Medical Cannabis as a treatment option

Chronic pain

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Overview

What is Chronic Pain?

Chronic pain is pain that lasts for longer than three months. It can be caused by a past injury or an ongoing medical condition such as arthritis or diabetes. Sometimes people have chronic pain without a clear reason.

Chronic pain often lasts longer than the issue that first caused it. This is due to long term changes in the nervous system. Pain caused by nerve damage is called neuropathic pain.

Causes

Pain is part of the body’s normal response to injury. When a part of the body is damaged, nerve cells in the area send a signal to the brain through the spinal cord. The brain then translates this signal into the sensation of pain. Normally, the signal stops when the injury has healed, however in chronic pain the signal often continues.

Some health conditions that cause chronic pain include:

  • Arthritis
  • Back problems
  • Previous injury or surgery
  • Migraine
  • Endometriosis
  • Infections
  • Fibromyalgia
  • Multiple sclerosis
  • Nerve damage from diabetes (diabetic neuropathy)
  • Cancer

In some cases, chronic pain occurs without an obvious cause.

Symptoms

Chronic pain can affect any part of the body. The pain may be there all the time or it may come and go.

Pain feels different for each person. Some people describe their pain as stabbing, burning, tingling or like “pins and needles”. Other people have aching, dull pain.

Pain can be throbbing or constant. Intense pain can cause nausea.

Some people with chronic pain find it hard to move certain parts of their body. They could have reduced strength, flexibility and stamina. Others have stiffness, swelling, cramps or spasms.

Complications

People with chronic pain may find it difficult to socialise and and carry out day-to-day activities such as working, bathing, cooking and exercise.

Chronic pain is a source of emotional distress, leading to depression and anxiety.

Some people with chronic pain have difficulty getting to sleep or may wake from sleep because of pain. This can cause changes in sleep patterns and fatigue.

Established Treatments

It is not always possible to get rid of chronic pain completely. Treatment focuses on “pain management” rather than “pain cure”. The goal is to minimize the effect of pain on a person’s life.

Treatment of chronic pain is highly individualised. Although tests and imaging are used, results are often normal in people with chronic pain. Doctors consider a number of factors when choosing a treatment plan, including:

  • Physical examination
  • Pain characteristics
  • Impact of pain on daily activities
  • Previous and current treatments
  • Any other symptoms

They may use just one type of treatment or combine several different therapies. In many cases, doctors work with other healthcare professionals in a team to treat chronic pain.

Medicines for Chronic Pain

Painkillers used for chronic pain include:

  • Paracetamol
  • Non steroidal anti inflammatory drugs (NSAIDs) e.g. ibuprofen, aspirin, naproxen
  • Opioids e.g. morphine, oxycodone, buprenorphine
  • Tramadol
  • Medicated creams and ointments

Some medicines usually used to treat other health conditions are also useful for chronic pain, such as:

  • Antidepressants (e.g. amitriptyline, venlafaxine, duloxetine)
  • Antiepileptic drugs (e.g. gabapentin, pregabalin)
  • Muscle relaxants (e.g. baclofen)
Other Techniques
  • Physical therapy
  • Relaxation/meditation techniques
  • Cognitive behavioural therapy (CBD)
  • Acupuncture
  • Occupational therapy
  • Injection of numbing or pain relieving medicines
  • Devices that affect nerve signals
  • Surgery

Your doctor can provide more information about treatment of chronic pain.

Treatment with Medical Cannabis

The cannabis plant contains many compounds which affect the human body in different ways. Cannabinoids THC (Δ9-tetrahydrocannabinol) and CBD (cannabidiol) are the most abundant active compounds. THC is responsible for the intoxicating effects of cannabis.

The endocannabinoid system is part of the pain signalling process. It is thought cannabis can suppress pain by interacting with the endocannabinoid system, specifically the CB1 receptor.

A systematic review (Lynch and Campbell, 2011) of 18 high quality randomised trials concluded that “cannabinoids are a modestly effective and safe treatment option for
chronic non-cancer (predominantly neuropathic) pain”.

Findings are limited by short trial duration and small sample size. Long term effects of cannabis usage and interactions with other medicines are not yet fully understood. Further large scale trials of longer duration are needed before any conclusions can be drawn on the use of cannabis-based medicines in chronic pain.

