Patent ID: 7662408

Claim:
A sustained release preparation comprising a combination of first microcapsules which gradually release a GnRH agonist or a salt thereof for 5 to 8 months, and second microcapsules which gradually release a GnRH agonist or a salt thereof for 1 week to 5 months so that blood concentration of the GnRH agonist within one week after administration is about 2 ng/mL or higher, wherein: (a) the first microcapsules comprise: (i) a GnRH agonist or a salt thereof, and (ii) a lactic acid polymer having a weight-average molecular weight of about 18,000 to about 30,000; and (b) the second microcapsules comprise: (i) a GnRH agonist or a salt thereof, and (ii) a lactic acid-glycolic acid polymer (75/25 (mol %)) having a weight-average molecular weight of 8,000 to about 12,000, or a lactic acid polymer having a weight-average molecular weight of about 13,000 to about 18,000, wherein the ratio of first microcapsule to second microcapsule is from 5:1 to 20:1 expressed as weight ratios of the GnRH agonist or a salt thereof.