels of tolerance

In general, all medicinal products not only have a desired effect but also undesired effects, i.e. side effects. However, these do not always occur and do not affect everyone. Whether or not a side effect occurs depends on various factors, for example on the patient’s underlying or accompanying conditions or even on the use of other medicinal products. While one person can tolerate a medicinal product well and not have any side effects, another may find that it causes side effects. Hereditary predisposition and gender can also play a role here.

All medicinal products have side effects. However, these do not always occur and do not affect everyone.

Certain hereditary factors can affect the breakdown of medicinal products

Whether or not side effects occur can, for example, depend on differences in certain liver enzymes (CYP enzymes), which are responsible for breaking down medicinal products. In some people, certain genetic factors lead to the body breaking down some active substances more slowly. This makes them more prone to side effects.

Gender differences

Differences can also exist between the way men and women metabolize and break down a medicinal product. This can mean that different doses should be used depending on a person’s gender. Such gender-specific aspects are being increasingly taken into account in modern medicine.

Where can information about side effects and their prevalence be found?

All known side effects and their prevalence are listed in the package leaflet (package insert) and the specialist information for doctors. Prevalence information is divided into several categories, ranging from “very common” to “very rare”:

  • very common: more than 1 in 10 people
  • common: 1 to 10 in 100 people
  • uncommon: 1 to 10 in 1,000 people
  • rare: 1 to 10 in 10,000 people
  • very rare: less than 1 in 10,000 people
“Very common” means that a side effect is experienced by more than one in ten people.

What should people do in the event of side effects?

If minor, temporary side effects occur after taking medication, you can first wait and see what happens. You can also check the package insert for information about the effect.

In the event of more prolonged side effects or side effects that are getting worse, medical advice should be obtained – even if the symptoms are only mild. In the event of severe symptoms, you should instantly contact a doctor or, in an emergency, the emergency services on 112.

Reporting side effects

Doctors are obliged to report side effects. However, patients can also choose to report them. Information about how to do this can be found in the package insert. This should not be done without medical consultation however. A doctor usually has the necessary information to assess whether the medication taken could cause the symptom.

Reporting to the responsible authorities

Side effects can be reported to the responsible authorities. Depending on the type of medicinal product, this can be the Federal Institute for Drugs and Medical Devices (BfArM) or the Paul Ehrlich Institute (PEI). The easiest way to report side effects is online.

Alternatively, side effects can be reported to the relevant authorities by telephone.

Reporting to the authorization holder

Side effects can also be reported to the authorization holder. This is usually the pharmaceutical company indicated on the packaging. The relevant contact details can be found in the package insert.

Important information

The following information is important when reporting a side effect:

  • Information about the person who experienced the side effect (for example age and gender)
  • A description of the side effect
  • The dose and name of the medicinal product suspected to have caused the side effect (trade name and active substance name)
  • The batch details of the medicinal product (these can be found on the packaging)
  • All other medicinal products taken/injected at the same time (including over-the-counter medicinal products, herbal medicinal products and contraceptives)
  • All of the health problems of the person who experienced the side effect

Important: It is advisable to start by discussing any serious and/or unexpected side effects with a doctor. They can then be reported to the relevant authority (BfArM or PEI).

What measures protect patients?

Side effects that were already identified in clinical trials prior to a medicinal product being authorized are subjected to a benefit-risk assessment during the authorization procedure. However, medicinal products are also continually monitored for new, previously unknown risks of use and side effects following their authorization. New findings are therefore also incorporated into the ongoing benefit-risk assessment. This enables the authorities to respond quickly and reasonably with appropriate measures.

Examples of potential measures include:

  • an order requiring the manufacturer to perform further trials on the safety of the medicinal product
  • restrictions on the use of a medicinal product
  • additional training material with recommendations for patients on what they should do in the event of a side effect – identifiable by the blue hand symbol
  • additions or changes to the package insert and specialist information

Red hand letters notify medical professionals 

It can take a while for the package insert and specialist information to be updated. Despite this, doctors and pharmacists should be notified about new findings as quickly as possible. This is where red hand letters come in. These are sent to medical professionals by the authorization holder in consultation with the relevant authorities and provide information about new usage risks as well as the measures that can be used to minimize them.

The benefit must outweigh the risk

As a general rule, the benefit of a medicinal product must outweigh the risks of its use. If the benefit is extremely great – for example because the medicinal product cures the patient of cancer – more severe side effects are justifiable. On the other hand, headache tablets or cough medicine should only have very mild side effects. The same applies to medicinal products used to prevent illnesses, for example vaccines.

Important: If, after authorization, it is found that the risks of a medicinal product outweigh its benefits after all, the authorization can be temporarily withdrawn or permanently revoked to protect patients.

In cooperation with the Federal Institute for Drugs and Medical Devices (BfArM).

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