Hypotonic formulations of hydrogel forming polymers, preferably poloxamers, have been developed for enhanced delivery through mucosa of therapeutic, diagnostic, prophylactic or other agents, to epithelial tissues, especially those having a mucosal coating. The polymers are administered at a concentration above, at or less than their critical gelling concentration (CGC) under isotonic conditions. The hypotonicity of the formulation is adjusted so that the polymer gels at the lower concentration. A Poloxamer gel administered into the vagina or colorectum at its CGC will form a “plug” of gel in the lumen.
