Pain is a very individual experience. It is related to actual or potential damage of tissue and includes displeasing emotions. Pain can be decreased or increased by many things. Analgesics are drugs that help to alleviate pain without loss of consciousness. Opioid analgesics were originally obtained from the opium plant. There are three groups of opioid analgesics that interact with opioid receptors to bring pain relief. The first group is the opioid agonists. These drugs stimulate the activity of opioid receptor sites in the body. The second group, the opioid agonistsantagonists, obstruct some receptor sites and stimulate others. These drugs are less addictive than the opioid agonists. The last group, the opioid antagonists, reverse the effects of the opioids and are given for opioid overdose. This chapter will also discuss the nonopioid analgesic, acetaminophen (Tylenol). This drug has both antipyretic and analgesic properties. It is often found in combination with opioid agonists.