Drug Monitoring

Question 1

What do you test before starting biologic drugs

Answer 1

CXR- TB
Bloods - hepatitis B, hepatitis C, and HIV. (dont get this confused with booking bloods where they test Hep B HIV and syphillus)

Question 2

At what ALT factor (ie X2 or X3 or X4) are statins contraindicated and wehn do u check this?

Answer 2

before 3 months and 12 months
3x

dont get confused and do 30% increase (which is the maximum (well 29% is) that creatinine can go down before you need to consider stopping ACE-I- You dont stop immediately tho, retake bloods in 1-2 weeks then stop).

Question 3

when do you measure teico, vanco, gent and lithium levels?

Answer 3

Lithium: The goal is to monitor the steady-state concentration at its lowest point (trough), which occurs 12 hours after the dose. Monitoring earlier may not reflect true steady-state levels due to distribution phases. weekly till stable.

Vancomycin: The trough level (lowest concentration just before the next dose) is important because it ensures enough drug is present to cover the infection while minimizing the risk of toxicity. The longer monitoring window reflects the pharmacokinetics of the drug and when the steady-state trough is most accurately measured.

Gentamicin: Both peak (to ensure bacterial killing) and trough (to avoid toxicity) levels are monitored. Peak is typically measured soon after the dose (1hr), and trough (18-24hr) is measured just before the next dose.

Teicoplanin: Due to its long half-life, less frequent monitoring is needed, and it primarily focuses on ensuring effective trough levels after the 3rd-5th dose.

Question 4

if pre dose (trough) levels of gent are high what do you do?

Answer 4

increase interval

Question 5

if post dose (peak) levels of gent are high waht do you do?

Answer 5

decrease dose

Question 6

Which two drugs have a really long half life- so much so that when you stop the drug, they continue to have effect on the body? and you may see side effects even a year later?

Answer 6

• Hydroxychloroquine- even following discontinuation of the offending drug may progress for over a year as it is caused by build up of hydroxychlororquine in the retina.
• Similar to amiodarone in the sense that even when you discontinue this the effects may still be seen as it has such a long half life

Question 7

LFT monitoring for terbenifine

Answer 7

Perform baseline LFT.
Monitor hepatic function before treatment, and then periodically after 4 to 6 weeks’ of treatment.
Discontinue if abnormalities in LFTs.
Advise the patient to stop terbinafine and seek prompt medical assessment if they develop symptoms of liver injury (e.g. flu-like illness, gastrointestinal symptoms, pruritus, and jaundice), infection (e.g. fever, sore throat), or mouth ulcers

Question 8

statins are continued at 3 months if…

Answer 8

reduction in non HDL cholesterol by 40% at 3 months

Question 9

What do you monitor and how often do you monitor for statin therapy ?

Answer 9

what dont you monitor!

1. LFTs- classic- liver injury - dont give if >3X ULN. Do LFT again at 3 months with HbA1C.
2. CK- classic- myopathy, only take if muscle aches before starting therapy or during therapy - repeat after
   7 days if 5x elevated. if concentrations are still raised but less than 5x ULN, the statin should be started at a lower dose
3. before treatment - LFT, LIPID PROFILE, TFT and U+E
4. Fasting BG or HbA1c before starting and at 3 months = High-risk diabetes candidates because it can increase the risk of diabetes.

remember it has to be a high intensity statin- ATORVOSTATIN IS FIRST LINE and if non LDH level doesnt decrease by 40% you must increase statin dose or add ezetimibe.
The lipid target is low-density lipoprotein (LDL) cholesterol levels of 2.0 mmol/L or less or non-HDL cholesterol levels of 2.6 mmol/L or less.

Question 10

How often do you measure HbA1c in someone who is pre diabetic?

Answer 10

annually

Question 11

methotrexate monitoring and why

Answer 11

pre testing

NO CXR needed
pregnancy test
fbc - pancytopenia
ue - predominantely renally excreted. cant get rid of it and can become toxic
lft - toxic

in view of dyscrasia, liver cirrhosis and toxicity risk.

