Therapeutic Drug Monitoring/ Interpreting Lab Data

Question 1

What is a high risk medicine?

Answer 1

A medicine that has a high risk of causing injury or harm if misused or used in error.

Question 2

Are error rates higher in high risk medicines?

Answer 2

Not necessarily but if there is an error it can have more significant consequences

Question 3

Give some examples of high risk medicines.

Answer 3

Methotrexate
Insulin
Lithium
Anticoagulants
Antibiotics
Injectable sedatives
Opioids
Antipsychotics
Insulin
Infusion fluids

Question 4

What is a narrow therapeutic range?

Answer 4

Drugs in which there is only a small difference between the minimum effective concentration in blood and the minimum toxic concentration in blood

Question 5

Name some drugs with a narrow therapeutic range.

Answer 5

Carbamazepine
Gentamicin
Digoxin
Phenytoin
Theophylline
Vancomycin
Warfarin

Question 6

What is the role of the pharmacist in therapeutic drug monitoring?

Answer 6

Ensure safety
Ensure quality
Ensure efficacy
Support patients

Question 7

Do all drugs require monitoring?

Answer 7

Yes but to different degrees.

Question 8

Why do all drugs require some degree of monitoring?

Answer 8

Ensuring efficacy and safety and minimising risk to patient.

Question 9

What should we consider when monitoring therapy?

Answer 9

Is the medicine working?
Is the disease state improving?
Is the medicine causing side effects or toxicity?
Is the medicine affecting other existing health problems?

Question 10

What do we monitor in cardiovascular disease?

Answer 10

Heart Rate
Blood pressure - medication based on age,ethnicity and comorbidities
Chest pain (and referred pain) - MI or differential diagnosis?
Oedema - cracking in lungs or swollen ankles and feet
Shortness of breath (pulmonary oedema
Weight loss/gain
Exercise tolerance (ECG)
Troponin
Creatine Kinase
Does patient need GTN for angina symptoms?

Question 11

What do we monitor in infection?

Answer 11

Temperature
White cell count
Inflammatory markers - CRP and ESR
Microscopy, culture and sensitivity
Symptoms (improvement?)

Question 12

What do we monitor in diabetes?

Answer 12

Blood glucose
HBA1c
Insulin dose requirements
Hypoglycaemia
Hyperglycaemia
Macrovascular complications such as CVD
Microvascular complications (retinopathy, neuropathy, renal disease)

Question 13

What do we monitor if patient is in pain?

Answer 13

Pain score - using universal pain assessment tool
What makes pain better or worse?
Is pain worse at specific times of day?
Analgesic use - reductions in dose or going from opioid back down to paracetamol
Respiration rate (opioid use can cause respiratory depression)

Question 14

What do we monitor in respiratory conditions?

Answer 14

Dyspnoea (shortness of breath)
PEFR (Peak Expiratory Flow Rate - using peak flow meter)
FEV1 , FVC
Respiratory rate
Reliever use

Question 15

What should we monitor when a patient is on ACE inhibitors?

Answer 15

Blood Pressure
Pulse
Serum potassium (risk of HYPERkalaemia)
Creatinine
Urea
Dry cough
Postural hypertension

Question 16

What should we monitor when a patient is on analgesics?

Answer 16

Pain score
Usage - do they still need strong analgesics? Should dose be decreased?

Question 17

What should we monitor when a patient is on opioids?

Answer 17

Constipation (laxative usually given but NOT bulk forming)
Nausea and vomiting
Respiratory rate
Antimuscarinic side effects

Question 18

What should we monitor when a patient is on antibiotics?

Answer 18

Infections - symptoms getting better?
Nausea and vomiting
Diarrhoea
Class specific effects ?

Question 19

What should we monitor when a patient is on anticoagulants?

Answer 19

INR
Unexplained bleeding or bruising
Vitamin K intake

Question 20

What should we monitor when a patient is on antidepressants?

Answer 20

Mood
Sodium (HYPOnatraemia is most common in SSRIs)
Antimuscarinic side effects

Question 21

What should we monitor when a patient is on a beta-2 agonist?

Answer 21

Shortness of breath
Respiratory rate
PEFR (Peak Expiratory Flow Rate0
Nervous tension
Fine tremor
Palpitations

Question 22

What should we monitor when a patient is on statins?

Answer 22

Cholesterol levels
Liver function tests
Myalgia (muscle weakness - as statin use can lead to RHADOMYOLYSIS)

Question 23

What should we monitor when a patient is on diuretics?

Answer 23

Blood pressure
Urea and Electrolytes (usually LOWERS serum electrolytes)
Serum Uric acid (risk of GOUT + hyperuricaemia)
Oedema

Question 24

What should we monitor when a patient is on digoxin?

