Daniela Alejandra Quinteros

An efficient ternary complex of acetazolamide with HP-ß-CD and TEA for topical ocular administration

In order to enhance the ocular bioavailability of acetazolamide (ACZ), a multicomponent complex with hydroxypropyl-ss-cyclodextrin (HP-ss-CD) and triethanolamine (TEA) was prepared to be applied topically. In vitro corneal permeation across isolated rabbit cornea of proposed ACZ formulations and the marketed AZOPT(R) formulation (1% w/v brinzolamide) was studied. Formulations were also tested for their effect on the intraocular pressure (IOP) in rabbits. (1)H- and (13)C-NMR experiments were undertaken to verify the real inclusion of ACZ in the ACZ-HP-ss-CD-TEA multicomponent complex. The binding of ACZ to HP-ss-CD in the presence of TEA is described. The increase of TEA concentration decreases the apparent equilibrium constant for the ACZ-HP-ss-CD complex. The ternary system ACZ-HP-ss-CD-TEA seemed to be able to reduce IOP in about 30%. This effect was sustained for 4 h after instillation. In vitro corneal permeation studies demonstrated that the ACZ permeation was increased. RMN experiments indicated that TEA can weaken the association between ACZ and HP-ss-CD increasing the drug ocular hypotensive effect by increasing the free drug available for absorption. Our formulations were considered practically non-irritant. These results indicate that the ternary system ACZ-HP-ss-CD-TEA might be a useful tool for formulating aqueous ACZ eye drop solutions.

Improvement of Acetazolamide Ocular Permeation Using Ascorbyl Laurate Nanostructures as Drug Delivery System

PURPOSE To evaluate the performance of 6-O-Lauryl-l-ascorbic acid nanostructures (coagels) as vehicles for acetazolamide (AZM) in ophthalmic administration by in vitro and in vivo experimental tests. METHODS The systems of coagel + AZM were evaluated in terms of their in vitro release (dialysis membrane), permeability (isolated cornea), pharmacological effectiveness [intraocular pressure (IOP)-reduction in normotensive rabbits], and potential irritant effects. RESULTS The results concerning AZM permeation were better when vehiculized in coagels compared with ringer solution, which was evident from the AZM steady-state flux and P(app) values (J=1.43 μg/min and P(app)=3.04 cm.s(1)). As a consequence of this increase in permeation, the coagel-AZMs were more effective in lowering the IOP, according to the results obtained from the in vivo assays. Coagels loaded with 0.4% (W/W) of AZM showed a higher hypotensive effect in rabbits compared with the commercial formulation AZOPT(®) (brinzolamide 1%), mainly due to the prolonged effect of the former. In all cases, the intensity of irritation was time dependent. The sodium lauryl sulphate solution (2%) used as a positive control produced serious injury 30 min postadministration. This effect caused irritation, which decreased slowly and even at 180 min, the discomfort was still considerable. However, in the case of coagels, a mild-to-moderate effect was observed. CONCLUSIONS The incorporation of AZM in coagels seems to improve the ocular bioavailability of this drug. Coagel-AZM 0.4% showed a higher hypotensive effect, with a mild-to-moderate irritant effect. These systems could be administrated in human beings, although more detailed studies still need to be carried out.

Design of a colonic delivery system based on cationic polymethacrylate (Eudragit E100)-mesalamine complexes

In this work, the design and evaluation of a colonic drug delivery system containing mesalamine (M) is presented. The main goal was to enable M to reach the first part of the colon, where the drug could then be released. To facilitate this, a tablet core was coated with two thin layers. The first compounded by chitosan, which was responsible for core protection in the small intestine until it reached the colon. Once at the colon, microbiological enzymatic activity of the caecal content would degrade the Ch layer, thus triggering drug release. The second layer, the outer one, was compounded with Eudragit L100 (EL), with its function being to avoid the dissolution of the Ch-covered core along the gastro intestinal tract (GIT). In order to achieve a modulated drug release, carbomer P934 (1%) was also included. Dissolution studies showed that the formulation seemed to behave as predicted. The amount of M released from the coated tablet was less than 10% at pH = 1.2 and 6.8. However, when the coated tablet was evaluated in a medium with a caecal content of pH = 7.4, the M delivery was immediately triggered owing to enzymatic activity of the microflora. In this medium, ∼ 60% of M was released in a period of 3 h. Although these results are promising, further studies are still necessary to evaluate the possible in vitro/in vivo correlations.

