Pharmacy Practice: Therapeutic Drug Monitering

1. THERAPEUTIC DRUG MONITERING
Dr. Sangameshwar B. Kanthale
sbkrscp@gmail.com
Rajarshi Shahu College of Pharmacy, Buldhana

2. Therapy- Treatment given to
patient
Administration of potent
medication
Therapeutic window-
Concentration maintained
between minimum effective
and maximum safe
concentration
Potent drug-narrow range
Slight variation and non
compliance could prove fatal
effect.
‘ NEED FOR TDM’

3.  Need for TDM
 Treatment are super specialized.
 Patient take more than one medication
 Interactions may happen
 Patients not following prescription
 2 major sources of variability
- pharmacokinetics (dose and plasma concentration)
- pharmacodynamics (drug conc. at the receptor site)
ADME CONSIDERED IN TDM

4. Categories of drugs require TDM
 Cardiac drug
 Antiepileptic
 Bronchodilators
 Immunosuppressant
 Anti-cancer drugs
 Psychiatric drug

5. Which drugs requires monitoring?
 Showing marked pharmacokinetic variability
 Concentration related to ADR
 Narrow therapeutic index
 Defined therapeutic concentration range
 In which desired therapeutic effect is difficult to
monitor

6. When should TDM be requested?
 Drug assay are expensive
 TDM is used to assist the drug therapy
 Appropriate indication for TDM includes-
1. A patient with inadequate clinical response
2. A patient with irreversible sign and symptoms
3. To minimize risk of drug toxicity
4. To individualize dosing for some drugs
5. To help to predict patient dose requirement
6. To assist medication compliance
7. To identify poison and to assess the severity of
poisoning in emergency

7.  Management of therapy using plasma concentration
Request to laboratory
Analysis Quality Assessment
Report Interpretation clinical action
Record previous report

8. Factors considered during TDM
 Factors affect serum drug concentration and need to be
considered during interpretation of the assay.
1. Patient demographics
- patient information
- patient age
- address, occupation, reference
- indication for TDM
- etiology
- past treatment, present treatment
- investigation

9.  Dosage regiment and duration of therapy
 Pathological factors
- patient abnormalities
i.e. vomiting, diarrhea, inflammation
 Alcohol and tobacco use
- non specific microsomal enzyme induction
- result in increased clearance and decrease serum
concentration.
i.e. phenytoin, theophylline

10.  Medicine or Sampling error
- TDM is incompatible with drug administration
record
 Laboratory errors
- Laboratory error is suspected result should be
repeated or sent to different lab
 Sampling time
- Serum concentration depend on time when the
blood is drawn for assay
- Time and date should be monitored

11.  Patient compliance
- Concentration is lower than accepted their may
be possibility of non- compliance
 Individual capacity of ADME
- Renal impairment
- Hepatic impairment
 Altered protein binding

13. Role of Pharmacist
 Multidisciplinary function
 Requires collaborative work
1. Initial optimization of drug, dosage form, interval,
route of administration in view of individual variables
2. Assessment and adjustment of dosage regiment for
patients with hemodialysis or peritoneal dialysis
3. Assessment of possible cause.
- i.e. non compliance, bioavailability problem,
medication error, interaction
4. Management of acute drug intoxication

14. Scenario of TDM in India
 TDM is available in two ways
1. Clinical Pharmacology department
2. Private medical laboratories

15. Number of factors influence the use of TDM in
India
 Cost
 Alternative medical service
 Malnutrition
 Ethnic difference
 Variation in bioavailability