Application of a Biomagnetic Measurement System (BMS) to the Evaluation of Gastrointestinal Transit of Intestinal Pressure-Controlled Colon Delivery Capsules (PCDCs) in Human Subjects

Purpose. For determination of the transit time through various partsof the gastrointestinal (GI) tract, we developed a method that providesthe location of disintegration and drug release. This method involves GImagnetomarkergraphy (GIMG) using a 129-channel Shimadzu vectorbiomagnetic measurement system (BMS).Methods. To magnetically label the pressure-controlled colon deliverycapsule (PCDC) containing 75.0 ± 0.5 mg of caffeine as a tracer drug,small capsule caps containing 90 mg of ferric oxide powdered magnetite(Fe₂O₃) were attached to PCDCs. After orally administration to fastedhuman volunteers, saliva samples were collected hourly and salivarycaffeine concentration was measured. At the same time, locations ofthe magnetic PCDC were detected by BMS just after the PCDCs weremagnetized with the coils of a magnetic resonance imaging (MRI)system. The magnetic field distributions were analyzed and theestimated positions were shown on the MRI picture of the same subject'sabdominal structure.Results. We magnetized PCDC with permanent magnets or anelectromagnet before ingestion and the estimated locations of PCDC in the GItract exhibited high estimation error. In order to increase the precision ofestimated localization of PCDCs, PCDCs were magnetized within thecoils of the MRI. As a result, these PCDCs had strong magnetic dipolesthat were parallel to the sensor unit of BMS in every measurement,and therefore the spatial resolution of the PCDC's two-dimensionalpositions in the organs of the GI tract was within a range of severalmillimeters.Conclusions. GIMG is a powerful tool for the study of colon deliveryefficiencies of PCDCs. The main advantage of GIMG is the capabilityto obtain even more detailed knowledge of the behavior and fate ofsolid pharmaceutical formulations during GI passage.