One DNA test that tells your GP exactly how your body processes medications — from painkillers and antidepressants to breast cancer treatment. No more trial-and-error prescribing.
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Includes GP interpretation & clinical report
Pharmacogenomics — abbreviated as PGx — is the science of how your DNA determines the way your body breaks down and responds to medications. The same drug at the same dose can be life-saving for one patient and completely ineffective — or toxic — for another, simply because of inherited differences in drug-metabolising enzymes.
The most clinically significant of these enzymes is CYP2D6, part of the cytochrome P450 superfamily. CYP2D6 is responsible for metabolising approximately 20–25% of all commonly prescribed medications — including widely used painkillers, antidepressants, antipsychotics, heart drugs, and the breast cancer treatment tamoxifen.
A single PGx cheek swab test — done once in your lifetime — maps your genetic variants across CYP2D6, CYP2C19, CYP2C9 and related genes. The result is a personalised prescribing guide that your GP can use for every relevant medication, for the rest of your life.
PGx testing is not yet routinely available on the NHS for most indications. Despite strong clinical evidence — including guidelines from the Clinical Pharmacogenetics Implementation Consortium (CPIC) and FDA-approved labelling recommendations — access in the UK remains limited to specialist oncology settings. Private clinics like Lambert Medical Practice can offer this test now, giving you a significant head start in personalised, safer medicine.
Your CYP2D6 genotype places you into one of four metaboliser phenotypes. Each has profound implications for drug safety and efficacy. Many of your existing prescriptions may need to be reviewed in light of your result.
5–10% of the population
Little or no CYP2D6 enzyme activity. Drugs that depend on CYP2D6 activation (prodrugs) will have no effect. Drugs that are inactivated by CYP2D6 will accumulate to toxic levels.
Codeine produces no morphine — zero pain relief. Tamoxifen produces insufficient endoxifen — cancer recurrence risk rises.
5–11% of the population
Reduced CYP2D6 activity. Similar to PM but less severe. Standard doses of CYP2D6 substrates may be partially effective or produce elevated side-effect profiles.
Subtherapeutic tamoxifen response. Opioid analgesia variable. Antidepressant levels may accumulate.
56–70% of the population
Standard CYP2D6 activity. Medications work as expected at standard doses. Drug labelling and guidelines are generally written for this metaboliser type.
Standard prescribing appropriate. Phenoconversion by co-medications still possible — check interactions.
3–6% of the population (up to 29% in some ethnic groups)
Greatly amplified CYP2D6 activity (often due to gene duplication). Prodrugs are converted too rapidly, causing dangerous toxicity. Other drugs are cleared too fast for efficacy.
Codeine can cause fatal respiratory depression. FDA has contraindicated codeine in children partly for this reason.
Your genetic phenotype can be overridden by drugs you are already taking. Strong CYP2D6 inhibitors such as paroxetine (Seroxat), fluoxetine (Prozac), and bupropion can convert a normal metaboliser into a functional poor metaboliser — a phenomenon called phenoconversion. This is especially important when co-prescribing pain medications or tamoxifen alongside antidepressants. Our PGx report flags all drug–gene interactions explicitly, including phenoconversion risks.
Tamoxifen is the standard endocrine treatment for oestrogen receptor-positive (ER+) breast cancer — the most common breast cancer type, accounting for approximately 80% of cases. However, tamoxifen itself is a prodrug: it has minimal pharmacological activity until converted by the liver into its active metabolites, primarily endoxifen.
Endoxifen is up to 100 times more potent than tamoxifen as an antioestrogen. The entire therapeutic effect of tamoxifen treatment depends on this conversion — and the conversion is performed almost entirely by the CYP2D6 enzyme.
Studies show that CYP2D6 poor and intermediate metabolisers produce significantly less endoxifen, associated with increased breast cancer recurrence and mortality across multiple clinical populations. A meta-analysis of 33 studies confirmed that PM phenotype individuals face higher risk of breast cancer recurrence and/or mortality with reduced CYP2D6 activity. Additionally, many antidepressants commonly co-prescribed with tamoxifen (SSRIs for hot flushes) are potent CYP2D6 inhibitors — effectively abolishing the drug's benefit.
The Clinical Pharmacogenetics Implementation Consortium (CPIC) recommends CYP2D6 genotyping before initiating tamoxifen therapy. Poor metabolisers should be considered for alternative treatments (e.g. aromatase inhibitors in post-menopausal women) or higher tamoxifen doses. Normal and ultrarapid metabolisers may have their SSRIs changed to avoid phenoconversion.
| CYP2D6 Phenotype | Endoxifen Production | Therapeutic Outcome | CPIC Recommendation |
|---|---|---|---|
| Poor Metaboliser | Very low | Reduced efficacy; ↑ recurrence risk | Consider aromatase inhibitor or higher tamoxifen dose |
| Intermediate Metaboliser | Reduced | Partial response; variable | Monitor endoxifen levels; consider alternatives |
| Normal Metaboliser | Adequate | Standard expected response | Tamoxifen appropriate; avoid CYP2D6 inhibitor SSRIs |
| Ultrarapid Metaboliser | High | Potentially enhanced response; monitor side effects | Standard tamoxifen; monitor for increased toxicity |
Codeine, tramadol, and hydrocodone are widely prescribed for acute and chronic pain. What many patients — and some clinicians — do not realise is that these drugs are all prodrugs requiring CYP2D6 activation to produce pain relief. The same genetic variation that makes tamoxifen ineffective can render these opioids completely ineffective or dangerously toxic.
