Properties of in situ gelling nasal inserts containing estradiol/methyl β-cyclodextrin

A Review on Cyclodextrins/Estrogens Inclusion Complexes

This review focuses on the methods of preparation and biological, physiochemical, and theoretical analysis of the inclusion complexes formed between estrogens and cyclodextrins (CDs). Because estrogens have a low polarity, they can interact with some cyclodextrins' hydrophobic cavities to create inclusion complexes, if their geometric properties are compatible. For the last forty years, estrogen-CD complexes have been widely applied in several fields for various objectives. For example, CDs have been used as estrogen solubilizers and absorption boosters in pharmaceutical formulations, as well as in chromatographic and electrophoretic procedures for their separation and quantification. Other applications include the removal of the endocrine disruptors from environmental materials, the preparation of the samples for mass spectrometric analysis, or solid-phase extractions based on complex formation with CDs. The aim of this review is to gather the most important outcomes from the works related to this topic, presenting the results of synthesis, in silico, in vitro, and in vivo analysis.

Novel in situ gelling vaginal sponges of sildenafil citrate-based cubosomes for uterine targeting

Sildenafil citrate (SIL), a type 5-specific phosphodiesterase inhibitor, demonstrates valuable results in the management of infertility in women; however, the absence of vaginal dosage form in addition to the associated oral adverse effects minimize its clinical performance. The present study is concerned with SIL uterine targeting following intravaginal administration via optimization of cubosomal in situ gelling sponges (CIS). An emulsification method was employed for preparation of cubosomal dispersions incorporating glyceryl monooleate as a lipid phase and poloxamer 407 as a surfactant with or without polyvinyl alcohol as a stabilizer. Cubosomes were estimated regarding entrapment efficiency (EE%), particle size, and in vitro drug release. Chitosan (2% w/w) was incorporated into the optimum formulation and then lyophilized into small sponges. For the CIS, in vivo histopathological and pharmacokinetic studies were conducted on female Wistar rats and compared with intravaginal free SIL sponges (FIS) and oral SIL solution. SIL-loaded cubosomes showed EE% ranging between 32.15 and 72.01%, particle size in the range of 150.81–446.02 nm and sustained drug release over 8 h. Histopathological study revealed a significant enlargement in endometrial thickness with congestion and dilatation of endometrial blood vessels in intravaginal CIS compared to intravaginal FIS and oral-treated groups. The pharmacokinetic study demonstrated higher AUC_0–∞ and C_max with oral administration compared to intravaginal CIS or intravaginal FIS indicating potential involvement of first uterine pass effect after intravaginal administration. Finally, intravaginal CIS could be considered as a promising platform for SIL uterine targeting with minimized systemic exposure and side effects.

Cyclodextrin-Based Formulations: A Non-Invasive Platform for Targeted Drug Delivery

Cyclodextrins (CDs) are recognized as promising pharmaceutical excipients due to their unique ability to form water-soluble inclusion complexes with various poorly soluble compounds. The numerous investigations on CDs and their use in nanomedicine have received considerable attention in the last three decades, leading to the rapid development of new CD-containing formulations that significantly facilitate targeted drug delivery and controlled drug release, with consequent improvements in drug bioavailability. This MiniReview highlights the efficacy and recent uses of CDs for non-invasive drug delivery. Using ophthalmic and nasal drug delivery as examples, an overview of chemical properties, mechanisms of CDs on drug solubilization, stabilization and permeation, along with their toxicological profiles relevant to nasal and ocular administration, are provided and discussed. The recent development and application of CD-based nanocarrier systems for targeted drug delivery are summarized.

