The purpose of the present study was to investigate the effect of seed particles on the precipitation behavior of weak base drugs in the small intestine. A simple in vitro infusion method was used to mimic in vivo processes. Dipyridamole, pioglitazone, topiroxostat, chlorpromazine, cinnarizine, and ketoconazole were used as model drugs. A drug was dissolved in 0.01 N HCl and infused into a pH 6.5 buffer. The existence of seed particles significantly affected the concentration-time profiles of the model drugs in the buffer. The maximum concentration was significantly reduced in the presence of seed particles (except for cinnarizine). In the case of dipyridamole, pioglitazone, and topiroxostat, the precipitants were crystalline from the beginning of precipitation. In contrast, the precipitants of ketoconazole, cinnarizine, and chlorpromazine were a mixture of amorphous and crystals. In conclusion, the presence of seed particles significantly affected the precipitation behavior of weak base drugs.
Keywords: amorphous; crystal; gastric pH; oral absorption; precipitation; seed particle; weak base.