Percutaneous penetration and dermal metabolism of triclosan (2,4, 4'-trichloro-2'-hydroxydiphenyl ether)

triclosan is widely used in many products that contact the skin of consumers. This study compares in vivo and in vitro skin absorption of triclosan and determines the potential of skin to metobolize it prior to entering the blood stream. After in vivo topical application of a 64.5mM alcoholic solution of [(3)H]triclosan to rat skin, 12% radioactivity was recovered in the faeces, 8% in the carcass 1% in the urine, 30% in the stratum corneum and 26% was rinsed from the skin surface at 24 hours after application. Free triclosan and the glucuronide and sulfate conjugates of triclosan were found in urine and faeces. triclosan penetrated rat skin more rapidly and extensively than human skin in vitro. 23% of the dose had penetrated completely through rat skin into the receptor fluid by 24 hours, whereas penetration through human skin was only 6.3% of the dose. Chromatographic analysis of the receptor solutions showed that triclosan was metabolized to the glucuronide, and to a lesser extent to the sulfate, during passage through the skin. triclosan glucuronide appeared rapidly in the receptor fluid whereas triclosan sulfate remained in the skin. Although the major site of metabolism was the liver, conjugation of triclosan in skin was also demonstrated in vitro and in vivo, particularly to the glucuronide conjugate which was more readily removed from the skin. The in vitro system provides a reasonable estimate of dermal absorption in vivo for the rat. Therefore by extrapolation of the comparative in vitro data for human and rat skin it is reasonable to deduce that dermal absorption in human of triclosan applied at the same dose is about one-third of that in the rat in vivo.

Furazolidone residues in pigs: criteria to distinguish between treatment and contamination

The use of furazolidone in food-producing animals has been banned in the EU. The ban can most effectively be enforced by monitoring for bound residues containing the 3-amino-2-oxazolidinone (AOZ) moiety. Unlike the parent drug, AOZ residues are stable and can be detected for prolonged periods after cessation of treatment. However, AOZ can be passed from pig-to-pig following brief exposure of unmedicated animals to housing that previously contained medicated pigs. We describe criteria by which a distinction may be drawn between pigs treated illegally with the drug and pigs that contain detectable AOZ residues as a result of exposure to contaminated housing. These criteria are that illegally treated pigs will have a concentration ratio of AOZ in bile:kidney of less than 0.3; while unmedicated pigs will have a concentration ratio of AOZ in bile:kidney of greater than 3.0. Using this criteria, 12 pigs, either treated with the drug or exposed to contaminated housing were analysed in a blind study. The pigs were classified as 'Treated' or 'Contaminated' on the basis of the criteria described above. All 12 pigs were assigned to the correct group. This shows that it is possible to differentiate between furazolidone abuse and contamination.

Effect of cyclodextrins and polymers on triclosan availability and substantivity in toothpastes in vivo

The aqueous solubility of triclosan is only about 10 microg/mL. This very low solubility can hamper its biological activity in the oral cavity, which could explain the mixed clinical results obtained from triclosan toothpaste trials. Triclosan availability in a silica-based toothpaste was improved through cyclodextrin solubilization. The triclosan in vivo availability was optimized through a series of phase-solubility studies and triclosan release studies. It was found that in toothpastes, natural beta-cyclodextrin (betaCD) was just as good a solubilizer as the more water-soluble betaCD derivatives. Furthermore, the amount of cyclodextrin could be reduced by as much as 60% through the addition of a small amount of carboxymethylcellulose (CMC), without affecting triclosan release from the toothpaste. Optimally, cyclodextrins resulted in an almost 3-fold enhancement of triclosan availability compared to an identical toothpaste containing no cyclodextrin. In vivo studies in humans showed that replacing triclosan with triclosan/betaCD in the toothpaste resulted in only moderate improvement in triclosan substantivity. However, replacing triclosan with triclosan/betaCD/CMC complex resulted in significant improvement in triclosan substantivity. Furthermore, the in vivo studies showed that replacing free triclosan with triclosan/betaCD/CMC complex resulted in an almost 3-fold increase in initial triclosan concentration in saliva after brushing and about 2-fold increase in duration of activity.

