If prescription opioid users continue to use opioids at greater quantities and longer time periods than intended, they may begin to develop anxious hunger for these feelings of euphoria and relaxation leading to substance dependence. Psychologically, users crave the drug and want to consume it despite being aware of the negative consequences. Physiologically, the body experiences negative symptoms in the absence of opioids—a phenomenon known as acute opioid withdrawal syndrome.

Both craving opioids and fearing withdrawal often leads to taking more drugs than were prescribed, which leads to a tolerance. As tolerance develops, users’ brains become less responsive to the drugs and they seek out ways to hasten or enhance the desired effect. This includes taking dangerously higher doses, using different substances with “higher” impact (such as heroin), or employing different methods of ingestion such as snorting or intravenous injection. These behaviors indicate an escalating pattern of prescription drug abuse that may result in overdose death.