19. Antibiotics requiring therapeutic drug monitoring

Extended interval (once daily) gentamicin / tobramycin
Take a pre-dose level 18-24 hours after 1st dose.
Levels should be <1mg/l
Normal renal function - (creatinine clearance >60ml/min) give next dose when due.Check pre-dose levels every 3-5 days.
Impaired renal function - monitor levels daily

Multiple daily dosing gentamicin / tobramycin
(BD or TDS)
Take trough and peak levels after 24 hours i.e. at the 3rd dose for BD dosing and at the 4th dose for TDS dosing.
Pre-dose / trough level 0.5 to 2.0mg/l
Peak level 6.0 to 10.0mg/l
Normal renal function - monitor levels every 3-5 days
Impaired renal function - monitor levels daily

Vancomycin
Take pre-dose levels prior to 3rd dose.
Give the 3rd dose as prescribed and amend 4th dose according to levels
Pre-dose level 5-15mg/l
Normal renal function - (creatinine clearance >60ml/min) check levels every 3-5 days.
For severe infections higher levels may be advised by microbiology.

Teicoplanin
Monitoring is required for patients with impaired renal function / to ensure therapeutic plasma levels.
Ensure that usual BD loading dose is given
Take pre-dose level on day 4 to 7.
Severe infection - pre-dose level 20-60mg/l
Mild - moderate infection - pre-dose level 10-60mg/l
Regular monitoring may be required in renal impairment
Assays are performed on Tuesdays and Fridays

Amikacin - (multiple daily dosing)
Pre-dose level 5-10mg/l
1 hour peak 20-25mg/l

Voriconazole
Pre-dose level 0.25 - 6.00 mg/l (Mon and Thurs)
For therapeutic drug monitoring assays are performed twice daily by biochemistry, including weekends.
For further information seek advice from microbiology or biochemistry.
The following are carried out at the mycology reference lab. For further advice contact ext 2124.

Itraconazole
To ensure therapeutic levels as problematic absorption.
Random level 5-15mg/l (oral therapy)
For IV therapy please send pre-dose, 1 hour post dose and 4-6 hours post dose samples

Flucytosine
Monitor levels at 2nd to 3rd dose and twice weekly thereafter. Monitor more frequently in renal impairment
Pre-dose level 30-40mg/l
Peak (30 minutes post IV infusion or 2 hours post oral therapy) 70-80mg/l
Levels >100mg/l are potentially toxic