Xanthine derivatives

A xanthine derivative represented by Formula (I) or its pharmaceutically acceptable salt:

• ##STR33## wherein R.sup.1 and R.sup.2 independently represent lower alkyl, lower alkenyl, or lower alkynyl;
• R.sup.3 represents hydrogen, lower alkyl, lower alkenyl, or lower alkynyl;
• R.sup.4 represents lower alkyl, or aryl which is optionally substituted with 1 to 4 substituents independently selected from the group consisting of lower alkyl, hydroxy, lower alkoxy, halogen, nitro, amino, lower alkylamino, di-lower alkylamino, benzyloxy, phenyl and phenoxy, wherein said lower alkyl substituent and lower alkoxy substituent are each optionally substituted with 1 to 3 substituents independently selected from the group consisting of halogen, nitro, lower alkoxy and amino;
• R.sup.5 and R.sup.6 independently represent hydrogen, lower alkyl, or lower alkoxy, or R.sup.5 and R.sup.6 are combined together to represent --O--(CH.sub.2).sub.p --O-- (where p is an integer of 1 to 3);
• n represents 0, 1 or 4;
• and m represents 1 or 2, with the proviso that R.sup.1 and R.sup.2 are not methyl.