FBC UE LFT weekly until stabilised (like lithium is) then 3 monthly
be advised to report all symptoms and signs suggestive of infection, especially sore throat

Question 12

lithium monitoring and why?

Answer 12

pre testing
BMI, FBC, U+E incl. calcium and TFT

monitoring
lithium levels- weekly, when concentrations are stable, linear pharmokinetics as it is unchanged in body (double the dose double the concentration) every 3 months for the first year, and every 6 months thereafter.
BMI, FBC, U+E incl. calcium and TFT 6 monthly .

why?
Leukocytosis
Insomnia
Thirst, tremor
Hypothyroidism
Increased Urination
Muscle weakness, and malaise

Question 13

antipsychotics monitoring and why?

Answer 13

Blood glucose, lipid profile, weight and prolactin.

diabetes, metabolic syndrome including fatty liver. risk highest in first 3 months to 1 year.

Risk highest for olanzapine.

pre treatment
lipids, weight, fasting BG, prolactin

monitoring
lipids, weight for first 3 months then yearly with antipsychotic drugs. Fasting BG and prolactin at 6 months. Prolactin yearly thereafter

Patients taking olanzapine (or clozapine) require more frequent monitoring of lipids and weight: every 3 months for the first year, then yearly. Fasting BG after 1 month!!! then every 6 months. Prolactin at 6 months. Prolactin yearly thereafter.

Question 14

which drugs have monitoring weekly until stable then every 3 months for first year?

Answer 14

1. lithium
2. methotrexate
3. (olanzapine) not weekly just 3 monthly
4. azathiopurine
5. clozapine (weekly for first 18 weeks, then 2 weekly for first year)

Question 15

What is monitored for clozapine?

Answer 15

FBC weekly for first 18 weeks, then 2 weekly for a year, monthly for second year.

Patients taking olanzapine (or clozapine) require more frequent monitoring of lipids and weight: every 3 months for the first year, then yearly. Fasting BG after 1 month!!! then every 6 months. Prolactin at 6 months. Prolactin yearly thereafter.

Question 16

ACE I monitoring and why?

Answer 16

BP and U+E baseline.

U+E 1–2 weeks after each upward titration. If K+ 5-5.9 check pt is not on any other drugs that may be causing this and if not then reduce or stop ACEI and recheck in 5-7 days.
BP 4 weeks after each dose change. If creatinine rise ≥30% or eGFR declines ≤25% and pt is not on any other drugs that may be causing this then reduce or stop it and recheck in 5-7 days. If they are - reduce or stop this drug first and keep ACE-I the same and recheck in 5-7 days.

Question 17

Diuretics monitoring and why?

Answer 17

Recheck renal function, serum electrolytes, and blood pressure 1–2 weeks after starting treatment.

Question 18

Azathiopurine monitoring and why?

Answer 18

pretreatment
Thiopurine methyltransferase

Monitoring
FBC weekly until stable (like lithium, methotrexate and clozapine) then 3 monthly.

Question 19

Iron monitoring and why?

Answer 19

In all people, a serum ferritin level of less than 30 micrograms/L confirms a diagnosis of iron deficiency.

fbc at 4 weeks- Hb should rise 20g/L
Once haemoglobin concentration and red cell indices are normal:
- Continue iron treatment for 3 months to aid replenishment of iron stores, and then stop.

• Then monitor the person’s full blood count periodically — for example, at 3, 6, 12, and 24 months.

Question 20

Amiodarone monitoring requirments. Dont get this confused with azathiopurine.

Answer 20

Amiodarone
pre treatment - K+ levels (similar to digoxin- low K+ - arrhythmia inducing, CXR, and LFTs

monitoring- TFT (including TSH T3 and T4) every 6 months, LFTs every 6 months. and watch out for phototoxic reaction (even after discontinuation).

