Pharmacogenetics

Pharmacogenetics

 

Scientific Foundation of Pharmacogenetics

Pharmacogenetics (PGX) is the study of genetic differences or variations in metabolic pathways which can affect individual responses to drugs, both in terms of therapeutic effect as well as adverse effects.  PGX testing is a type of genetic test that predicts a patient’s likelihood to experience an adverse event or not respond to a given drug.  PGX testing can be conducted via a non-invasive buccal swab test that is simple, fast, easy, and convenient. The test results can be used to greatly increase the safety and effectiveness of drug therapy. According to a recent study, PGX studies have provided an overwhelming amount of evidence regarding the influence of genetic variations and drug responses. Awareness of the genetic variations of a patient with a response to certain drugs can help physicians decide which type of drug therapy may be appropriate and most effective for individual patients and can also help the physician avoid drugs that may cause adverse reactions. Several drugs can cause severe or life-threatening reactions in patients with certain genetic variations. Some patients may experience sub-therapeutic or ineffective responses with certain drugs due to genetic variations.

In the US there are over 2 million adverse drug reactions (ADR) hospitalizations annually, with 125,000 of those resulting in death.  Adverse drug reactions are considered the fourth leading cause of death in the United States.    ADR’s are reported to cost as much as $136 billion dollars annually.  The more drugs a patient takes, the higher the risk is of an ADR.  Patients taking over 11 drugs have a 96% chance of an ADR and the average Medicare patient is on 5-8 drugs.

PGX testing not only will lower the annual ADR hospitalizations, but will save lives, money, and make drug therapy more safe and effective.  Many US organizations including John Hopkins, Mayo Clinic, Duke Medical Centre, Vanderbilt University Medical Centre, HCA (Hospital Corporation of America), and RCIVA Dallas have noticed the benefit of PGX and have adopted the testing.

Why Should a Physician Order PGX Testing?

With advances in medicine, the future of healthcare will be dependent on a physician’s ability to offer Personalized Medicine, especially in regards to prescription drug therapy.  Until recently, drugs had been developed with the idea that each drug works pretty much the same in all individuals. But genomic research has changed that “one size fits all” approach and has opened the door to more a sophisticated method of writing prescriptions.   Pharmacogenetics (PGX) is the study of genetic variations in metabolic pathways which can affect an individual’s response to drugs, both in terms of therapeutic effect as well as adverse effects. PGX testing enhances a physician’s ability to provide appropriate treatment plans while also reducing his clinical liability and providing numerous patient benefits.

  • Allows for safe and more effective medicine
  • Reduces the risks of side effects and overdose
  • Minimizes adverse drug interactions
  • Allows the physician to know the right dose

Improving Patient Outcomes

Pharmacogenetic (PGX) testing helps physicians find more personalized, effective, and safer medicine by understanding the patient’s ability to metabolize medications, reducing adverse effects, avoiding drug interactions, and time-consuming drug trials. Pharmacogenetic testing can be particularly useful in chronic pain management. Knowing a patient’s genotypes prior to prescribing pain medicine can help minimize debilitating side effects and addictions to narcotic medications. Pharmacogenetic testing can mean the difference between a treatment failure and a successful outcome.

Current Articles on Pharmacogenetics

Who Should Physicians Test?

  • Any patient who requires a higher-than-standard dosage to achieve the desired result
  • Any patient who has had a severe adverse drug reaction
  • Any patient who has had unexpected or unexplained responses to medications
  • Any patient who has had multiple unsuccessful drug trials
  • Any patient who has health issues in multiple organ systems
  • Any patient who has had multiple drug types prescribed

All of the above-mentioned criteria indicate that a patient is at an increased risk for being an abnormal metabolizer, and could be in danger from adverse events and serious side effects from prescription drug use.

Drugs, the Conditions they Treat, and PGX Warnings
The table below is a compilation of medications that have clearly stated warning labels in regards to pharmacogenetic variations.  These warnings appear in different sections of the labeling. For instance, numerous medications listed below are actually “Black Box Labeled”.  For other medications, the pharmacogenetic warnings are present under the contraindications section or indications and usage. The drugs usages range widely from antidepressants and schizophrenia medications to drugs used to treat pain and acid reflux.