  • Multicenter, Double-Blind, Randomized, Placebo-Controlled, Parallel-Group Study of the Efficacy, Safety, and Tolerability of THC:CBD Extract and THC Extract in Patients with Intractable Cancer-Related Pain
    This study compared the efficacy of a THC:CBD extract, a THC extract and a placebo for relieving pain in patients with advanced cancer. This trial was double-blind which means neither the patients nor the staff knew which treatment was administered.

    177 participants with cancer pain not adequately controlled with opioids were divided into three groups and given either the THC:CBD extract, the THC extract or a placebo for two weeks. They recorded their pain severity on a numeric scale.

    Results found that THC:CBD performed better than the placebo whereas the THC group showed a nonsignificant change. Twice as many patients in the THC:CBD group had a reduction of more than 30% from their original pain score in comparison with the placebo.

    Both treatments were well tolerated. 60% of patients had side effects including somnolence, dizziness and nausea, mostly of mild or moderate severity. One patient experienced fainting most likely due to THC.

  • Sativex successfully treats neuropathic pain characterised by allodynia: A randomised, double-blind, placebo-controlled clinical trial
    This double-blind study looked into the effect of Sativex - a mouth spray containing THC and CBD - on neuropathic pain. The treatment was added to participants’ existing pain relief medicines.

    125 patients with neuropathic pain and allodynia (increased sensitivity to pain) were divided into two groups and given either the THC:CBD product or a placebo for five weeks. During the study, patients recorded their pain on a numeric scale.

    Results found that 26% of patients in the THC:CBD group had at least a 30% reduction in pain score and 20% had at least a 50% reduction compared with 15% and 8% of patients in the placebo group. The mean reduction of dynamic allodynia was 20% in the THC:CBD group, compared to 5% in the placebo group.

    The THC:CBD group reported more sedative and gastrointestinal side effects than the placebo group; one patient in the THC:CBD group had transient mucosal ulcerations.

  • Preliminary assessment of the efficacy, tolerability and safety of a cannabis-based medicine (Sativex) in the treatment of pain caused by rheumatoid arthritis.
    This double-blind trial compared a cannabis-based medicine (Sativex) with a placebo for treatment of pain caused by rheumatoid arthritis.

    58 patients with rheumatoid arthritis were divided into two groups and given either the cannabis-based medicine or a placebo for five weeks. Patients rated pain on movement, pain at rest, morning stiffness and sleep quality on a numeric scale.

    Results found that the cannabis-based medicine “produced statistically significant improvements in pain on movement, pain at rest, quality of sleep. There was no effect on morning stiffness”.

    The majority of side effects were mild or moderate. No serious adverse effects were reported in the cannabis-based medicine group.

  • Comparison of analgesic effects and patient tolerability of nabilone and dihydrocodeine for chronic neuropathic pain: randomised, crossover, double blind study
    This double-blind study compared nabilone - a man-made compound similar to THC - with the weak opioid painkiller dihydrocodeine for chronic neuropathic pain. Treatments were added to participants’ existing pain relief medicines.

    96 patients with chronic neuropathic pain were given the first treatment for six weeks, followed by a two week washout period and then the second treatment for six weeks. They recorded their pain on a numeric scale.

    The results concluded that statistically, “dihydrocodeine was a better treatment for chronic neuropathic pain than nabilone. More patients had clinically significant pain relief from dihydrocodeine, although a small number of patients responded well to nabilone.”

    Side effects of both treatments were mild. Nabilone caused nausea more frequently than dihydrocodeine while the opioid was associated with more tiredness and nightmares. Neither drug caused major adverse events.

  • Tetrahydrocannabinol Does Not Reduce Pain in Patients With Chronic Abdominal Pain in a Phase 2 Placebo-controlled Study.
    This study compared the efficacy and tolerability of THC with a placebo for chronic pain.

    65 patients with chronic abdominal pain were divided into two groups and given either a tablet containing purified THC or a placebo for 50-52 days. Patients recorded their pain in a diary during this period.

    Results found that pain scores “did not differ significantly between the THC and placebo groups”. Seven patients in the THC group stopped treatment due to side effects compared with two in the placebo group. All side effects were mild or moderate.

References available at end of page.

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Related Advocacy Groups

There are several organizations in Australia which provide information and support to people with chronic pain and their families. Below are links to their websites:

Australian Pain Management Association

Pain Australia

Chronic Pain Australia

Research Articles