Concerns about pain medicines

Pain is almost always manageable. But some people may not want to take pain medicines because they are scared of side effects, addiction or losing control. Some people also hold certain beliefs about pain medicines that make them worry about taking these drugs.

Side effects

Some pain medicines can cause side effects. The most common side effects are drowsiness, constipation, nausea, vomiting and dry mouth. Some of these side effects may go away after you take the drugs for a period of time. Other side effects might not go away. The healthcare team can help with managing side effects by changing the medicine or dose or by treating the side effect.


Many people fear that taking pain medicines can lead to addiction. Taking pain medicine regularly is very different from addiction. A key part of addiction is a mental dependence on the drug. This happens when the need to take a drug becomes a craving or an impulse that is more than just physical. Addiction to pain drugs while they are being used to treat cancer pain is not common.

The body can get used to some drugs if they are taken for a long period of time. This is called physical dependence and it is a normal physical response. When it’s time to stop taking pain medicines such as opioids the healthcare team will slowly lower the dose so that the body has time to adjust.

Losing control

Some people may worry about losing control, getting a mental high or not being aware of what’s going on if taking pain medicines. When prescribed painkillers are taken properly, they don’t cause a mental high or loss of control.

Pain medicines, opioids in particular, can make you feel sleepy or cause changes in mental alertness when they are first taken or when the dose is increased. This side effect is not part of addiction or psychological dependence, and it usually goes away within a few days. Drowsiness can also be caused by the body needing to catch up on rest now that the pain is under control.

Pain medicines affect everyone differently. Talk to the healthcare team if pain medicine is still causing drowsiness or changes in mental alertness after taking it for 3 days. The healthcare team will make sure that the dose of the pain medicine is just enough to keep the pain under control. Sometimes adjusting the dose or changing the type of painkiller can help lessen drowsiness or changes in mental awareness.

Believing that pain medicines will not work when needed

Sometimes the body will get used to a drug so that a higher dose is needed for it to work. This is known as drug tolerance. When someone develops a tolerance to a pain medicine, they may worry that it will not work when they really need it. Drug tolerance usually doesn’t happen with medicines used to treat cancer pain. If it does, the healthcare team can adjust the dose slightly or prescribe a different type of medicine.

Believing that pain medicines will shorten life

Some people think that using an opioid like morphine will shorten their life. This is not true. Using opioids regularly to control pain doesn’t damage internal organs or cause permanent side effects. In many cases, these stronger drugs are needed to control pain and they can be used for a long time. In fact, there is some evidence that people live longer when their pain is better controlled.

Expert review and references

  • American Cancer Society. Pain control: a guide for those with cancer and their loved ones. Atlanta, GA: American Cancer Society; 2011.
  • American Cancer Society. Cancer Pain. 2015.
  • American Society of Clinical Oncology. Managing Cancer-Related Pain: A Guide for Patients, Families and Caregivers. 2017.
  • Cancer Research UK. Cancer and pain control. Cancer Research UK; 2014:
  • National Cancer Institute . Cancer Pain (PDQ®) Health Professional Version . 2017 :
  • Watson P, Watt-Watson J . Pain medications . Canadian Pain Society and Canadian Pain Coalition . Pain Resource Centre . 2012 .

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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