NOVELTY - Preparation of 5-amino-2,3-dihydrophthalazine-1,4-dione salts with alkali metals (I), comprises: solving 5-nitro-2,3-dihydrophthalazine-1,4-dione in water solution of metal hydroxy moiety (II) to form a solution of 5-nitro-2,3- dihydrophthalazine-1,4-dione alkali salt; catalytically transforming 5-nitro-2,3-dihydrophthalazine-1,4-dione into (I) at 40-90 degrees C by means of hydrogen under pressure of 1-4 MPa, at presence of catalyst of transition metal on active carbon; and separating crystalline (I) by diluting water solution with lower alcohol or cyclic lower ether.    USE - The process is useful for preparing (I), which are useful: in medicine; and as additives to compositions other than pharmaceutical composition. 5-Amino-2,3-dihydrophthalazine-1,4-dione sodium salt is useful for manufacturing of a drug of the properties regulating biosynthetic processes in cells including the system of macrophages and bone marrow, for treating heart diseases (myocardial infarction and myocarditis), for treating pancreas diseases (pancreas inflammatory states and diabetes); for treating and prophylaxis of head, maxillofacial area and neck diseases. 5-Amino-2,3-dihydrophthalazine-1,4-dione sodium salt, optionally in combination with 5-amino-2,3-dihydrophthalazine-1,4-dione lithium salt, is useful for manufacturing of a drug of properties regulating biosynthetic processes in cells including: the system of macrophages, asthrocytes, microglia and dendrite cells; for treatment of the nervous system diseases (Alzheimer's disease) and psychic diseases (depression syndromes and anxiety states) (all claimed). (I) are used in medicine as agents of immunomodulating, anti-inflammatory and anti-oxidation properties. 5-Amino-2,3-dihydrophthalazine-1,4-dione sodium salt is useful for treatment and prophylaxis of inflammatory diseases of oral cavities (periodontitis, gingivitis, stomatitis), nasal cavities (rhinitis) and sinuses of maxillofacial area (sinusitis), pharynx and larynx (tonsillitis, laryngitis, pharyngitis), middle ear (otitis), abscesses, phlegmons, furuncles, carbuncles of face and neck, lymphadenitises of face and neck, inflammatory diseases of brain and its meninges, including sepsis. The efficacy of (I) to treat alloxan diabetes was tested in rats using biochemical tests. The result showed that 5-amino-2,3-dihydrophthalazine-1,4-dione sodium salt reduced glucose level from 9.07 greater than or equal to 0.45 mmol/l to 4.16 greater than or equal to 0.56 mmol/l.    ADVANTAGE - The process: is simple, safer and more economical; has no stage of luminal forming and hence separation step is avoided and the product is less toxic; is performed in hermetically closed apparatus and no toxic hydrazine hydrate gets into the air; and provides high yield of (I), which are easily soluble in water and physiological saline, more stable, have prolonged activity, and do not reveal allergy-inducing, teratogenic and mutagenic effects. The water solution obtained by the method is easily biodegradable and does not affect biological treatment plants work.    DETAILED DESCRIPTION - Preparation of 5-amino-2,3-dihydrophthalazine-1,4-dione salts with alkali metals of formula (I), comprises: solving 5-nitro-2,3-dihydrophthalazine-1,4-dione in water solution of metal hydroxy moiety of formula (MOH) (II) to form a solution of 5-nitro-2,3- dihydrophthalazine-1,4-dione alkali salt; catalytically transforming 5-nitro-2,3-dihydrophthalazine-1,4-dione into (I) at 40-90 degrees C by means of hydrogen under the pressure of 1-4 MPa, at the presence of a catalyst of a transition metal (platinum, palladium) on active carbon; and separating crystalline (I) by diluting the water solution with lower alcohol or cyclic lower ether after cooling to -5 degrees C to -15 degrees C, where 5-nitro-2,3-dihydrophthalazine-1,4-dione is formed by reacting 3-nitrophthalic acid anhydride with hydrazine hydrate in anhydrous acetic acid at 100-110 degrees C and distilling off the mixture of acetic acid and water.    M = Li, Na or K.