Cyclodextrin Multicomponent Complexation and Controlled Release Delivery Strategies to Optimize the Oral Bioavailability of Vinpocetine

Enantiospecific crystallisation behaviour of malic acid in mechanochemical reactions with vinpocetine

We report an intriguing example of enantioselectivity in the formation of new multicomponent crystalline solid containing vinpocetine and malic acid. Several experimental data sets confirmed that the multicomponent system presents a clear enantiospecific crystallisation behaviour both in the solid-state and in solution: only the system consisting of vinpocetine and L-malic acid produces a free-flowing solid consisting of a new crystalline form, while the experiments with D-malic acid produced an amorphous and often deliquescent material. The new vinpocetine-L-malic system crystallizes in the monoclinic space group of P21 and in a 1:1 M ratio, where the two molecules are linked through intermolecular hydrogen bonds in the asymmetric unit. The vinpocetine-DL-malic system was partially crystalline (with also traces of unreacted vinpocetine) with diffraction peaks corresponding to those of vinpocetine-L-malic acid. Solid-state NMR experiments revealed strong ionic interactions in all the three systems. However, while vinpocetine-L-malic acid system was a pure and crystalline phase, in the other two systems the presence of unreacted vinpocetine was always detected. This resulted in a significant worsening of the dissolution profile with respect to vinpocetine-L-malic pure crystalline salt, whose dissolution kinetics appeared superior.

Zero-order release and bioavailability enhancement of poorly water soluble Vinpocetine from self-nanoemulsifying osmotic pump tablet

Solid self-nanoemulsifying (S-SNEDDS) asymmetrically coated osmotic tablets of the poorly water-soluble drug Vinpocetine (VNP) were designed. The aim was to control the release of VNP by the osmotic technology taking advantage of the solubility and bioavailability-enhancing capacity of S-SNEDDS. Liquid SNEDDS loaded with 2.5 mg VNP composed of Maisine™ 35-1, Transcutol^® HP, and Cremophor^® EL was adsorbed on the solid carrier Aeroperl^®. S-SNEDDS was mixed with the osmotic tablet excipients (sodium chloride, Avicel^®, HPMC-K4M, PVP-K30, and Lubripharm^®), then directly compressed to form the core tablet. The tablets were dip coated and mechanically drilled. A 3²*2¹ full factorial design was adopted. The independent variables were: type of coating material (X₁), concentration of coating solution (X₂), and number of drills (X₃). The dependent variables included % release at 2 h (Y₁), at 4 h (Y₂), and at 8 h (Y₃). The in vivo performance of the optimum formula was assessed in rabbits. Zero-order VNP release was obtained by the single drilled 1.5% Opadry^® CA coated osmotic tablets and twofold increase in VNP bioavailability was achieved. The combination of SNEDDS and osmotic pump tablet system was successful in enhancing the solubility and absorption of VNP as well as controlling its release.

Embryo-fetal development studies with the dietary supplement vinpocetine in the rat and rabbit

Dietary supplement and natural product use is increasing within the United States, resulting in growing concern for exposure in vulnerable populations, including young adults and women of child-bearing potential. Vinpocetine is a semisynthetic derivative of the Vinca minor extract, vincamine. Human exposure to vinpocetine occurs through its use as a dietary supplement for its purported nootropic and neuroprotective effects. To investigate the effects of vinpocetine on embryo-fetal development, groups of 25 pregnant Sprague-Dawley rats and 8 pregnant New Zealand White rabbits were orally administered 0, 5, 20, or 60 mg vinpocetine/kg and 0, 25, 75, 150, or 300 mg/kg daily from gestational day (GD) 6-20 and GD 7-28, respectively. Pregnant rats dosed with vinpocetine demonstrated dose-dependent increases in postimplantation loss, higher frequency of early and total resorptions, lower fetal body weights, and fewer live fetuses following administration of 60 mg/kg, in the absence of maternal toxicity. Additionally, the rat fetuses displayed dose-dependent increases in the incidences of ventricular septum defects and full supernumerary thoracolumbar ribs. Similarly, albeit at higher doses than the rats, pregnant rabbits administered vinpocetine displayed an increase in postimplantation loss and fewer live fetuses (300 mg/kg), in addition to significantly lower fetal body weights (≥75 mg/kg). In conclusion, vinpocetine exposure resulted in similar effects on embryo-fetal development in the rat and rabbit. The species differences in sensitivity and magnitude of response is likely attributable to a species difference in metabolism. Taken together, these data suggest a potential hazard for pregnant women who may be taking vinpocetine.

