See attached example that shows one way to do this using a text model. Basically you need a dose column for oral, a dose column for IV, and you use 2 dosepoints in the model with a bioavailability term for the oral dose. Please post if you have any questions.
Thank you for your response. In your example, both the oral and IV administration were used in a single episode. In mine, the same subjects were studied on 2 separate occasions, and received the drug IV once and SC on the other occasion. I tried to setup the data as in your example, but it does not work, presumably because I do not specify that the occasions are separate (and there is a single ID per subject - my setup works fine when I give a different ID for the IV and SC treatments).