Determination of the Solid Content of Active Pharmaceutical Ingredient Powders in Suspension-Type Pharmaceutical Oral Jelly Using Time-Domain NMR.

This study determined the content of solid active pharmaceutical ingredient (API) powders dispersed in suspension-type pharmaceutical oral jellies using a low-field time-domain NMR (TD-NMR). The suspended jellies containing a designated API content were prepared and tested. Acetaminophen (APAP), indomethacin (IMC) and L-valine were used as test APIs. First, this study measured the T relaxation rate (the reciprocal of T relaxation time) by the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, and then evaluated whether the API content could be determined by the acquired T relaxation rate. The T relaxation rate negatively correlated with API content to a certain extent, but their correlation was not sufficient for achieving a precise determination. Subsequently, the solid-echo pulse sequence measurement was adopted for this study. We found that NMR signals corresponding to solid components strongly correlated with API content. Thus, this method achieved a precise determination of API contents in suspended jellies. In addition, this study confirmed the effect of API particle size on the T relaxation rate by using an L-valine-containing jelly: the T relaxation rate became faster when a smaller API size was incorporated into the suspended jelly, while there was no difference in terms of the NMR signals measured by solid-echo pulse sequence. From these findings, TD-NMR could be a powerful tool for evaluating the API dispersion state in suspended oral jellies.