Posted by Jost on September 22, 2006, at 17:44:47
In reply to how to know if i reach/maintain therapeutic levels, posted by iforgotmypassword on September 21, 2006, at 20:55:19
I found a couple of references:
One from "Have You Phenotyped Your Patient Lately?"
SHELDON H. PRESKORN, MD
Journal of Practical Psychiatry and Behavioral Health, March 1996,115-117
"I then ask if they have ever used therapeutic drug monitoring (TDM) to determine what plasma level of a tricyclic antidepressant (TCA) a patient has developed on a given done of a TCA. Most answer: "Yes."
I then point out that using TDM with such drugs is tantamount to assessing (i.e., phenotyping) the functional status of CYP 2D6 activity in that patient since that activity is the principal factor that determines what plasma TCA level the patient will develop on a given dose of a TCA. Note that dose here refers to the dose the patient is actually taking, not what the physician is prescribing. (For a detailed discussion of cytochrome P450 enzymes, see my November 1995 column.)
In this column, I continue a series devoted to understanding why different patients respond differently to the same dose of the same drug. Here I focus on the role of TDM, which is a refinement of the standard dose-response strategy and involves measuring the concentration of the drug achieved in a specific patient on a specific dose. The concentration in plasma is typically used as a surrogate for the concentration at the site of action because it is relatively easy to obtain and is correlated with concentration in other body compartments (e.g., a specific receptor in the brain). The goal of TDM is typically to ensure that the patient is on a dose that will produce a plasma drug concentration within a range that usually provides a therapeutically desired response in the majority of patients without undue adverse effects. Advances such as TDM have been made possible by research in clinical pharmacology and pharmacogenetics. They can help clinicians detect the reasons behind the interindividual differences that determine much of the variance in response among patients receiving the same dose of the same drug."
Another reference is a more comprehensive discussion:
I guess it's hard to know whether you've come close to a dose that could produce adverse reactions-- although for TCAs, it seems that the information is more reliable than for many more recent ADs.
Jost
poster:Jost
thread:687995
URL: http://www.dr-bob.org/babble/20060919/msgs/688248.html