A method of preparing a mucoadhesive film formulation by preparing a film forming composition including lambda carrageenan as a film forming polymer, at a concentration of about 1-7% by weight, a plasticizer at a concentration of about 1-15% by weight, a biologically active substance, and purified water distributing the film forming composition as a wet film layer onto a solid surface and allowing the film layer to dry. A mucoadhesive film obtained by the method and a film dosage unit.
