A preparation in the form of syrup comprising a liposomal complex of CM-glucan (carboxymethylated glucan), arginine, and iodine, with the addition of vitamins of group B and, optionally, amino acids and/or taurine, is able to combat adenotonsillar hypertrophy in so far as it improves the normal activity of the immune system and favours trophism of the adenotonsillar lymphoid tissue. Thanks to the controlled release, due to the presence of the liposomal/phosphoglucan complex, the preparation is particularly indicated for administration in single daily doses.