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1. Prof. Shaikh Abusufiyan
Part-01: Therapeutic Drug
Monitoring
Pharma Learning

2. At the end of this e-learning session you are able to…
A. Define TDM, Explain criteria and indications of
TDM.
B. Justify. Why TDM is needed in case of Digitalis and
phenytoin.
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3. Therapeutic Drug Monitoring (TDM)
• Measurement or interpretation of drug
blood or plasma drug concentration.
• with the purpose of:
• Optimising a patients drug therapy and
clinical outcome.
• Minimizing the risk of drug induced toxicity.

4. CRITERIA FOR TDM
1. The drug should have narrow TI where:
• Small change in dose results in:
• loss of efficacy (If the dose is lowered)
• Toxicity (If dose is increased)
• Ex. Digoxin, Theophylline, Lithium and Phenytoin

5. 2.Drug having non-linear
pharmacokinetics ex. Phenytoin
• Because it has potentially
clinically important interactions
• or it is associated with large
pharmacokinetic variations
between individuals.

6. 3. Beneficial concentration response
relationship exist between blood drug
concentration and pharmacological effects.
• Preferably with respect to both clinical
efficacy and toxicity.
4. When there is no other easily measurable
physiological parameter ex. BP

7. Q&A
Q.1 What is the purpose of TDM?
Q.2 Give example of Drug with narrow Therapeutic
index?
Q.3 Give criteria of TDM?
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8. When should TDM??
• Appropriate indications for TDM include:
1. Patient with inadequate clinical response:
• Ex. Transplant patient to ensure
cyclosporine concentrations

9. 2. A patient with sign and symptoms
of drug toxicity ex. Persistent
nausea with theophylline
• To minimize the risk of drug toxicity
• Ex. Nephrotoxicity and ototoxicity
associated with aminoglycoside therapy

10. 3. To individualize dosing for
drugs
with an unpredictable dose
response curve: Ex. Phenytoin

11. • To predict a patient dose requirements.
• Individualised rapid dose titration
while minimizing the risk of toxicity.
• To asses medication compliance Ex.
Patients with poor seizure control

12. • To identify poisons and to asses the severity
of poisoning ex. Paracetamol poisoning.
• The effectiveness of antidotes and the
excretion of poisons
can be monitored by measuring the
concentration of poison.
Patient with Poison

13. Justify. Why TDM is required for Digoxin
• Heart failure:
• 0.6 to 1.0 nmol/L
• Arterial Failure:
• 0.6 to 2.6 nmol/L
1. Narrow Therapeutic Index
2. Half life 30-50 hrs which may lead
to cumulative toxicity

14. 3. Also low serum potassium --> potentiate
toxicity despite serum digoxin
concentration is within TI.
4. Plasma concentration may be elevated
by drugs --> like amiodarone, quinidine,
verapamil and diltiazem.

15. Justify. why TDM is required for
Phenytoin?
• Therapeutic range for anticonvulsant
therapy:
• 10 to 20 mg/l
– Narrow therapeutic index
• Adult half life 10 to 30 hrs
– Possibility of cumulative toxicity

16. • Plasma concentration --> may be elevated by
amiodarone, azole antifungals, cimetidine, diltiazem,
fluoxetine etc.
• Small increase in dose --> give disproportionate increase
in plasma conc- Non linear pharmacokinetic.
• In patient with hypoalbuminemia and sever renal failure
• Free conc of drug will be More

17. Reference:
• Dr. H. P. Tipnis and Dr. Amrita Bajaj. Clinical Pharmacy, 3rd
edition. Carrier Publication Pg. No:395-411
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19. Q&A
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20. Prof. Shaikh Abusufiyan
Part-02: Therapeutic Drug
Monitoring
Pharma Learning

21. At the end of this e-learning session you are able to…
A. Discuss Factors affecting the
interpretation of TDM.
1

22. Interpreting TDM results
• Factors affecting the interpretation of TDM result:
• Minimum information needed while interpretation is:
• Indication for therapy
• Dosing regimen
• Duration of therapy
• Time of last dose
• Time of sample
• Reason why TDM is requested

23. • Drug conc. should always be interpreted based on
the clinical circumstances of the individual patients.
1. Patient data:
• Age, sex & lean body wt.
• Imp for renally cleared drugs
• It allow estimation of creatine clearance

24. 2. Dosing regimen (Dose, Dosing frequency,
route of administration) and duration of therapy:
• Sufficient time should be elapse
to allow steady state to be achieved before TDM is
performed.

