Drug Monitoring

Question 1

When do you montior vancomycin? When do you give the next dose?

Answer 1

TROUGH
After you have given the one loading dose - and GIVE before waiting for the results to come back.

in long-term treatment:
* Daily levels are not typically necessary unless there’s concern about renal function or toxicity.
* In stable patients, monitoring for vancomycin and gentamicin is generally done every 2-3 days, while teicoplanin may only need weekly monitoring.
* If levels aren’t available before the next dose, base dosing on previous levels and clinical judgment, but adjust dosing promptly once results return.

7. vancomycin - we dont need to wait for dose to come back we give then adjust after. why?
   The difference in timing between vancomycin and gentamicin levels mainly comes down to their pharmacokinetics and the nature of their therapeutic windows:
8. Therapeutic Window and Toxicity Risk:
   
   • Gentamicin has a narrow therapeutic index, meaning there’s a small difference between the dose needed for efficacy and the dose that causes toxicity, particularly to the kidneys and ears. Monitoring levels before dosing is crucial because even small changes in dosing can lead to toxicity, especially in patients with renal impairment.
   • Vancomycin, while also having nephrotoxic and ototoxic potential, has a wider therapeutic window compared to gentamicin. Therefore, although monitoring levels is important, it’s generally less urgent to wait for levels before continuing the next dose.
9. Pharmacokinetics:
   
   • Gentamicin is an aminoglycoside with concentration-dependent killing, meaning its effectiveness relies on reaching a high peak concentration. In addition, gentamicin has a rapid elimination rate and a short half-life, so close monitoring of trough levels helps ensure levels aren’t remaining high between doses.
   • Vancomycin works via time-dependent killing, where its effectiveness is more about the total exposure over time. Vancomycin also has a longer half-life, so levels can be adjusted during ongoing therapy rather than needing to adjust every dose.

Question 2

When do you montior teicloplanin? When do you give the next dose?

Answer 2

TROUGH
if giving for 7 days
at the end of loading dose regime (i.e., day 3,4,5)
You give the next dose at whatever time it is scheduled on the maintenance table- you do not wait for the results of the levels to come back

in long term treatment:
* Daily levels are not typically necessary unless there’s concern about renal function or toxicity.
* In stable patients, monitoring for vancomycin and gentamicin is generally done every 2-3 days, while teicoplanin may only need weekly monitoring.
* If levels aren’t available before the next dose, base dosing on previous levels and clinical judgment, but adjust dosing promptly once results return.

Question 3

When do you montior gentamicin? When do you give the next dose?

Answer 3

FOR MULTIPLE DAY DOSING REGIME YOU HAVE TO DO PEAK (1 HOUR AFTER ADMINISTRATING) AND TROUGH

When initiating it via loading regime you do the first trough after you have given the one loading dose - and you wait for the results to come back before giving the next dose.
Ideally, trough is taken 18-24hr. If taken 6-14 use the nomogram.

in long term treatment:
* Daily levels are not typically necessary unless there’s concern about renal function or toxicity.
* In stable patients, monitoring for vancomycin and gentamicin is generally done every 2-3 days, while teicoplanin may only need weekly monitoring.
* If levels aren’t available before the next dose, base dosing on previous levels and clinical judgment, but adjust dosing promptly once results return.
In adults

*For multiple daily dose regimens, blood samples should be taken approximately 1 hour after intramuscular or intravenous administration (‘peak’ concentration) and also just before the next dose (‘trough’ concentration). If the pre-dose (‘trough’) concentration is high, the interval between doses must be increased. If the post-dose (‘peak’) concentration is high, the dose must be decreased.

For once daily dose regimens, consult local guidelines on serum concentration monitoring.

7. vancomycin - we dont need to wait for dose to come back we give then adjust after. why?
   The difference in timing between vancomycin and gentamicin levels mainly comes down to their pharmacokinetics and the nature of their therapeutic windows:
8. Therapeutic Window and Toxicity Risk:
   
   • Gentamicin has a narrow therapeutic index, meaning there’s a small difference between the dose needed for efficacy and the dose that causes toxicity, particularly to the kidneys and ears. Monitoring levels before dosing is crucial because even small changes in dosing can lead to toxicity, especially in patients with renal impairment.
   • Vancomycin, while also having nephrotoxic and ototoxic potential, has a wider therapeutic window compared to gentamicin. Therefore, although monitoring levels is important, it’s generally less urgent to wait for levels before continuing the next dose.
9. Pharmacokinetics:
   
   • Gentamicin is an aminoglycoside with concentration-dependent killing, meaning its effectiveness relies on reaching a high peak concentration. In addition, gentamicin has a rapid elimination rate and a short half-life, so close monitoring of trough levels helps ensure levels aren’t remaining high between doses.
   • Vancomycin works via time-dependent killing, where its effectiveness is more about the total exposure over time. Vancomycin also has a longer half-life, so levels can be adjusted during ongoing therapy rather than needing to adjust every dose.

Question 4

What do you test before starting biologic drugs

Answer 4

CXR- TB
Bloods - hepatitis B, hepatitis C, and HIV.

Question 5

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

Answer 5

before 3 months and 12 months
3x

Question 6

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

Answer 6

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.

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 7

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

Answer 7

increase interval

Question 8

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

Answer 8

decrease dose

Question 9

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 9

• 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