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Internal organs often hurt.
We've all experienced the uncomfortable painful sensation
in our bellies caused by food poisoning.
We've heard about pain induced by appendicitis,
kidney stones, acute heart attack,
and even during menstruation in women.
These are all forms of acute visceral pain which may occasionally be extremely strong.
Visceral pain can become chronic.
Although, much less known many people suffer different forms of chronic visceral pain.
This pain typically involves the abdomen and the pelvic areas,
although chronic pain in the chest is not uncommon as well.
But let's focus on the abdominal and pelvic pain.
Chronic visceral pain can be grossly divided into two major categories.
The first is inflammatory pain,
such as that caused by gastric ulcer or inflammatory bowel disease like,
Crohn's disease and ulcerative colitis.
The second category includes a whole host of dysfunctional pain syndromes.
To refresh our memories,
dysfunctional pain is pain which can be associated with inflammation or neural injury.
This includes; irritable bowel syndrome,
painful bladder syndromes, a condition called chronic prostatitis and many others.
The treatment of these conditions differs from one patient to another,
and depends primarily on their diagnosis.
Nowadays, ulcers are treated with antibiotics and anti-acid drugs.
Inflammatory bowel diseases are treated with anti-inflammatory,
immune-suppressant and biological therapies.
And in contrast, dysfunctional pain syndromes do not require specific therapy,
and are treated symptomatically only.
Many patients with chronic visceral pain unhappy with their treatment outcome,
explore the cannabis option.
At this point it's important to know that
CB1 and CB2 receptors are located in visceral organs,
so both inflammatory and dysfunctional visceral pain syndromes
can theoretically be expected to respond to medical cannabis.
This is supported by animal studies.
In one study, an abdominal reflex in response to colon distension was tested.
This is a way of testing the response to
painful non-inflammatory visceral stimuli in anesthetized rats.
The reflex was suppressed by injecting into
the abdominal cavity a cannabinoid which selectively activates CB1 receptors.
This shows that activation of
CB1 receptors can be effective for dysfunctional visceral pain.
In another study in mice,
the colon was experimentally inflamed.
Injection of a drug blocking the enzyme responsible for degradation of endocannabinoids,
resulted in significant reduction in the inflammation.
This points to a possible anti-inflammatory effect of cannabinoids in visceral organs.
These findings, as well as numerous others,
support the understanding that cannabinoids may have an effect on
visceral pain by acting at the periphery not only on the brain.
Human studies do not always concur with those performed in animals.
A study in healthy volunteers failed to show a cannabinoid
induced pain attenuating effect on colon distention in these subjects.
Unfortunately, to date there are no clinical trials on
the effectiveness of medical cannabis for chronic visceral pain.
Yet an American survey aimed at assessing the prevalence of use and
the perceived benefits of cannabis among
patients with inflammatory bowel disease was recently published.
Of the nearly 300 patients surveyed over 12% were
active recreational cannabis users and almost 40% were past users.
Among current and past users,
16% use cannabis for symptoms relieve,
and the majority reporting that it was very
helpful for relief of abdominal pain, nausea, and diarrhea.
Importantly, the other half of patients who had never used cannabis,
expressed an interest in using it for their abdominal pain where it's legally available.
A closely related North American survey of nearly 350 men assessed
the effectiveness of cannabis for a condition known
as chronic pelvic pain or chronic prostatitis.
Almost 50% of responders reported using cannabis.
Overall, about 60% found cannabis to be somewhat very effective.
Improvement was noted in some but not in all the symptoms included pain,
muscle spasm, sleep, and mood.
Of importance is the fact that this condition does not
tend to remit spontaneously and yet paradoxically,
most patients chose not to use cannabis regularly.
In summary, evidence from basic science clearly indicates that the use of cannabinoids
is potentially effective in relieving
pain and other symptoms originating from internal organs.
This is an area which clearly demands further research.
Proper clinical studies have not been published to date and the available surveys
suggest that although cannabis use is prevalent among patients with visceral pain,
most use it rarely or inconsistently.
Elon EisenbergProfessor of Neurology and Pain Medicine
