Prozac Gene Test Good For Patients, Royal College Of Psychiatrists

Main Category: Depression
Also Included In: Genetics;  Psychology / Psychiatry
Article Date: 05 Jul 2008 - 0:00 PDT

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People who suffer depression that does not respond to medication could be treated successfully if a simple genetic blood test was made more widely available in the UK.

Four out of 10 people with depression have a genetic abnormality that prevents them responding to anti-depressant medication, according to research presented at the Royal College of Psychiatrists' Annual Meeting in London this week.

The research, which was carried out at the Mayo Clinic Mood Disorders Unit in the USA, showed that a quarter of those with a genetic abnormality produce a liver enzyme that either stops Prozac working or causes unpleasant side-effects.

Since 2003, the Mayo Clinic has offered genotyping to patients who either report significant side-effects to antidepressants or have no response.

They have identified four genes that interfere with the efficacy of antidepressant medication, including two that prevent metabolising the drug (CYP2D6 and CYP2C19) and two more that prevent the brain from absorbing or transporting serotonin.

Professor David Mrazek, chair of the Department of Psychiatry at the Mayo Clinic College of Medicine, said: "One in 10 of our patients have abnormal CYP2D6, the gene most commonly implicated in treatment-resistant depression. This means that they are poor at metabolising some common anti-depressant medication including Prozac and Seroxat. As a result, they may get adverse effects including nausea, headache, vomiting and sexual problems, from a regular or even low dose of the drug."

So far, genotyping - which costs about £150 per gene tested - is not widely available in the UK.

"The cost of the test may be a barrier to more frequent use of genotyping," Professor Mrazek said. "But most good insurance companies now pay for the test for people who have treatment-resistant depression, either because the drugs don't work or they suffer excessive side-effects. It is now proven beyond doubt that in many cases, unpleasant side effects can be avoided with this simple blood test."

Genotyping for depression became widely known in the USA following publication of the best-seller autobiography, Mommies Cry Too, by Carolyn Brink in 2006. Brink was diagnosed with severe postpartum depression shortly after the birth of her first child. But her treatment with three different antidepressants made the depression worse and led to suicidal feelings. She claimed the Mayo Clinic saved her life when the genotyping test showed that the antidepressant medication she was taking became toxic in her bloodstream due to her low metabolism rate for this type of medication.

Reference
The Annual Meeting of the Royal College of Psychiatrists, Imperial College, London, 1 - 4 July 2008

The Royal College of Psychiatrists
www.rcpsych.ac.uk