Opioids for chronic pain

Opioids are drugs whose effects are similar to the opium found in the opium poppy. The classic representative of this class of drugs is the opium alkaloid morphine.
Opioids act in the central nervous system. There they mediate various effects, including the attenuation of incoming pain signals. Due to this property, opioids are often used to treat moderate to severe acute pain conditions (e.g. after operations or serious injuries).
Depending on the dosage, treatment with opioids can also be accompanied by side effects such as nausea, constipation, itching, increased sweating, drowsiness, confusion or respiratory depression.
The use of opioids is not without risk and should be under constant medical supervision. Opioids lead to physical dependence, i.e. abrupt discontinuation can lead to physical withdrawal symptoms. In addition, uncontrolled use can lead to psychological dependence in the sense of addiction.

A basic distinction must be made between cancer-related and non-cancer-related pain.
Opioids may have a place in the treatment of severe acute pain (e.g. after operations or serious injuries, for a few days to a few weeks), as well as in cancer-related pain. Chronic non-cancer pain should never be treated with opioids alone, if possible. The scientific data show that opioids are no more effective than other pain medications in this case. Before considering pain therapy with opioids, various other therapeutic measures should therefore already have been taken or at least tried (physical, physiotherapeutic, medicinal, interventional, psychological).
The use of opioids involves various risks, which can be significantly influenced by patient-specific factors (age, concomitant diseases, concomitant medication, etc.). In order to avoid serious complications, a detailed medical risk-benefit assessment is always necessary before starting pain therapy with opioids.

According to the German AWMF guideline on the use of opioids for non-cancer-related pain, pain therapy with opioids can be considered for the following indications:

• Pain in diabetic polyneuropathy
• Pain after shingles (post-herpetic neuralgia)
• Chronic osteoarthritis pain
• Chronic back pain
• Phantom limb pain
• Chronic pain after spinal cord injury
• Chronic pain due to nerve root damage
• Chronic pain in rheumatoid arthritis

If possible, the duration of treatment should be limited to 4 to 12 weeks. During this time, other treatment options should be evaluated and tried so that the use of opioids can be discontinued at a later date. Opioid therapy should only be continued for longer than 12 weeks if there is a clear, significant reduction in pain.

If there is uncertainty about whether opioid therapy should be attempted or continued for longer than 12 weeks, an intravenous opioid test carried out on an outpatient basis can be helpful. Through the recorded intravenous administration of a short-acting opioid, it is usually possible to find out whether a pain condition can be effectively treated with an opioid or not.

Treatment with opioids is NOT recommended for the following non-cancer-related pain conditions:

• Migraine
• Tension type headache
• Chronic lower abdominal pain
• Irritable bowel syndrome
• Fibromyalgia syndrome (possible exception: tramadol)
• Chronic inflammatory bowel disease (Crohn's disease, ulcerative colitis)
• Chronic pancreatitis
• Various psychiatric illnesses

Long-term use of opioids can result in the following undesirable effects:

• Loss of sexual desire
• impotence
• Severe tooth damage and even complete tooth loss
• Cycle disorders in women
• Increased overall mortality
• Passivity / Lack of motivation
• Memory disorders
• Increased risk of falling

Opioids lead to physical dependence. With the correct indication and dosage, as well as regular medical re-evaluation, the probability of addiction is low. However, if the indication is questionable and use is uncontrolled, there is a risk of psychological dependence in the sense of addiction.

Pain therapy with an opioid should be re-evaluated periodically and should only take place under regular medical supervision. If it is unclear whether treatment with an opioid is providing pain relief, efforts should be made to discontinue this treatment.
In cases of doubt, an intravenous opioid test carried out on an outpatient basis can make it easier to decide whether or not to continue treatment.

During the first 1 - 2 weeks of therapy, during the adjustment phase, when increasing the dose or when switching to another opioid, driving or operating machinery must be avoided. During this time, side effects are common, which limit the ability to react.
Alcohol should only be consumed with caution during treatment with opioids. Alcohol further impairs the ability to react, so driving should be avoided after drinking alcohol.

• Häuser W, et al., Clinical practice guideline: Long-term opioid use in non-cancer pain. Dtsch Arztebl Int 2014; 111: 732–40.
• Manchikanti L, et al., Opioids for Chronic Non-Cancer Pain: American Society of Interventional Pain Physicians (ASIPP) Guidelines. Pain Physician 2017; 20:S3-S92
• Gustorff B., Intravenous opioid testing in patients with chronic non-cancer pain. Eur J Pain. 2005 Apr;9(2):123-5.