[TDM] Drug monitoring Flashcards
Hydroxychloroquine - when starting medication
Check visual acuity and fundoscopy - may result in a severe and permanent retinopathy
How should you check tacrolimus levels?
Measuring a trough level before the morning or evening dose is the correct way to check a tacrolimus level.
After a transplant, the optimal level might be 6–10 ng/mL.
What does the initial dose of ramipril depend on?
Renal function
Renal function and electrolytes should be checked before starting ACE inhibitors (or increasing the dose) and monitored during treatment (more frequently if side effects mentioned are present).
What should predose ‘trough’ concentrations of vancomycin be?
10–15 mg/L
If ferrous sulphate 1 tablet daily is not tolerated, what should you do?
Reduced if not tolerated to 1 tablet once daily on alternate days.
How long should iron replacement (e.g. with ferrous sulphate) be given for?
Monitor haemoglobin concentration within the first 4 weeks of treatment, then regularly thereafter to assess response (e.g. every 4 weeks).
Once haemoglobin is within the normal range, treatment should be continued for around a further 3 months to replenish the iron stores.
What will provide the most accurate plasma-digoxin concentration?
Level taken at least 6 hours post dose
What is important to monitor when phenytoin is given IV?
ECG - associated with cardiac arrhythmias!
When a patient is on aminophylline, what level is monitored and when?
The ideal level for theophylline is 10–20 mg/L.
Aminophylline is monitored therapeutically in terms of plasma-theophylline concentrations; a blood sample should be taken 4–6 hours after starting treatment.
It is worth noting that it is not an ‘aminophylline’ level that is checked, but a ‘theophylline’ level. Aminophylline is a simply a stable mixture of combined theophylline and ethylenediamine.
How should aminophylline be given?
Over at least 20 minutes (by very slow IV infusion)
What should be monitored by a GP when a patient takes fluoxetine?
The presence of a rash
How is the dose of enoxaparin determined?
dose-adjusted in low eGFRs (<30 mL/min) but also in adults under 50 kg to prevent excessive anticoagulation
Note that patients under 50 kg should also have lower dose paracetamol to prevent hepatotoxicity.
In a patient at risk of hypercapnic respiratory failure, what should be monitored?
ABG
Ventilation (non-invasive or invasive) may be required if this patient develops hypercapnic respiratory failure.
Peripheral oxygen saturations should be monitored continuously, however, will not detect a rise in carbon dioxide levels.
What to check 15 mins after starting a blood transfusion to detect risk of acute tranfusion reaction>
Heart rate, blood pressure and temperature
What should be monitored when enoxaparin is given?
Platelet counts should be measured just before treatment with unfractionated or low molecular weight heparin, and regular monitoring of platelet counts may be required if given for longer than 4 days.
ALSO: potassium
Can cause heparin-induced thrombocytopenia.
Which electrolyte should be monitored in patients taking enoxaparin?
Potassium
This is because enoxaparin and unfractioned heparin can inhibit aldosterone, therefore causing a rise in serum potassium. An increased risk of hyperkalaemia is seen in chronic renal failure, acidosis, diabetes mellitus and those with a high starting potassium.
When is anti-factor Xa activity indicated in patients taking heparin?
Increased risk of bleeding (e.g. in renal impairment and those who are underweight or overweight).
Frequency of monitoring of FBC with clozapine use
Every week for the first 18 weeks and every second week up to 1 year
How often should lithium levels be checked?
Serum lithium level should be re-checked one week after every dose change and then weekly until levels are stable. Following stabilisation of lithium levels, they can be monitored every 3 months. Lithium levels are usually checked 12 hours post-dose. Toxicity occurs at serum levels above 1.5mmol/L.
Urea & electrolytes should be checked at least every 6 months. If there is a decline in renal function, then monitoring should occur more regularly.
Serum calcium level should be checked at least every 6 months. Lithium can cause hyperparathyroidism and hypercalcaemia.
Thyroid function tests should be checked every 6 months due to the risk of thyrotoxicosis.
