Therapeutic Drug Monitoring Flashcards
What is therapeutic drug monitoring?
the measurement of drugs and/or their metabolites in body fluids-usually blood-to maintain therapeutic benefits
What is the definition of drugs (for the purpose of this class)?
medications that are prescribed by medical providers
What is the definition of therapeutic range (TR)?
the dose, or concentration, range of a drug within which the drug produces the desired therapeutic effect
What is the result if a drug is outside of the therapeutic range?
Inefficacy or toxicity
What are the two main purposes of TDM?
- Ensure correct drug dosages for the T.R.
- Identify drug-drug interactions if multiple drugs are taken together
When would TDM be appropriate for a drug?
- The drug has a narrow therapeutic range
- Marled pharmacokinetic variabilities
- Critical adverse effects
All of the following are what?
Age
Gender
Genetics
Diet
Co-administered drugs
Naturopathic agents
Factors that influence drug concentrations and efficacy
Define pharmacokinetics
Study of the movement of drugs in the body
What does pharmacokinetics tell us?
Provides a time-course of drug concentrations in the body as a function of absorption, distribution, metabolism, and excretion
What is bioavailability?
The fraction of the administered dose that eventually reaches its site of action
The following are all examples of what?
Oral—most common, least invasive
Intravenous (IV)—most direct & effective
Intramuscular (IM)
Subcutaneous (SC)
Aerosol
Transdermal patch
Rectal
Routes of administration
What are the three factors that effect the efficiency of absorption from GI tract?
- Dissociation from its administered form
- Solubility in GI fluids
- Diffusion across GI membranes
T/F:
In order for a drug to passively diffuse from the GI tract to the bloodstream, it must be in the hydrophilic state.
FALSE
The drug must be in the hydrophobic state (nonionized)
Drugs will be absorbed in the GI tract ____ in healthy people.
Predictably
Weak acids are efficiently absorbed by the __a__; weak bases are absorbed in the __b__
a) Stomach
b) intestine
Drug absorption is affected by what?
Changes in intestinal motility, pH, inflammation
T/F:
Absorption is not changed wen someone is getting older, becomes pregnant, or develops a pathological condition.
FALSE
What is the definition of drug distribution?
The movement of a drug between blood circulation and tissues and organs and the relative proportion of the drug in the tissues
____ ____ affects the ability of a drug to leave circulation
Lipid Solubility
What is a free fraction?
The portion of a drug that exerts a pharmacologic effect
Free fractions can diffuse out of the __a__ and into the __b__ and __c__ spaces.
a) vasculature
b) interstitial
c) intracellular
What is the formula for drug distribution?
The volume of distribution of a drug = (dose of the drug) / (concentration of the drug)
The following are characteristics of what protein?
Majority of plasma protein constituents
Major transporter of drugs
Changes in concentration affects free vs bound
Albumin
T/F:
Most drugs are subject to binding with serum protein constituents to form drug-protein complexes
TRUE
Only ________ fractions can interact with the site of action to result in a biologic response
Free/unbound
All drugs absorbed from the intestine (except rectum) enter what system?
Hepatic portal system
What is the first pass effect?
The phenomenon in which a drug is metabolized, results in a reduced concentration o the drug before reaching the circulatory system
What are the consequences of impaired liver function?
- Reduced ability to metabolize
- Effects ability to perform biotransformation to produce the therapeutically active metabolite of the drug
- May require dosing adjustments
What are xenobiotics?
Makes up the most drugs. They are exogenous substances capable of entering biochemical pathways that are meant for endogenous substances
_____ is the biochemical pathway responsible for a large portion of drug metabolism
Hepatic mixed function oxidase (MFO) systems
What are the two basic function of MFO?
- Involves taking hydrophobic substances & through a series of enzymatic reaction, converts them to water soluble products
- Products can then be transported into the bile or released into general circulation for elimination by renal filtration
Result of Phase 1 reactions in MFO
To produce reactive intermediates
Result of Phase 2 reactions in MFO
Conjugate functional groups to reactive sites in water-soluble products