What are the most common opioid painkillers and how do they work?

Prescription drugs containing opioids are intended for short-term relief of acute pain, for example after surgery, and for treating patients at the end of life. These include tramadol, codeine, oxycodone, morphine, methadone and fentanyl. According to guidelines from the National Institute for Health and Care Excellence, they should not be used to treat long-term chronic primary pain. Opioid drugs travel through the blood and bind to opioid receptors in our brain. This blocks feelings of pain, increases feelings of pleasure and can reduce the anxiety and stress caused by pain.

According to the NHS, the side effects of opioid painkillers include excessive sleepiness, confusion and constipation. They make breathing shallower and slower and less responsive to increased oxygen demand. They have a negative effect on the immune system. And they also affect hormone levels and the way they keep the body and mind in balance. Some people may become more sensitive to pain (hyperalgesia) when taking opioid medication.

Why are they addictive?

Dr Lars Williams, anaesthetist and pain specialist at NHS Greater Glasgow & Clyde Pain Service, explains in a forthcoming edition of Pain Matters magazine that we all produce our own opioids (endorphins) which act on the opioid receptors found throughout the body’s pain system. However, because opioid painkillers are much stronger than the opioids our bodies produce, the first time you take a drug from the morphine family, the effect is very strong. With each subsequent use, the effect wears off as the opioid receptors become less sensitive, so increasingly higher doses are required. This leads to physical dependence and causes more pain and withdrawal symptoms when the dose is reduced or stopped.

What are the signs of addiction?

They vary from patient to patient but include taking larger and larger doses when the body no longer accepts the existing dose for pain relief and demands the next dose; withdrawal symptoms when the prescription has expired; and the inability to reduce the dose. Withdrawal symptoms may include heart palpitations, panic attacks, nausea, pain, sweating, and tremors.

I just had surgery and was prescribed codeine. How do I avoid becoming dependent?

Your doctor should explain how to take your medicine safely. Read the directions on the pack and do not exceed the stated dose or for how long you are taking it. If you continue to have pain, make an appointment with your GP to discuss how to relieve your symptoms.

What should you do if you think you are too dependent on opioid prescriptions?

If you need support with problems related to prescription medicines, speak to your GP or contact WithYou, a drug, alcohol and mental health charity. You can speak to a trained counsellor for free and in confidence using the webchat service at wearewithyou.org.uk.