Lecture 21 Aminoglycosides TDM Flashcards
What are the dosing strategies for aminoglycosides?
Extended Interval Dosing: less toxic than conventional dosing, takes advantage of conc-dependent killing (Cmax/MIC), cost savings, Contra: pt on dialysis, synergy use, abnormal clearance, endocarditis, surgical prophylaxis
Precaution: chronic ascites or serious liver disease, pt with auditory and vestibular disease, pregnancy/post-partum
Conventional: used in pt populations contra for extended interval, synergy dosing (with beta-lactams for aerobic Gram (-) or with vancomycin for Gram (+))
What is the general outline of steps for extended interval dosing with aminoglycosides?
A: calculate IBW to determine start dose (unless ABW < IBW, then use ABW
or if ABW > IBW by 20% or BMI > 30 use DW) ⇒ 5-7 mg/kg based on IBW, use 7 for severe infections, infuse over 1 hour
B: draw post-infusion levels or use nomogram (need CrCl) to verify interval (>60 = Q24, 40-59 = Q36, 20-39 = Q48, <20 = consult if applicable to use)⇒ draw trough level after 1st dose OR draw 2 levels at 8 and 12 hours from start of infusion, calculate pt specific K, calculate trough conc at 24 hours ⇒ if Ctr </= 1 mg/L continue 24 hr dosing, if >1 mg/L then extend dosing interval (ex. Q36, Q48, etc)
C: monitor efficacy and toxicity
What is the general outline of steps for conventional dosing with aminoglycosides?
A: determine IBW (if ABW < IBW use ABW, or use DW if ABW > IBW by 20% or BMI > 30) and dose accordingly based on which aminoglycoside selected
B: calculate CrCl and estimate interval (>80 = Q8H, 50-79 = Q12H, 20-49 = Q24H, <20 = use serum levels to adjust)
C: obtain Css pre and post peak levels ⇒ Pre-level within 30 min before dose and post-level 30 min after 30 min infusion, then run through equations to determine dose,, D: Monitor for WBC, temp, neutrophils, CrCl, ototoxicity, Css around 3rd dose
