The object of this thesis is to review the pharmacology of opioids as drugs of abuse. It focuses on the pharmacology of opioids, its antagonist, naloxone, and their use in the current rise in opioid related overdoses. Opioids are still an important part of pain management and WHO still recommends them in certain cases. Their abuse potential is however very high and an increase in their use has resulted in an increase in opioid related deaths worldwide. A number of risk factors have been associated with opioid abuse showing that careful consideration is needed before prescribing them as analgesics.