Posted: July 26th, 2016

Phenotyping for drug activity has to revolve around biochemical observation.

Phenotyping and genotyping
Phenotyping for drug activity has to revolve around biochemical observation. Certainly, the gross overall reaction to a drug would constitute phenotype as well, but in the true sense of the term, the real phenotype is what happens at the chemical level. Here are the protocols:
Functional phenotyping is defined as determining the presence/absence and activity/lack of activity of a particular metabolic enzyme in a tissue biopsy.
Metabolic phenotyping measures the level of metabolites in a person after administration of a drug, such as administering caffeine and measuring the concentration of caffeine metabolites in a blood sample.
Genotyping for drug activity involves, as you have guessed, identifying the specific gene(s) that determine the outcome of the drug activity, right down to their nucleic acid sequence. Anything as small as a SNP can severely alter the activity, and usually results in an ADR. Genes influence and/or control activity of any pharmaceutical:
• by controlling the synthesis, and, if necessary, the up-regulation of, binding sites for the drug.
• by controlling the synthesis of enzymes necessary to convert the administered form of the drug into its active form (yes, these are usually two different things).
• by controlling both the intracellular and intercellular transport of the drug.
• by dictating the length of time the active form of the drug is in its target.
• by controlling the conversion of the drug into a product which is excreted.