Therapeutic Drug Monitoring (Bishop | F) Flashcards
What is TDM?
It is the analysis, assessment, and evaluation of circulating concs. of drugs in serum, plasma, / whole blood (WB)
What is the purpose of TDM?
To ensure that a given drug dosage produces maximal therapeutic benefit and min. toxic adverse effects
When is TDM used?
It is used when safe dosage regimens have not been established and a trial and error approach is not appropriate
In TDM, where is std dosage derived?
It is derived from observations in healthy population
TDM involves what?
It involves quantitative evaluation of circulating drug conc.
What are the key factors of TDM?
1) Route of administration
2) Rate of absorption
3) Distribution of drug within body
4) Rate of elimination
What are the different routes of administration?
1) Intravenous (IV)
2) Intramuscular (IM)
3) Subcutaneous (SC)
4) Transcutaneous
5) Suppository
6) Oral administration
What is the principle of IV (w/c is 1 of the routes of administration)?
Injected directly into circulation
What is the principle of IM (w/c is 1 of the routes of administration)?
Injected into muscle
What is the principle of SC (w/c is 1 of the routes of administration)?
Injected just under skin
What is the principle of transcutaneous (w/c is 1 of the routes of administration)?
Inhaled or absorbed through skin
What is the principle of suppository (w/c is 1 of the routes of administration)?
Rectal delivery
What is the principle of oral administration (w/c is 1 of the routes of administration)?
By mouth
For orally administered drugs, efficiency of absorption from GIT depends on what factors?
1) Formulation of drug
a. Tablets
b. Capsules
c. Liquid solutions
2) Uptake by transport mechanisms intended for dietary constituents vs. passive diffusion
3) Changes in :
a. Intestinal motility
b. pH
c. inflammation
d. food
e. other drugs
4) Variation among population
5) Age
6) Pregnancy
7) Pathologic conditions
What are the types of drugs?
1) Free (unbound)
2) Bound
What is the characteristic of free fraction of drug?
It can interact w/ site of action and cause biologic response
The percentage of free fraction of drug depends on what?
1) Physiologic parameters
2) Biochemical parameters
The physiologic and biochemical parameters where the percentage of free fraction of the drug depends on are what?
1) Inflammation
2) Malignancies
3) Pregnancy
4) Hepatic disease
5) Nephrotic syndrome
6) Malnutrition
7) Acid-base disturbances
The percentage of free fraction of drug also depends on what?
Conc. of other substances competing for binding sites
What is the principle of drug distribution?
1) Ability of drug to diffuse out of circulation
2) Depends on lipid solubility of drug
What is the principle of drug elimination?
Rate of change of drug conc. over time varies continuously in relation to conc. of drug
What is the elimination equation?
ΔC/ΔT = -kC
What are the cmpts related to drug elimination?
1) Metabolic clearance
2) Renal clearance
What is the system of metabolic clearance?
Hepatic mixed function oxidase (MFO) system
What are the events that occur in hepatic MFO system?
1) Converts hydrophobic substances into H2O-soluble ones
2) Transports them into bile or circulation, eliminates them by filtration
What is pharmacokinetics?
It is the mathematic modeling of drug conc. in circulation
Pharmacokinetics assists in what?
It assists in establishing or modifying a dosage regimen
Pharmacokinetics takes into account what?
It takes into account all factors that determine conc. of a serum drug and its rate of change (absorption, distribution, and elimination)
What is the timing for sx collection?
It is critical
When does trough concs. occur (in sx collection)?
Right before next dose
When does peak concs. occur (in sx collection)?
1 hr after oral dose
What is the sx of choice for TDM?
1) Serum
2) Or plasma
What are the cmpts of pharmacogenomics?
1) Responders
2) Non-responders
Who are responders (in pharmacogenomics)?
Pts benefitting from therapeutic and desired effects of drug
Who are non-responders (in pharmacogenomics)?
Pts not benefitting from therapeutic and desired effects of drug
What is pharmacogenomics?
Therapeutic effectiveness of drugs has been attributed to inter-individual variation in genetic polymorphisms of drug metabolism pathways