Pain pharmacology: focus on opioids.

The incidence of chronic pain is estimated to be 20-25% worldwide. Although major improvements in pain control have been obtained, more than 50% of the patients reports inadequate relief. It is accepted that chronic pain, if not adequately and rapidly treated, can become a disease in itself, often intractable and maybe irreversible. This is mainly due to neuroplasticity of pain pathways. In the present review I will discuss about pain depicting the rational for the principal pharmacological interventions and finally focusing on opioids, that represent a primary class of drug to treat pain.