Effect of polymer molecular weight and of polymer blends on the properties of rapidly gelling nasal inserts

The objective was to investigate the potential of polymer molecular weight (MW) and polymer blends for the control of drug release from in situ gelling nasal inserts prepared by lyophilization of solutions of model drugs (oxymetazoline HCl, diprophyllin) and polymers. Drug release, polymer solution viscosity, water uptake and mass loss, mechanical properties, and bioadhesion potential were measured. Sonication was effective to reduce the viscosity/polymer MW of carrageenan solutions. Nasal inserts prepared from sonicated carrageenan showed an insignificant reduction in water uptake with sonication time and no disintegration of the gel matrix. In contrast, inserts of different MW Na-alginates revealed a reduced water uptake and an increased mass loss with lower MW. Inserts prepared from carrageenan/low MW Na-alginate blends took up more water at a higher low MW Na-alginate content. Sonicated carrageenan inserts released oxymetazoline HCl independent of the sonication time and diprophyllin with only a slight reduction in the release rate. Release of both drugs from Na-alginate inserts was slow from high MW inserts because no insert dissolution occurred. Increasing the Na-alginate content of inserts prepared from polymer blends accelerated the drug release enabling release rates over a broad range. The bioadhesion potential of Na-alginate inserts was strongly reduced for the low MW grades because of dissolution of the inserts. Xanthan gum and Carbopol 971 blended with Na-alginate formed inserts with poor bioadhesion. The use of polymer blends to control the drug release from nasal inserts was superior to the use of polymers of different MW.

Parameters affecting the drug release from in situ gelling nasal inserts

The purpose of the study was to investigate the influence of physicochemical drug properties, drug loading, and composition of the release medium on the drug release from in situ gelling nasal inserts. Sponge-like nasal inserts of carrageenan and HPMC K15M with the model drugs oxymetazoline HCl, diprophyllin, and acetaminophen (APAP) were prepared by lyophilization. Drug release studies at different drug loadings were performed in various release media. Raman analysis, DSC, and SEM were conducted to analyze the physical state of the drugs in the inserts. All drugs were dissolved in the solid HPMC inserts and were released at similar rates at all investigated loadings except for the least soluble APAP. APAP concentrations in the hydrating HPMC K15M inserts in excess of its solubility limit resulted in reduced relative release rates at higher drug loadings. Drug-polymer interactions (formation of less soluble drug-polymer salts) resulted in a slower release of oxymetazoline HCl from carrageenan inserts than from HPMC K15M inserts. Changes in the composition of the release medium affected the water uptake of carrageenan but not of HPMC K15M inserts. Oxymetazoline release from carrageenan inserts increased with higher Na+-content of the medium because of ion exchange and at low (pH 2) as well as at high pH (pH 10). The osmolality of the release medium had no effect. The solubility of the drug, its physical state in the polymer matrix, and drug-polymer interactions governed the drug release from nasal inserts. The release from inserts prepared with oppositely charged polymers and drugs was influenced by electrostatic drug-polymer interactions and by the composition of the release medium.

In situ gelling, bioadhesive nasal inserts for extended drug delivery: in vitro characterization of a new nasal dosage form

The purpose of this study was the preparation and characterization of sponge-like, in situ gelling inserts based on bioadhesive polymers. Hydrophilic polymers (carrageenan, Carbopol, chitosan, hydroxypropyl methylcellulose (HPMC) K15M and E5, sodium alginate, sodium carboxy methylcellulose (NaCMC), polyvinyl pyrrolidone (PVP) 90, xanthan gum) were dissolved with/without the model drug oxymetazoline HCl in demineralized water and lyophilized into small inserts. The drug release, water uptake, mechanical properties, X-ray diffraction and bioadhesion potential of the nasal inserts were investigated. A sponge-like structure of nasal inserts was formed with amorphous, but not with crystalline polymers during the freeze-drying process. The insert hardness increased with the glass transition temperature of the polymer (PVP25<PVP30<PVP90). The bioadhesion potential was governed by the polymer ability to interact with mucin/agar (highest for carrageenan, Carbopol, xanthan gum and NaCMC). Inserts prepared from low molecular weight polymers resulted in polymer dissolution and fast drug release (HPMC E5, Na-alginate, PVP90). The drug release from inserts prepared from high molecular weight polymers (carrageenan, Carbopol, chitosan, HPMC K15M, NaCMC, xanthan gum) was a complex interplay of osmotic forces, water uptake and electrostatic interactions between drug and polymer. The drug release decreased with higher polymer content and increased drug loading of the insert. Bioadhesive nasal inserts have a high potential as new nasal dosage form for extended drug delivery.