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PubMed1983

Determination of benzalkonium chloride in the presence of interfering alkaloids and polymeric substrates by reverse-phase high-performance liquid chromatography.

A specific assay for the analysis of benzalkonium chloride in the presence of interfering substances was conducted. The approach involved complexing benzalkonium chloride in an ophthalmic system with methyl orange, extraction of the complex into 1,2-dichloroethane, and subsequent analysis by reverse-phase high-performance liquid chromatography. Since the method separates each homologue of benzalkonium chloride, homologues not resident in the ophthalmic system were added as internal standards to improve both recovery and precision in the method.

Alkaloids↗
PubMed1983

Effect of nutrient depletion on the sensitivity of Pseudomonas cepacia to antimicrobial agents.

Pseudomonas cepacia depleted of various nutrients showed marked variation in sensitivity to cetrimide, chlorhexidine, and benzalkonium chloride. In all cases cells depleted of magnesium were the most resistant. It is proposed that these observations may be due to alterations of the envelope of P. cepacia in response to changes in the growth environment. This may have profound implications for investigations of the resistance of this organism both in vivo and in vitro.

Anti-Infective Agents, Local↗
PubMed1984

Determination of benzalkonium chloride by gas chromatography.

A new, simple, and useful approach for the analysis of benzalkonium chloride is presented. A gas chromatography (GC) has been used to pyrolyze benzalkonium chloride in a specific and reproducible manner to yield two tertiary amines for each homologue of benzalkonium chloride present. These are separated by GC and are used to determine the homologue composition of the benzalkonium chloride. These determinations can be made with an analysis time of 25 min/sample.

Benzalkonium Compounds↗
PubMed1985

Cholesterol monohydrate dissolution rate studies in aqueous micellar sodium chenodeoxycholate solutions.

The dissolution rate of cholesterol monohydrate in various concentrations of sodium chenodeoxycholate (1) was significantly influenced by the addition of strong electrolytes. The mass transfer resistances decreased with increasing electrolyte concentrations and attained an asymptotic minimum value predicted and experimentally established for the convective/diffusion-controlled situation. Reduction of the interfacial barrier to dissolution was many times more sensitive to Mg2+ than to Na+ at equimolar concentrations. Cholesterol monohydrate solubilities increased nonlinearly with increasing 1 in 0.01 M phosphate buffer at pH 8.0 and was not influenced by the presence of strong electrolytes. Measured diffusion coefficients gave supporting evidence that the effective micellar size remained the same within the various experimental systems up to 116 mM chenodeoxycholate. The experimental findings indicated that the interfacial barrier is electrostatic in character. They are consistent with the phenomenon of diffusion of negatively charged micelles toward a negatively charged cholesterol monohydrate surface and the subsequent collision complex transfer of cholesterol molecules at the crystal surface. The results and mechanistic interpretations are also in accord with the previous model studies on cholesterol monohydrate dissolution in the presence of mixed micelles composed of nonionic and ionic surfactants.

Benzalkonium Compounds↗
PubMed1987

Direct determination of benzalkonium chloride in ophthalmic systems by reversed-phase high-performance liquid chromatography.

High-performance liquid chromatography has been used to quantitate benzalkonium chloride (alkylbenzyldimethylammonium chloride) in complex ophthalmic formulations at or below concentration levels of 50 ppm. The method involves a one-step dilution for sample preparation and direct injection; therefore, recovery and/or conversion problems are nonexistent. The assay is quick, specific, reproducible, and simple. This new approach makes routine determinations far simpler than previous methods and is especially useful for product stability studies and quality control procedures.

Benzalkonium Compounds↗
PubMed1993

Determination of benzalkonium chloride in ophthalmic solutions containing tyloxapol by solid-phase extraction and reversed-phase high-performance liquid chromatography.

A procedure using solid-phase extraction (Supelcoclean CN) followed by HPLC [Beckman Ultrasphere CN, acetonitrile:phosphate solution (60:40, v/v)] was developed and validated to quantitate the quaternary ammonium preservative benzalkonium chloride in an experimental ophthalmic formulation containing the polymeric material tyloxapol. This procedure makes routine determinations of benzalkonium chloride at concentrations of 0.0035 to 0.01% simpler than the traditional ion-pairing colorimetric methods. This method is quick, specific, and especially useful for drug product stability studies. In addition, because the method distinguishes each homologue, it can be extended to routinely determine the homologue ratio for quality control purposes.

