The 20 Millilitre Habit: Dispensing Volume for Antiseptic Mouth Rinse and the Cost of the Oversized Cup

Antiseptic mouth rinse is prescribed at a label dose of 10 mL but commonly dispensed in brim-filled cups of 20 or 30 mL. This study costs a stated course of twice-daily rinsing for 14 days (28 doses) from a 300 mL bottle priced at USD 4.50, at dispensing volumes of 10, 15, 20, and 30 mL. At the label dose a course uses 280 mL and costs USD 4.20; at 20 mL it uses 560 mL and costs USD 8.40; at 30 mL, 840 mL and USD 12.60. A case of twelve bottles provides 12.9 complete courses at the label dose against 6.4 at 20 mL. The dispensing rule that follows is to measure the dose, not fill the cup. This study is simulated, not measured. SIMULATED, NOT MEASURED.