Converted by CYP2D6 into morphine. PM patients receive no analgesia. UM patients risk respiratory depression and death from standard doses.
Requires CYP2D6 conversion to O-desmethyltramadol. PM/IM phenotypes show poor pain control; UM phenotypes face increased adverse events and respiratory depression.
PM patients produce less hydromorphone (active metabolite). UM patients have elevated risk of adverse effects. CPIC provides dosing recommendations based on genotype.
A 2024 study in Biomedicine & Pharmacotherapy (Muriel et al.) of 263 chronic non-cancer pain patients found that patients taking CYP2D6 inhibitors alongside opioids had significantly higher neuropathic pain scores and lower pain relief — demonstrating how drug–drug–gene interactions directly impair analgesic outcomes in real-world clinical practice.
Without PGx testing, a GP prescribing codeine to a poor metaboliser is prescribing a drug that will never work for that patient. A PGx test identifies this immediately and allows a switch to a non-CYP2D6-dependent opioid (such as morphine, buprenorphine, or oxymorphone) from the very first prescription.
| Drug Category | Examples | CYP2D6 Role | PM Risk | UM Risk |
|---|---|---|---|---|
| Opioid analgesics | Codeine, tramadol, hydrocodone | Activation (prodrug) | No effect | Toxicity / death |
| Breast cancer | Tamoxifen | Activation → endoxifen | Cancer recurrence ↑ | Enhanced effect |
| Antidepressants (TCAs) | Amitriptyline, nortriptyline, clomipramine | Inactivation | Toxicity / cardiotoxicity | Subtherapeutic |
| Antidepressants (SSRIs) | Paroxetine, fluoxetine, fluvoxamine | Inactivation + inhibition | Drug accumulation | Rapid clearance |
| Antidepressants (SNRIs) | Venlafaxine, duloxetine | Inactivation | Elevated levels | Reduced effect |
| Antipsychotics | Aripiprazole, risperidone, haloperidol | Inactivation | Concentration-related toxicity | Reduced efficacy |
| Cardiovascular | Metoprolol, carvedilol, propafenone | Inactivation | Bradycardia / hypotension | Reduced beta-blockade |
| Anti-platelet | Clopidogrel (via CYP2C19) | Activation | Treatment failure / stroke risk | Variable |
| ADHD | Atomoxetine | Inactivation | High exposure / side effects | Reduced response |
Book online or call 0208 133 5694. A brief initial consultation with one of our GPs ensures the PGx test is appropriate for your needs and medications.
A buccal swab takes less than a minute. No blood draw, no fasting, no preparation. You can take your normal medications as usual that day.
Your sample is analysed at an accredited laboratory using our FDA-cleared genotyping panel. All genomic data is processed and stored on UK-based servers.
You receive a comprehensive report mapping your genetic profile across CYP2D6, CYP2C19, CYP2C9 and other pharmacogenes. Each drug is scored with CPIC-graded clinical action levels.
One of our GPs contacts you to discuss your results in the context of your current medications. You leave with a clear, personalised prescribing plan — and your report can be shared with any future doctor, anywhere, for life.
Knowing your CYP2D6 type before commencing tamoxifen therapy is recommended by international pharmacogenomics guidelines. Don't start treatment blind.
If codeine or tramadol are providing inconsistent or no relief, or if you've experienced unexpected side effects, your CYP2D6 type may explain why.
TCAs and several SSRIs depend on CYP2D6 for metabolism. If you have tried multiple antidepressants with poor response or intolerable side effects, a genetic explanation may exist.
Taking multiple medications increases the risk of drug–gene and drug–drug–gene interactions. A PGx test identifies your baseline genetic risk before complications arise.
Clopidogrel is a prodrug activated by CYP2C19. Poor metabolisers face reduced antiplatelet protection. PGx testing has specific relevance before stenting or post-MI management.
Even if you are currently well, a PGx profile is a once-in-a-lifetime investment. When future prescriptions are needed, your GP has the data to act immediately — without trial-and-error.
All genomic data from our PGx panel is processed and stored exclusively on UK-based servers. Your DNA information is never transferred to the United States or any third country. We comply fully with UK GDPR and NHS Digital data security standards.
Our PGx testing is informed by peer-reviewed literature and international guidelines:
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One cheek swab. A lifetime of safer, smarter medication decisions. FDA-cleared, GP-interpreted, UK data-hosted. Available now at Lambert Medical Practice, Surbiton.
380 Ewell Road, Tolworth, Surbiton KT6 7BE | Mon–Fri 9:00–18:00 | Sat 9:00–14:00
PGx testing is still a niche offering in the UK private healthcare market. Most London clinics do not yet provide it. At Lambert Medical Practice, we combine an FDA-cleared testing panel, UK-only data hosting, and GP-led interpretation — giving you not just a laboratory report, but a clinically actionable prescribing guide.
Our test uses a validated, clinically approved pharmacogenomics platform — not a consumer-grade ancestry kit.
Your genomic data is never transferred to the USA. Stored and processed on UK servers in full compliance with UK GDPR.
You don't just receive a PDF of variants — our GP reviews your full medication list against your genetic profile and provides clear clinical recommendations.
Our interpretations follow the Clinical Pharmacogenetics Implementation Consortium guidelines — the same standards used in leading academic medical centres worldwide.
Also consider a comprehensive health check
Pair your PGx test with our full health screening panel or comprehensive blood tests for a complete picture of your health — genetic and biochemical.
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