Hybrid Formulations of Liposomes and Bioadhesive Polymers Improve the Hypotensive Effect of the Melatonin Analogue 5-MCA-NAT in Rabbit Eyes

For the treatment of chronic ocular diseases such as glaucoma, continuous instillations of eye drops are needed. However, frequent administrations of hypotensive topical formulations can produce adverse ocular surface effects due to the active substance or other components of the formulation, such as preservatives or other excipients. Thus the development of unpreserved formulations that are well tolerated after frequent instillations is an important challenge to improve ophthalmic chronic topical therapies. Furthermore, several components can improve the properties of the formulation in terms of efficacy. In order to achieve the mentioned objectives, we have developed formulations of liposomes (150–200 nm) containing components similar to those in the tear film and loaded with the hypotensive melatonin analog 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT, 100 µM). These formulations were combined with mucoadhesive (sodium hyaluronate or carboxymethylcellulose) or amphiphilic block thermosensitive (poloxamer) polymers to prolong the hypotensive efficacy of the drug. In rabbit eyes, the decrease of intraocular pressure with 5-MCA-NAT-loaded liposomes that were dispersed with 0.2% sodium hyaluronate, 39.1±2.2%, was remarkably higher compared to other liposomes formulated without or with other bioadhesive polymers, and the effect lasted more than 8 hours. According to the results obtained in the present work, these technological strategies could provide an improved modality for delivering therapeutic agents in patients with glaucoma.

Spray dried microspheres based on chitosan: A promising new carrier for intranasal administration of polymeric antigen BLSOmp31 for prevention of ovine brucellosis

Previous studies have demonstrated that parenteral immunization with polymeric antigen BLSOmp31 induced a strong immune response and conferred protection against Brucella ovis in rams. This work describes the development of a novel formulation strategy for the delivery of BLSOmp31 in the nasal mucosa. Chitosan microparticles were prepared by spray-drying technology processes and recombinant chimera BLSOmp31 was loaded by passive adsorption onto chitosan microspheres, which were characterized by means of the evaluation of size, zeta potential, morphology, and loading and release rate of BLSOmp31. The mucoadhesive properties of microspheres were evaluated by studying the interaction between microparticles and mucin. The antigen BLSOmp31 integrity was investigated by SDS-PAGE. The yield of production of spray-drying process was 68.95%. Microspheres had a good sphericity, 1-10 μm of particle size and had a positive charge. The loading capacity was found to be 45.19%. The initial fast release of BLSOmp31 from chitosan microparticles was 60%. The BLSOmp31 integrity was not affected by passive adsorption (ionic interaction). The amount of mucin adsorbed on the surface of CMs-BLSOmp31 was lower than on the surface of blank CMs at neutral pH. In vivo studies were carried out in rams. Intranasal immunization induced systemic and local antibodies. In conclusion, the use of BLSOmp31-loaded chitosan spray-drying microspheres offers a promising way for nasal mucosal vaccination in sheep against brucellosis.

Equilibrium and Release Properties of Aqueous Dispersions of Non-Steroidal Anti-Inflammatory Drugs Complexed with Polyelectrolyte Eudragit E 100

Equilibria and release properties of aqueous systems consisting of a set of five non-steroidal anti-inflammatory drugs (AH) complexed with the cationic polymethacrylate Eudragit E 100 (EU) are reported in this study. The composition (EU(AH)50 (HCl)50) having fifty mole percent of each counterion (A− and Cl−) produces clear, stable aqueous dispersions in which a remarkably high proportion of AH (higher than 98%) is condensed with the PE under the form of ion pairs. This property expands the interval of pH in which AH are aqueous soluble. The set of AH contains members with and without an alpha methyl group (-(CH3)CH-COOH: Flurbiprofen, Naproxen, Ketoprofen) and (-CH2-COOH: Diclofenac, Indomethacin). The proportion of ion pairs in the complexes was lower in the former group. Release of AH from the complexes toward a saline (NaCl 0.9%) solution was assayed in Franz cells. The five complexes behaved as drug carriers that exhibited a slow drug release with a remarkable zero order. In line with the percentages of counterionic condensation observed, release rates from -(CH3)CH-COOH complexes were clearly higher than those of -CH2-COOH ones.

Interaction between Eudragit® E100 and anionic drugs: Addition of anionic polyelectrolytes and their influence on drug release performance

In this work, we report results concerning the study of solid complexes compounded by a cationic polymethacrylate (Eudragit® E100, Eu) and mesalazine (M) (Eu-M(x) complex). The influence of an anionic polyacrylic acid polymer (carbomer, C) on dissolution behavior of M from the complex was evaluated (Eu-M(x) C(y) complex). The dissolution profiles and solvent front movements of solid matrices in different media (water, buffer pH 7.4, 0.9% NaCl) were investigated and ionic interactions among Eu, M, and C were determined through Fourier transform infrared (FT-IR) spectroscopy. For Eu-M(x) complexes, the affinity between M and Eu modulated the delivery of free M in solution, with the dissolution media affecting the delivery rate mainly due to an ionic interchange process between M and anionic electrolytes (i.e., Cl(-)). FTIR spectroscopy allowed the ionic interaction between Eu and M to be verified. The addition of C (Eu-M(x) C(y) ) influenced the dissolution behavior of these matrices. As the amount of C was increased, the release mechanism changed from diffusion (Eu-M(50) ) or anomalous (Eu-M(100)) to zero order (Eu-M(x) C(50)). This variation in rate delivery was also affected by the dissolution media, as occurred with Eu-M(x) complexes. The formation of the gel layer during the dissolution process, as consequence of Eu-M(x) C(y) matrices hydration, was influenced by C amount and dissolution media.

