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Conclusion, continued

Drugs metabolized primarily by CYP enzymes:
  • Methamphetamine - CYP2D6
  • Amphetamine - CYP2D6
  • MDMA - CYP2D6 and CYP3A4
  • Cocaine - A minor metabolite of cocaine is norcocaine. CYP3A4 is the metabolizing enzyme. The majority of cocaine metabolism is by hydrolysis by non CYP enzymes.
  • THC - CYP2C9, CYP2C19, and CYP3A4
  • Codeine - CYP2D6. Codeine also has glucuronide conjugates.
  • Hydrocodone - CYP2D6 and CYP3A4
  • Oxycodone - CYP2D6 and CYP3A4
Pharmacogenomics is the study of how individual variations in the human genome affect responses to medications. Pharmacogenomic testing is now performed in conjunction with drug testing in some laboratories. The purpose is to detect genetic variations (polymorphisms) seen with poor and rapid metabolizers that would subject the patient to variable metabolism and thus make them more susceptible to drug-drug interactions
The concentration of drug detected in urine depends on many factors--the amount and frequency of use of a drug, the affinity of the drug for the enzyme, the rate of the enzyme reaction, the concentration of the enzyme, the susceptibility of the enzyme to induction or inhibition, body mass, age, liver and kidney health, overall health, genetics, age, diet, fluid intake, urine pH…the list goes on. Due to the many factors involved, it is impossible to draw a correlation between the results of a drug test and the time the drug was taken, the dose, or the frequency of use.