In this master thesis the pharmacological properties of nonsteroidal anti-inflammatory drugs are described. More specifically are described OTC drugs, such as acetylsalicylic acid, ibuprofen, naproxen, and paracetamol. Nonsteroidal anti-inflammatory drugs are used to treat the pain of various etiologies, inflammations, fever, rheumatoid diseases. They are one of the oldest medicines at all, often purchased outside the pharmacy and applied irrationally, without the recommendation and control of healthcare professionals. They (non)selectively inhibit the enzyme cyclooxygenase (two isoenzymes COX1 and COX2), in that way they reduce prostanoid formation: prostaglandin, prostacyclin and thromboxane, which is the basis of analgesic, antipyretic and anti-inflammatory effects, but also various side effects. The use of nonsteroidal anti-inflammatory drugs is most commonly associated with gastrointestinal, cardiovascular and renal side effects. On the other hand, selective COX-2 inhibitors show less gastrointestinal side effects, but more cardiovascular. Particular attention should be paid to vulnerable groups of patients, such as children, pregnant women and breastfeeding women, as well as older people. Pharmacist by talking to a patient, monitoring therapy, and counseling on choosing "right" medicines contribute to effective and safe self-medication and can prevent the possible unwanted consequences of irrational drug use.