Pharmacogenetics in practice: a guide for physicians and pharmacies

Reviewed by Dr. Daniel Wallerstorfer, molecular biologist and founder of Novogenia · Updated: 13 October 2026 · Reading time: 7 min

In short

Pharmacogenetics studies how genes influence the way drugs work: for some people the standard dose is too strong, for others too weak. A handful of well-researched genes – such as CYP2D6, CYP2C19, CYP2C9, VKORC1, SLCO1B1, DPYD and TPMT – affect painkillers, antidepressants, anticoagulants and antiplatelet drugs, statins, acid blockers and cancer drugs. International guidelines such as CPIC and DPWG translate a genotype into concrete recommendations. Who may order pharmacogenetic testing differs between Germany, Austria and Switzerland. One rule applies everywhere: decisions about medication are made by the treating physician.

Same pill, different people

Between 2017 and 2020, something happened that had never been done on this scale: 18 hospitals, nine community health centers and 28 community pharmacies in seven European countries – Austria among them – tested patients for 50 gene variants in 12 genes before a new prescription. 6,944 people took part. Anyone with a relevant result for their drug was treated according to the recommendations of the Dutch guideline group DPWG. In this group, 21.0% experienced clinically relevant side effects in the first twelve weeks, compared with 27.7% in the control group receiving standard care (Swen et al., Lancet, 2023).

That is pharmacogenetics in everyday care. Genes help determine how the body absorbs, converts and eliminates a drug – and therefore whether the standard dose is too strong, just right or too weak for a given person. For your practice, this means: knowing the genes gives you one more building block for choosing drug and dose with precision. The decision always rests with the treating physician.

I am a molecular biologist and the founder of Novogenia. In our genetic lab in Eugendorf near Salzburg, Austria, we have performed more than 30 million analyses so far. With this guide, I want to show you how pharmacogenetics works, which guidelines point the way and how to use them in a medical practice, pharmacy or clinic – within the legal framework of Germany, Austria and Switzerland.

The basics: genes, enzymes, guidelines

Many drugs are broken down by enzymes in the liver – and some are only activated there. Genes provide the blueprint for these enzymes, and they come in variants that work faster, slower or not at all. This gives rise to metabolizer types, from poor to ultrarapid. How this works, and why the logic flips for prodrugs such as codeine, is explained in What is pharmacogenetics?.

A handful of genes carry most of the clinical load: CYP2D6, CYP2C19, CYP2C9, VKORC1, SLCO1B1, DPYD, TPMT and NUDT15, plus HLA-B as a special case from the immune system. They affect painkillers, antidepressants, anticoagulants and antiplatelet drugs, statins, acid blockers and cancer drugs (Key genes).

To turn a genotype into a recommendation, there are guidelines: from the international consortium CPIC, from the Dutch DPWG and in the drug labels themselves. How they are structured and how to read them is shown in Guidelines: CPIC, DPWG and drug labels.

In practice: medical practice, pharmacy, clinic

Pharmacogenetics delivers its value where drugs are prescribed, dispensed and reviewed. Chapter 2 shows how to get there:

Medical practice and clinic: from the indication through information, consent and the sample to the result that feeds into the treatment decision (Pharmacogenetics in medical practice).
Pharmacy: medication review and counseling – and in which countries pharmacies may offer or order pharmacogenetic tests themselves (Pharmacogenetics in the pharmacy).
Result: from genotype to phenotype to recommendation – and how to explain the result in plain words (Understanding and communicating results).
Timing: test a panel once and use the result for later prescriptions – or test specifically before a particular drug (Pre-emptive or reactive testing?).

One rule runs through every chapter: a pharmacogenetic result is a decision aid. Decisions about medication – stopping, switching, changing the dose – are made by the treating physician.

The law: three countries, three approaches

Who may offer or order pharmacogenetic analyses is regulated differently in each country. Switzerland takes its own path and explicitly opens pharmacogenetics to other health professions:

Country	Classification	Who orders
Germany	Diagnostic genetic examination: the Genetic Diagnostics Act explicitly lists clarifying whether genetic traits can influence the effect of a drug (Section 3 No. 7(c) GenDG).	Physicians only (Section 7(1) GenDG); plus written consent (Section 8), information by the physician (Section 9) and an offer of genetic counseling after the result (Section 10).
Austria	The Gene Technology Act distinguishes four types of medical analyses relating to diseases and disease predispositions (Section 65 GTG); it does not explicitly mention pharmacogenetics.	Section 68 GTG requires ordering by a specialist only for types 3 and 4, and Section 69 GTG requires information by a specialist for types 2 to 4. Purely pharmacogenetic analyses can therefore also be offered by partners.
Switzerland	Genetic testing in the medical field under the GUMG (Federal Act on Human Genetic Testing).	Physicians as a rule (Art. 20 GUMG). Dentists, pharmacists and chiropractors may also order pharmacogenetic tests under certain conditions (Arts. 5–8 GUMV).