25. 4. Indication for therapy:
• Ex. Digoxin prescribe for 2
different indications
• Heart failure:
• 0.6 to 1.0 nmol/L
• Arterial Failure:
• 0.6 to 2.6 nmol/L

26. 5. Reduced Protein binding:
• Malnutrition's and nephropathy:
• Reduces the conc of plasma protein
• It increases free plasma conc of drugs strongly
bound to plasma.
• Measurement of total & free drug conc -->
useful.

27. Q&A
Q.1 What minimum information is needed for
interpretation of result of TDM?
Q.2 In which types of drugs patient data is
important?
Q.3 How malnutrition's and nephropathy effect
concentration of drug in plasma?
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28. 6. Drug interaction:
• Result should be interpreted in light of
patient other drug therapy.
• Ex. In presence of Amiodarone or verapamil.
Increase in unexpectedly high concentration of
Digoxin
produces toxicity

29. 7. Pathophysiology of patients:
• Patient comorbidity should be consider
Ex. Vomiting, Dialarhoea & IBD -->
• Alter absorption
• Alter serum drug concentration

30. 7. Alcohol use
• Produces Hepatic microsomal Enzyme induction
• Increase clearance & decrease serum conc of
hepatically cleared drugs

31. 8. Tobacco use/ cigarette smoking:
• Increase hepatic clearance --> clozapine &
theophylline
• Patient recently stop smoking
unexpectedly high conc of above drugs

32. 9. Medication & sampling error:
• Ex. Wrong dose of gentamycin may have
been given.
• Blood may be mistakenly drawn from
another patient with the same name.

33. 10. Laboratory error:
• If all other causes of unexpected results are
ruled out --> laboratory error may be the
explanation.
Solution:
• Repeat the assay
• Blood sample can be sent to another laboratory

34. Reference
• Dr. H. P. Tipnis and Dr. Amrita Bajaj. Clinical Pharmacy, 3rd
edition. Carrier Publication Pg. No:395-411
• Parthasarathi. A text book of clinical pharmacy practice. Pg
No. 395 to 411.

35. 5

36. Q&A
Quiz-Attendance/Feedback:
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37. Reference
• Dr. H. P. Tipnis and Dr. Amrita Bajaj. Clinical Pharmacy, 3rd
edition. Carrier Publication Pg. No:395-411
• Parthasarathi. A text book of clinical pharmacy practice. Pg
No. 395 to 411.

38. Prof. Shaikh Abusufiyan
Part-03: Therapeutic Drug
Monitoring
Pharma Learning

39. At the end of this e-learning session you are able to…
A. Explain effect of timing of blood
sample on TDM.
B. Discuss role of Pharmacist in TDM.
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40. Timing of blood sample
• Measure concentration of drug
may differ significantly depending on
when sample was taken.
• Blood sample for TDM --> should be
both peak and trough sample

41. • Drug with short half life
• Collected --> at the end of the dose
interval
• Immediately before the next dose
• Ex. theophylline/ Vancomycin

42. Drugs with long half life (More than 24 hrs):
• Sample can be collected --> at any
time once distribution is complete.
• Ex. Blood sample for digoxin assay
can be obtained 6-24 hrs after dose
administration.

43. Communication of results
• By telephone
• By hard copy
• By online pathology reporting system

44. Q&A
Q.1 What must be the timing of blood sample in
case of drugs with short half life.
Q.2 Enlist different methods of communication of
TDM result.
4

45. Role of the pharmacist
1. Clinical pharmacist should provide advise to medical staff on
the appropriate use and timing of TDM and assist with interpretation of
result.

46. Role of the pharmacist
2. He also involve in:
• Initial selection of drug regimen
• Taking into account age, sex, B.W, race, renal failure etc he should take
decision about:
• drug choice
• Dosing interval
• Route of administration
• Dosage form of drug

47. 3. Adjustment of dosage regimen
based on TDM results and patient
clinical response.

48. 4. Assessment of possible causes for unexpected results:
• Non-compliance
• Bioavailability problems
• Medication errors
• Drug interaction
• Pharmacogenetic variability

49. 5. Dose adjustment for patients on haemodialysis or peritoneal
dialysis.
6. Provision of information of poisons

50. Reference
• Dr. H. P. Tipnis and Dr. Amrita Bajaj. Clinical Pharmacy, 3rd
edition. Carrier Publication Pg. No:395-411
• Parthasarathi. A text book of clinical pharmacy practice.
Pg No. 395 to 411.

51. 1

52. Quiz-Attendance/Feedback:
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