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Medical Marijuana for Chronic Pain – Is it right for you?

Medical marijuana use has been growing at a rapid rate. While cannabis has been used for pain relief for hundreds of years the evidence on its validity remains limited. Despite this, the widespread legalization and commercialization of medical marijuana has made it a popular treatment option for those suffering from chronic pain. When multiple drugs and treatments fail to bring relief, people are increasingly turning to medical marijuana.

The evidence is overwhelming that marijuana can relieve certain types of pain, nausea, vomiting and other symptoms caused by such illnesses as multiple sclerosis, cancer and AIDS — or by the harsh drugs sometimes used to treat them.

~Dr. Joycelyn Elders, MD, former US Surgeon General

As a physician I have sympathy for patients suffering from pain and other medical conditions. Although I understand many believe marijuana is the most effective drug in combating their medical ailments, I would caution against this assumption due to the lack of consistent, repeatable scientific data available to prove marijuana’s benefits.

~Bill Frist, MD, former US Senator

While the safety and efficacy of medical marijuana is a hotly contested debate, the role your genetics plays in how you will respond to opioids, NSAIDs and medical marijuana is quite clear. People respond to opioids and cannabis differently – and a simple PGx test can help predict your response.

Many people take excessive doses of opioids yet experience inadequate pain relief. Resistance to opioids can be conferred by multiple factors. Variations in the OPRM1 gene, which encodes the m-opioid receptor, can result in decreased sensitivity to opioids. Individuals with this variant (15% of Caucasians and 40% of Asians) need higher doses to get the same relief as those without the variant. Inherited deficiencies in the CYP2D6 enzyme reduces one’s response to oxycodone, tramadol, codeine (Tylenol 3) and other pro-opioids. To be effective the pro-opioids must be metabolized by CYP2D6 to more potent forms such as hydrocodone and hydromorphone. People who are slow or ultrarapid CYP2D6 metabolizers can experience debilitating side effects or get no relief when given standard doses. PGx-guided prescribing can reduce these risks.

The effect of cannabis can similarly depend on pharmacogenetic factors. THC is the active component in cannabis responsible for both its psychogenic and analgesic effects. Liver enzymes convert THC into the active metabolite 11-OH-THC and then the inactive metabolite THCCOOH. Genetics plays a role because THC is metabolized by enzymes that are encoded by genes, which leaves the possibility for genetic variation. CYP2C9 is the most important enzyme for the metabolism of THC. The CYP2C9*3 variant is common in Europeans and results in decreased enzyme activity. This means a reduced ability to metabolize THC and subsequent increased sensitivity to its effects as the active THC lingers for longer in the bloodstream. Individuals with this variant should be wary about using cannabis for pain relief as it can lead to adverse effects. 30% of people who use cannabis for pain discontinue treatment due to side effects. Awareness of this variant prior to cannabis use could allow one to predict whether or not they will experience side effects and tailor their dose accordingly. This allows you to maximize pain relief while minimizing adverse effects.

Another important consideration is the high cost of cannabis. Many insurance providers in Canada have limited reimbursement for cannabis as the annual costs can reach $40,000 per patient. A PGx test can demonstrate to you and your healthcare provider why your body is not responding to traditional treatment options (i.e. opioids) and may help you secure reimbursement for medical cannabis.

If you have consulted your physician and are ready to try medical marijuana for pain management what can you do to optimize your response? The answer may lie in a PGx test.

If you would like to learn more about the power of PGx testing to optimize medication for pain relief please subscribe to our blog and follow us on Facebook and Twitter.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guidelines for Codeine Therapy in the Context of Cytochrome P450 2D6 (CYP2D6) Genotype

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