Systemic exposure of vinpocetine in pregnant Sprague Dawley rats following repeated oral exposure: An investigation of fetal transfer

Vinpocetine is being used worldwide by people of all ages, including pregnant women, for its purported multiple health benefits. However, limited data is available addressing the safety/toxicity of vinpocetine. The National Toxicology Program conducted studies to examine potential effects of vinpocetine on the developing rat. Disposition data is helpful to put the fetal findings into context and provide information on the potential risk for humans. The current study reports the systemic exposure and toxicokinetic (TK) parameters of vinpocetine and metabolite, apovincaminic acid (AVA), in pregnant Harlan Sprague Dawley rats, fetuses and amniotic fluid following oral gavage exposure of dams to 5 and 20mg/kg vinpocetine from gestational day 6 to 18. Vinpocetine was absorbed rapidly in dams with a maximum plasma concentration (Cmax) reaching ≤1.37h. Predicted Cmax and area under the concentration versus time curve (AUC) increased less than proportionally to the dose. Vinpocetine was rapidly distributed to the peripheral compartment. More importantly, significant transfer of vinpocetine from dam to fetuses was observed with fetal Cmax and AUC≥55% of dams. Vinpocetine was cleared rapidly from dam plasma with an elimination half-life of ≤4.02h with no apparent dose-related effect. Vinpocetine was rapidly and highly metabolized to AVA with AVA plasma levels in dams ≥2.7-fold higher than vinpocetine, although in the fetuses, AVA levels were much lower than vinpocetine. Comparison of current rat data with literature human data demonstrates that systemic exposure to vinpocetine in rats following repeated exposure to 5mg/kg is similar to that following a single human relevant dose of 10mg suggesting that the findings from the toxicology study may be relevant to humans.

Structure of the inclusion complex of β-cyclodextrin with lipoic acid from laboratory powder diffraction data

The crystal structure of the inclusion complex of β-cyclodextrin with lipoic acid was determined from laboratory powder diffraction data. Thermogravimetric data was used to estimate the number of water molecules in the crystal structure. Lipoic acid is included in β-cyclodextrin through its primary face with the five-membered ring reaching the center plane of the cyclodextrin cavity and its fatty acid chain adopting a bent conformation. Lipoic acid and β-cyclodextrin form a channel-like packing which is stabilized by guest–host hydrogen bonding and close contacts, host–host intermolecular interactions and hydrogen bonding involving the water molecules.

Enhanced oral bioavailability of vinpocetine through mechanochemical salt formation: physico-chemical characterization and in vivo studies

PURPOSE

Enhancing oral bioavailability of vinpocetine by forming its amorphous citrate salt through a solvent-free mechanochemical process, in presence of micronised crospovidone and citric acid.

METHODS

The impact of formulation and process variables (amount of polymer and citric acid, and milling time) on vinpocetine solubilization kinetics from the coground was studied through an experimental design. The best performing samples were characterized by employing a multidisciplinary approach, involving Differential scanning calorimetry, X-ray diffraction, Raman imaging/spectroscopy, X-ray photoelectron spectroscopy, solid-state NMR spectroscopy, porosimetry and in vivo studies on rats to ascertain the salt formation, their solid-state characteristics and oral bioavailability in comparison to vinpocetine citrate salt (Oxopocetine(®)).

RESULTS

The analyses attested that the mechanochemical process is a viable way to produce in absence of solvents vinpocetine citrate salt in an amorphous state.

CONCLUSION

From the in vivo studies on rats the obtained salt was four times more bioavailable than its physical mixture and bioequivalent to the commercial salt produced by conventional synthetic process implying the use of solvent.

Physical-chemical characterization of binary and ternary systems of ketoprofen with cyclodextrins and phospholipids

Binary and ternary interaction products of ketoprofen (an anti-inflammatory drug very poorly water soluble) with phospholipids (phosphatidylcholine (EPC3) and phosphatidylglycerol (EPG)) and cyclodextrins (beta-cyclodextrin and its methylated derivative (MebetaCd)), were prepared to evaluate their ability in improving drug dissolution properties. The different binary and ternary drug-carrier(s) systems were obtained by microwave irradiation, in order to investigate the effectiveness of such a newly proposed preparation technology in bringing about effective solid-state interactions among the components. The effect of different experimental conditions such as microwave irradiation power (500 and 750 W) and treatment time (5, 10 and 15 min) on the physicochemical properties of the products has been also assessed. All solid systems were characterized by differential scanning calorimetry (DSC) analysis, supported by X-ray powder diffractometry, and examined for dissolution properties. The study pointed out the better performance of ternary systems than the binary ones and allowed selection of the best drug-phospholipid-Cd combination and of the most effective preparation conditions. In particular drug-EPC3-MebetaCd ternary systems obtained by using the greatest microwave irradiation energy and the longest treatment time exhibited complete drug amorphization and allowed achievement after 60 min of almost 80% dissolved drug, with an increase in dissolution efficiency of 10.7 and 1.4 times in comparison with drug alone and the corresponding drug-Cd binary system, respectively. The synergistic effect between cyclodextrin and phospholipid in enhancing the drug dissolution properties has been attributed to the combination of the surfactant properties of phospholipids and the wetting and solubilizing power of cyclodextrins and/or the possible formation of a "multicomponent" complex.