Answer 24

Serum potassium - if patient already has HYPOkalaemia then toxicity is more likely
Creatinine - renal function can cause accumulation of digoxin
Heart rate - BRADYCARDIA is a sign of toxicity
TDM - plasma conc. of digoxin

Question 25

Is amiodarone a cytochrome P450 inhibitor or inducer?

Answer 25

INHIBITOR

Question 26

What is important when stopping amiodarone treatment?

Answer 26

It has a long half-life so patient may still get drug interactions or side effects such as grey skin.

Question 27

What does an INR LOWER than target suggest?

Answer 27

Risk of developing a clot.

Question 28

What effect does smoking have on theophylline concentrations in the plasma?

Answer 28

It decreases levels of theophylline so if a person suddenly stops smoking they are at risk of theophylline toxicity.

Question 29

Why do we monitor laboratory data?

Answer 29

1. Confirming diagnosis - e.g. glucose tolerance in diabetes mellitus 2. Assessing severity - e.g. renal failure 3. Checking treatment response 4. Selecting appropriate drug and dose - e.g. if patient has hypokalaemia use a potassium sparing diuretic 5. Warning against contraindicated drugs - e.g. nephrotoxic antibiotics in renal failure 6. Safety especially when using high risk drugs 7. Identifying disturbances caused by drugs - e.g. loop and thiazide diuretics can cause HYPOkalaemia or HYPOnatraemia. 8. Identifying asymptomatic imbalances 9. Differentiate high levels from low 10. Decide on appropriate route of administration 11. Corresponding with doctors

Question 30

What can lab data reference values vary between?

Answer 30

Laboratories, hospitals and countries as well as age groups and genders

Question 31

What rule applies to MOST imbalances?

Answer 31

To ALWAYS treat the underlying cause. - removing/reducing a drug - modifying diet accordingly

Question 32

What is responsible for fluid balance in the body?

Answer 32

The kidneys and cell membranes that maintain osmolality. (sodium out and potassium in)

Question 33

What do we look at to understand a patient's fluid input vs output?

Answer 33

Fluid balance chart whilst accounting for losses such as through diarrhoea and vomiting.

Question 34

What is monitored to measure serum osmolality?

Answer 34

Sodium, potassium, glucose and urea.

Question 35

What happens when there is a high serum osmolality?

Answer 35

Increase in ADH secretion Water is reabsorbed so urine is more concentrated and plasma is less concentrated This is so total body water content and salt content can remain consistent.

Question 36

What are some symptoms of hypernatraemia? HIGH LEVELS OF SODIUM

Answer 36

- 150mmol/L : thirst, lethargy, irritability, headache, stupor - 170 mmol/L : seizure, coma, death

Question 37

What do we need to consider when finding the cause of HYPERnatraemia?

Answer 37

Loss of body water OR gain in body sodium.

Question 38

What are some reasons for loss in body water?

Answer 38

Dehydration Vomiting Diarrhoea Burns Diseases such as diabetes insipidus Diabetic ketoacidosis

Question 39

What are some reasons for gain in body sodium?

Answer 39

Drugs : antacids, antibiotics, dispersible tablets, mineralocorticoid effects of steroids, lactulose, methyldopa, oestrogens

Question 40

How is HYPERnatraemia treated?

Answer 40

Drink water if due to water loss Restrict sodium intake if due to sodium gain

Question 41

How is SEVERE hypernatraemia treated?

Answer 41

Glucose 5% IV fluids

Question 42

Which drugs can be used in HYPERnatraemia ?

Answer 42

Loop and thiazide diuretics

Question 43

What are some symptoms of hyponatraemia? LOW LEVELS OF SODIUM

Answer 43

Can be symptomless At < 130mmol/L : lethargy, weakness, headache, postural hypotension

Question 44

What do we need to consider when finding the cause of HYPOnatraemia?

Answer 44

Loss of body sodium and gain in body water

Question 45

What are some reasons for loss of body sodium?

Answer 45

Vomiting Diarrhoea Salt-losing kidney disorders Addison's disease/adrenal insufficiency

Question 46

What are some reasons for gain in body water?

Answer 46

Drugs: ACEi, carbamazepine, Lithium, NSAIDs, SSRIs Surgery or injury Renal disease Congestive heart failure Cirrhosis with ascites Age (very young or very old)

Question 47

How is HYPOnatraemia treated?

Answer 47

Fluid restriction if gain in water Slow sodium tablets (NaCl) if loss of sodium Diuretics (sodium should be monitored)

Question 48

How is SEVERE hyponatraemia treated?

Answer 48

If <120mmol/L or water intoxication use IV sodium chloride 0.9% or hypertonic saline.