The Swiss conditions are specific: a defined selection of variants is tested, the results have known clinical significance, and therapeutic or preventive measures are available (Art. 5(2) GUMV). If the test concerns a prescription-only drug prescribed by another professional, the pharmacist consults that professional first (Art. 7(2) GUMV). The details are covered in Law: who may offer pharmacogenetics? and Data protection and consent.

Who this guide is written for

General practitioners: a pharmacogenetic result adds to the medication overview – especially for people who take several drugs.
Specialists: cardiology (clopidogrel), psychiatry (antidepressants), pain medicine (opioids), oncology, hematology and gastroenterology (fluoropyrimidines, thiopurines) – fields whose drugs are covered by CPIC guidelines.
Pharmacies: medication review and counseling, and in Austria and Switzerland their own routes to testing. More on the pharmacy as a place for health in the Pharmacy guide.
Clinics: structured processes from sample to result, embedded in medication management.

If you also want to offer analyses on nutrition and metabolism alongside pharmacogenetics, you will find the basics in the Nutrigenetics guide.

All chapters at a glance

Chapter 1 · Basics

What is pharmacogenetics?Same dose, different effect: metabolizer types made simple. Key genes: CYP2D6, CYP2C19 and moreWhich genes affect which groups of drugs. Guidelines: CPIC, DPWG and drug labelsHow a genotype becomes a recommendation.

Chapter 2 · In practice

Pharmacogenetics in medical practiceFrom the indication to the treatment decision. Pharmacogenetics in the pharmacyMedication review, counseling and the pharmacy’s role. Understanding and communicating resultsFrom genotype to phenotype – explained clearly. Pre-emptive or reactive testing?A panel in advance or a test before the drug.

Chapter 3 · Law & offer

Law: who may offer pharmacogenetics?Germany, Austria and Switzerland compared. Data protection and consentProcessing and storing genetic data securely. Offering pharmacogenetics: the processFrom sample kit to result with Novogenia.

All 10 articles are also listed by chapter at the end of this page.

How we do it at Novogenia

What you can expect from Novogenia:

Our own lab: We analyze samples in our own genetic lab in Eugendorf near Salzburg, Austria. Novogenia has been around since 2009; more than 30 million analyses have been performed so far, and our partners are based in 69 countries.
Medical spectrum: Pharmacogenetics is part of our medical range of analyses (“Therapy: pharmacogenetics & therapy optimization”).
Clear roles: Where national law requires it, we offer medical analyses only through physicians, and they are interpreted by physicians. In Austria, pharmacogenetic analyses can also be offered by partners.
Quality: CLIA-certified, working to ISO 15189, ISO 9001:2015 (Quality Austria) and an Austrian license for medical genetics.
Training: The NOVO Academy has a lecture called “Drug Intolerance” on CYP enzymes and metabolizer types – currently in English, Czech, French, Portuguese, Italian and Dutch, not yet in German.
Partners only: Novogenia sells exclusively through partners.

Frequently asked questions

What is pharmacogenetics?

Pharmacogenetics studies how inherited gene variants influence the effect and tolerability of drugs. It is mostly about enzymes that break down or activate drugs, about transporters and about a drug’s target structures. The result helps choose drug and dose more precisely; the decision is made by the treating physician.

Which genes matter most in practice?

For many commonly prescribed drugs, CYP2D6, CYP2C19, CYP2C9, VKORC1, SLCO1B1, DPYD, TPMT and NUDT15 are relevant, plus HLA-B as a gene of the immune system. The international consortium CPIC has published guidelines for all of these genes.

Who may order a pharmacogenetic test?

That depends on the country. In Germany, the physician reservation of the Genetic Diagnostics Act applies. In Switzerland, physicians order tests as a rule; pharmacists, dentists and chiropractors may also order pharmacogenetic tests under certain conditions. In Austria, the Gene Technology Act requires ordering by a specialist only for certain types of analysis relating to diseases and disease predispositions; it does not explicitly mention pharmacogenetics.

Does a pharmacogenetic result replace the physician’s decision?

No. The result is a decision aid alongside age, kidney and liver function, co-medication and the clinical picture. Whether a drug is stopped, switched or dosed differently is decided solely by the treating physician.

Which guidelines exist for pharmacogenetics?

The best known are the guidelines of the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG). Add to these the drug labels themselves, the PharmGKB knowledge base and guidelines from Canada and France. In most cases, their recommendations agree.

Pharmacogenetics in your practice or pharmacy?

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Note: This guide is general information for businesses and professionals and does not replace medical or legal advice. The genetic traits determined in a genetic analysis are well documented (each gene included is backed by at least three independent studies); recommendations derived from them are logical conclusions, not scientifically proven. Pharmacogenetic results do not replace a medical decision: any change to medication is made only by the treating physician. Regulations can change; errors and changes excepted.