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Chronic pain

The most frequent complaint that patients look for medical help with is pain. There are several different types of pain, and unfortunately none of the currently-prescribed pharmacological treatments for pain work completely for certain types. A particular example is that of pain caused by damaged nerves (such as that which causes phantom limb pain), which does not respond well to existing medications.

Severe chronic pain is usually treated with opiates, but these are addictive, and tolerance develops so that the dose has to be increased. The risk of severe side effects such as nausea is great, and additionally the user feels drugged, and finds it difficult to function properly. Family life may suffer as patients find it hard to relate to other people, and even reading to children is difficult. Synthetic analgesics are non-addictive but they are not powerful enough.

Cannabis has fewer side effects than other analgesics, and users report it "rounds off" the pain quickly after smoking. An Institute of Medicine report contains a minimal list of 5 situations in which cannabis-based medicines are of use in treating pain:

• There are medical conditions or patients in which they are more effective than any currently available medication.
• They have a broad clinical spectrum of efficacy and a unique side effect profile that differs from other analgesics.
• They have synergistic interactions with other analgesics.
• They exhibit "side effects" which are considered useful in certain clinical situations.
• Their efficacy is enhanced in patients who have developed tolerance to opioids.

Some people have used cannabis to control pain for 20 years or more, and many report that they were able to kick their addiction to opiates with small amounts of cannabis. One strange fact is that more experienced users get a greater pain-relieving effect from cannabis than novices. Experienced users also are able to function normally and ignore the psychoactive effects. Cannabis may be better at controlling the different types of pain.

Cannabis has had a long history of use as an analgesic, and was widely used in 19th century Britain, including in the royal household. Dr. J. Russell Reynolds, Fellow of the Royal Society and Physician to Queen Victoria reported in the Lancet in 1890 that he had been prescribing cannabis for 30 years and considered it "one of the most valuable medicines we possess". According to Reynolds indian hemp remained effective as an analgesic for months and even years without an increase in the dose.

It seems that cannabis shares some method of action with opioids, but the mechanism with which it accomplishes its analgesic effects differs. This indicates that they may produce an additive effects when used in conjunction with current medicines. In addition they might provide help to patients who do not react satisfactorily to other treatments. Much anecdotal evidence seems to indicate that this is the case.

Indeed, the British Medical Association has gone on record as stating that 'the prescription of nabilone, THC and other cannabinoids...should be permitted for patients with intractable pain'. Other official bodies have found similar results. A House of Lords report summed up the situation stating that 'there is scientific evidence that cannabinoids possess painrelieving properties, and some clinical evidence to support their medical use in this indication'. In a press conference on October 26th 1997, the US Society for Neuroscience claimed that 'substances similar to or derived from marijuana...could benefit the more than 97 million Americans who experience some form of pain each year'.

For the complete collection of testimonies from medical users of cannabis, see our medical testimony database.

Despite the long history of use of cannabis as an analgesic, and the obvious problems with synthetic drugs, the War on Drugs prevented people from reconsidering cannabis until the mid-seventies, when several studies were published.

Patients suffering from cancer usually suffer from severe pain. This can be for a number of reasons, such as the invasion of their bones, inflammation or damage caused to nerves. It is a form of pain which is notoriously hard to treat effectively.

At the University of Iowa Noyes et al (1975a) gave oral THC or a placebo at random to hospitalised cancer patients who were in severe pain. The THC relieved pain for several hours at very low doses and longer periods at higher doses (15 - 20 mg). It also acted as a sedative at the higher dose. It had fewer physical side effects than other commonly used analgesics. There was no incidence of nausea or vomiting unlike many other analgesics - indeed more than half of the patients had an increased appetite.

Then Noyes et al conducted another study (1975b). This time they gave codeine, THC and placebo to 36 patients with advanced cancer. Codeine and cannabis were equally effective, but some patients found the psychoactive effects of THC uncomfortable. However these people did not know they were going to take a psychoactive drug and were obviously frightened. If they had been told beforehand perhaps they would not have been uncomfortable. Many of the patients however felt they generally had a sense of well-being that was absent before. As a result of this experiment, the researchers estimated that 10mg of THC was roughly equivalent to 60mg of codeine.

A study revealing potential additive effects of THC on standard medication was done by Holdcroft et al (1997). It centred on a patient who had severe chronic pain of gastrointestinal origin. The patient used morphine as an analgesic.It was found that the patient required a substantially lower amount of morphine when they were treated with oral THC in the form of cannabis oil.

