Drug Monitoring Flashcards
How frequently should patients on methotrexate be monitored?
The BNF recommends that patients have FBC, LFTs and U&Es monitored before commencing treatment. These should be repeated every 1 - 2 weeks until therapy has stabilised and thereafter every 2 - 3 months. Patients should also be advised to report any signs of infection. Methotrexate should be avoided in severe hepatic and renal impairment.
what is an important investigation to do on patient taking oral contraceptive pill Microgynon?
Blood pressure.
BNF recommends annual BP monitoring because hypertension is known to increase risk of CVD associated with the COCP. Women using COCP with hypertension are at an increased risk of stroke, MI and PAD.
Women with a SBP >160 or a DBP >100 should not receive the COCP.
How frequently should fasting blood glucose be measured when on antipsychotics?
FBG is measured at baseline, after one month of treatment and again at 4-6 months of treatment. Antipsychotics such as olanzapine can increase the risk of developing diabetes.
What is the most appropriate blood tests and interval for monitoring of leflunomide?
FBC and LFT are measured before commencing treatment and then every 2 weeks for the first six months.
This can then be reduced to two-monthly FBC and LFTs.
What is the blood tests and interval for monitoring of ciclosporin?
- BP, lipids, U&Es and LFT before starting treatment
- U&Es repeated every two weeks for the first 3 months and monthly thereafter
- Lipids repeated after the first month of treatment
- LFTs and magnesium (no specific timeline)
Most appropriate first test before starting atorvastatin?
Liver function tests (LFTs)
All statins need to be used with caution in patients with iver disease and are contraindicated in patients with grossly abnormal LFTs.
What is the most important blood result to have when deciding on the dosing of Vancomycin?
Serum creatinine.
It is largely cleared through the body by the kidneys and therefore in impaired renal function the dose is reduced.
Overdosing can cause nephrotoxicity, ototoxicity and neurotoxicity.
What is the recommended time to measure digoxin levels in patient on digoxin?
The recommended time to measure Digoxin levels is 6 - 12 hours post-oral ingestion.
If measurements are taken too soon after ingestion, they may deliver erroneously high results that falsely indicate digoxin toxicity. If they are taken too long after ingestion they may deliver erroneously low results that may falsely indicate a sub-therapeutic digoxin dose.
How to titrate dose of levothyroxine for patients being overtreated for hypothyroidism?
BNF suggests in the absence of frank toxicity, to up and down titrate doses at 25 to 50 microgram intervals. After titration, thyroid levels should be checked again in 2 - 4 weeks.
Blood tests and monitoring intervals for azathioprine?
FBC is monitored weekly for the first four weeks of treatment. After this period, the freuqncy of monitoring can be reduced to at least every 3 months.
Consider measuring thiopurine methyltransgerase (TPMT) activity before commencing treatment with thiopurine drugs. Patients with reduced TPMT enzyme activity have increased risk of myelosuppression.
Which blood tests and monitoring interval for methotrexate?
FBC, LFTs, U&Es monitored before commencing therapy.
Repeated every 1 - 2 weeks until therapy has stabilised and then every 2 -3 months after this.
Advantage of warfarin over DOACs?
Warfarin can be more easily reversed in acute bleeds with vitamin K than DOACs. In serious bleeds this can be supplemented with FFP or prothrombin complex concentrate.
DOACs like apixaban can only be reversed by the antidote Andexanet alfa and dabigatran has a reversal agent called idarucizumab.
How to monitor tacrolimus levels?
Through serum tacrolimus level - immediately before morning dose.
Pre-dose trough level is used to determine the next day’s dose.
What investigation is most appropriate before starting treatment with clozapine?
Full blood count.
BNF recommends that clozapine requires monitoring of white cells weekly for the first 18 weeks, then forntnightly for one year and then monthly thereafter.
Most serious SE is agranulocytosis resulting in neutropenia.
What tests should be checked for patients on lithium?
Lithium level, TFT, U&E.
The BNF advises that renal and thyroid function should be checked every 6 months in patients who take lithium.
