Equilibrium state at supersaturated drug concentration achieved by hydroxypropyl methylcellulose acetate succinate: molecular characterization using (1)H NMR technique.
The maintenance mechanism of the supersaturated state of poorly water-soluble drugs, glibenclamide (GLB) and chlorthalidone (CLT), in hydroxypropyl methylcellulose acetate succinate (HPMC-AS) solution was investigated at a molecular level. HPMC-AS suppressed drug crystallization from supersaturated drug solution and maintained high supersaturated level of drugs with small amount of HPMC-AS for 24 h. However, the dissolution of crystalline GLB into HPMC-AS solution failed to produce supersaturated concentrations, although supersaturated concentrations were achieved by adding amorphous GLB to HPMC-AS solution. HPMC-AS did not improve drug dissolution and/or solubility but efficiently inhibited drug crystallization from supersaturated drug solutions. Such an inhibiting effect led to the long-term maintenance of the amorphous state of GLB in HPMC-AS solution. NMR measurements showed that HPMC-AS suppressed the molecular mobility of CLT depending on their supersaturation level. Highly supersaturated CLT in HPMC-AS solution formed a gel-like structure with HPMC-AS in which the molecular mobility of the CLT was strongly suppressed. The gel-like structure of HPMC-AS could inhibit the reorganization from drug prenuclear aggregates to the crystal nuclei and delay the formation of drug crystals. The prolongation subsequently led to the redissolution of the aggregated drugs in aqueous solution and formed the equilibrium state at the supersaturated drug concentration in HPMC-AS solution. The equilibrium state formation of supersaturated drugs by HPMC-AS should be an essential mechanism underlying the marked drug concentration improvement.
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Keisuke
K
Ueda
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Kenjirou
K
Higashi
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Keiji
K
Yamamoto
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Kunikazu
K
Moribe
D002626:Chemistry, Pharmaceutical / Q000379:methods; D002752:Chlorthalidone / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D005905:Glyburide / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D004364:Pharmaceutical Preparations / Q000737:chemistry; D011208:Powders; D012995:Solubility; D012996:Solutions; D013678:Technology, Pharmaceutical; D014961:X-Ray Diffraction
D004364:Pharmaceutical Preparations; D011208:Powders; D012996:Solutions; C048331:hydroxypropylmethylcellulose acetate succinate; D008747:Methylcellulose; D002752:Chlorthalidone; D005905:Glyburide
1H NMR measurement; amorphous drug; crystallization inhibition; hydroxypropyl methylcellulose acetate succinate; supersaturated solution