Using this type of formulation the drug is assumed to be administered in solution. This type of formulation can only be combined with the Administration type Oral. However, e.g. by using the Zero Order function with an End time = 0, a bolus administration of a drug in solution into every compartment can also be simulated. For an intravenous administration types, i.e. intravenous bolus injection and intravenous infusion, the drug is assumed to be administered in solution. In that case only, a formulation building block is not required.