PK Flow

Use a PK flow to represent a mass flow between PK compartments. To connect two PK compartments with a flow:

Click the flow button in the Model toolbox, or right-click and select Insert > Flow.
Use the pointer to click on the first and second PK compartments of the flow.

Note that lag time for an absorption model is indicated in the absorption or central compartments.

Different types of default PK flows are added depending on which compartments they connect:

•If the absorption compartment is connected to a central, peripheral, or elimination compartment, the default PK flow is a micro parameter, one-way flow. The default parameter name for the PK flow changes depending on the direction on which the flow moves, and on which compartments are being connected. For example, if the flow moves from the absorption compartment to another compartment, the parameter name for the forward movement (Kfwd) is Ka. The default parameter name for any backward PK flow is K12.

•The default PK flow between the central or peripheral compartments and the elimination compartment is named CL, and it is a clearance/volume parameter, one-way flow.

•The default PK flow between the central and peripheral compartments is named Q, and it is a clearance/volume parameter, with a two-way flow.

To specify PK flow options

Use the pointer to select a PK flow.
Click Parm multiple times to toggle through the parameterization options for the model.

Micro: Enter a variable name for the flow into the second compartment in the Kfwd field or use the default. If the 2Way checkbox is also checked, enter a variable name for the flow back into the first compartment in the Kbak field.

Clearance/Volume: Enter a variable name for the clearance in the CL field or use the default.

Saturating: Enter variable names in the Vmax field for the maximum metabolic rate and in the Km field for the fractional metabolic rate or use the defaults.

Click the 2Way checkbox to change the PK flow to a two-way flow; uncheck it to create a one-way flow.
Click Draw multiple times to toggle through the options for drawing the PK flow in the Graphical model interface.

Diagonal: Draws the diagonal flow.
Horizontal First: Draws the flow horizontally from the first compartment.
Vertical First: Draws the flow vertically from the first compartment.