M.Fabrizio Saettone

Solid lipid nanoparticles (SLN) as ocular delivery system for tobramycin

Aim of this study was to evaluate solid lipid nanoparticles (SLN) as carriers for topical ocular delivery of tobramycin (TOB). The SLN were in the colloidal size range (average diameter below 100 nm; polydispersity index below 0.2) and contained 2.5% TOB as ion-pair complex with hexadecyl phosphate. The preocular retention of SLN in rabbit eyes was tested using drug-free, fluorescent SLN (F-SLN): these were retained for longer times on the corneal surface and in the conjunctival sac when compared with an aqueous fluorescent solution. A suspension of TOB-loaded SLN (TOB-SLN) containing 0.3% w/v TOB was administered topically to rabbits, and the aqueous humour concentration of TOB was determined up to six hours. When compared with an equal dose of TOB administered by standard commercial eyedrops, TOB-SLN produced a significantly higher TOB bioavailability in the aqueous humour.

Evaluation of ocular permeation enhancers: In vitro effects on corneal transport of four β-blockers, and in vitro/in vivo toxic activity

Abstract The efficacy and toxicity of a series of prospective ocular penetration enhancers (benzalkonium chloride, EDTA, non-ionic surfactants, surface-active heteroglycosides and bile salts) was investigated in vitro, using isolated rabbit corneas. As test drugs four β-blocking agents were used, chosen in order of increasing lipophilicity: atenolol (AT), timolol (TM), levobunolol (LB) and betaxolol (BX). The increased corneal hydration induced by the enhancers was taken as an index of cellular and tissue damage; the ocular irritancy of the agents was also tested in rabbits in vivo. In the absence of enhancers, the apparent corneal permeability coefficients of the four drugs were in the order AT ⋍ TM

Cytotoxicity of potential ocular permeation enhancers evaluated on rabbit and human corneal epithelial cell lines

A series of prospective ocular permeation enhancers, benzalkonium chloride (BAC), cetylpyridinium chloride (CPC), ethylenediaminetetraacetic acid (EDTA), polyoxyethylene (20) stearyl ether (PSE) and polyethoxylated castor oil (PCO) were tested for cytotoxicity on cultures of rabbit (RCE) and human (HCE) corneal epithelial cells. The cells were treated for 5,15 and 60 min with different concentrations of the test substances, in serum-free medium and in medium containing 15% foetal bovine serum (FBS). The cytotoxicity was evaluated by WST-1 test. The EC(50) values for HCE, after 15 min exposure and in the presence of FBS, indicate the following order of cytotoxicity: PSE> or =BAC>CPC>EDTA>PCO. After 1 h exposure the order of decreasing cytotoxicity was PSE> or =BAC>CPC>PCO>EDTA. In all cases the presence of FBS appeared to exert a protective effect against the cytotoxic effect.

Solubilization of tropicamide by hydroxypropyl-β-cyclodextrin and water-soluble polymers: in vitro/in vivo studies

1% (w/v) aqueous solutions of tropicamide (TR), a poorly water-soluble mydriatic-cycloplegic drug, are usually obtained by adjusting the pH to approximately 5.0, at the expense, however, of ocular tolerance and bioavailability. The capacity of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to solubilize TR in pH 7.4 0.02 M phosphate buffer was investigated in the absence and presence of hydrophilic polymers (PVP, CMC and HPMC). Approximately 3.5% (w/v) HP-beta-CD was required to solubilize 1% (w/v) TR in pH 7.4 buffer at room temperature. The required amount was reduced to 0.9% (w/v) by heating at 120 degrees C in the presence of 0.1% (w/v) HPMC. Mydriatic activity tests in rabbits showed an improved bioavailability and maximal mydriatic response for two CD formulations, with and without HPMC, when compared to standard 1% (w/v) TR eyedrops, buffered at pH 5.0. The improved in vivo behaviour of the CD formulations are likely due to their physiological pH, resulting in a reduced irritant effect, although an effect of HP-beta-CD on corneal permeability cannot be dismissed a priori.

Effect of different terpene-containing essential oils on permeation of estradiol through hairless mouse skin.

