Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Pain that persists longer than 3 to 6 months is considered chronic pain. Chronic pain affects a large amount of the world population and it is an extensive public health problem. Pathogenesis of chronic pain is still not completely clarified. It is considered to be the result of different neuroplastic processes, especially central senzitation, a phenomenon of hyperexcitation of central neurons caused by a repetitive stimulus from afferent neurons. Chronic pain occurs in various conditions, and can be of malignan or non malignan etiology. Drugs are largely used for chronic pain treatment. The treatment is usually planned according to the WHO’s three step ladder. In the first stage nonopioid analgesics are indicated (paracetamol, NSAID, acetylsalicylic acid) but if the pain persists the therapy proceeds to the second stage involving weak opioids (codeine, tramadol, pentazocine...) in combination with or without non opioid analgesics. The last, third stage, involves usage of strong opioids (morphine, fentanyl, buprenorphine...) in combination with non opioid analgesics. Through the whole therapy scheme adjuvant drugs may be used, such as anticonvulsants, antidepressants, local anesthetics and corticosteroids.