Benzalkonium Compounds↗
PubMed1994

Alkali halide-assisted penetration of neostigmine across excised human skin: a combination of structured water disruption and a Donnan-like effect.

The penetration of neostigmine across excised human skin mounted in flow-through diffusion cells, delivered from a 0.28 M aqueous solution, was below detection limits. The presence of either NaCl or LiCl in the donor solution caused significant fluxes of neostigmine, with permeability coefficients (Kp's) in the range of 10(-6) cm min-1. Paradoxically, low concentrations of NaCl or LiCl (0.25 and 0.5 M) were more effective in this respect than the 1 M solution, which was the least effective concentration in the range of 0.25-3 M. Thus, the dependence of the experimental Kp values on inorganic ion concentration followed a biphasic course, suggesting the participation of two distinctive mechanisms in the penetration-enhancement process. The early phase corresponding to 0.25 and 0.5 M NaCl or LiCl is being partly ascribed to a decrease in the viscosity of lamellar water caused by the influx of the respective hydrated ions, hydration of LiCl or NaCl being more extensive at low alkali halide concentration that at higher ones (reference cited). The late phase corresponding to 2 and 3 M LiCl and NaCl is partly ascribed to a Donnan-like effect whereby the presence of a large excess of poorly diffusible common ion (Na+ or Li+) enhances the partitioning into the skin of the more diffusible ion, in this case neostigmine cation. The presence of inorganic ions at different concentrations had no effect on the partial molal volume of neostigmine bromide (Vi infinity = 223.5 cm3 mol-1), which was practically the same for all concentrations of either LiCl and NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzalkonium Compounds↗
PubMed2000

Benzalkonium chloride and gentamicin cause a leak in corneal epithelial cell membrane.

The purposes of this study are to characterize the pathophysiological effects of benzalkonium chloride and gentamicin on corneal epithelial cells and to determine the concentration dependent effect of these agents on membrane currents of these cells. Rabbit corneal epithelial cells were isolated and subdivided into small, medium and large cells according to their cell capacitance. Using whole cell clamp technique, potassium current of corneal epithelial cells was recorded. Transmembrane current was measured again after bathing in benzalkonium chloride 1, 3, 10, 30 and 100 micrometer ml(-1)for 3 min. The effect of gentamicin was tested at concentrations of 0.4, 1.0, 2.0, 4.0 and 10 mg ml(-1). Synergistic effect of gentamicin of the above mentioned concentrations in the presence of benzalkonium chloride 1 microgram ml(-1)was also measured. We found that small corneal epithelial cells had the highest depolarization-gated, outward potassium current density and large cells had the lowest current density, while medium cells had a current density in between. Benzalkonium chloride induced a concentration dependent increase in the leak current with increasing concentration from 1 to 100 microgram ml(-1). The increase of leak current in medium and large cells was less than that in the small cells. Gentamicin also caused a concentration dependent increase in leak current density from 0.4 to 10.0 mg ml(-1). The increase in leak current density was statistically significant when the concentration was 2.0 mg ml(-1)or higher in small corneal epithelial cells and 1.0 mg ml(-1)or higher in the medium and large cells. Benzalkonium chloride 1.0 microgram ml(-1)augmented the effect of gentamicin on epithelial cell membrane. The extent of enhancement was more prominent in larger than smaller cells. Using whole-cell clamp technique, we were able to determine the threshold concentration of gentamicin and benzalkonium chloride on the integrity of corneal epithelial cell membrane. The toxic action of both agents is mediated by an increase in leak current. We propose that the whole-cell clamp technique is a sensitive and useful tool in determining cytotoxic effects of various agents.

Animals↗
PubMed1995

Release of arachidonic and linoleic acid metabolites in skin organ cultures as characteristics of in vitro skin irritancy.

