1. A medical preparation for the treatment and prophylaxis of infectious and inflammatory diseases, comprising benzyldimethyl[3-(myristoilamino)propyl] ammonium chloride and a pharmaceutical diluent, characterized in that contains comprising benzyldimethyl[3-(myristoilamino)propyl]ammonium chloride as monohydrate. 2. The medical preparation according to claim 1, characterized in that contains water and/or alcohol as a pharmaceutical diluent and monohydrate benzyldimethyl[3-(myristoilamino)propyl]ammonium chloride in 0.01-1.0%. 3. The medical preparation according to claim 1, characterized in that contains any base of vegetable, animal or synthetic origin as a pharmaceutical diluent with the following component ratio: vegetable, animal or synthetic baseá99.0-99.9 benzyldimethyl[3-(myristoilamino)propyl]ammonium chloride, monohydrate 1.0-0.01 4. Use a medical preparation according to claims 1-3 for the treatment and prophylaxis of infectious and suppurative inflammatory diseases of different aetiology and localization and a preparation having antiseptic, disinfecting, spermicidal, antiviral and immuno-modulating action.