In vivo dissolution of poorly water-soluble drugs: Proof of concept based on fluorescence bioimaging

Abstract

In vitro‒in vivo correlation (IVIVC) of solid dosage forms should be established basically between in vitro and in vivo dissolution of active pharmaceutical ingredients. Nevertheless, in vivo dissolution profiles have never been accurately portrayed. The current practice of IVIVC has to resort to in vivo absorption fractions (F _a). In this proof-of-concept study, in vivo dissolution of a model poorly water-soluble drug fenofibrate (FNB) was investigated by fluorescence bioimaging. FNB crystals were first labeled by near-infrared fluorophores with aggregation-caused quenching properties. The dyes illuminated FNB crystals but quenched immediately and absolutely once been released into aqueous media, enabling accurate monitoring of residual drug crystals. The linearity established between fluorescence and crystal concentration justified reliable quantification of FNB crystals. In vitro dissolution was first measured following pharmacopoeia monograph protocols with well-documented IVIVC. The synchronicity between fluorescence and in vitro dissolution of FNB supported using fluorescence as a measure for determination of dissolution. In vitro dissolution correlated well with in vivo dissolution, acquired by either live or ex vivo imaging. The newly established IVIVC was further validated by correlating both in vitro and in vivo dissolution with F _a obtained from pharmacokinetic data.

Keywords: Aggregation-caused quenching; Bioimaging; Fenofibrate; Fluorescence; IVIVC; In vivo dissolution.

Graphical abstract

Figure 1

Schematic demonstration of correlation among in vitro dissolution, in vivo dissolution and absorption fraction of drug crystals (A), and the rationale of the ACQ-based fluorescent bioimaging of fenofibrate crystals (B). Current IVIVC is established between in vitro dissolution and F_a as a makeshift. Nevertheless, authentic IVIVC should be established between in vitro and in vivo dissolution.

Figure 2

SEM photographs of FNB raw material (A) and FNB-HCs (B); size distribution of FNB raw crystals and FNB-HCs (C); DSC thermograms (D); powder X-ray diffractograms (E).

Figure 3

In vitro fluorescent stability of FNB-HCs in buffers of different pHs (ABS; acetate buffered saline; PBS: phosphate buffered saline) and pure water (A) and in different bio-relevant fluids (B). SGF, simulated gastric fluid; FeSSIF, fed-state simulated small intestinal fluid; FaSSIF, fasted-state simulated small intestinal fluids. Validation of dissolution by measuring the drug: in buffers and water (C); in different bio-relevant fluids (D). Data are expressed as mean ± SD (n = 3). Fluorescent spectra of FNB-HCs in aqueous ethanol (E) and the plot of fluorescent intensity vs. water content (F).

Figure 4

In vitro dissolution of FNB-HCs determined by monitoring either FNB (red line) or fluorescence (A, blue line) and correlation (B) that highlight synchronicity between drug dissolution and fluorescence quenching. Data are expressed as mean ± SD (n = 3).

Figure 5

In vivo dissolution based on live imaging of residual FNB-HCs. Live images of SD rats after oral administration of FNB-HCs gavage (A). Comparison of in vivo dissolution profile obtained from residual percentage of fluorescent intensity (blue line) with the in vitro dissolution profile (B, red line) and IVIVC established between them (C). Data are expressed as mean ± SD (n = 3).

Figure 6

In vivo dissolution based on ex vivo imaging of residual FNB-HCs. Ex vivo images of the whole isolated GI segments after oral administration of FNB-HCs by gavage (A). Comparison of the in vivo dissolution profile obtained from residual percentage of fluorescent intensity in the stomach (blue line) and the in vitro dissolution (B, red line) and IVIVC established between them (C). Data are expressed as mean ± SD (n = 3).

Figure 7

Mean plasma concentration of fenofibric acid vs. time plot in rats post administration of FNB-HCs by gavage (A); normalized values of F_avs. time (B); correlation between F_a and in vitro dissolution (C); correlation between F_a and in vivo dissolution (D). Data are expressed as mean ± SD (n = 5).