What are opioids?

Opioids (sometimes called opiates) are medicines used to treat pain. Many doctors will start off prescribing a weak painkiller such as Tylenol (acetaminophen) or Advil (ibuprofen). If these do not work, depending on the type of pain you have, your doctor may consider prescribing an opioid.

Opioids are usually divided up into two groups:

  • Weak opioids - include codeine, dihydrocodeine, and tramadol. 
  • Strong opioids - include oxycodone, morphine, fentanyl, hydromorphone, buprenorphine, and methadone.

    Opioids can differ a lot in strength. The stronger ones may be ten times stronger than the weakest. Strong opioids are usually prescribed for more severe types of pain - for example, if you have had an operation or have been injured in a car accident. They may also be considered for people who have long-term (chronic) pain, when other painkillers have not worked. They are also often used for pain in people with cancer.

How do opioids work?

Opioids work by binding to certain receptors (opioid receptors) in the central nervous system (brain and spinal cord), the gut and other parts of the body. This leads to a decrease in the way you feel pain and your reaction to pain and it increases your tolerance for pain.


Opioids, when taken for a long time, can cause tolerance, dependence and addiction. 

Tolerance: if you have been taking opioids for a long time, they do not work as well as they did in the beginning. You may need a higher dose to treat your pain. This is called tolerance.

Dependence: if you gradually become more tolerant of the opioid, you may become dependent on it. This is NOT the same as addiction. It means that if you miss a dose, or stop the opioid suddenly, you may have withdrawal symptoms. You may need to keep taking the medicine to avoid the withdrawal symptoms. Dependence is treated by a planned gradual reduction in the opioid medicine. The dose is gradually reduced in such a way that your body can become used to it, so that you do not experience withdrawal symptoms. This does not mean you are addicted to the opioid.

Addiction: this is an excessive craving for the opioids. There is uncontrollable and compulsive use of the medicine. People who are addicted still have cravings for the opioids even after they have reduced them slowly so that they are no longer dependent. Some people are more likely to develop addiction than others and seem to be particularly sensitive to the cravings.


Withdrawal symptoms: these occur if you have developed a physical dependence to opioids as above and then stop taking them suddenly. Withdrawal symptoms include:

  • Feeling anxious or agitated
  • Not sleeping (insomnia)
  • Sweating
  • Muscle pains
  • Feeling sick (nausea) or being sick (vomiting)
  • Diarrhea
  • Tummy cramps
  • Yawning