You do not need U+E because dosing of amiodarone is indepdent of renal function and renal failure is not a recgonised side effect

Azathiopurine doesn’t affect the lungs and is generally safer than amiodarone, Amiodarone is a dirty drug. The only real risks you have to be aware of with azathiopurine is bone marrow suppression and skin cancer. This is reflected in the fact there is more monitoring requriments for amiodarone (LFT, TFT vs FBC for azathiopurine).

Lung toxicity, including interstitial pneumonitis, lung fibrosis, and bronchiolitis obliterans organising pneumonia, is the most significant side-effect of amiodarone, affecting 3-17% of patients.

Question 21

which of the following parameters is most important to monitor during therpay with digoxin?

1. plasma concentration
2. serum creatinine
3. serum sodium
4. CXR
5. Blood pressure

Answer 21

drug monitoring questions, when you don’t know what the answer is and one of the options is serum creatinine- this wont come up in the ‘monitoring’ section of BNF. To check if this is the right answer you need to look at the ‘renal impairment’ section, and this will tell you what to do.

So for this question, the key answer was serum creatinine because digoxin is renally excreted

Question 22

Answer 22

Question 23

Lansoprazole monitoring?

Answer 23

Mg levels

Question 24

Naproxen monitoring?

Answer 24

U+E, BP, signs of heart failure or kidney failure. remember though diclofenic is worse than naproxen (diclofenic is stronger and naproxen is commonly prescribed in GP as you saw- there are less CI to it)

Question 25

How long missing clozapine can you go before needing to titrate the dose again?

Answer 25

48 hours!
its almost the same rules as contraceptives in the sense that if you miss 2 pills (48hr) you may need emergency contraception.

clozapine- short half life then i assume! (8hrs!)

Question 26

when is the risk of liver damage highest when using terbenifine?

Answer 26

first 6 weeks- it doesnt necessarily increase with longer use.

It is very rare.

Question 27

ACE-I K+ rules? how is this different for HTN and HF

Answer 27

An increase in creatinine up to 30% from baseline and an increase in K+ up to 5.5mmol/L is acceptable after starting an ACE inhibitor IN HEART FAILURE.

Bloods should be repeated in a further 2 weeks. remember vincent Northey (you thought ?addisons but ACEI alone can cause serious K+!)

If K+ was >5.5mmol/L, performing an ECG would be appropriate. ECG changes in hyperkalaemia include tall-tented T waves, a prolonged PR interval, wide QRS complexes and small or absent p waves.

In HTN - if 5-5.5 Investigate other causes of hyperkalaemia and treat accordingly ie. stop or reduce the dose of potassium-sparing diuretics (amiloride, triamterene, spironolactone) or nephrotoxic drugs (such as nonsteroidal anti-inflammatory drugs).
If serum potassium persists between 5.0 and 5.9 mmol/L despite these measures, reduce the dose of ACE inhibitor to a previously tolerated lower dose and recheck levels in 5–7 days.

Question 28

perioperative management of warfarin. if it has been stopped 5 days ago, surgery is in 1 day and INR is 1.5 what do you do?

Answer 28

If INR is 1.5 and over phytomenadione (vitamin K1) by mouth (using the intravenous preparation orally [unlicensed use]) should be given.

Question 29

is it more important to get a patient to report unexplained bruises or bleeding or that you need to measure their renal function if theyre on CICLOSPORIN?

Answer 29

It is the only immunosuppressant that is virtually non myelotoxic however it is extremely ototoxic

Question 30

in a heart failure patient with dyspnoea starting on heart failure medication, what is a better parameter to measure to see if its improving their condition? - BNP, exercise tolerance, creatine, troponin, HR?

Answer 30

Exercise tolerance. Bnp is too expensive.

Question 31

What medications can be toxic at theurapeutic levels?

Answer 31

your ototoxic antibiotics like gentamicin and vancomycin.

Classically it is phenytoin, lithium, digoxin, ciclosporin, tacrolimus, methotrexate and theophylline.