N.sup.G -monomethyl-L-arginine hydrochloride derivatives and their use in the treatment of septic shock

摘要

Crystalline N.sup.G -monomethyl-L-arginine hydrochloride is disclosed. At least three distinguishable isomorphic forms are present. The solid salt can be made by dissolving N.sup.G -monomethyl-L-arginine in hydrochloric acid and crystallising out N.sup.G -monomethyl-L- arginine hydrochloride. The crystallising step requires several months at low temperature. However, the process can be facilitated by seeding with crystals of N.sup.G -monomethyl-L-arginine hydrochloride. Alternatively, crystalline N.sup.G -monomethyl-L-arginine hydrochloride can be prepared by dissolving a salt of N.sup.G -monomethyl-L-arginine other than the hydrochloride salt with hydrochloric acid and removing the original salt forming ion by crystallising out the hydrochloride salt.