A dosage unit including a probiotic component, a pH buffering agent, and a tonicity buffering agent. A dosage unit including a probiotic component, a polymeric matrix component, and a tonicity buffering agent, wherein the tonicity buffering agent is present in an amount and configuration suitable to provide a localized isotonic medium upon addition of the dosage unit to 50 mL of 0.1 N HCl (aq).