Drug Name Use Enzyme
Amitriptyline

Bulimia

PTSD

CYP2D6 poor metabolizers
Aripiprazole Schizophrenia CYP2D6 poor metabolizers
Atomoxetine ADHD CYP2D6 poor metabolizers
Carisoprodol Musculoskeletal injuries CYP2C19 poor metabolizers
Carvedilol

Heart Failure

Hypertension

CYP2D6 poor metabolizers
Celecoxib

Pain

Inflammation

CYP2C19 poor metabolizers
Cevimeline Dry mouth due to Sjorgen’s disease CYP2D6 poor metabolizers
Citalopram (1)(2) Depression CYP2C19 poor metabolizers
Clobazam

Epilepsy

Anxiety

CYP2C19 poor metabolizers
Clomipramine Psychiatry CYP2D6 poor metabolizers
Clopidogrel Heart disease CYP2C9 intermediate or poor metabolizers
Clozapine Schizophrenia
CYP2D6 poor metabolizers
Codeine Pain CYP2D6 ultra-rapid metabolizers
Desipramine Depression CYP2D6 poor metabolizers
Dexlansoprazole (1) GERD CYP2C19 poor metabolizers
Dexlansoprazole (2) GERD CYP1A2 genotypes
Dextromethorphan and Quinidine Cough Suppressant CYP2D6 poor metabolizers
Diazepam

Anxiety

Acute alcohol withdrawal

Seizures

CYP2C19 poor metabolizers
Doxepin

Depression

Anxiety

CYP2D6 poor metabolizers
Drospirenone and Ethinyl Estradiol Preventing pregnancy CYP2C19 poor metabolizers
Esomeprazole GERD CYP2C19 poor metabolizers
Fluoxetine

Depression

OCD

Bulimia

CYP2D6 poor metabolizers
Flurbiprofen

Pain

Inflammation

CYP2C19 poor metabolizers
Fluvoxamine

Depression

Social phobia

OCD

CYP2D6 poor metabolizers
Galantamine Alzheimer’s disease CYP2D6 poor metabolizers
Iloperidone Schizophrenia CYP2D6 poor metabolizers
Imipramine Depression CYP2D6 poor metabolizers
Lansoprazole Acid reflux CYP2C19 poor metabolizers
Nefazodone Depression CYP2D6 poor metabolizers
Nortriptyline Depression CYP2D6 poor metabolizers
Omeprazole

Acid reflux

Stomach ulcers

CYP2C19 poor metabolizers
Pantoprazole GERD CYP2C19 poor metabolizers
Paroxetine

Depression

OCD

Anxiety

PTSD

CYP2D6 poor metabolizers
Perphenazine Schizophrenia CYP2D6 poor metabolizers
Pimozide Tourette’s syndrome CYP2D6 poor metabolizers
Prasugrel Anticoagulant CYP2C19 poor metabolizers
Propafenone Cardiac arrhythmia CYP2D6 poor metabolizers
Propranolol

Tremors

Angina

Hypertension

Heart rhythm disorders

CYP2D6 poor metabolizers
Protriptyline Depression CYP2D6 poor metabolizers
Quinidine Cardiac arrhythmia CYP2D6 poor metabolizers
Rabeprazole GERD CYP2C19 poor metabolizers
Risperidone Schizophrenia CYP2D6 poor metabolizers
Tetrabenazine Huntington’s chorea CYP2D6 poor metabolizers
Thioridazine Schizophrenia CYP2D6 poor metabolizers
Ticagrelor Clot prevention CYP2C19 poor metabolizers
Tolterodine

Overactive bladder

Urinary incontinence

CYP2D6 poor metabolizers
Tramadol Pain CYP2D6 poor metabolizers
Trimipramine Depression CYP2D6 poor metabolizers
Venlafaxine Depression CYP2D6 poor metabolizers
Voriconazole Fungal infections CYP2C9 intermediate or poor metabolizers
Vortioxetine Depression CYP2D6 poor metabolizers
Warfarin Clot prevention

CYP2C9 intermediate or poor metabolizers

VKORC1

Important Note for Physicians:If patients suffer with any of the conditions listed in this table, it can be assumed that medical necessity for PGX Testing may be validated if the physician is attempting to choose the safest and most effective medication.

 

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