**1. Introduction**

Acute and chronic pain is a complex disease process that can be difficult to treat. Despite new developments in medications and technology, nonsteroidal antiinflammatory drugs (NSAIDs) and opioids are among the most widely prescribed medications in the world [1, 2]. In addition to NSAIDs and opioids, adjunctive pharmacologic agents to include antidepressants, cannabinoids and ketamine have increased in popularity. This chapter aims to review commonly prescribed pain medications with a focus on their classification categories, mechanisms of action, and major side effect profiles.
