Development and pharmacokinetics of nimodipine-loaded liposomes

Involvement of the serotoninergic system in the anxiolytic action mechanism of a liposomal formulation containing nimodipine (NMD-Lipo)

In the search for anxiolytic drugs with fewer adverse effects, calcium blockers were proposed as a benzodiazepines (BZDs) alternative. In this context, the anxiolytic effect of nimodipine has been demonstrated. However, its low bioavailability and solubility could be improved by using nanostructured drug delivery systems such as liposomes. In this way, liposomal formulation containing nimodipine (NMD-Lipo) was developed. The NMD-lipo is a formulation capable of improving the kinetic characteristics of the drug, as well as the anxiolytic effect of nimodipine. In this work, the serotonergic system participation in the anxiolytic mechanism of the liposomal formulation containing nimodipine (NMD-Lipo) was investigated. A possible 5-HT1A receptor mediation on the NMD-Lipo anxiolytic effect was demonstrated by using WAY 100635 (5-HT1A receptor antagonist) since the antagonist reversed the NMD-Lipo anxiolytic effect in the light/dark test and elevated plus maze test. The results demonstrated that the NMD-Lipo administration had anxiolytic activity through 5-HT1A receptors without causing sedation or compromising the motor coordination of the tested animals.

Loading Amlodipine on Diamond Nanoparticles: A Novel Drug Delivery System

Background

Diamond nanoparticles (Nanodiamond) are biocompatible drug delivery platforms with outstanding surface properties. Their passage into the brain has been confirmed previously. Thus, nanodiamond could provide a drug delivery system to shuttle several drugs through the blood-brain barrier (BBB) which represents a real challenge for the effective delivery of several drugs into the brain. Amlodipine is a calcium channel blocker that cannot pass through BBB and may elicit neuroprotective effects to reverse calcium-induced excitotoxicity and mitochondrial dysfunction that underlie several neurologic disorders including Alzheimer’s disease and stroke.

Aim

The study aimed to investigate the loading of amlodipine on nanodiamond particles.

Methods

Nanodiamond particles were oxidized in a strong oxidizing acidic mixture of sulfuric and nitric acids. Adsorption of amlodipine on nanodiamond particles was achieved in alkaline pH using various concentrations of sodium hydroxide. The loaded amlodipine was determined by high-performance liquid chromatography and confirmed by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy.

Results

The highest percentage (41%) of loaded amlodipine onto nanodiamond particles was achieved in alkaline medium using 2 mM NaOH at a corresponding pH of 8.5. Also, characteristic FTIR bands of amlodipine and nanodiamond were shown obviously in the nanodiamond–amlodipine conjugates. Moreover, the successful loading of amlodipine on diamond nanoparticles was confirmed by transmission electron microscopy.

Conclusion

The present study demonstrates the successful loading of amlodipine onto nanodiamond particles. These findings offer a potential for applying diamond nanoparticles as a drug delivery system to shuttle amlodipine into the brain and open the door to deliver other similar drugs into the brain.

Calcium channel blockers and dementia

Degenerative dementia is mainly caused by Alzheimer's disease and/or cerebrovascular abnormalities. Disturbance of the intracellular calcium homeostasis is central to the pathophysiology of neurodegeneration. In Alzheimer's disease, enhanced calcium load may be brought about by extracellular accumulation of amyloid-β. Recent studies suggest that soluble forms facilitate influx through calcium-conducting ion channels in the plasma membrane, leading to excitotoxic neurodegeneration. Calcium channel blockade attenuates amyloid-β-induced neuronal decline in vitro and is neuroprotective in animal models. Vascular dementia, on the other hand, is caused by cerebral hypoperfusion and may benefit from calcium channel blockade due to relaxation of the cerebral vasculature. Several calcium channel blockers have been tested in clinical trials of dementia and the outcome is heterogeneous. Nimodipine as well as nilvadipine prevent cognitive decline in some trials, whereas other calcium channel blockers failed. In trials with a positive outcome, BP reduction did not seem to play a role in preventing dementia, indicating a direct protecting effect on neurons. An optimization of calcium channel blockers for the treatment of dementia may involve an increase of selectivity for presynaptic calcium channels and an improvement of the affinity to the inactivated state. Novel low molecular weight compounds suitable for proof-of-concept studies are now available.

Investigation into the effect of varying l-leucine concentration on the product characteristics of spray-dried liposome powders

Objectives

Spray-dried formulations offer an attractive delivery system for administration of drug encapsulated into liposomes to the lung, but can suffer from low encapsulation efficiency and poor aerodynamic properties. In this paper the effect of the concentration of the anti-adherent l-leucine was investigated in tandem with the protectants sucrose and trehalose.

Methods

Two manufacturing methods were compared in terms of their ability to offer small liposomal size, low polydispersity and high encapsulation of the drug indometacin.

Key findings

Unexpectedly sucrose offered the best protection to the liposomes during the spray drying process, although formulations containing trehalose formed products with the best powder characteristics for pulmonary delivery; high glass transition values, fine powder fraction and yield. It was also found that l-leucine contributed positively to the characteristics of the powders, but that it should be used with care as above the optimum concentration of 0.5% (w/w) the size and polydispersity index increased significantly for both disaccharide formulations.

Conclusions

The method of liposome preparation had no effect on the stability or encapsulation efficiency of spray-dried powders containing optimal protectant and anti-adherent. Using l-leucine at concentrations higher than the optimum level caused instability in the reconstituted liposomes.