Detection of tulobuterol crystal in transdermal patches using terahertz pulsed spectroscopy and imaging

Applicability of a Terahertz Pulsed Spectroscopy (TPS) and a Terahertz Pulsed Imaging (TPI) for detection of tulobuterol (TBR) crystals in transdermal patches was investigated. Because TBR has high permeability in dermis, crystalline TBR in patch matrices contributes to controlling the release rate of TBR from a matrix. Therefore, crystalline TBR is one of the important factors for quality control of TBR transdermal tapes. A model tape that includes 5 w/w%, 10 w/w%, 20 w/w% or 30 w/w% of TBR was measured by TPS/TPI. TBR crystals in the matrices were successfully detected by TPI. Identification of TBR in an image of a crystal-like mass was done by comparison between the spectra of tapes and a TBR standard substance. These results indicate that TPS and TPI are applicable to identifying crystalline lumps of an active drug in tapes for quality control.