Treatment of ocular infections with topical antibacterials

Topically applied ophthalmic antibacterial preparations are widely used in the treatment of patients with superficial ocular infections. In addition, they are frequently used to augment treatment for intraocular infection administered systemically or via local instillation. Direct application delivers high concentrations of antimicrobial agents to the surface of the eye conveniently, quickly and with minimal systemic exposure to the agent. However, antibacterials are rapidly dissipated from the tear film and intraocular penetration of topical antibacterial agents is generally poor, necessitating intensive application for successful treatment of corneal infections. Therapeutic concentrations are rarely achieved at other sites in the eye. This article reviews what is known of the pharmacokinetics of topical ocular agents and how this information can be used to optimise ocular persistence and penetration and minimise systemic absorption of antibacterials. A review of the features of the most commonly employed topical antibacterials suggests that for the treatment of uncomplicated bacterial conjunctivitis there is little difference between the various agents in terms of clinical efficacy, although chloram-phenicol should be used with care because of its potential haematological toxicity. Carefully considered therapy is imperative for bacterial keratitis; fortified beta-lactam/aminoglycoside combinations are often used for these infections. The fluoroquinolones appear promising, but caution is necessary in treating keratitis of unknown aetiology with these agents alone because of inherent and emerging acquired resistance among Gram-positive bacteria.

Local delivery of chlorhexidine using a tooth-bonded delivery system

Films containing 20% w/w chlorhexidine base (particle size 63-125 microm) in poly(epsilon-caprolactone), MW 35,000-45,000, were prepared by solvent evaporation and sections attached to the mesio-lingual and mesio-buccal surfaces of the lower first molar in healthy volunteers. Saliva (<1.5 microl) was collected on Periopaper and chlorhexidine concentrations measured by HPLC were typically higher in the area immediately adjacent to the tooth-bonded film sections and lower at more distant sites. Analysis of variance of chlorhexidine concentrations, adjacent to the film sections, showed concentrations were significantly different on the buccal and lingual sides of the tooth and depended on the time of sampling (n=5, P<0.05).

[Iodine status and the used of iodized antiseptics in the mother-newborn pair]

Iodine status was evaluated by assessment of urinary iodine excretion in 221 mothers and their 223 newborns. During the first month after childbirth, 59.3 per cent of the mothers and 26.5 per cent of the newborns received applications of iodized antiseptic containing Polyvidone-iodine. 50.2 per cent of the newborns and 24.9 per cent of the mothers had a urinary iodine of more than 20 micrograms/dl (iodine excess). For the mothers and the newborns who had received applications of iodized antiseptic, 38.2 per cent and 74.6 per cent had an iodine excess, respectively. This iodine excess is directly related to use of iodized antiseptic. Such high iodine levels may contribute to the risk of thyroid disorders, and particularly to transient congenital hypothyroidism at a critical age for normal development of the nervous system.

Diurnal variation in the metabolism of S-carboxymethyl-L-cysteine in humans

The routes of metabolism of S-carboxymethyl-L-cysteine in humans are dependent on the time of dosing. Administration of 750 mg of S-carboxymethyl-L-cysteine (Day 1) during the day at 8:00 AM followed by a 8:00 AM to 4:00 PM urine collection revealed that S-carboxymethyl-L-cysteine S-oxide was the major urinary metabolite produced. The 4:00 PM to midnight urine collection resulted in S-(carboxymethylthio)-L-cysteine being identified as the major urinary metabolite. However, the administration of 750 mg of S-carboxymethyl-L-cysteine (day 15) during the night at midnight and analysis of the midnight to 8:00 AM urine collection found that thiodiglycolic acid was the major urinary metabolite, whereas thiodiglycolic S-oxide was identified as the major urinary metabolite in the 8:00 AM to 4:00 PM urine collection. A diurnal variation in the metabolism of S-carboxymethyl-L-cysteine was seen and, in particular, the timing of S-carboxymethyl-L-cysteine administration had a profound effect on the identity of urinary S-oxide metabolites produced. After administration at 8:00 AM the urinary S-oxides produced were S-carboxymethyl-L-cysteine S-oxide and S-methyl-L-cysteine S-oxide but at midnight the major urinary S-oxide metabolite produced was thiodiglycolic acid S-oxide.

Microbial decontamination of human donor eyes with povidone-iodine: penetration, toxicity, and effectiveness

BACKGROUND/AIMS

Povidone-iodine (PVP -I) is applied for microbial decontamination of human eyes donated for transplantation. Concentrations and immersion times vary greatly. The effectiveness and toxicity of PVP-I were assessed for different decontamination protocols.

