An in-line drug delivery pack that connects in-line with an intravenous (IV) line and allows for the mixing of diluent with a drug reagent to be delivered to the patient. An internal drug bed bypass mechanism is tailored to apportion diluent flow between the bypass and the drug bed. The apportionment is selected to achieve a solution concentration suitable for IV administration as the dried reagent is dissolved. Thus, both dissolution and precisely tailored dilution are performed in the same simple device.