3. DEFINITION
Therapeutic drug monitoring refers to the individualization of
dosage by maintaining plasma or blood drug concentrations
within a target range (Therapeutic range, therapeutic window).
It manages the drug therapy in individual patient often
requires evaluation of response of the patient to the
recommended dosage.
4.
5. HISTORY OF TDM
The science of Therapeutic Drug Monitoring grew out of the
recognition that: Certain drugs have a narrow therapeutic
range.
In concentrations above the upper limit of the range, the
drug can be toxic.
In concentrations below the lower limit of the range, the
drug can be ineffective.
Not all patients have the same response at similar doses
6. HISTORY CONT…
These findings led to the development of Clinical
Pharmacology departments.
However, not everyone embraced TDM testing. Some believed
that TDM testing provided little or no value.
Studies were initiated to determine the clinical value of TDM
testing, and in certain instances clear clinical value was
demonstrated.
Today there are over 20 therapeutic drugs which are
routinely monitored
7. TDM IN INDIA
TDM was introduced in India in mid 1980s and last 20 years
have seen its growth.
TDM in India exists in mainly 2 settings:
–In Large teaching hospitals through Dept. of Clinical
Pharmacology.
–In Private sector (Biochemistry Labs, dedicated CPU
units in Corporate hospitals like Apollo)
8. FUNCTIONS
Select drug
Design dosage regimen
Evaluate patient response
Determine need for measuring serum concentration
Assay for drug concentration in biological fluids
Perform pharmacokinetic evaluation of drug
concentration
Re-adjust the dosage regimen
9. CONCEPT OF TDM
TDM is based on the principle that for some drugs there is
close relationship between the plasma level of the drug and its
clinical effect.
The main aim of therapeutic drug monitoring is to find out an
effective medication against the disease without any dangerous
toxic action.
The purpose of TDM is to individualize the dosage to achieve
maximum efficacy of a drug and at the same time minimize
adverse drug reactions.
10. WHEN TDM IS REQUIRED
The drug has a narrow therapeutic index
A direct relation exists between the drug or metabolite levels
in plasma and the pharmacological or toxic effects.
11. WHEN TDM IS NOT REQUIRED
The pharmacological effects can be clinically quantified.
When concentration effect relationship remains unestablished.
Drugs with wide therapeutic range such as beta blockers and
calcium channel blockers.
Dosage need not be individualized.
12. WHY TDM?
To achieve optimal drug therapy.
To achieve desired pharmacological effect of a drug within
shortest possible time with no toxicity
To benefit the patient medically and economically by reducing
hospital stay and drug related toxicity.
To monitor individual complicating factors like patient
characteristics, diseases and drug interactions.
13. There are several classes of drugs commonly monitored to
ensure correct blood concentration, including the following:
Antiepileptics (Phenytoin, Valproic acid etc.)
Antiarrythmics (Digitalis, lignocaine etc.)
Antibiotics (Gentamycin, amikacin, tobramycin)
Antineoplastics (Methotrexate)
Antimanics (Lithium)
Bronchodilators (Theophylline)
Immunosuppressives (Cyclosporine)
14. TDM PROCESS
1 • Decision to request drug level
2 • Biological sample
3 • The request
4 • Laboratory measurement
5 • Result communication by laboratory
6 • Clinical interpretation
7 • Therapeutic management
15. CLINICAL SIGNIFICANCE OF TDM
Maximizes efficacy
Avoids toxicity
Identifies therapeutic failure – Non compliance, sub therapeutic
dose
Facilitates adjustment of dosage
New dose = Old dose X Desired Css/Old Css
Facilitates the therapeutic effect of drug by achieving target
drug concentration
Identify poisoning, drug toxicity and drug abuse
16. LIMITATIONS OF TDM PROCESS
Scientific accuracy of a drug assays
Laboratory variability in reporting
Limited accessibility and infrastructure facility in rural areas
Validity of suggested target ranges
Lack of training and skills
Cost involved