The differing mechanism of analgesic action cannabis uses compared to existing (mainly opioid) medications means that not only are additive effects likely, but it could be useful in patients resistant to existing medications, and be useful in treating pain which existing medications fail to deal with adequately. The National Institutes of Health suggested that 'Neuropathic pain represents a treatment problem for which currently available analgesics are, at best, marginally effective. ...THC...may be useful in this inadequately treated type of pain'. The findings of Growing et al (1998) concurred with this conclusion, and suggested that this might be the area of greatest medical potential.

Maurer et al (1990) found that a paraplegic patient, who suffered leg pain, gained pain-relief after taking a single dose of THC.

Staquet et al (1978) did a trial using a nitrogen analogue of THC. This too showed significant analgesic effects, and was effective as both codeine and secobarbital. A further study using the synthetic THC analogue Levonantradol was done by Jain et al (1981). The trial population was patients who had moderate to severe post-operative pain. They were administered Levonantrodol by injection, and found significant pain relief as a result.

In Canada, Milstein et al (1975) studied the analgesic effect of smoked cannabis in normal subjects. Half of them had used cannabis before. The researchers caused pain by pressing onto the subjects thumbnails. The subjects were able to withstand more pressure after they had smoked cannabis. Strangely, the analgesic effect was greater in the experienced users.

A article by Noyes and Baram (1974) showed that cannabis relieved the pain of a headache in three patients with an equivalent or better efficacy than aspirin or ergotamine tartrate. Petro (1980) found that two patients suffering pain from a muscle spasticity disorder had a reduction in their discomfort after inhaling cannabis.

Recently, it has been found that the body's natural cannabinoid, anandamide is involved in the control of pain. Calignano et al (1998) found that rats release anandamide when cells are damaged. This then causes seemingly pain-relieving effects in the areas of the brain and spinal cord that process pain stimuli. An ACM bulletin in 1998 demonstrated that when anandamide is used with another naturally occuring compound in the body, palmitylethanolamide, pain was reduced by up to 100 times.

Calignano A. et al (1998) Control of pain by endogenous cannabinoids, Nature 394: 277-281.

Growing L et al (1998) Therapeutic use of cannabis: clarifying the debate, Drug and Alcohol Review 17: 445-452.

Holdcroft A et al (1997) Pain relief with oral cannabinoids in familial Mediterranean fever. Anaesthesia, 52: 483

House of Lords Select Committee on Science and Technology (1998) Science and Technology - Ninth report. Science and Technology Committee Publications, UK.

Institute of Medicine (1999) Marijuana and medicine: Assessing the science base. National Academy Press

Jain AK, Ryan JR, McMahon FG, Smith G. (1981) Evaluation of intramuscular levonantradol
and placebo in acute postoperative pain. Journal of Clinical Pharmacology 21 :320S-326S.

Maurer M. et al. (1990) Delta-9-tetrahydrocannabinol shows antispastic and analgesic effects in a single case double-blind trial. European Archives of Psychiatry and Clinical Neuroscience 240: 1-4.

Milstein S.L., MacCannell K., Karr, G. and Clark S. (1975) Marijuana-produced changes in pain tolerance: Experienced and non-experienced subjects. International Pharmacopsychiatry 10: 177-182.

National Institutes of Health (1997) Workshop on the Medical Utility of Marijuana: Report to the Director. Washington, D.C.

Noyes R., Baram D. (1974) Cannabis analgesia. Compr. Psychiatry 15 : 531.

Noyes R., Brunk S.F., Baram D.A. and Canter A. (1975a) Analgesic effect of delta-9-tetrahydrocannabinol. Journal of Clinical Pharmacology 15: 139-143.

Noyes R., Brunk S.F., Avery D.H. and Canter A. (1975b) The analgesic properties of delta-9-tetrahydrocannabinol and codeine. Clinical Pharmacology and Therapeutics 18: 84-89.

Petro D. (1980) Marihuana as a therapeutic agent for muscle spasm and spasticity. Psychosomatics 21: 81-85.

Reynolds J.R. (1890) Therapeutic uses and toxic effects of Cannabis indica. Lancet 1: 637

Science: Cannabinoid/anandamide-receptor systems involved in peripheral control of pain, ACM Bulletin, July 26, 1998.

Staquet M, Gantt C, Machin D. (1978) Effect of a nitrogen analog of tetrahydrocannabinol on cancer pain. Clinical Pharmacology and Therapeutics 23:397401.