Can my medicine cause adverse reactions?
All medicines can cause adverse reactions. An adverse reaction means a harmful and other than intended effect caused by the medicine.
What kinds of adverse reactions can occur?
The types of adverse reactions vary among medicine groups. The most common adverse reactions caused by medicines are stomach or intestinal symptoms originating from the gastrointestinal tract, such as nausea, vomiting, diarrhoea, stomach pains, or constipation. Skin reactions are also common adverse reactions. Somewhat often occurring adverse reactions include symptoms originating from the nervous system, such as tiredness, headache, and dizziness.
Adverse reactions can be mild enough for the user to continue the medication. Adverse reactions are often at their worst in the beginning of the treatment but become milder in a couple of days and may even disappear altogether as treatment continues.
Adverse reactions that occur in the beginning of a treatment may be caused by the system not yet being accustomed to the medicine. Headache and nausea, for example, are general, mild and, as the treatment continues, transient adverse reactions when beginning the use of birth control pills and antidepressants, among others.
What causes adverse reactions?
It is not always easy to tell whether a symptom is caused by the illness being treated or whether it is an adverse reaction to the medicine.
An adverse reaction may most commonly be caused by a medicine's mode of action. Antibiotics, for example, kill both the bacteria that cause the illness and the body's own useful bacteria, such as intestinal bacteria. Diarrhoea may be caused by the elimination of the patient's own intestinal bacteria.
Sometimes, an adverse reaction may be caused by a medicine having a too strong effect. A beta blocker intended to moderate heart rate, for example, can lower heart rate too much. Some medicines have an effect on the body via the autonomic nervous system, in which case dryness of the mouth and eyes, slow heart rate, constipation, or blurriness of near vision, etc., may occur in addition to the therapeutic effect.
Some adverse reactions may be caused by a medicine having an effect in an undesired place, such as constipation caused by an adverse reaction to strong painkillers.
Adverse reactions may also occur when a medicine is used for too long. The use of nasal sprays that contract the mucous membranes of the nose on adults and over ten-year-olds for longer than ten days, and longer than five days on children between two and ten years of age, may damage the mucous membranes or maintain the congestion of the nose (for example, xylometazoline). You can also be allergic to the medicinal substance or an excipient of the medicine.
How can I avoid adverse reactions?
When you are prescribed a new medicine, let the doctor or nurse know all of your possible allergies to medicinal substances and your other medications. If an adverse reaction is caused by a medicine's too strong effect, reduction of the dose in consultation with the doctor may reduce the problems caused by the medication.
Also tell pharmaceutical personnel in the pharmacy about your other medications and your possible allergies to medicinal substances when buying over-the-counter medicines.
Before starting to take a medicine, ensure that you know how to use your medicine correctly.
What do I do if adverse reactions occur?
Find out whether the symptoms are related to the medication and whether they will possibly disappear as the treatment continues. You can check the possible adverse reactions caused by the medicine, for example, from the package leaflet or by calling the pharmacy. Find out whether you can do something about the adverse reaction. The use of lactic acid bacteria, for example, may help soothe your stomach when a course of antibiotics has caused a slight diarrhoea.
The acceptability of the adverse reactions caused by a medicinal treatment varies depending on the severity of the illness. In case of a serious illness, even severe adverse reactions caused by the medicine must sometimes be accepted.
You can discuss continuing or stopping the use of a medicine with a doctor or the pharmacy staff.
The Finnish Medicines Agency Fimea maintains a national adverse medicine reaction database into which doctors, dentists, pharmacists, Masters of Science (Pharmacy), and medicine users can report adverse reactions to medicines they have noticed or suspect.