Neutron activation-based gamma scintigraphy in pharmacoscintigraphic evaluation of an Egalet® constant-release drug delivery system

Janne Marvola (Corresponding Author), Hanna Kanerva, Lillian Slot, Maija Lipponen, Tommi Kekki, Heikki Hietanen, Sirpa Mykkänen, Kari Ariniemi, Kai Lindevall, Martti Marvola

    Research output: Contribution to journalArticleScientificpeer-review

    20 Citations (Scopus)


    This paper is a report from a pharmacoscintigraphic study with an Egalet® constant-release system containing caffeine and natural abundance samarium oxide. First the formulation was tested in vitro to clarify integrity during irradiation in the nuclear reactor. Then six healthy male volunteers were enrolled into the in vivo study. The in vitro release of caffeine obeyed all the time linear zero-order kinetics. The in vivo release of radioactive Sm2O3 consisted of three consequent linear phases with different slopes. The release rate was fastest while the product was in the small intestine and slowest when the product was in the descending colon. In terms of the bioavailability of caffeine, the most important factor seemed to be the residence time in the ascending and transverse colon. A long residence time in these sections led to high AUC values for caffeine.
    Original languageEnglish
    Pages (from-to)3 - 10
    Number of pages8
    JournalInternational Journal of Pharmaceutics
    Issue number1-2
    Publication statusPublished - 2004
    MoE publication typeA1 Journal article-refereed


    • gamma scintigraphy
    • neutron activation
    • samarium
    • imaging
    • controlled release
    • in vitro-in vivo correlation


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