Nasal absorption kinetic behavior of azetirelin and its enhancement by acylcarnitines in rats

Loss of the V-ATPase B1 subunit isoform expressed in non-neuronal cells of the mouse olfactory epithelium impairs olfactory function

The vacuolar proton-pumping ATPase (V-ATPase) is the main mediator of intracellular organelle acidification and also regulates transmembrane proton (H(+)) secretion, which is necessary for an array of physiological functions fulfilled by organs such as the kidney, male reproductive tract, lung, bone, and ear. In this study we characterize expression of the V-ATPase in the main olfactory epithelium of the mouse, as well as a functional role for the V-ATPase in odor detection. We report that the V-ATPase localizes to the apical membrane microvilli of olfactory sustentacular cells and to the basolateral membrane of microvillar cells. Plasma membrane V-ATPases containing the B1 subunit isoform are not detected in olfactory sensory neurons or in the olfactory bulb. This precise localization of expression affords the opportunity to ascertain the functional relevance of V-ATPase expression upon innate, odor-evoked behaviors in B1-deficient mice. This animal model exhibits diminished innate avoidance behavior (revealed as a decrease in freezing time and an increase in the number of sniffs in the presence of trimethyl-thiazoline) and diminished innate appetitive behavior (a decrease in time spent investigating the urine of the opposite sex). We conclude that V-ATPase-mediated H(+) secretion in the olfactory epithelium is required for optimal olfactory function.

The use of absorption enhancers to enhance the dispersibility of spray-dried powders for pulmonary gene therapy

BACKGROUND

Pulmonary gene therapy requires aerosolisation of the gene vectors to the target region of the lower respiratory tract. Pulmonary absorption enhancers have been shown to improve the penetration of pharmaceutically active ingredients in the airway. In this study, we investigate whether certain absorption enhancers may also enhance the aerosolisation properties of spray-dried powders containing non-viral gene vectors.

METHODS

Spray-drying was used to prepare potentially respirable trehalose-based dry powders containing lipid-polycation-pDNA (LPD) vectors and absorption enhancers. Powder morphology and particle size were characterised using scanning electron microscopy and laser diffraction, respectively, with gel electrophoresis used to assess the structural integrity of the pDNA. The biological functionality of the powders was quantified using in vitro cell (A549) transfection. Aerosolisation from a Spinhaler dry powder inhaler into a multistage liquid impinger (MSLI) was used to assess the in vitro dispersibility and deposition of the powders.

RESULTS

Spray-dried powder containing dimethyl-beta-cyclodextrin (DMC) demonstrated substantially altered particle morphology and an optimal particle size distribution for pulmonary delivery. The inclusion of DMC did not adversely affect the structural integrity of the LPD complex and the powder displayed significantly greater transfection efficiency as compared to unmodified powder. All absorption enhancers proffered enhanced powder deposition characteristics, with the DMC-modified powder facilitating high deposition in the lower stages of the MSLI.

CONCLUSIONS

Incorporation of absorption enhancers into non-viral gene therapy formulations prior to spray-drying can significantly enhance the aerosolisation properties of the resultant powder and increase biological functionality at the site of deposition in an in vitro model.

Alkanoylsucroses in nasal delivery of low molecular weight heparins: in-vivo absorption and reversibility studies in rats

The efficacy of alkanoylsucroses in enhancing nasal absorption of low molecular weight heparin (LMWH) and the time span of action of these agents on the nasal membrane has been investigated. In this regard, LMWH formulated with alkanoylsucroses was administered nasally to anaesthetized male Sprague-Dawley rats and the absorption of LMWH was determined by measuring plasma antifactor Xa activity. The duration of action of these agents at the site of administration was investigated by an in-vivo reversibility study. The potency and efficacy of dodecanoylsucrose was compared with that of sodium glycocholate. Alkanoylsucroses used in this study include dodecanoylsucrose, decanoylsucrose and octanoylsucrose. These agents enhance nasal absorption of enoxaparin in a dose-dependent and chain-length-dependent manner. Of the agents tested, dodecanoylsucrose was found to be the most potent in enhancing nasal absorption of LMWH. The bioavailability of enoxaparin formulated with alkanoylsucroses was increased by several folds compared with enoxaparin formulated in saline. The reversibility study with dodecanoylsucrose showed that the effect of alkanoylsucroses faded away with time and the duration of action of this agent at the site of administration was 120-140 min. Dodecanoylsucrose was found to be twice as potent as sodium glycocholate. Overall, the nasal absorption of LMWH was effectively enhanced by co-administration of alkanoylsucroses and the effect of alkanoylsucroses on nasal epithelium was found to be reversible. The potency of these agents depends on their hydrophobic chain lengths.

