Tutorial 8. Year 1.
Mankind and Pharmacogenetics
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Pharmacogenetics concerns genetic variations in drug response. Among normal subjects, kinetic parameters (e.g., Michaelis constant [Km], maximum rate of reaction [V max]) of drug-metabolizing enzymes often differ widely, and drug elimination rates measured in vivo vary by fourfold to more than forty fold, depending on the drug and population studied. Numerous twin and family studies have shown that genetic factors are mainly responsible for these large interindividual variations.
Pharmacogenetics has clinical consequences and biologic significance. When prescribing drugs, physicians must consider that the inherent capacity to clear a drug may differ among patients. A patient with rapid metabolism may require larger, more frequent doses to achieve therapeutic concentrations; a patient with slow metabolism may need lower, less frequent doses to avoid toxicity, particularly for drugs with a narrow margin of safety.
Many environmental and developmental factors can interact with each other and with genetic factors to affect drug response (see Fig. 301-1). For example, increasing age affects other factors, thereby complicating drug disposition.
The foregoing is a cut and paste from the Merck site, further information on the science may be found here:
http://www.merck.com/mrkshared/mmanual/section22/chapter301/301a.jsp
Considerable intellectual power, not to mention money is being directed towards this matter of individual and racial biological idiosyncrasy. Not unnaturally the further one delves into the subject from the science angle, the greater the complexity that one encounters, what was once a tree becomes a great forest in which lurk all manner of strange creatures. Mainly one would suppose because the simple observational overview has been abandoned, and Minotaur like we are consigned to the maze. Consider the following;
"To give to each Nation its own type of medicine, the theoricam best
suited to it, as it behooves. For I can well realize that my prescriptions
may turn out to be ineffectual among the foreign Nations, and that foreign
recipes may turn out to be ineffectual in our Nation. That is to say that I
write for Europe, and I do not know whether Asia and Africa may profit from
it".
Paracelsus.
The words of a Master. Simple, clear and unambiguous and after all did he not also state;
"Everything that is within can be known by that which is without".
This clarity and simplicity is all that is required, if we are bent on doing what our duty as healers demands of us. If our heart is in the right place then we may be assured of the guidance needed in times of perplexity. All our needs in Nature are catered for, and as a healer the first command is from the Hippocratic Corpus; "First do no harm" that is also simple clear and unambiguous.
Each person is a unique entity, a twig upon a branch of a tree of common roots. Adjust your instruments accordingly.
"Medicine should be based upon truth and not verbal sleight of hand.
Practice should not be based upon speculative theory; Theory should be
derived from practice".
Paracelsus
Ivor Hughes
Auckland, New Zealand 2005