Purpose of the present investigation was to evaluate six terpene-containing essential oils for their capacity to promote permeation of estradiol (ES) through hairless mouse skin in vitro. Tests on cajuput, cardamom, melissa, myrtle, niaouli and orange oil, all used at the 10% w/w concentration in propylene glycol (PG), evidenced niaouli oil (NIA) as the best permeation promoter for ES. Tests on the main terpene components of NIA (1,8 cineole, alpha-pinene, alpha-terpineol and D-limonene), evaluated neat (10% w/w in PG) or in admixture, confirmed the better promoting activity of whole NIA. The present data point to the validity of complex terpene mixtures, such as that composing NIA, as transdermal penetration enhancers for moderately lipophilic drugs like ES.

A collaborative evaluation of the cytotoxicity of two surfactants by using the human corneal epithelial cell line and the WST-1 test

This study was undertaken to investigate the use of the in vitro test WST-1, an assay of cell proliferation and viability, for a preliminary safety evaluation of topical ophthalmic preparations. The cytotoxicity of two surfactants, benzalkonium chloride (BAC) and polyoxyethylene-20-stearyl ether (Brij78, PSE) was independently investigated in four laboratories in the EU by using an immortalized human corneal epithelial (HCE) cell line. The HCE cells were exposed to BAC and PSE for 5 min, 15 min, and 1 hour, and the results of the HCE-WST-1 tests were collected and compared. After one-hour exposure, the EC(50) values in BAC-treated cells in the presence of serum ranged between 0.0650 +/- 0.0284 (mean +/- SD) mM, and those in the absence of serum 0.0296 +/- 0.0081 mM. The corresponding values for PSE were 0.0581 +/-.0300 mM and 0.0228 +/-.0063 mM. There were variations in the results between different laboratories, with coefficients of variation ranging from 31 to 121%, mean 58%. The use of one-hour exposure time is to be preferred, and the elimination of serum in the culture medium is recommended to avoid both underestimation of toxic effects and variability of the test results.

Evaluation of theophylline tablets compacted by means of a novel ultrasound-assisted apparatus

Abstract A model formulation containing theophylline and Eudragit® RL was compacted, at energies ranging between 15 and 150 J, by means of a laboratory-scale, novel tabletting machine in which compaction was effected by ultrasound, rather than by mechanical energy. Comparison of the technological and physico-chemical characteristics of the resulting tablets with those of tablets obtained with a conventional tabletting machine evidenced significant differences, suggesting sintering as the main mechanism operating in ultrasound-assisted compaction. The ultrasound-compacted tablets released the drug at lower rates with respect to conventional tablets. The novel technique migh prove useful for the development of sustained-release oral dosage forms containing theophylline or other suitable drugs.

Formulation and Preliminary in vivo Testing of Rufloxacin-Cyclodextrin Ophthalmic Solutions

Aim of the present work was to investigate the effect of somecyclodextrins (CDs) on the solubility and ocular bioavailability of rufloxacin base (RUF), with theultimate goal of developing an ophthalmic formulation. Phase solubility studies of RUF inpH 7.4 buffer were carried out in the presence of β-cyclodextrin (β-CD),hydroxypropyl-β-cyclodextrin (HP-β-CD) and γ-cyclodextrin(γ-CD). The effect of hydroxypropyl methylcellulose (HPMC) on RUF solubility was evaluated after heating the solutionscontaining HP-β-CD at 120 °C.A significant enhancement of RUF solubility was achieved by associatingthe drug with CDs, particularly HP-β-CD. This CD formed with RUF a less stablecomplex than that formed by β-CD, but did not suffer the solubility limitations ofthe parent CD, and showed a higher solubilizing capacity than γ-CD. Addition of 0.25%(w/v) HPMC to solutions containing HP-β-CD increased the solubilizing effect of this CD,thus allowing reduction of the amount necessary for solubilization of 0.3% (w/v) RUF.Preliminary pharmacokinetic data in rabbits indicated that theocular bioavailability of 0.3% (w/v) RUF solubilized by HP-β-CD was higher when compared witha 0.3% (w/v) RUF suspension used as reference.

Ophthalmic emulsions and suspensions

The most common ophthalmic dosage forms are solutions, ointments, and suspensions. According to a recent article [1], these account for nearly 90% of currently available ophthalmic formulations in ...