One-month sustained release microspheres of 125I-bovine calcitonin. In vitro-in vivo studies.
To obtain a 1-month release formulation of 125I-bovine calcitonin, microspheres were prepared with three different PLA copolymers, PLGA I (mol. wt. [MW]=30000), polyethyleneglycol (PEG)-PLGA (MW=34000) and PLGA II (MW=12000) using the double emulsion method. The release of 125I-bovine calcitonin was assayed in vitro using dialysis bags at 37 degrees C in isotonic phosphate buffer (pH 7.4). The in vitro release results indicated a very slow release rate for an optimal 1-month sustained release formulation. 125I-bovine calcitonin microspheres were administered under the skin on the back of Wistar rats and the radioactivity at the injection site was subsequently measured over a 4-week period. The in vitro and in vivo profiles were affected by the weight average molecular weight of the copolymers. The 125I-bovine calcitonin release rate was faster from microspheres prepared with PLGA II (MW=12000) than from microspheres prepared with higher molecular weight copolymers (PLGA I and PEG-PLGA). Microspheres prepared with PLGA II (MW=12000) release 100% of the dose in 1 month, in vivo release profiles presented two phases, during the first 2 weeks approximately 70% of the 125I-bovine calcitonin injected was released, followed by a second slower phase.
Diaz
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Departamento de Ingeniería Química y Tecnología Farmacéutica, Av. Astrofísico Francisco Sánchez s/n. Facultad de Farmacia, Universidad de La Laguna, 38200 La Laguna, Spain.
Llabrés
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M
Evora
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C
D000818:Animals; D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D002116:Calcitonin / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics*; D002417:Cattle; D003692:Delayed-Action Preparations; D007457:Iodine Radioisotopes; D008297:Male; D008863:Microspheres; D010316:Particle Size; D011092:Polyethylene Glycols; D011098:Polyglactin 910; D051381:Rats; D017208:Rats, Wistar
D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D007457:Iodine Radioisotopes; C102418:poly(lactic-glycolic acid)-poly(ethyleneglycol) copolymer; D011098:Polyglactin 910; D011092:Polyethylene Glycols; D002116:Calcitonin