Dear Rxperts,
Running the following code:
=======================================================
twlo=10; twhi=20; wt=154; vd=0.5; cl=0.046; tau=6; t=3; F=1;
wtkg <- wt/2.2 # convert lbs to kg
vd.pt <- wtkg * vd # compute weight-based vd (L)
cl.pt <- wtkg * cl # compute CL (L/hr)
k <- cl.pt/vd.pt # compute k (hr^-1)
cave <- round((twhi - twlo)/log(twhi/twlo),2)
doserate <- (cl.pt * cave)/F
# maintenance dose (Dm)
total_dose_tau <- round(doserate * tau,0)
Cmax <- total_dose_tau/vd.pt
Cmin <- Cmax * exp(-k * tau)
AR <- 1/(1 - exp(-k * tau))
Cmaxss <- Cmax * AR
Cminss <- Cmin * AR
Cfluctss <- (Cmaxss - Cminss)
Ct <- (Cmaxss * exp(-k * t))
dose_loading_vd <- round(Cmaxss * vd.pt,0)
dose_loading_dm <- round(total_dose_tau * AR,0)
options(digits=2)
c("Ther. Win. (mg)"=twlo,"to"=twhi,"Wt (kg)"=wtkg,"Vd (L)"=vd.pt,"CL
(L/hr)"=cl.pt,"Cave (mg)"=cave,"D/tau (mg/hr)"=doserate,"tau
(hr)"=tau,"Total Dose (mg)"=total_dose_tau,"Cmax (mg)"=Cmax,"Cmin
(mg)"=Cmin,"AR"=AR,"Cmaxss (mg/L)"=Cmaxss,"Cminss (mg/L)"=Cminss,"Cfluct
(mg/L)"=Cfluctss,"C(t) (mg/L)"=Ct,"DL wVd (mg)"=dose_loading_vd,"DL wDm
(mg)"=dose_loading_dm)
===========================================================================
Gives
Ther. Win. (mg) to Wt (kg) Vd (L) CL
(L/hr) Cave (mg)
10.0 20.0 70.0 35.0
3.2 14.4
D/tau (mg/hr) tau (hr) Total Dose (mg) Cmax (mg) Cmin
(mg) AR
46.5 6.0 279.0 8.0
4.6 2.4
Cmaxss (mg/L) Cminss (mg/L) Cfluct (mg/L) C(t) (mg/L) DL wVd
(mg) DL wDm (mg)
18.8 10.8 8.0 14.3
658.0 658.0
But, there is an error from R?
AR * total_dose_tau = 658 but that is wrong
Total Dose (mg) = 279 * AR (=2.4) = 670
Please help. I don't want to harm anyone. A difference of 12 mg of a highly
toxic drug can at the very least cause significant harm.
--
Oscar
Oscar A. Linares, MD
Translational Medicine Unit
La Plaisance Bay, Bolles Harbor
Monroe, Michigan 48161
Department of Medicine,
University of Toledo College of Medicine
Toledo, OH 43606-3390
Department of Internal Medicine,
The Detroit Medical Center (DMC)
Harper University Hospital
Wayne State University School of Medicine
Detroit, Michigan 48201
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