Entrapping efficiency and drug release profile of an oil-in-water (o/w) emulsion formulation using a polydimethylsiloxane-coated glass bead assay.
Evaluation of entrapping efficiency is difficult for an o/w emulsion formulation containing a lipophilic oily drug, isocarbacyclin methyl ester (TEI-9090), by commonly employed techniques (dialysis, ultrafiltration, or gel filtration), because of its adsorption to the system materials. Employing this characteristic of TEI-9090, we developed an adsorption technique with polydimethylsiloxane-coated glass beads (PDMS-GB). The assay is based on the quantitative adsorption of unentrapped TEI-9090 to the PDMS-GB. The entrapping efficiency of a 10% soybean oil emulsion containing [3H]TEI-9090 (1 microgram/mL) assayed by this method approached 100%. The PDMS-GB assay was performed for the emulsion diluted 100 times with physiological saline at different time intervals after dilution over a period of 24 hr. A plot of [3H]TEI-9090 in the emulsion particles versus time showed rapid release within 1 hr, followed by very slow release, reaching equilibrium. Applying first-order kinetics, the data were found to fit to a biexponential equation over the first hour of release. The terminal release resembled the first-order release of the drug from the phospholipid-rich infranatant, which was separated from the creamy layer by ultracentrifugation of the emulsion and contained 35% [3H]TEI-9090. These results suggest that the drug is released from two components in the emulsion.
Minagawa
T
T
Research Center, Taisho Pharmaceutical Co., Ltd., Saitama, Japan.
Kohno
Y
Y
Suwa
T
T
Tsuji
A
A
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003692:Delayed-Action Preparations; D004129:Dimethylpolysiloxanes; D004655:Emulsions; D011464:Epoprostenol / Q000008:administration & dosage / Q000031:analogs & derivatives; D005898:Glass; D007700:Kinetics; D011465:Prostaglandins, Synthetic / Q000008:administration & dosage; D012995:Solubility; D013024:Soybean Oil; D014461:Ultracentrifugation; D014867:Water
D003692:Delayed-Action Preparations; D004129:Dimethylpolysiloxanes; D004655:Emulsions; D011465:Prostaglandins, Synthetic; D014867:Water; D013024:Soybean Oil; C052840:TEI 9090; D011464:Epoprostenol