To find an easier way to estimate and use serum levels of vancomycin and aminoglycosides.
The one compartment model with volume of distribution (Vd) in liters, and drug clearance (CLd) in liters/day was examined with drug clearance approximated by creatinine clearance (CCR). This model generally gives a reasonable approximation for vancomycin and the aminoglycosides. The equation for serum level half-life (T1/2) = 0.693 * VD / CLd was used, along with peak serum level (P) and trough serum level (T), to give a useful one-compartment equation called DEATH.
Define D as mg of drug given per day. Define H as number of drug half-lives between doses of the drug. Define E as drug excretion = CCR. Define the amplitude A as P-T. Define T = 2. Manipulation gives D = E*A*T/H. Example1: CCR = 40. You desire vancomycin P = 32 and T = 8. Then E = 40, A = 24, and the number of half-lives from 32 down to 8 is 2 . D = 40*24*2/2 = 960. If vancomycin Vd = 40 L, each dose would be 40*(32-8) = 960. Hence your dosing would be 960 mg QD. Example2 CCR = 20, tobramycin 200 mg QD, estimated tobramycin VD = 20 L. Then E = 20, A = 10 and D = 200. Then 200 = 20*10*2/H. Hence H = 2 half-lives. Thus the trough T must be 1/4 of the peak P, and since P-T = 10, then P = 13.3 and T = 3.3. Example3: Amikacin 500mg Q 12h gives trough = 10. Amikacin Vd = 25 L. D = 1000, A = 20. The peak = T+20 = 30. Peak of 30 to trough 10 requires 1.5 half-lives. Using the DEATH equation: 1000 = E*20*2/1.5 gives E = CCR = 38 ml/min.
The DEATH equation D=E*A*T/H can be used to estimate dose, serum levels, and CCR.
The DEATH equation is useful for vancomycin and aminoglycosides.
Terry Fagan, None.