Therapeutic drug monitoring Flashcards
What are the 4 main principles of pharmacokinetics
- Absorption
- Distribution
- Metabolism
- Excretion
What are the 6 factors that affect the pharmokinetics of a drug
- Age
- Weight
- Sex
- Genetrics
- Diseases
- Drug interactions
What is pharmacokinetics
studies how drugs move through the body, covering four primary processes: absorption, distribution, metabolism, and excretion
What is the MEC
Minimum Effective Concentration: This is the minimum concentration of the drug above which therapeutic value of the drug is seen
What is the MTC
Minimum Toxic Concentration: upper concentration above which the rate and severity of adverse effects become
unacceptable
What could be the 4 possible causes of a lower than expected conc. of a drug in a patient
- Incorrect dose given to the patient
- Patient is non adherent to the patient
- Rapid elimination of the drug
- Time when the sample was taken is incorrect
What are the possible causes of a higher than normal conc. of the drug 4
- Error in the dose regimen
- Decreased renal or hepatic function
- Timing of the sampling
- No response despite therapeutic conc. [tolerance]
When can you safely say that you have reached the steady state
This occurs after at least 5 half lives after the last dose change
What is therapeutic drug monitoring
Measurement of drug concentration in the body fluids
Why is it important to do TDM 4
- Avoid toxicity
- Optimize the dose of the drug
- Detect any changes in pharmacokinetics
- Monitor adherence to the drugs
What are the 6 main factors that influence pharmacokinetics
- Age
- Weight
- Sex
- Genetics
- Disease
- Drug interaction
Which drugs are suitable for TDM 4
- High interpatient variability in the plasma concentration
- Narrow therapeutic range
- When there is a high correlation between the plasma conc. and then clinical effect
- There is availability and it is cost effective
What are the factors related to a patient that indicate TDM 3
- Lack of a clinical response
- To monitor the adherence to drugs
- Suspected toxicity
What are the co morbidities that would indicate TDM in patients 3
- Drug- drug interactions
- Renal and hepatic disease
- GIT issues that could result in decreased absorption
What are the possible causes of lower concentrations than what is expected
- Incorrect dose was given
- Patient is non adherent
- Rapid elimination of the drug is present [Induction, genetics, increased renal excretion]
- Timing of the sample was taken at the incorrect time
What are the causes of higher than normal concentration
- Error in the dose regimen
- There is a decrease in renal and hepatic function
- Slowed elimination
- Timing of the sampling is incorrect
When is the steady state achieved
At least 5 half lives after the last dose change
What is zero order kinetics
The body eliminates a fixed amount of the drug per unit of time. The elimination is linear irrespective of the conc. of the drug
What is first order kinetics
This is where the rate of elimination is proportional to the drug conc..Elimination is exponential on a concentration vs. time graph.
What is meant by a Capacity-saturable metabolism
This is where the drug elimination become saturated at higher drug concentrations and so there is a transition from a first order
