Dr Simon Hendricks on Pharmacogenomics

According to the 2020 study ‘Economic analysis of the prevalence and clinical and economic burden of medication error in England’1, it is “estimated that 237 million medication errors occur at some point in the medication process in England annually, 38.4% occurring in primary care; 72% have little/no potential for harm and 66 million are potentially clinically significant. Prescribing in primary care accounts for 34% of all potentially clinically significant errors. Definitely avoidable adverse drug events (ADEs) are estimated to cost the NHS £98,462,582 per year, consuming 181,626 bed days, and causing/contributing to 1,708 deaths.”

In addition, we know from other studies that there is also a significant amount of drug wastage in prescribing, approximately £300 million. This could be because patients do not take their medication as intended for various reasons, either because there is a lack of efficacy or there are side effects. For these, there are genomic factors at play in some individuals. 

As a community, we need to better understand how best to take genomic factors into consideration. 

We know now that 90% of commonly prescribed drugs only work in 30 – 50% of people. This can be a real case of trial and error - where a drug doesn’t work or side effects occur, the patient may be switched to a different dose, wait for a response and adjust the drug selection as appropriate. This can contribute to drug wastage and is not a great experience for patients either.

Going back to the ADEs and, of those 237 million medication errors that occur at some point in the medication process in England annually, some of these are serious and will require hospital admission. From that, it was extrapolated that 6.5% of all hospital admissions have a medication error component. Even when you are in hospital, about 15% of patients will experience ADEs during their stay due to factors such as changing of doses. From prescribing in community, approximately 6.5% patients will go to hospital due to ADEs and of these, 15% of patients have some sort of ADE in hospital, equating to approximately 8,000 NHS beds that are used for treating those who have ADEs. 

This is where FDB can come in, by incorporating pharmacogenomics knowledge and utilising all that we can to reduce the likelihood of ADEs.  

When we are trying to work out patient susceptibility or a lack of effect in prescribing, there are elements that we at FDB currently take into consideration, i.e. age, sex, what drugs the patient is on, other diseases, renal impairment etc. We do all this, with excellent results, but the genomic element could help improve our use of drugs even more and target even more appropriately. 

We already know – and there is a strong evidence base for this - that there are around 60 common drugs which have a genomic influence. This means from a pharmacokinetic perspective how the body actually deals with the drugs - how they are absorbed, how they are metabolised. 

There is great work going on out there with projects such as the 100,000 Genomes Project2, which means that we can get a better understanding of how there are differences in the DNA sequences for some particular enzymes and that there could be a genetic explanation for why a particular drug does not work for a particular patient. 

There is also great work being done by Clinical Pharmacogenetics Implementation Consortium (CPIC)  and Wales Gene Park Genomic Facility (WPG)  organisations that are researching what the various different genes of and the effect of enzymes.  

Understand what variants of a particular gene we have through genomics testing will be hugely significant.  

As we do not yet have this genomic information in the NHS there is an educational piece which needs to be carried out for prescribers, so people start thinking: what is pharmacogenomics? Who are the patients I need to be more careful with when prescribing? What are the 60 common drugs which have a genomic influence, and what are they?

Pharmacogenomic variants could hold the key as to why some patients aren't getting the prescribing effect they should be getting. At FDB, we are at the vanguard of this emerging science and are looking to add this alongside all the current checks we carry out – to make our understanding as patient-centric as possible and to provide even more enhanced prescribing support. 


1 Economic analysis of the prevalence and clinical and economic burden of medication error in England https://qualitysafety.bmj.com/content/qhc/30/2/96.full.pdf 
2 https://www.genomicsengland.co.uk/about-genomics-england/the-100000-genomes-project/