Absorption enhancers for nasal drug delivery

This paper describes the basic concepts for the transmucosal delivery of drugs, and in particular the use of the nasal route for delivery of challenging drugs such as polar low-molecular-weight drugs and peptides and proteins. Strategies for the exploitation of absorption enhancers for the improvement of nasal delivery are discussed, including consideration of mechanisms of action and the correlation between toxic effect and absorption enhancement. Selected enhancer systems, such as cyclodextrins, phospholipids, bioadhesive powder systems and chitosan, are discussed in detail. Examples of the use of these enhancers in preclinical and clinical studies are given. Methods for assessing irritancy and damage to the nasal membrane from the use of absorption enhancers are also described. Finally, the mucosal use of absorption enhancers (chitosan) for the improved nasal delivery of vaccines is reported with reference to recent phase I/II clinical studies.

Brain delivery of vasoactive intestinal peptide (VIP) following nasal administration to rats

The aim of this work was to study in rats the nasal route for the brain delivery of the vasoactive intestinal peptide (VIP) neuropeptide. After evaluating VIP stability in solutions obtained from nasal washes, the effect of formulation parameters (pH 4-9, 0-1% (w/v) lauroylcarnitine (LC), hypo- or isoosmolality) on the brain uptake of intranasally administered VIP (10(-8)M)/125I-VIP (300,000 cpm/ml) was studied, using an in situ perfusion technique. Brain radioactivity distribution was assessed by quantitative autoradiographic analysis. Results were compared to intravenously administered VIP. With a hypotonic formulation at pH 4 containing 0.1% LC and 1% bovine serum albumin, VIP stability was satisfactory and loss by adsorption was minimal. Using this formulation, around 0.11% of initial radioactivity was found in the brain after 30 min perfusion and was located in the olfactory bulbs, the midbrain and the cerebellum. HPLC analysis of brain and blood extracts demonstrated the presence of intact VIP in brain and its complete degradation in the blood compartment. By intravenous administration, no intact VIP was found either in brain or in blood. In conclusion, intact VIP could be delivered successfully to the brain using the intranasal route for administration.

Inhalation therapy: new delivery systems

The objective of this article is to provide an overview of recent advances in inhalation drug delivery. Problems, advantages, limitations, and developments encountered by different inhalation devices and the agents used in these for the purpose of pulmonary delivery are discussed. A critical appraisal is presented and finally the future directions especially in research of the inhaled therapeutics and aerosols are described.

Nasal absorption and biodistribution of plasmid DNA: an alternative route of DNA vaccine delivery

Nasal administration is emerging as a new route of DNA vaccine delivery. We aimed to study the extent of absorption and biodistribution of intranasally administered plasmid DNA. After intranasal administration, the level of plasmid DNA in the serum peaked at 1.5 h. The ratio of the area under the concentration (AUC) after intranasal administration of DNA over the AUC after intravenous administration was 0.14. At 15 min post inoculation, the highest organ distribution was observed in the liver and the cervical lymph nodes showed the highest level among the lymph nodes. At 24 h a higher localization of plasmids to the brain than to the lung and spleen was notable. A significant level of mRNA expression was observed in the lymph nodes. These results suggest that plasmid DNA can be substantially absorbed and distributed to the lymph nodes after intranasal administration, partly explaining the systemic immunogenicity of intranasally administered plasmid DNA vaccines.

Effects of pH and dose on nasal absorption of scopolamine hydrobromide in human subjects

PURPOSE

The present study was conducted to evaluate the effects of formulation pH and dose on nasal absorption of scopolamine hydrobromide, the single most effective drug available for the prevention of nausea and vomiting induced by motion sickness.

METHODS

Human subjects received scopolamine nasally at a dose of 0.2 mg/0.05 mL or 0.4 mg/0.10 mL, blood samples were collected at different time points, and plasma scopolamine concentrations were determined by LC-MS/MS.

RESULTS

Following administration of a 0.2 mg dose, the average Cmax values were found to be 262+/-118, 419+/-161, and 488+/-331 pg/ mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At the 0.4 mg dose the average Cmax values were found to be 503+/-199, 933+/-449, and 1,308+/-473 pg/mL for pH 4.0, 7.0, and 9.0 formulations, respectively. At a 0.2 mg dose, the AUC values were found to be 23,208+/-6,824, 29,145+/-9,225, and 25,721+/-5,294 pg x min/mL for formulation pH 4.0, 7.0, and 9.0, respectively. At a 0.4 mg dose, the average AUC value was found to be high for pH 9.0 formulation (70,740+/-29,381 pg x min/mL) as compared to those of pH 4.0 (59,573+/-13,700 pg x min/mL) and pH 7.0 (55,298+/-17,305 pg x min/mL) formulations. Both the Cmax and AUC values were almost doubled with doubling the dose. On the other hand, the average Tmax, values decreased linearly with a decrease in formulation pH at both doses. For example, at a 0.4 mg dose, the average Tmax values were 26.7+/-5.8, 15.0+/-10.0, and 8.8+/-2.5 minutes at formulation pH 4.0, 7.0, and 9.0, respectively.

CONCLUSIONS

Nasal absorption of scopolamine hydrobromide in human subjects increased substantially with increases in formulation pH and dose.