Medicines That Heal but Can Harm: Pharmacogenetics (PGx)
At a glance
Ever wondered why a medicine can be a lifesaver for someone else but a disaster for you? Pharmacogenetics (PGx) explains why, and why it should be a priority.
- Big problem: A noticeable chunk of hospital beds is filled by people harmed by their medicines.
- Different genes, different reactions: The same dose can be too weak, just right, or dangerously strong depending on your genes.
- Small panel, big reach: A few dozen key genes already influence how we respond to 100+ common medicines.
- Future-proof info: One PGx test can guide many prescriptions across your lifetime, not just one drug today.
Medicine heals and hurts
Recent national and international studies suggest that around 2–6% of all hospital admissions are primarily caused by adverse drug reactions (ADRs); in older adults and those on many medicines, the proportion is even higher.
Among emergency readmissions, about 1 in 5 can be traced back to unwanted side effects, and many of these are considered potentially preventable.
At the same time, 1.4 billion adults worldwide are living with hypertension (high blood pressure) – a major reason for taking long-term medication. Nearly half don’t know they have it, and only about 1 in 5 have their blood pressure under good control.
So we have a double challenge:
- Many people need complex medication plans.
- A significant number get hurt by them or don’t respond as expected.
Pharmacogenetics is one of the tools that can help shift that balance.
What is pharmacogenetics, really?
Pharmacogenetics (PGx) looks at how your genes influence the way you process and respond to medicines:
- Enzyme genes affect how quickly you break down a drug.
- Transporter genes affect where the drug goes in the body.
- Receptor and target genes affect how strongly it works.
The Clinical Pharmacogenetics Implementation Consortium (CPIC) now publishes evidence-based guidelines covering 34 genes and 164 drugs, turning genetic results into concrete prescribing advice.
In practice, a relatively small panel of genes can touch a large fraction of common prescriptions over a person’s life.
3. Concrete gene–drug examples (that people actually recognise)
Here are some everyday medicines people recognise where small genetic differences can change how well the drug works or how likely side effects are.
| Health area | Gene(s) | Medicines people recognise | What the gene can change |
|---|---|---|---|
| Pain & anaesthesia | CYP2D6 | Codeine Tramadol | Low CYP2D6 activity: little or no activation, so you may get no pain relief. Very high CYP2D6 activity: rapid activation, so you may make too much morphine and have a higher risk of breathing problems. |
| Mental health | CYP2C19 | Citalopram Escitalopram Sertraline | Slow metabolisers: higher blood levels, so more side-effects. Ultra-rapid metabolisers: lower blood levels, so less benefit. |
| Mental health | CYP2D6 | Tricyclic antidepressants (e.g., amitriptyline, nortriptyline) Many antipsychotics | Low CYP2D6 activity: higher drug exposure, which can increase sedation and other side-effects; for some tricyclics, it can increase the risk of rhythm problems. Very high CYP2D6 activity: lower drug exposure, which can reduce benefit for some drugs. |
| Heart & clotting | CYP2C9 + VKORC1 | Warfarin | Certain variants increase sensitivity, so a much lower dose is needed. Without dose adjustment, the risk of serious bleeding is higher, especially early in treatment. |
| Heart & clotting | CYP2C19 | Clopidogrel | Loss-of-function variants reduce activation, so clopidogrel may work less well. This can increase risk in high-risk settings, for example after stent placement. |
| Cholesterol & statins | SLCO1B1 | Simvastatin (and some other statins) | Risk variants raise statin levels in muscle, which can increase muscle pain. Rarely, this can progress to serious muscle injury. |
| Cancer | DPYD | 5-fluorouracil (5-FU) Capecitabine | Reduced DPYD activity means the drug clears more slowly. Standard doses can cause severe or life-threatening toxicity. |
| Autoimmune / IBD / transplant | TPMT + NUDT15 | Azathioprine 6-mercaptopurine | Low activity can cause metabolite build-up. This can lead to dangerous bone-marrow suppression (low white cells and higher infection risk). |
| Severe skin reactions | HLA-B*57:01 | Abacavir | Strongly predicts a dangerous hypersensitivity syndrome. |
| Severe skin reactions | HLA-B*15:02 | Carbamazepine (especially in some Asian ancestries) | Associated with Stevens�Johnson syndrome and toxic epidermal necrolysis. Risk is higher in populations where the variant is more common. |
Note: These are not rare edge cases: most people carry at least one clinically relevant PGx variant, and older adults on multiple medicines are particularly expose
What pharmacogenetics can and can’t do
- It can turn trial and error into smarter first guesses, especially in people taking many medicines or with a history of bad reactions.
- It won’t magically pick the one perfect drug.
- It does help rule out the worst drug to dose combinations for a given person.
- It doesn’t replace diagnosis, clinical monitoring or listening to symptoms.
How HealthCode.Gene fits in
At HealthCode.Gene, we fit into pharmacogenetics in two ways: we model, and we make it usable.
- Model: Build PGx prediction models for drug response, toxicity/adverse reaction risk, dose stratification, and PRS (where appropriate).
- Translate: Turn model outputs and PGx lab reports into clear, actionable explainers for patients, clinicians, and product teams.
- Enable use:
Create visuals/one-pagers and support research groups, clinics/medical spas, and startups in designing and communicating PGx-aware products and pilots.
Downloadable Resources
why genes matter for health
get PDFDownload our PDF guide “Why Genes Matter for Health” for a handy summary of key references on polygenic risk scores, pharmacogenetics, and gene–lifestyle interactions, designed to inform health decisions and enhance patient outcomes.
Pharmacogenetics Insights
Access our pharmacogenetics report to understand how your genes affect medication responses. This resource is essential for both patients and healthcare providers.Get a free PGx kitGenetics and weight gain
Download our detailed guide on how genetic factors influence weight gain and management. Understand the science behind your body’s responses to diet and exercise.Download NowUnderstanding Metabolic Diseases
Get insights into metabolic diseases with our comprehensive resource. Learn about the genetic components and lifestyle factors that play a role in these conditions.Download NowPolygenic risk score models/ explained
order your polygeneic risk score to be explained
