The Basics of Pharmacogenetics – Genetically Guided Prescribing by A/Prof Ajeet Singh

Posted on: August 20, 2019
Last Updated: August 25, 2019

Prof Ajeet Singh is an academic private psychiatrist whose research has focused on genetically guided prescribing (pharmacogenetics) of antidepressants, particularly the role of the blood-brain-barrier. Dr Singh is the Founder of CNSDose, an academic member of the Clinical Pharmacogenetics Implementation Consortium (CPIC), and member of the Genetic Tests in Psychiatry Taskforce, International Society of Psychiatric Genetics (ISPG).

Author Quotes  

Pharmacogenetics is the impact of genes on prescribing; which med, which dose, whether a med is likely to help.

It’s getting cheap. One test per lifetime, so if it has clinical utility then it could have lots of health economic impacts.


Dr Singh begins his presentation with an explanation of pharmacogenetics and the advancement of precision (or personalised) medicine.  

He goes on to explain how gene chips are used in genome studies, focusing on drug metabolism elimination transport (DMET) chips and discusses the relevance of pharmacokinetics vs pharmacodynamics in prescribing psychotropics. 

Moving on, he talks about genome-wide association studies (GWAS) and demonstrates how these non-hypothesis association studies look for regions that might have a big effect (family studies), and which might then be identified as a new marker for diagnosis.  

This video ends with a look at what is meant by the Candidate Gene Association Study (CGAS) and of the levels of uncertainty in the identification of haplotypes used. 

Take-Home Points  

  • Genetic testing companies will grow in number over the next few years  
  • Testing involves the use of haplotype chunks with tag SNPs 
  • Genome studies have considerable statistical power issues  
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