Modelling the primary drying step for the determination of the optimal dynamic heating pad temperature in a continuous pharmaceutical freeze-drying process for unit doses

In the pharmaceutical industry, traditional freeze-drying of unit doses is a batch-wise process associated with many disadvantages. To overcome these disadvantages and to guarantee a uniform product quality and high process efficiency, a continuous freeze-drying process is developed and evaluated. The main differences between the proposed continuous freeze-drying process and traditional freeze-drying can be found firstly in the freezing step during which the vials are rotated around their longitudinal axis (spin freezing), and secondly in the drying step during which the energy for sublimation and desorption is provided through the vial wall by conduction via an electrical heating pad. To obtain a more efficient drying process, the energy transfer has to be optimised without exceeding the product and process limits (e.g. cake collapse, choked flow). Therefore, a mechanistic model describing primary drying during continuous lyophilisation of unit doses based on conduction via heating pads was developed allowing the prediction of the optimal dynamic power input and temperature output of the electric heating pads. The model was verified by experimentally testing the optimal dynamic primary drying conditions calculated for a model formulation. The primary drying endpoint of the model formulation was determined via in-line NIR spectroscopy. This endpoint was then compared with the predicted model based endpoint. The mean ratio between the experimental and model based predicted drying time for six verification runs was 1.05 +/- 0.07, indicating a good accordance between the model and the experimental data

Thermal imaging as a noncontact inline process analytical tool for product temperature monitoring during continuous freeze-drying of unit doses

Freeze-drying is a well-established technique to improve the stability of biopharmaceuticals which are unstable in aqueous solution. To obtain an elegant dried product appearance, the temperature at the moving sublimation interface T-i should be kept below the critical product temperature T-i,T-crit during primary drying. The static temperature sensors applied in batch freeze-drying provide unreliable Ti data due to their invasive character. In addition, these sensors are incompatible with the continuous freeze-drying concept based on spinning of the vials during freezing, leading to a thin product layer spread over the entire inner vial wall. During continuous freeze-drying, the sublimation front moves from the inner side of the vial toward the glass wall, offering the unique opportunity to monitor T-i via noncontact inline thermal imaging. Via Fourier's law of thermal conduction, the temperature gradient over the vial wall and ice layer was quantified, which allowed the exact measurement of T-i during the entire primary drying step. On the basis of the obtained thermal images, the infrared (IR) energy transfer was computed via the Stefan-Boltzmann law and the dried product mass transfer resistance (R-p) profile was obtained. This procedure allows the determination of the optimal dynamic IR heater temperature profile for the continuous freeze-drying of any product. In addition, the end point of primary drying was detected via thermal imaging and confirmed by inline near-infrared (NIR) spectroscopy. Both applications show that thermal imaging is a suitable and promising process analytical tool for noninvasive temperature measurements during continuous freeze-drying, with the potential for inline process monitoring and control

Development of a nanocrystalline Paclitaxel formulation for HIPEC treatment

To develop a nanocrystalline paclitaxel formulation with a high paclitaxel-to-stabilizer ratio which can be used for hyperthermic intraperitoneal chemotherapy (HIPEC). Paclitaxel (PTX) nanocrystals were prepared via wet milling using Pluronic F127(A (R)) as stabilizer. The suitability of paclitaxel nanosuspensions for HIPEC treatment was evaluated by analyzing the cytotoxicity of both stabilizer and formulation, and by determining the maximum tolerated dose (MTD) and bioavailability. The effect on tumor growth was evaluated by magnetic resonance imaging (MRI) at day 7 and 14 after HIPEC treatment in rats with peritoneal carcinomatosis of ovarian origin. Monodisperse nanosuspensions (+/- 400 nm) were developed using Pluronic F127(A (R)) as single additive. The cytotoxicity and MTD of this nanocrystalline formulation was similar compared to Taxol(A (R)), while its bioavailability was higher. MRI data after HIPEC treatment with a PTX nanocrystalline suspension showed a significant reduction of tumor volume compared to the non-treated group. Although no significant differences on tumor volume were observed between Taxol(A (R)) and the nanosuspension, the rats treated with the nanosuspension recovered faster following the HIPEC procedure. Nanosuspensions with a high paclitaxel-to-stabilizer ratio are of interest for the treatment of peritoneal carcinomatosis of ovarian origin via HIPEC