Incorrect F when F changes over the course of a lag time

[kylebaron]

Current behavior: bioavailability is set from whatever is in play at the time of a dose. This creates a problem when lag times are being used and the dose is actually given at a time when bioavailability has changed since the apparent administration.

In the example below, there is a lag time of 1 and both doses happen (apparently at time 0); so we should see
100 x 0.7 + 200 * 0.1 = 90 units in the dosing compartment at time 1. We don't see this because both doses see the 0.1 as the bioavailability.

library(mrgsolve)
#> 
#> Attaching package: 'mrgsolve'
#> The following object is masked from 'package:stats':
#> 
#>     filter

mod <- mread("1005", project = modlib())
#> Loading required namespace: xml2
#> Building 1005 ... done.

code <- '
$PARAM CL = 1, V = 10, KA = 1
$MAIN
ALAG_A = 1;
if(self.amt==100) F_A = 0.7; 
if(self.amt==200) F_A = 0.1;
$PKMODEL cmt = "A,B", depot = TRUE
'

mod <- mcode("foo", code)
#> Building foo ... done.

data <- data.frame(amt = c(100,200), evid = 1, time = 0, ID = 1, cmt = 1)

mrgsim(mod, data, recsort = 3, end = 1)
#> Model:  foo 
#> Dim:    4 x 4 
#> Time:   0 to 1 
#> ID:     1 
#>     ID time  A B
#> 1:   1    0  0 0
#> 2:   1    0  0 0
#> 3:   1    0  0 0
#> 4:   1    1 30 0

^{Created on 2023-11-13 with reprex v2.0.2}

One solution is bioavailability gets stored in the record object early on and is always read from that specific record object rather than this global bioavailability floating around.