METHODS

Human donor eyes and corneas were immersed in different concentrations (5-100 mg/ml) of PVP-I for different times (2-30 minutes). The penetration of iodine into the corneal tissue was assessed by x ray microanalysis. Microbial contamination was determined by taking cultures of the limbal areas and storage solutions and by incubation of the corneoscleral buttons in antibiotic-free culture medium. Cytotoxicity of PVP-I for corneal fibroblasts in culture was assessed using the MTT assay.

RESULTS

Depending on concentration and immersion time iodine was found to penetrate into the epithelium, Bowman's layer, and stroma in amounts equivalent to 2-40 mg/ml PVP-I. The MTT assay demonstrated that 2.5 mg/ml PVP-I caused total damage to fibroblasts in vitro. Rinsing eyes with tap water and subsequent immersion in PVP-I reduced the rate of contamination from 82 out of 106 to 69 out of 106 and 37 out of 106, respectively. Antibiotics in the storage medium further reduced contamination from about 40% to 3%. Microbial contamination was not reduced by increasing the concentration and immersion times beyond 5 mg/ml PVP-I for 2 minutes.

CONCLUSION

Immersion of human donor eyes in 5 mg/ml PVP-I solution for 2 minutes significantly reduces microbial contamination of donor corneas without relevant penetration of iodine into the corneal layers. Higher PVP-I concentrations and longer immersion times do not further reduce contamination, whereas the amount of iodine penetrating the corneal layers is elevated above the level cytotoxic for corneal fibroblasts. In view of this, concentrations above 5 mg/ml of PVP-I and immersion periods over 2 minutes are not recommended for reduction of the contamination rate of donor eyes.

[Evaluation of methods of drug release rate in root canal disinfection controlled-release delivery system containing metronidazole]

OBJECTIVE

To measure the release rate of drug in controlled-release delivery system containing metronidazole.

METHODS

Drug release tests in vitro, in vivo and through the roots of extracted teeth were performed. The release rate of metronidazole was calculated after 1 day, 3 days, 7 days and 10 days, and the results were statistically analyzed.

RESULTS

Significant difference was observed among the total drug release rate in vitro, in vivo and through the roots of extracted teeth (P < 0.01). There was no statistically significant difference between the release test in vivo and through the roots of extracted teeth in vitro (P > 0.05).

CONCLUSION

The method of using extracted teeth and the controlled release medium at 37 degrees C, pH7.4 was close to the situation in vivo, and it was an effective method to measure the drug release rate of the root canal disinfection controlled-release delivery system.

Ethanol treatment of tendon allografts: a potential HIV inactivating procedure

The penetration rate of ethanol in human tendons was studied to in order to define the conditions which were necessary to achieve an inactivating concentration against the Human Immunodeficiency Virus (HIV) within the tendon. The rate of alcohol penetration was found to be slow and did not differ with different types of tendons. An average ethanol concentration of 14% (v/v) was measured in human tendons after they had been immersed for 2 h in 70% (v/v) ethanol, and a concentration of 19% (v/v) was reached after 3 h. Ethanol immersion of human tendons may represent an additional safety procedure in inactivating the HIV virus provided the duration is at least 3 h.

A novel assay for the distribution of pyrithione biocides in bacterial cells

Sodium pyrithione and zinc pyrithione (NaPT and ZnPT, respectively) are widely used as cosmetic preservatives and metal chelating agents. They are commonly assayed using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). However, a simple quantitative colorimetric assay has not been previously reported for these compounds. This paper describes the development of a spectrophotometric assay for the quantification of the pyrithiones which is based on the chelation of copper (II) ions by the biocides. This assay was developed in order to facilitate the determination of the distribution of these biocides in the Gram-negative bacteria Escherichia coli NCIMB 10,000 and Pseudomonas aeruginosa NCIMB 10,548. Sodium pyrithione was exhibited only in the cytosol of E. coli and Ps. aeruginosa. Zinc pyrithione, however, was assayed in the cytosol of both bacteria and was found in the cell envelope of Ps. aeruginosa. These findings suggest that the pyrithione biocides are active within bacterial cells as well as at the cell membrane.

