Soybean oil

MTX was purchased from Huzhou Zhanwang Pharmaceutical Co. (Huzhou, China). Capryol 90, Peceol, Plurol^® diisostearique, Transcutol P, and Labrasol were obtained from Gattefosse (Saint-Priest Cedex, France). Peanut oil, corn oil, soybean oil, sesame oil, castor oil, cotton seed oil, Span 80, and Tween^® 80 were purchased from Daejung Chemical Co. (Siheung, South Korea). Coconut oil, linseed oil, mineral oil, and olive oil were purchased from Samchun Chemical Co. (Pyeongtaek, South Korea). Cremophor EL and Cremophor RH40 were obtained from BASF (Ludwigshafen, Germany). Calcium silicate was supplied by Hanmi Pharm. Co. (Suwon, South Korea). All other chemicals and solvents were of reagent grade and were used without further purification.

Sildenafil (base) was supplied by Huons Pharm. Co. (Ansan, South Korea). Polyvinylpyrrolidone (PVP, K30), Solutol HS15 and Cremophor EL were purchased from BASF (Ludwigshafen, Germany). Dextran, polyvinyl alcohol (PVA), hydroxypropyl methylcellulose 2910 (HPMC), pyrogenic silica (HDK N20 Pharma), hydroxypropyl cellulose low viscosity (HPC-L), carboxymethyl cellulose sodium (Na-CMC), poloxamer 188, PEG 4000 and hydroxypropyl beta-cyclodextrin (HP-β-CD) were kindly offered from Hanmi Pharm. Co. (Suwon, South Korea). Soybean oil, sorbitan monooleate (Span 80), olive oil, polysorbate (Tween 80) and corn oil were provided by Daejung Chem. Co. (Siheugn, South Korea). Peceol, Capryol 90 (propylene glycol monocaprylate), Plurol diisosterarique, Labrafil M2125CS, Transcutol HP, Lauroglycol FCC and Labrasol were acquired from Gattefosse (Saint-Priest Cedex, France). Medium-chain triglycerides (Captex 300) were purchased from Abitec (Columbus, OH, USA). Mineral oil and linseed oil were obtained from Samchun Chemical Co. (Pyeongtaek, South Korea). Gelatin and sesame oil were purchased from Wako Chemicals Co. (Tokyo, Japan). All other chemicals and solvents were of reagent grade; they were used with or without further purification.