An opioid is a potent analgesic drug used to treat severe pain. Opioids are derived from the opium poppy plant and produce the effect of dulling the senses and sometimes inducing sleep.
Opioids are highly effective in treating back pain for less than two weeks to treat post-operative pain or severe acute episodes of low back pain. After the initial two weeks, the body rapidly builds a natural tolerance to opioids and they lose their effectiveness.
Sometimes opioids are used to treat chronic pain as well. Side effects of opioids use can include impairment of mental function and drowsiness, constipation, and possibly addiction.