Metabolism of 1-(3,4-dichlorobenzyl)-5-octylbiguanide in the dog

1. The biotransformation of 1-(3,4-dichlorobenzyl)-5-octylbiguanide (OPB-2045), a new potent biguanide antiseptic, was investigated in male beagle dogs. Urinary and faecal excretion of unchanged compound and metabolites were studied following a single subcutaneous injection of 14C-labeled compound at a dose of 1 mg/kg. 2. Four urinary metabolites were structually identified using synthetic standards and/or spectral data as 3,4-dichlorobenzoic acid, 6-[5-(3,4-dichlorobenzyl)-1-biguanidino] hexanoic acid (DM-210), 4-[5-(3,4-dichlorobenzl)-1-biguanidino] butanoic acid (DM-212) and 5-[5-(3,4-dichlorobenzyl)-1-biguanidino] pentanoic acid (DM-213). 3. The predominant radioactive substances in the excreta were DM-213 and DM-210 at 26.1% and 25.5%, respectively, of the dose. No unchanged compound was detected in the urine, and in the faeces it was only 2% of the dose.

In vitro assessment of the antimicrobial activity of a local sustained release device containing amine fluoride for the treatment of oral infectious diseases

Dental caries and periodontal diseases are chronic infectious diseases caused by oral bacteria. Local sustained release delivery systems extend the time in which the drug is present in the oral cavity, thus enhancing its therapeutic potential while reducing its side effects. Amine-fluorides (AmF) are known anticaries agents and have recently been found to have an antibacterial effect against periodontal pathogens and caries-associated bacteria. The purpose of this in vitro study was to assess the antimicrobial activity of a local sustained release device (LSRD) containing AmF on Streptococcus sobrinus 6715. LSRD was prepared from an ethylcellulose matrix containing AmF. Release kinetics of AmF from the LSRD was measured simultaneously with its antimicrobial activity. The organic amine and the fluoride were released in different kinetics profiles: The fluoride was released faster than the organic amine. The antimicrobial activity of AmF was measured on planktonic bacteria in solution and on bacteria as part of experimental dental plaque. During a 10-day period, the concentration of the released AmF was above its MIC and no bacterial growth was observed. Bacterial counts in the dental plaque were reduced by 1 to 2 log units. Hence, the LSRD containing AmF has the potential to serve as a medicament in prevention and treatment of dental caries and periodontal diseases.

Povidone-iodine liposomes--an overview

In recent years, liposomes have been increasingly explored as novel drug delivery systems, and several liposome-based drug products have been approved in Europe, the USA and Japan. Depending on size, composition and surface characteristics, liposomes interact specifically with biological structures. Liposomal drug products provide a topical activity at the desired locus of action and are deemed more effective and less toxic than conventional drug formulations. The combination of povidone-iodine (PVP-I) and liposomes unites the exceptional microbicidal activity of the antiseptic substance with the excellent tolerability and lack of immunogenicity of liposomes; in addition, liposomes provide a moist molecular film for the wound environment. The multilamellar vesicles act as microreservoirs hence prolonging the release of the active ingredient. Although no commercial product for repeated application on the eye is currently available, PVP-I has been used in ophthalmology not only for pre- and postoperative antisepsis, but also for the treatment of bacterial and viral conjunctivitis and for prophylaxis against ophthalmia neonatorum. For these indications, liposomal formulations with 2.5 and 5.0% PVP-I were developed. These eye drops are isotonic with tear fluid at pH 6. First in vitro tests demonstrated an excellent antimicrobial efficacy, and a placebo-controlled clinical study on volunteers showed a very good local tolerability. A study on rabbits demonstrated positive results of the PVP-I liposome eye drops compared to placebo and the broadspectrum antibiotic Polyspectran in a standardized model of Staphylococcus aureus deep eye infection. The other aim is a well-tolerated liposomal PVP-I hydrogel for improved antiseptic wound treatment with moisturizer. It has been reported that liposomes are enriched at the wound bottom for direct action against infection and support of wound healing. An animal study on the efficacy and tolerability of different formulations of a hydrogel with PVP-I liposomes in deep dermal burn wounds has indicated an outstanding quality of wound healing with smooth granulation tissue, less inflammation, less wound contraction and no hyperkeratotic reactivity, especially with the 3% PVP-I liposome formulation.

