Abstract: Provided herein is an aqueous bumetanide-containing liquid that can suitably be used for transmucosal administration of bumetanide. The aqueous liquid includes 0.3-5 wt. % bumetanide, 2-30 wt. % of a non-ionic surfactant having an HLB of more than 10, and 65-94 wt. % water, in which the liquid has a pH at 25° C. in the range of 5-9 and each of the bumetanide and the non-ionic surfactant is dissolved and/or contained in colloidal particles having a diameter of less than 50 nm. The aqueous liquid offers the advantage that it can accommodate relatively high concentrations of bumetanide. Excellent bioavailability can be achieved upon transmucosal administration of the aqueous bumetanide-containing liquid. The aqueous liquid further offers the highly desirable advantage that it does not cause irritation, e.g. stinging or itching, when administered in this manner.