Therapeutic Drug Monitoring (TDM)
PST 06106
Basic
Pharmacotherapy
Session 2: Therapeutic Drug Monitoring (TDM)
Learning Tasks
By the end of this session students are expected to be able to:
Define therapeutic drug monitoring
List principles and outline concepts of therapeutic drug monitoring
Outline criteria for therapeutic drug monitoring
List drugs that qualify for therapeutic drug
monotoring
Explain clinical significance of therapeutic drug monitoring
List limitations of therapeutic drug monitoring
Principles and Concepts of Therapeutic Drug Monitoring
Therapeutic
drug monitoring (TDM)
is defined as the use of drug concentration measurements in plasma as an aid to the management of drug therapy for the cure, alleviation or prevention of
disease. TDM
enables the assessment of the efficacy and safety of a particular medication in a variety of clinical settings
.
TDM aims at improving patient care by adjusting the dose of drugs for which clinical experience or clinical trial have shown it improved outcome in the general or special populations
Principles and Concepts of Therapeutic Drug Monitoring
Cont
…..
Therapeutic Drug Monitoring aims to individualize therapeutic regimens for optimal patient benefit and avoid both
sub therapeutic
and toxic plasma drug concentrations.
Specifically, TDM is a practice applied to a small group of drugs in which there is a direct relation between plasma drug concentration and pharmacological response
Therefore, close relationship between the plasma level of the drug and its clinical effect is essential.
If such a relationship does not exit TDM is of little value.
The measurement of plasma level is justified only when the information provided is of potential therapeutic benefit.
Principles and Concepts of Therapeutic Drug Monitoring
Cont.…..
In summary, TDM process involves the following;
Administration of a predetermined dose of drug
Collection of blood samples
Determination/measurements of blood samples using analytical procedures
Evaluation of Clinical effect of drug
Development/Adjustment
of dosage
regimen
Activity: Buzzing
What
are the criteria for therapeutic drug monitoring?
Criteria for therapeutic drug monitoring
The drug in question has a narrow therapeutic range,
eg
: Lithium, phenytoin, and digoxin
A direct relationship exists between the drug or drug metabolite levels in plasma and the pharmacological or toxic effects,
The therapeutic effect can not be readily assessed by the clinical observation,
Large individual variability in steady state plasma concentration exits at any given dose
Appropriate analytic techniques are available to determine the drug and metabolite
levels
Criteria for therapeutic drug
monitoring
Cont
…
Drugs for which relationship between dose and plasma concentration is unpredictable,
e.g
Phenytoin
Non compliance
Therapeutic failure
Major organ failure
Prevention of adverse drug effects
Drugs that qualify for therapeutic drug monitoring
Cardio
active drugs
amiodarone,
digoxin,
digitoxin
disopyramide
,
lignocaine,
procainamide,
propranolol and
quinidine
Drugs that qualify for therapeutic drug
monitoring Cont.….
Aminoglycoside
gentamycin,
A
mikacin
and tobramycin
Anti Cancer
methotrexate
Antidepressants
:
lithium
tricyclic
antidepressants
Drugs that qualify for therapeutic drug monitoring Cont.….
Antiepileptic
drugs
Phenytoin,
phenobarbitone
benzodiazepines,
carbamazepine,
Valproic
acid and
ethosuximide
Bronchodilators :
theophylline
Therapeutic drug monitoring process
Fig 2.1: Summary of TDM Process
Clinical significance of Therapeutic drug monitoring
…
Drug levels from TDM are used in conjunction with other clinical data to assist practitioners in determining how a patient is responding.
Drug levels provide a basis for individualizin
g
patient dosage regimens.
Drug levels assist in determining if a change in patient-specific
pharmacokinetics
has occurred during a course of treatment, whether as a result of a change in physiological state, a change in diet, or addition of other drugs.
Clinical significance of Therapeutic drug
monitoring Cont.
…
Maximizes drug efficacy
Helps in avoidance of drug toxicity
Identifies therapeutic failure due to
subtherapeutic
level
May help to identifies patients who are non compliant
Limitation of Therapeutic
D
rug
M
onitoring(TDM)
There may be some factors that may lead to incorrect interpretation of plasma drug levels such as;
Non-compliance of patient leading to low plasma drug levels
Low dose administered which leads to
subtharapapeutic
concentrations
Patient suffer from mal-absorption
Drug with low bioavailability may also lead to
subtherapeutic
concentrations
Concomitant drugs that could affect the plasma levels of the drug in question
Limitation of Therapeutic Drug Monitoring(TDM
) Cont.….
Hepatic or renal dysfunction
Diseases related to genetic factors affecting drug metabolism
.Time of administration of the drug is not accurate.
Dose administration error.
Inaccurate time of sampling, or timing was before steady-state is reached
Wrong site of sampling.
Lab assay error.
Limitation of Therapeutic Drug Monitoring(TDM) Cont.….
Effect of age
There is a great variability in response to drugs at extremes of age.
As an example, elderly patients are more sensitive to the CNS depressant effect of drugs but are less sensitive to cardiovascular effects of Propranolol.
It is well known that children are more sensitive to morphine.
Pregnancy
Many drugs can be affected by pregnancy state.
As an example, drug levels of phenytoin and
phenobarbitone
are lower during pregnancy
Key Points
TDM is a very important and widely used technique throughout the treatment process.
TDM is used when there is a sufficient relationship between the plasma level of the drug and its clinical effect
Evaluation
What is therapeutic drug monitoring?
What are steps involved during therapeutic drug monitoring?
What are criteria for therapeutic drug monitoring
What the clinical significance of therapeutic drug monitoring
References
Wells
BG,
DiPiro
J,
Schwinghammer
T (2013), Pharmacotherapy Handbook (6th Ed). New York, NY: McGraw-Hill.
DiPiro
JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey ML, (2008): Pharmacotherapy: A Pathophysiologic Approach (7th
ed
): New York, NY: McGraw-Hill.
Katz M D., Matthias KR., Chisholm-Burns M A., Pharmacotherapy(2011) Principles & Practice Study Guide: A Case-Based Care Plan Approach: New York, NY: McGraw-Hill.
Schwinghammer
TL, Koehler JM (2009) Pharmacotherapy Casebook: A Patient-Focused Approach (7th
ed
): New York, NY: McGraw-Hill.
Unataka kutumiwa notes hizi kupitia WhatsApp?Kwa notes zilizopangiliwa vizuri kwa kusoma offline au PDF, bonyeza kitufe hapa chini. Ujumbe wenye Level, Semester, Module na Topic utaandaliwa moja kwa moja.TUMIWA NOTES WHATSAPP