Analysis of the intranasal distribution of ointment

OBJECTIVE

The use of intranasal ointment sniffed into the nasal cavity is widely recommended as a method to lubricate the nose and to prevent drying and crusting of the nasal mucosa and secretions. This therapy is often prescribed to patients with problems with minor episodes of epistaxis, after nasal packing has been removed, and in patients complaining of excessive dryness or crusting within the nose. Various preparations have been used for this purpose. At our institution Polysporin ointment is one of the commonly used preparations. This study evaluated the distribution of Polysporin ointment within the nasal cavities of subjects with no symptoms related to the nasal cavity.

CONCLUSIONS

The results of the study raise doubts about the effectiveness of this therapy.

Percutaneous penetration of 2-phenoxyethanol through rat and human skin

2-Phenoxyethanol applied in methanol was absorbed (64 +/- 4.4% at 24 hr) through unoccluded rat skin in vitro in the static diffusion cell with ethanol/water as receptor fluid. By comparison (43 +/- 3.7% in 24 hr) was absorbed in the flow-through diffusion system with tissue culture medium as receptor fluid. 2-Phenoxyethanol applied in methanol was absorbed (59.3 +/- 7.0% at 6 hr) through unoccluded human skin in vitro in the flow-through diffusion cell with tissue culture medium. With both unoccluded cells, 2-phenoxyethanol was lost by evaporation but occlusion of the static cell reduced evaporation and increased total absorption to 98.8 +/- 7.0%. Skin, post mitochondrial fraction, metabolized phenoxyethanol to phenoxyacetic acid at 5% of the rate for liver. Metabolism was inhibited by 1 mM pyrazole, suggesting involvement of alcohol dehydrogenase. However, first-pass metabolism of phenoxyethanol to phenoxyacetic acid was not detected during percutaneous penetration through viable rat skin in the flow-through system. First-pass metabolism in the skin does not therefore have an influence on systemic availability of dermally absorbed phenoxyethanol. These measures of phenoxyethanol absorption through rat and human skin in vitro agree well with those obtained previously in vivo.

125I uptake competing with iodine absorption by the thyroid gland following povidone-iodine skin application

Povidone-iodine solution is widely used to disinfect the skin surface or prevent suppuration during human and animal surgery. Using radioisotope 125I, we examined whether iodine may be absorbed and then concentrated in the thyroid gland when povidone-iodine solution is applied to the skin of rats or mice. The competition for 125I uptake was examined in mice and rats after the application of povidone iodine to the skin. We also traced the process of absorbed 125I in the thyroid glad during the fixation for tissue preparations. Povidone-iodine applied to the skin significantly reduced the uptake of 125I both in mice and rats. Significant flux of 125I from the thyroid gland in povidone-iodine treated animals was noted during the thyroid fixation of tissue preparations. From these results, povidone-iodine application to the skin instead of stable KI administration may be practical for preventing the uptake of 125I by the thyroid gland during 125I compound administration for medical therapy. In animal experiments concerning thyroid functions, careful attention must be paid when povidone-iodine is used for disinfection in animal surgery.

Buccoadhesive tablets for the slow delivery of cetylpyridinium chloride: design and in vitro/in vivo analysis

A buccoadhesive slow-release system constituted by a monolayer tablet was developed for the administration of cetylpyridinium chloride (CPC). Tablet composition was based on a mixture of a bioadhesive polymer with conventional excipients. Three different polymers (Methocel K4M, Noveon AA1, Carbopol 974P) in three different concentrations (10%, 20%, 30%) were used. The release profile and the adhesion properties of nine formulations were evaluated in vitro. Based on these results three formulations containing 10% w/w of the tested polymers were chosen to assess, with preliminary in vivo studies, the compliance and the residence time in the month of the systems. Tablets containing Noveon AA1 showed the best performances.

Direct evidence for uptake of intact liposomes encapsulating silver sulfadiazine by cultured human keratinocytes based on combined transmission electron microscopy and X-ray microanalysis

Cultured human keratinocytes were exposed to liposomally encapsulated silver sulfadiazine, free silver sulfadiazine, silver sulfadiazine cream, and a corresponding vehicle for 5 min to 24 h. Phagocytosis of intact liposomes by keratinocytes was demonstrated in vitro by combined X-ray microanalysis and electron microscopy. Silver as an active part of the antimicrobial served as an electron-dense marker.

