# Simulate from PKPD & QSP models in R

Welcome to the online home for mrgsolve. mrgsolve is an `R`

package for simulation from hierarchical, ordinary differential equation (ODE) based models typically employed in drug development. mrgsolve has been used for a wide variety of model applications, including pharamacokinetics (PK), pharmacokinetics/pharmacodynamics (PK/PD), physiologically-based pharmacokinetic (PBPK) modeling, and quantitative systems pharmacology. This site functions as a portal to all of the online resources that are available to help you learn mrgsolve and use it well to create useful simulations.

## mrgsolve is free, open-source software

mrgsolve is distributed as a package for `R`

and utilizes an ODE-solver from `ODEPACK`

which is freely-available in the public domain. We develop mrgsolve on github, with input and contributions from the pharmacometrics modeling and simulation community. We welcome feature requests and bug reports on the GitHub site issue tracker.

## Documentation

- User Guide: In-depth description and discussion about how mrgsolve works, including code block reference
- Package documentation: This is the pkgdown site for mrgsolve.
- R documentation: All mrgsolve documentation that you would find in the
`R`

help system - Doxygen documentation: How to use some of the provided C++ functions in your model
- Vignettes: Package vignettes
- Gallery: A GitHub repository of short, focused how-to vignettes
- Quick hit demos: Features that you might have a hard time finding in other documentation

## Links and Resources

- Benchmarks: We simulate data for certain scenarios from both NONMEM and mrgsolve and compare the outputs. All the code needed to run or confirm the outputs is included in the git repository. mrgsolve does not match NONMEM in every way; but there is substantial overlap so that a wide variety of models estimated in NONMEM can be simulated in mrgsolve.
- GitHub Page: Browse source code, find useful examples, get help installing, report issues
- mrgsolve home on CRAN
- Metrum Research Group: Our main website

## An example

The following is a simple example to illustrate the basics of how mrgsolve works. You can find more examples and usage vignettes in the links above or in the “Help Topics” menu in the nav bar at the top of the mrgsolve.github.io main page.

First, a model object is created. As an introduction, we will use a pre-coded model from an internal library.

An overview about this model

```
.
.
. ----------------- source: irm1.cpp -----------------
.
. project: /Users/kyleb/Rli...gsolve/models
. shared object: irm1-so-954b59b9df51
.
. time: start: 0 end: 24 delta: 1
. add: <none>
.
. compartments: EV1 CENT PERIPH RESP EV2 [5]
. parameters: CL V2 Q V3 KA KA2 KIN KOUT IC50 IMAX n
. VMAX KM [13]
. captures: CP [1]
. omega: 0x0
. sigma: 0x0
.
. solver: atol: 1e-08 rtol: 1e-08 maxsteps: 20k
. ------------------------------------------------------
```

Next, let’s create an intervention for the model. We do this with an event object.

Now, we simulate with our model object (`mod`

) and the event object (`e`

)

```
. Model: irm1
. Dim: 2402 x 8
. Time: 0 to 240
. ID: 1
. ID time EV1 CENT PERIPH RESP EV2 CP
. 1: 1 0.0 0.00 0.000 0.00000 5.000 0 0.0000
. 2: 1 0.0 100.00 0.000 0.00000 5.000 0 0.0000
. 3: 1 0.1 90.48 9.444 0.04781 4.903 0 0.4722
. 4: 1 0.2 81.87 17.851 0.18294 4.688 0 0.8926
. 5: 1 0.3 74.08 25.323 0.39390 4.426 0 1.2662
. 6: 1 0.4 67.03 31.953 0.67040 4.151 0 1.5977
. 7: 1 0.5 60.65 37.824 1.00324 3.882 0 1.8912
. 8: 1 0.6 54.88 43.013 1.38417 3.628 0 2.1507
```

And plot

The source code for this model:

```
$PROB
# Model: `irm1`
- Indirect response model, type 1
- Inhibition of response input
- Two-compartment PK model
- Optional nonlinear clearance
- Source: `mrgsolve` internal library
- Date: `r Sys.Date()`
- Version: `r packageVersion("mrgsolve")`
$PARAM @annotated
CL : 1 : Clearance (volume/time)
V2 : 20 : Central volume (volume)
Q : 2 : Inter-compartmental clearance (volume/time)
V3 : 10 : Peripheral volume of distribution (volume)
KA : 1 : Absorption rate constant 1 (1/time)
KA2 : 1 : Absorption rate constant 2 (1/time)
KIN : 10 : Response in rate constant (1/time)
KOUT : 2 : Response out rate constant (1/time)
IC50 : 2 : Concentration for 50% of max inhibition (mass/volume)
IMAX : 1 : Maximum inhibition
n : 1 : Emax model sigmoidicity
VMAX : 0 : Maximum reaction velocity (mass/time)
KM : 2 : Michaelis constant (mass/volume)
$CMT @annotated
EV1 : First extravascular compartment (mass)
CENT : Central compartment (mass)
PERIPH : Peripheral compartment (mass)
RESP : Response compartment
EV2 : Second extravascular compartment (mass)
$GLOBAL
#define CP (CENT/V2)
#define CT (PERIPH/V3)
#define CLNL (VMAX/(KM+CP))
#define INH (IMAX*pow(CP,n)/(pow(IC50,n)+pow(CP,n)))
$MAIN
RESP_0 = KIN/KOUT;
$ODE
dxdt_EV1 = -KA *EV1;
dxdt_EV2 = -KA2*EV2;
dxdt_CENT = KA *EV1 + KA2*EV2 - (CL+CLNL+Q)*CP + Q*CT;
dxdt_PERIPH = Q*CP - Q*CT;
dxdt_RESP = KIN*(1-INH) - KOUT*RESP;
$CAPTURE @annotated
CP : Plasma concentration (mass/volume)
```