Ocular Delivery of Flurbiprofen Based on Eudragit® E-Flurbiprofen Complex Dispersed in Aqueous Solution: Preparation, Characterization, In Vitro Corneal Penetration, and Ocular Irritation

A novel ophthalmic formulation based on the ionic complexation between Eudragit E 100 (EU) and flurbiprofen (FB) is proposed. The selected complex composition, named EU-FBH50 Cl50 , had the basic groups of EU completely neutralized with equal molar amounts of FB and HCl. This complex, obtained in the solid state, exhibited a high aqueous compatibility producing a colloidal dispersion with a high positive electrokinetic potential, in which more than 99% of FB was ionically condensed with EU. In bicompartimental Franz cells, FB diffusion from the complex was very slow. However, dispersion in 0.9% NaCl increased the FB release through an ionic exchange, providing an optimal constant rate of delivery. Corneal FB permeation from 0.1% EU-FBH50 -Cl50 dispersed in 0.9% NaCl solution was substantially more effective compared with 0.1% FB solution, EU-FBH50 -Cl50 (Dex), or Tolerane(®) (a marketed formulation). This complex formulation was shown to be innocuous for rabbit ocular tissues because no irritant effects were evidenced.

Development of a mechanism and an accurate and simple mathematical model for the description of drug release: Application to a relevant example of acetazolamide-controlled release from a bio-inspired elastin-based hydrogel.

Transversality between mathematical modeling, pharmacology, and materials science is essential in order to achieve controlled-release systems with advanced properties. In this regard, the area of biomaterials provides a platform for the development of depots that are able to achieve controlled release of a drug, whereas pharmacology strives to find new therapeutic molecules and mathematical models have a connecting function, providing a rational understanding by modeling the parameters that influence the release observed. Herein we present a mechanism which, based on reasonable assumptions, explains the experimental data obtained very well. In addition, we have developed a simple and accurate “lumped” kinetics model to correctly fit the experimentally observed drug-release behavior. This lumped model allows us to have simple analytic solutions for the mass and rate of drug release as a function of time without limitations of time or mass of drug released, which represents an important step-forward in the area of in vitro drug delivery when compared to the current state of the art in mathematical modeling. As an example, we applied the mechanism and model to the release data for acetazolamide from a recombinant polymer. Both materials were selected because of a need to develop a suitable ophthalmic formulation for the treatment of glaucoma. The in vitro release model proposed herein provides a valuable predictive tool for ensuring product performance and batch-to-batch reproducibility, thus paving the way for the development of further pharmaceutical devices.

Immune response induced by conjunctival immunization with polymeric antigen BLSOmp31 using a thermoresponsive and mucoadhesive in situ gel as vaccine delivery system for prevention of ovine brucellosis.

Control of ovine brucellosis with subcellular vaccines can solve some drawbacks associated with the use of Brucella melitensis Rev.1. Previous studies have demonstrated that the polymeric antigen BLSOmp31 administered by parenteral route was immunogenic and conferred significant protection against B. ovis in rams. Immunization with BLSOmp31 by conjunctival route could be efficient for the induction of mucosal and systemic immune responses. In this work, we evaluated the conjunctival immunization using a thermoresponsive and mucoadhesive in situ gel composed of Poloxamer 407 (P407) and chitosan (Ch) as vaccine delivery system for BLSOmp31 in rams. Serum samples, saliva, lacrimal, preputial and nasal secretions were analyzed to measure specific IgG and IgA antibodies. Cellular immune response was evaluated in vivo and in vitro. Immunization with BLSOmp31-P407-Ch induced high IgG antibody levels in serum and preputial secretions which remained at similar levels until the end of the experiment. Levels of IgG in saliva, lacrimal and nasal secretions were also higher compared to unvaccinated control group but decreased more rapidly. IgA antibodies were only detected in nasal and preputial secretions. BLSOmp31-P407-Ch stimulated a significant cellular immune response in vivo and in vitro. The induction of systemic and local immune responses indicates a promising potential of P407-Ch for the delivery of BLSOmp31 by conjunctival route.