Practical-TDM عملي

فارما / د.منة / طب عام ثالث

عملي(2) 9/3/2017

Practical Pharmacology-3rd Class- 2016

Therapeutic Drug Monitoring (TDM)

Definition:

Therapeutic Drug Monitoring (TDM): is a branch of clinical chemistry and clinical pharmacology that specializes in the measurement of drug concentrations in blood.

- Its main use is for drugs with a “Narrow Therapeutic Range”

i.e. drugs that can easily be under- or overdosed.

TDM aimed at improving patient care, by individually adjusting the dose of drugs for which clinical experience or clinical trials have shown it improved outcome in the general or special populations.

- There are numerous variables that influence the interpretation of drug concentration data:

1- Route and dose of the drug.

2- Time of blood sampling.
3- Handling and storage conditions.
4- Precision and accuracy of the analytical method.


Many different professionals are involved in TDM:

Physicians.

Clinical pharmacologists.
Clinical pharmacists.
Medical laboratory scientists.

Characteristics of drugs that subjected to therapeutic drug monitoring

- In pharmacotherapy, many medications are used without monitoring of blood levels.
- In a small group of drugs:
- Insufficient levels will lead to under treatment or resistance. &
- Excessive levels can lead to toxicity and tissue damage.

Examples of drugs analyzed by therapeutic drug monitoring:

Antiepileptics:
(such as Carbamezapine, phenytoin and valproic acid)
2- Mood stabilizers, especially lithium citrate.
3- Antipsychotics.
4- Cardiac glycosides e.g. Digoxin.
5- Bronchodilators e.g. theophylline.
6- Aminoglycoside antibiotics (gentamicin)


Note:
Therapeutic drug monitoring can also detect poisoning with the above drugs, when the suspicion arises.

High-performance liquid chromatography (HPLC):

Note: Sometimes referred to as high-pressure liquid chromatography.

Chromatographic technique: used to separate a mixture of compounds in analytical chemistry and biochemistry with the purpose of identifying, quantifying or purifying the individual components of the mixture.

HPLC Principles:

- HPLC depends on pumps to pass a pressurized liquid and a sample mixture through a column filled with a sorbent, leading to the separation of the sample components.
- The active component of the column, (the sorbent), is typically a granular material made of solid particles (e.g. silica, polymers, etc.) 2-50 micrometers in size.
- The components of the sample mixture are separated from each other due to their different degrees of interaction with the sorbent particles.

- The Pressurized Liquid is typically a mixture of solvents (e.g. water, acetonitrile and/or methanol) and is referred to as "mobile phase".
- The components of the sample mixture are separated from each other due to their different degrees of interaction with the sorbent particles.

Application (Uses) of HPLC:

1- Pharmaceuticals industry
a. To test the drug stability.
b. Determination of drug quantity in pharmaceutical dosage forms, e.g. paracetamol.
c. Determination of the quantity of drug in biological fluids.
2- Analysis of natural contamination
E g. Phenol & Mercury from sea water
3- Forensic test (الطب القضائي)
a. Determination of steroid in blood, or urine.
b. Detection of psychotropic drugs in plasma.