In vitro techniques make a major contribution to the development of alternatives to the in vivo "Draize" skin irritation test, and the development of sensitive and generally applicable in vitro endpoints of cutaneous toxicity is an area of intensive research. To investigate in vitro characteristics of cutaneous irritation, skin explants of rabbit and human origin were topically exposed to chemical irritants, after which the culture medium was analyzed for the presence of metabolites of both arachidonic and linoleic acid. In rabbits exposed to the potent irritant benzalkonium chloride, a direct relation was established between clinical signs of irritation and in vitro release of the proinflammatory mediator 12-hydroxyeicosatetraenoic acid (12-HETE) by the exposed skin. Histological examination revealed varying degrees of epidermal damage. 12-HETE was also the predominant hydroxy fatty acid released in a dose-dependent way by rabbit skin cultures after in vitro exposure to sodium dodecyl sulfate (SDS), benzalkonium chloride (BC), and formaldehyde (FA). Human skin cultures released, in addition to 12-HETE, predominantly 15-HETE and 13-hydroxyoctadecadienoic acid (13-HODE), omega-6 oxygenase products of arachidonic acid and linoleic acid, respectively. The irritant-induced release of hydroxy fatty acids was strongly inhibited by the lipoxygenase inhibitor eicosatetraynoic acid, indicating enzyme-mediated generation of these bioactive lipids. Comparison of hydroxy fatty acid release to more established markers of cytotoxicity (leakage of the cellular enzymes, such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH)) revealed that increased levels of 13-HODE, 9-HODE, 12-HETE, and ALT were specific markers of cutaneous irritancy in rabbit skin cultures.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1996

Prolonged adverse effects of benzalkonium chloride and sodium dodecyl sulfate in a primary culture system of rabbit corneal epithelial cells.

This investigation was undertaken to determine prolonged adverse effects of benzalkonium chloride (BzCl), a cationic surfactant, and sodium dodecyl sulfate (SDS), an anionic surfactant, after an initial treatment of and subsequent removal from a primary culture system of rabbit corneal epithelial cells. Metabolic integrity and cell growth were evaluated at specified periods after a 1-hr treatment with the surfactants because of their importance in tissue repair. Intracellular calcium ([Ca2+]i) and intracellular pH (pHi) were also measured because of their importance in cellular homeostasis. ATP/ADP ratios were used to assess metabolic integrity, and propidium iodide staining of cells was used to measure relative cell number and cell growth. Digitized fluorescence imaging was used to measure [Ca2+]i with fura-PE3 and pHi with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). BzCl induced a concentration-dependent decrease in ATP/ADP ratios 24 hr after its removal from the cultures, whereas SDS had minimal effects on metabolic integrity throughout the 48-hr postexposure measurement period. The proliferative response of cultures treated with SDS, however, was decreased when compared with BzCl-treated cells. BzCl induced an increase in [Ca2+]i, whereas SDS decreased [Ca2+]i 1-3 hr after removal of surfactants. BzCl produced a sustained decrease in pHi in surviving cells 1-4 hr after its removal, with a return to control values at 24-48 hr. SDS transiently increased pHi 1 hr after its removal and decreased pHi at the 48-hr post-treatment period. In conclusion, the two surfactants in vitro had distinctly different prolonged effects on corneal epithelial cells, which may suggest that BzCl and SDS differentially affect cellular recovery in vivo.

Adenosine Diphosphate↗
PubMed1999

Intrinsic myenteric denervation: a new model to increase the intestinal absorptive surface in short-bowel syndrome.

INTRODUCTION: Short-bowel syndrome (SBS) is caused by resection of massive portions of the small intestine and is characterized by symptoms related to malabsorption, of which severe weight loss is the most apparent. Surgical treatments for SBS are not yet satisfactory. In rats, the myenteric denervation by benzalkonium chloride (BAC) leads to development of megaileum with visceral dilatation and mucosal hyperplasia and increases the intestinal transit time. Such operation in the remaining intestinal segment after massive small bowel resection could increase the duration of contact between luminal nutrients and ileal mucosal epithelium, and furthermore, it could increase the superficial area of the mucosa. Thus, our aim in this study was to evaluate the epithelial morphology and body weight changes of animals after intrinsic ileal denervation associated with extensive small intestine resection. MATERIAL AND METHODS: Wistar rats were submitted to resection of 80% of small intestinal length (Group R). Another group (B) of animals also received topical serosal application of BAC 0.3%. Control animals were submitted to simulated surgery (Group C). Animals were weighed weekly and sacrificed after 90 days. Intestinal walls were collected for histological procedure and morphometry. RESULTS: At the end of the experimental period all groups showed weight increase, which was reduced in the R group (P < 0.01). Interestingly, the denervated Group B showed a marked increase in weight, similar to the control animals. Morphometric analysis of the mucosal layer area showed a major increase in mucosal surface area, mainly in Group B. CONCLUSIONS: Our results showed that the ileal intrinsic denervation associated with massive intestinal resection induced an increase in the superficial absorptive area and was able to improve the postsurgical conditions for the animals, with accentuated weight increase. This procedure may be a useful model for further studies related to the role of the enteric nervous system on intestinal adaptations after extensive resections and may provide a new approach for the surgical treatment of short-bowel syndrome.

Animals↗