Oct 6, 2022 - Health + Traits

After the Click: Adverse Drug Reaction 

Donna Gizza

Just two days after starting a course of citalopram, a common antidepressant, Donna Gizzi began to experience a slew of awful side effects. She felt so dizzy and disoriented that she had difficulty driving her car, recalling a frightening moment when she felt as though she was sitting still “while all the surrounding cars were going 100 miles per hour.”

She had been prepared for the mild nausea and drowsiness that often accompanies antidepressant treatment, but she was taken aback by the severity of the side effects she experienced. 

So Donna sought answers. She eventually got some from a 23andMe Pharmacogenetics report* – offered as part of a 23andMe+ membership – that looked at how her genes may impact how she processes different medications. 

The CYP2C19 Enzyme 

The CYP2C19 enzyme (pronounced sip-two-see-nineteen) helps the body metabolize certain medications. Specific DNA variants can affect how well the CYP2C19 enzyme works, and people with these variants may process certain medications slower or faster than normal. 

In Donna’s case, she had two copies of a variant associated with reduced function of the CYP2C19 enzyme, which made her a CYP2C19 poor metabolizer. This meant that she broke down certain drugs like citalopram more slowly and that these drugs stayed in her system longer, causing an increased chance of adverse effects.

Making Sense of the Past

After reading her report, everything clicked. 

Editor’s Note:

We’ve talked to hundreds of people about what they did ‘after the click,’ after they opened up a report and learned about an unknown risk for breast cancer, lung and liver disease, or cardiac and neurological issues.

The response isn’t one of fear but empowerment.

Suddenly they and their doctor have information they can use to follow up on a risk in order to prevent or treat a serious illness. And this is too often for risks they wouldn’t have known of otherwise.

Here is another in an occasional series about customers who were empowered to take action after getting an important genetic insight from 23andMe.

Read some of the previous After the Click stories here, here and here.

“All my adult life, I’ve had difficulty taking drugs,” Donna said. “I seem to react to everything I take. [Drugs] either do the opposite of what they’re supposed to do or don’t do anything at all. Once I learned I was a  predicted CYP2C19 poor metabolizer, I could put it all together.” 

Genetics seemed like a key part of the explanation, although other factors may also have played a role.

Donna shared her Pharmacogenetics report with her doctor, who immediately added it to her patient chart. “Now it’s in my chart that I’m a CYP2C19 poor metabolizer, so they’ll pay close attention to that in the future,” Donna explained. 

She’s also spreading the word to her family, friends, and anyone who will listen. “I just tell everybody I’m talking to about 23andMe. I think it’s important to find out if you have issues processing medications.”


*23andMe PGS Pharmacogenetic reports: The 23andMe test uses qualitative genotyping to detect 3 variants in the CYP2C19 gene, 2 variants in the DPYD gene and 1 variant in the SLCO1B1 gene in the genomic DNA of adults from saliva for the purpose of reporting and interpreting information about the processing of certain therapeutics to inform discussions with a healthcare professional. It does not describe if a person will or will not respond to a particular therapeutic and does not describe the association between detected variants and any specific therapeutic. Our CYP2C19 Pharmacogenetic report provides certain information about variants associated with metabolism of some therapeutics and provides interpretive drug information regarding the potential effect of citalopram and clopidogrel therapy. Results for SLCO1B1 and DPYD and certain CYP2C19 results should be confirmed by an independent genetic test prescribed by your own healthcare provider before taking any medical action. 


Test information should not be used to start, stop, or change any course of treatment and does not test for all possible variants that may affect metabolism or protein function. The PGS test is not a substitute for visits to a healthcare professional. Making changes to your current regimen can lead to harmful side effects or reduced intended benefits of your medication, therefore consult with your healthcare professional before taking any medical action. For important information and limitations regarding Pharmacogenetic reports, visit www.23andme.com/test-info.

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