Bioavailability of cinnarizine in dogs: effect of SNEDDS loading level and correlation with cinnarizine solubilization during in vitro lipolysis.

PURPOSE: To investigate the effect of increasing the loading level of the poorly soluble drug cinnarizine in a self-nanoemulsifying drug delivery system (SNEDDS) both in vitro and in vivo. METHODS: A fixed dose of cinnarizine was administered orally to dogs in solution in different amounts of SNEDDS vehicle. Furthermore, the SNEDDSs were characterised using the dynamic in vitro lipolysis model. RESULTS: Statistical differences in bioavailability were not obtained between the different amounts of SNEDDS vehicle, in spite of differences in the tendency of cinnarizine to precipitate during in vitro lipolysis of the treatments. Use of the SNEDDS concept decreased the variation in cinnarizine exposure observed between dogs as compared to administering cinnarizine in an aqueous suspension. CONCLUSIONS: Optimization of SNEDDSs towards keeping the drug compound in solution upon in vitro lipolysis of the SNEDDSs may not be as important as previously suggested.

Oral bioavailability of cinnarizine in dogs: relation to SNEDDS droplet size, drug solubility and in vitro precipitation.

The in vivo performance of self-nanoemulsifying drug delivery systems (SNEDDSs) with different in vitro physicochemical properties were determined with the purpose of elucidating the parameters determining the in vivo performance of SNEDDSs. The in vitro characterisation included the use of pulsed field gradient NMR and the dynamic lipolysis model. In vivo characterisation was carried out in dogs with elevated gastric pH. Four SNEDDSs containing cinnarizine were dosed orally, and the obtained PK profiles were related to in vitro characterisation data. The SNEDDSs with the lowest solubility of cinnarizine in the preconcentrates and the smallest droplet size had the highest AUC values after oral administration. No difference in C(max) and t(max) was observed between the SNEDDSs. Despite of precipitation occurring during in vitro lipolysis of one of the SNEDDS this SNEDDS performed as well in vivo as another SNEDDS that did not show any precipitation. The area under the colloidal dispersion curves as well as under the lipolysis curves could be used to rank order the in vivo performance of the SNEDDSs. Selection of in vitro optimisation parameters for SNEDDSs should be done carefully. It may not always be best to aim for the highest solubility in the preconcentrate and to avoid precipitation during in vitro lipolysis.

An investigation into the utility of a multi-compartmental, dynamic, system of the upper gastrointestinal tract to support formulation development and establish bioequivalence of poorly soluble drugs.

In recent years mechanical systems have been developed that more closely mimic the full dynamic, physical and biochemical complexity of the GI Tract. The development of these complex systems raises the possibility that they could be used to support formulation development of poorly soluble compounds and importantly may be able to replace clinical BE studies in certain circumstances. The ability of the TNO Simulated Gastro-Intestinal Tract Model 1 (TIM-1) Dynamic Artificial Gastrointestinal System in the 'lipid membrane' configuration to support the development of Biopharmaceutics Classification System Class 2 compounds was investigated by assessing the performance of various AZD8055 drug forms and formulations in the TIM-1 system under standard fasting and achlorhydric physiological conditions. The performance data were compared with exposure data from the phase 1 clinical study. Analysis of the AZD8055 plasma concentrations after tablet administration supported the conclusions drawn from the TIM-1 experiments and confirmed that these complex systems can effectively support the product development of poorly soluble drugs. Particularly, the TIM-1 system was able to show that AZD8055 exposure would increase in an approximately dose proportional manner and not be limited by the solubility or dissolution. Additionally, the investigations also showed that the exposure produced by a solution and a tablet would be the same. Specific instances when the TIM-1 system may not be predictive of clinical product performance have also been identified.

SNEDDS Containing Poorly Water Soluble Cinnarizine; Development and in Vitro Characterization of Dispersion, Digestion and Solubilization.

Self-Nanoemulsifying Drug Delivery Systems (SNEDDSs) were developed using well-defined excipients with the objective of mimicking digested SNEDDSs without the use of enzymes and in vitro lipolysis models and thereby enabling studies of the morphology and size of nanoemulsions as well as digested nanoemulsions by Cryo-TEM imaging and Dynamic Light Scattering. Four SNEDDSs (I-IV) were developed. Going from SNEDDS I to IV lipid content and solubility of the model drug cinnarizine decreased, which was also the case for dispersion time and droplet size. Droplet size of all SNEDDS was evaluated at 1% (w/w) dispersion under different conditions. Cinnarizine incorporation increased the droplet size of SNEDDSs I and II whereas for SNEDDSs III and IV no difference was observed. At low pH cinnarizine had no effect on droplet size, probably due to increased aqueous solubility and partitioning into the aqueous phase. Dispersion of the SNEDDSs in Simulated Intestinal Media (SIM) containing bile salts and phospholipids resulted in a decrease in droplet size for all SNEDDS, as compared to dispersion in buffer. Increasing the bile salt/phospholipid content in the SIM decreased the droplet sizes further. Mimicked digested SNEDDS with highest lipid content (I and II) formed smaller nanoemulsion droplet sizes upon dispersion in SIM, whereas droplet size from III and IV were virtually unchanged by digestion. Increasing the bile acid/phosphatidylcholine content in the SIM generally decreased droplet size, due to the solubilizing power of the endogenous surfactants. Digestion of SNEDDSs II resulted in formation of vesicles or micelles in fasted and fed state SIM, respectively. The developed and characterized SNEDDS provide for a better knowledge of the colloid phases generated during digestion of SNEDDS and therefore will enable studies that may yield a more detailed understanding of SNEDDS performance.