Introduction:
Due to the growing number of registered medicinal products, it is important to know about their mechanisms of action and adverse side effects. This also applies when diagnosing an otorhinolaryngology patient. The aim of this study was to review the literature and summarise various active substances and their relevant adverse effects.

Material and methods:
Available literature data and summary of product characteristics were analysed. The following adverse reactions were studied: dizziness, hoarseness, oral candidiasis, pharyngitis, ototoxicity, painful swelling of the salivary glands, nasal congestion, dysgeusia, nosebleeds, tinnitus, dry nose, and difficulty swallowing. To classify adverse reactions the MeDRA classification was used.

Results:
A list of individual adverse reactions and active substances that may cause them was prepared, along with the mechanism of causing a given adverse reaction. Dizziness was found to be caused by the largest number of drugs analyzed. The most severe adverse effects were irreversible ototoxicity (e.g., caused by intravenous aminoglycoside antibiotics) and embryotoxicity.

Conclusions:
Adverse effects of medicinal substances important in otorhinolaryngology, audiology, and phoniatrics are multifactorial, but knowledge of them is necessary to make a correct diagnosis.