An electrocardiogram should be performed prior to commencing lithium therapy.
Follow up checks for COCP use?
Weight + Blood pressure
All women who are on combined oral contraceptive pills should have their weight and blood pressure recorded before beginning therapy and as part of their follow-up. This is because women who are on the pill are at increased risk of developing hypertension and therefore are at increased risk of myocardial infarction and haemorrhagic stroke. There has been debate as to whether the pill causes significant weight gain, with some studies finding only a small percentage increase in some participants’ weight. However, weight should be checked routinely, as if a patient’s BMI is 35 or greater, they should be on a more suitable form of contraception.
Most appropriate set of blood tests to monitor for the risk of adverse effects associated with methotrexate therapy.
FBC, U&Es, LFTs
Patients on methotrexate are at risk of blood dyscrasias. This includes severe anaemia, leukopenia, and thrombocytopenia. Therefore, a full blood count is required. Additionally, methotrexate can lead to liver cirrhosis and so LFTs must also be checked. These blood tests should be checked every 1-2 weeks until therapy is stabilised. After this, patients can have their blood checked every 2-3 months.
Patients on methotrexate should be advised to let their GP know of any signs of infection, for example, sore throat, fever, shortness of breath or fatigue.
When using insulin-glucose infusion for hyperkalaemia, what should be monitored?
Capillary blood glucose should be monitored throughout the insulin-glucose infusion due to the risk of hypoglycaemia. The Renal Association guidelines on the management of hyperkalaemia advise blood glucose levels should be monitored at regular intervals up to 12 hours following the administration of an insulin-glucose infusion.
Conditions in which target INR of 2.5 is recommended?
- mitral valve replacement
- deep-vein thrombosis or pulmonary embolism
- atrial fibrillation
- cardioversion
- dilated cardiomyopathy
- mitral stenosis or regurgitation in patients with either atrial fibrillation, a history of systemic embolism, a left atrial thrombus, or an enlarged left atrium
- acute arterial embolism requiring embolectomy
Levothyroxine - TSH requirements?
Consider measuring thyroid stimulating hormone (TSH) level every three months until stabilised (two similar measurements within the reference range, 3 months apart), then yearly thereafter.
Investigations to perform before starting amiodarone
CXR, ECG, U&Es, TFTs, LFTs
Most appropriate option to monitor for the adverse effects of atorvastatin after 3 months of treatment.
Liver function tests should be repeated within 3 months of starting treatment and again at 12 months according to NICE guidelines. Use of statins can cause liver injury and hepatotoxicity, although liver failure is rare.
Monitoring for rivaroxaban
Patient-reported symptoms
Patients should be monitored for signs of bleeding or anaemia; treatment should be stopped if severe bleeding occurs.
No routine anticoagulant monitoring required (INR tests are unreliable).
What should be checked before changing the dose of ACE inhibitors?
Renal function and electrolytes should be checked before starting ACE inhibitors (or increasing the dose) and monitored during treatment (more frequently if side effects mentioned are present).
What are the most appropriate investigations which should be checked after 6 months of treatment to monitor for adverse effects of lithium therapy?
BMI, U&Es, TFTs
According to the BNF, patients on lithium therapy should have their TFTs and U&Es checked before beginning therapy. If the patient has cardiovascular disease or risk factors for it, they should also have an ECG performed.
Every 6 months, patients on lithium should have their BMI, U&Es (including eGFR), and TFTs checked. They should have them checked over a shorter interval if there is any evidence of impaired renal or thyroid function or raised calcium levels.
Rationale for monitoring:
* BMI is monitored as lithium is associated with weight gain.
* U&Es are monitored because lithium is associated with electrolyte disturbances and renal impairment.
* TFTs are monitored as lithium can cause hypothyroidism.
* ECGs are recommended in some patients due to the association of lithium and atrioventricular block as well as cardiomyopathy.
Gentamicin multiple daily dosing - changing interval vs dose?
Trough high= Increase interval
Peak high= Decrease dose
