Therapeutic Drug Monitoring/ Interpreting Lab Data Flashcards
What is a high risk medicine?
A medicine that has a high risk of causing injury or harm if misused or used in error.
Are error rates higher in high risk medicines?
Not necessarily but if there is an error it can have more significant consequences
Give some examples of high risk medicines.
Methotrexate
Insulin
Lithium
Anticoagulants
Antibiotics
Injectable sedatives
Opioids
Antipsychotics
Insulin
Infusion fluids
What is a narrow therapeutic range?
Drugs in which there is only a small difference between the minimum effective concentration in blood and the minimum toxic concentration in blood
Name some drugs with a narrow therapeutic range.
Carbamazepine
Gentamicin
Digoxin
Phenytoin
Theophylline
Vancomycin
Warfarin
What is the role of the pharmacist in therapeutic drug monitoring?
Ensure safety
Ensure quality
Ensure efficacy
Support patients
Do all drugs require monitoring?
Yes but to different degrees.
Why do all drugs require some degree of monitoring?
Ensuring efficacy and safety and minimising risk to patient.
What should we consider when monitoring therapy?
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?
What do we monitor in cardiovascular disease?
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?
What do we monitor in infection?
Temperature
White cell count
Inflammatory markers - CRP and ESR
Microscopy, culture and sensitivity
Symptoms (improvement?)
What do we monitor in diabetes?
Blood glucose
HBA1c
Insulin dose requirements
Hypoglycaemia
Hyperglycaemia
Macrovascular complications such as CVD
Microvascular complications (retinopathy, neuropathy, renal disease)
What do we monitor if patient is in pain?
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)
What do we monitor in respiratory conditions?
Dyspnoea (shortness of breath)
PEFR (Peak Expiratory Flow Rate - using peak flow meter)
FEV1 , FVC
Respiratory rate
Reliever use
What should we monitor when a patient is on ACE inhibitors?
Blood Pressure
Pulse
Serum potassium (risk of HYPERkalaemia)
Creatinine
Urea
Dry cough
Postural hypertension
What should we monitor when a patient is on analgesics?
Pain score
Usage - do they still need strong analgesics? Should dose be decreased?
What should we monitor when a patient is on opioids?
Constipation (laxative usually given but NOT bulk forming)
Nausea and vomiting
Respiratory rate
Antimuscarinic side effects
What should we monitor when a patient is on antibiotics?
Infections - symptoms getting better?
Nausea and vomiting
Diarrhoea
Class specific effects ?
What should we monitor when a patient is on anticoagulants?
INR
Unexplained bleeding or bruising
Vitamin K intake
What should we monitor when a patient is on antidepressants?
Mood
Sodium (HYPOnatraemia is most common in SSRIs)
Antimuscarinic side effects
What should we monitor when a patient is on a beta-2 agonist?
Shortness of breath
Respiratory rate
PEFR (Peak Expiratory Flow Rate0
Nervous tension
Fine tremor
Palpitations
What should we monitor when a patient is on statins?
Cholesterol levels
Liver function tests
Myalgia (muscle weakness - as statin use can lead to RHADOMYOLYSIS)
What should we monitor when a patient is on diuretics?
Blood pressure
Urea and Electrolytes (usually LOWERS serum electrolytes)
Serum Uric acid (risk of GOUT + hyperuricaemia)
Oedema
What should we monitor when a patient is on digoxin?
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
Is amiodarone a cytochrome P450 inhibitor or inducer?
INHIBITOR
What is important when stopping amiodarone treatment?
It has a long half-life so patient may still get drug interactions or side effects such as grey skin.
What does an INR LOWER than target suggest?
Risk of developing a clot.
What effect does smoking have on theophylline concentrations in the plasma?
It decreases levels of theophylline so if a person suddenly stops smoking they are at risk of theophylline toxicity.
Why do we monitor laboratory data?
- Confirming diagnosis - e.g. glucose tolerance in diabetes mellitus
- Assessing severity - e.g. renal failure
- Checking treatment response
- Selecting appropriate drug and dose - e.g. if patient has hypokalaemia use a potassium sparing diuretic
- Warning against contraindicated drugs - e.g. nephrotoxic antibiotics in renal failure
- Safety especially when using high risk drugs
- Identifying disturbances caused by drugs - e.g. loop and thiazide diuretics can cause HYPOkalaemia or HYPOnatraemia.
- Identifying asymptomatic imbalances
- Differentiate high levels from low
- Decide on appropriate route of administration
- Corresponding with doctors
What can lab data reference values vary between?
Laboratories, hospitals and countries as well as age groups and genders
What rule applies to MOST imbalances?
To ALWAYS treat the underlying cause.
- removing/reducing a drug
- modifying diet accordingly
What is responsible for fluid balance in the body?
The kidneys and cell membranes that maintain osmolality. (sodium out and potassium in)
What do we look at to understand a patient’s fluid input vs output?
Fluid balance chart whilst accounting for losses such as through diarrhoea and vomiting.
What is monitored to measure serum osmolality?
Sodium, potassium, glucose and urea.
What happens when there is a high serum osmolality?
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.
What are some symptoms of hypernatraemia?
HIGH LEVELS OF SODIUM
- 150mmol/L : thirst, lethargy, irritability, headache, stupor
- 170 mmol/L : seizure, coma, death
What do we need to consider when finding the cause of HYPERnatraemia?
Loss of body water OR gain in body sodium.
What are some reasons for loss in body water?
Dehydration
Vomiting
Diarrhoea
Burns
Diseases such as diabetes insipidus
Diabetic ketoacidosis
What are some reasons for gain in body sodium?
Drugs : antacids, antibiotics, dispersible tablets, mineralocorticoid effects of steroids, lactulose, methyldopa, oestrogens
How is HYPERnatraemia treated?
Drink water if due to water loss
Restrict sodium intake if due to sodium gain
How is SEVERE hypernatraemia treated?
Glucose 5% IV fluids
Which drugs can be used in HYPERnatraemia ?
Loop and thiazide diuretics
What are some symptoms of hyponatraemia?
LOW LEVELS OF SODIUM
Can be symptomless
At < 130mmol/L : lethargy, weakness, headache, postural hypotension
What do we need to consider when finding the cause of HYPOnatraemia?
Loss of body sodium and gain in body water
What are some reasons for loss of body sodium?
Vomiting
Diarrhoea
Salt-losing kidney disorders
Addison’s disease/adrenal insufficiency
What are some reasons for gain in body water?
Drugs: ACEi, carbamazepine, Lithium, NSAIDs, SSRIs
Surgery or injury
Renal disease
Congestive heart failure
Cirrhosis with ascites
Age (very young or very old)
How is HYPOnatraemia treated?
Fluid restriction if gain in water
Slow sodium tablets (NaCl) if loss of sodium
Diuretics (sodium should be monitored)
How is SEVERE hyponatraemia treated?
If <120mmol/L or water intoxication use IV sodium chloride 0.9% or hypertonic saline.
