Miglustat, an N-alkylated imino sugar, is a synthetic analogue of D-glucose. Miglustat is an inhibitor of the enzyme glucosylceramide synthase, which is a glucosyl transferase enzyme responsible for catalyzing the formation of glucosylceramide (glucocerebroside). Glucosylceramide is a substrate for the endogenous glucocerebrosidase, an enzyme that is deficient in Gaucher's disease. The accumulation of glucosylceramide due to the absence of glucocerebrosidase results in the storage of this material in the lysosomes of tissue macrophages, leading to widespread pathology due to infiltration of lipid-engorged macrophages in the viscera, lymph nodes, and bone marrow. This results in secondary hematologic consequences including sever anemia and thrombocytopenia, in addition to the characteristic progressive hepatosplenomegaly, as well as skeletal complications including osteonecrosis and osteopenia with secondary pathological fractures. Miglustat functions as a competitive and reversible inhibitor of the enzyme glucosylceramide synthase, the initial enzyme in a series of reactions which results in the synthesis of most glycosphingolipids. The goal of treatment with miglustat is to reduce the rate of glycosphingolipid biosynthesis so that the amount of glycosphingolipid substrate is reduced to a level which allows the residual activity of the deficient glucocerebrosidase enzyme to be more effective (substrate reduction therapy), reducing the accumulation of glucocerebroside in macrophages. In vitro and in vivo studies have shown that miglustat can reduce the synthesis of glucosylceramide-based glycosphingolipids. In clinical trials, miglustat improved liver and spleen volume, as well as hemoglobin concentration and platelet count. Inhibition of glycosphingolipid synthesis has also shown to reduce intracellular lipid storage, improve fluid-phase endosomal uptake and normalize lipid transport in peripheral blood B lymphocytes of NP-C patients, which results in a decrease in the potentially neurotoxic accumulation of gnagliosides GM2 and GM3, lactosylceramide and glucosylceramide, possibly preventing further neuronal damage. Other studies have also suggested that miglustat may indirectly modulate intracellular calcium homeostasis through its effects on glucosylceramide levels, and evidence has shown that an initiating factor in the pathogenesis of NP-C may be impaired calcium homeostasis related to sphingosine storage. Therefore, the effect that miglustat exerts on intracellular calcium levels may influence an important underlying pathogenic mechanism of NP-C. Miglustat is used for the treatment of adult patients with mild to moderate type 1 (nonneuropathic) Gaucher's disease for whom enzyme replacement therapy is not a therapeutic option (e.g. due to constraints such as allergy, hypersensitivity, or poor venous access). Now approved in some countries for the treatment of progressive neurological symptoms in adult and pediatric patients with Niemann-Pick disease type C (NP-C). Miglustat is marketed under the trade name Zavesca.