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Latimer: Personalized medicine one step closer

It is a wonderful feeling when finally, after many…trials one gets it right and the patient comes in saying they have never felt better.

I have written before about the promise of personalized medicine for psychiatry. I have been practicing psychiatry for 40 years and although we have made a lot of advances, it is still true that in selecting a medication we rely heavily on educated trial and error.

We simply have no way to know for sure how an individual will respond to each medication. This can be very frustrating for both patient and doctor. It not infrequently results in one or other giving up before a solution is found. Patients may drop out of therapy in their impatience and doctors too, may stop trying new approaches especially when faced with a less than cooperative patient.

It is a wonderful feeling when finally, after many unsuccessful, or only partially successful, trials one gets it right and the patient comes in saying they have never felt better of that they feel completely back to normal. Not everyone gets to that point.

I am very pleased to say that now, with the help of a large research grant, we can offer free genetic analysis to help in selecting the best medication in some cases. On October 15, 2014, the Genome Application Partnership Program (GAPP) announced that Assurex Health and the Centre for Addiction and Mental Health (CAMH) would receive $6 million from the Canadian federal government. The grant was allocated in support of the ‘Matching the Drug to the Patient: Safer and More Effective Drug Therapy for Mental Health Patients’ project. The GeneSight Psychotropic laboratory developed test analyzes how eight genes may affect a patient’s metabolism and response to 33 Health Canada approved antidepressant and antipsychotic medications.

GeneSight testing includes genotyping of pharmacokinetic genes from the Cytochrome P450 family and pharmacodynamic genes related specifically to the serotonin system. It takes into consideration how a combination of genetic variations can affect a patient’s ability to respond to a medication.

It is too soon to say how much this will affect outcomes in clinical practice, but I am hopeful. When a patient is not responding as expected, we now have the option to get a genetic analysis to learn whether there is anything peculiar about the way the body is metabolising the medication.

Some may require higher doses than normally recommended and some lower. Some will require a change in medication. So far I am mainly using this analysis with patients who are not responding to treatment or who seem more sensitive than normal to the side effects of medication. This can be very helpful.

At the moment this testing is being covered by the research grant but is quite expensive if done privately. I expect that if it is demonstrated to be clinically useful, it will someday be routinely available and hopefully covered by our provincial health plan. It could end up saving money for both patient and society by reducing the number of different medications tried before finding an effective treatment option.


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