The hydrochloride form shows incompatibility with the excipients used for oral dosage forms. There are several crystal forms of the free base, namely, alpha-anhydrate, beta-anhydrate, monohydrate, and trihydrate. The trihydrate form is unstable. The degree of crystallinity of the beta-anhydrate form is difficult to control. The monohydrate form is difficult to manufacture with constant quality. The serum levels of the compounds in rats are almost related to the dissolution rates in the JP 1st disintegration medium from the discs. The serum level of alpha-anhydrate is the lowest.