Preparation of three-month depot injectable microspheres of leuprorelin acetate using biodegradable polymers.
To obtain a three-month release injection of leuprorelin acetate, microspheres were prepared with copoly(DL-lactic/glycolic acid) or poly(DL-lactic acid) (PLA) using an in-water drying method, and drug release was evaluated. The content of water-soluble oligomers in the polymers was found to strongly affect the initial burst, and reducing the content to less than 0.1% was necessary to keep the first-day release below 10%. Drug loading of more than 15% also increased the initial drug release; the acceptable maximum loading was 12%. Elevation of the glass transition temperature of the microspheres was observed with an increase in drug loading. This suggests formation of a rigid structure, possibly with arrangement of the polymer around the drug cores like in a micelle. This structure provides a hydrophobic barrier against diffusion of the hydrophilic peptide, resulting in high trapping efficiency and long-term sustained release dependent on polymer erosion. The microspheres prepared with PLA having a m.w. of 12,000 to 18,000 provided linear sustained release and persistent serum levels of the drug in rats for over 3 months.
Okada
H
H
DDS Research Laboratories, Takeda Chemical Industries, Ltd., Osaka, Japan.
Doken
Y
Y
Ogawa
Y
Y
Toguchi
H
H
D000143:Acids / Q000032:analysis; D000818:Animals; D001672:Biocompatible Materials; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003692:Delayed-Action Preparations; D007279:Injections, Subcutaneous; D007773:Lactates; D019344:Lactic Acid; D016729:Leuprolide / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D008297:Male; D008863:Microspheres; D011091:Polyesters; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D051381:Rats; D017207:Rats, Sprague-Dawley
D000143:Acids; D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D007773:Lactates; D011091:Polyesters; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C033616:poly(lactide); D016729:Leuprolide