Protective effect of povidone-iodine ointment against skin lesions induced by sulphur and nitrogen mustards and by non-mustard vesicants

Mustard gas (sulphur mustard, SM) is a powerful vesicant employed as a chemical weapon. The present study demonstrates the effect of povidone iodine (PI) ointment against skin toxicity caused by SM. Gross and histopathological examinations showed that application of PI up to 20 min following exposure to the vesicant resulted in marked skin protection. The shorter the interval between exposure and treatment the better was the protection achieved. PI was also effective against other mustards such as carboxybutyl chloroethyl sulphide (CBCS) and mechlorethamine. The fact that PI protected the skin against agents which cannot be oxidized such as iodoacetic acid, divinylsulphone and cantharidine showed that the antidotal effect of PI was unrelated to oxidation of the nitrogen and sulphur atoms of the mustards. PI ointment is proposed as an efficient protective agent against skin toxicity caused by mustards and other alkylators.

Evaluation of Cetylpyridinium Chloride-Containing Mouthwashes Using In Vitro Disk Retention and Ex Vivo Plaque Glycolysis Methods

The Disk Retention Assay (DRA) is an in vitro method developed to measure the available level of cetylpyridinium chloride (CPC) in mouthwash formulations. This method is based on the binding of the cationic CPC molecule to the anionic surface of a cellulose filter disk. Aqueous CPC solutions demonstrate a linear response (A545) for concentrations up to 0.3%. Higher levels of CPC showed no increased response in the assay. Among common oral product ingredients, at relevant concentrations, surfactants are the primary compounds which inhibit CPC detection and hence, chemical availability. Poloxamer-407 decreased CPC availability to 60% at 0.1%, to 10% at 0.5%, and to 24-33% for 0.2-0.4%. Polysorbate-80 decreased CPC availability to 30% at 0.1% and 6% at 0.25%. A range (4-54%) of available levels of CPC were determined for several commercial products containing 0.045-0.05% nominal levels of CPC indicating significant formulation excipient influence. A plaque glycolysis (PG) assay was used to determine the biological activity of all mouthwash products analyzed by DRA. An experimental series of mouthwash formulations having nominal CPC levels of 0-0.10% demonstrated a good correlation (r2 = 0.955) between the calculated available level of CPC (DRA) and inhibition of plaque glycolysis. The calculated available level of CPC from select commercial mouthwash products, also fit the established correlation with biological activity. The combination of DRA and plaque glycolysis methods are valuable tools which can be used during development to maximize the biological activity of CPC mouthwash formulations prior to clinical evaluation.

Hydrolysis of triclosan monophosphate by dental plaque and selected species of oral micro-organisms

Triclosan monophosphate is a phosphorylated derivative of the antimicrobial agent, triclosan. In comparison with triclosan, it is highly soluble in aqueous solutions. It is hypothesized that, within the oral environment, triclosan monophosphate (which may be devoid of antimicrobial activity) will be hydrolyzed into triclosan by the action of microbial phosphatases. The liberated triclosan may then exert antimicrobial activity. To test this hypothesis, we designed experiments to measure the phosphatase activity of plaque and selected species of oral micro-organisms and to demonstrate hydrolysis of triclosan monophosphate. Tests comparing the minimal inhibitory concentration and minimal bactericidal concentration of triclosan and triclosan monophosphate were also undertaken. Dental plaque and the majority of the bacterial strains tested showed phosphatase activity against p-nitrophenyl phosphate which peaked below neutral pH (acid phosphatases) or above neutral pH (alkaline phosphatases). Dental plaque showed the highest levels of alkaline phosphatase (optimum at pH 9.0) and relatively high levels of acid phosphatase (optimum at pH 6.0 to 6.5). Dental plaque and selected species of micro-organisms were all capable of hydrolyzing triclosan monophosphate, albeit at different rates. The minimal inhibitory concentration and minimal bactericidal concentration values for triclosan monophosphate against eight bacterial strains were always considerably higher than the corresponding values for triclosan. Addition of triclosan monophosphate to an established culture (ca. 10(9) cfu/mL) of Capnocytophaga gingivalis growing continuously showed that triclosan monophosphate was rapidly hydrolyzed into triclosan with concomitant loss of total bacterial viability. It is therefore likely that triclosan monophosphate will be broken down into triclosan within the oral environment with concomitant antimicrobial activity.

N-[5-nitro-2-furfurylidene]-3-amino-2-oxazolidinone activation by the human intestinal cell line Caco-2 monitored through noninvasive electron spin resonance spectroscopy

The pathways participating in the metabolism of the nitrofuran antimicrobial drug N-[5-nitro-2-furfurylidene]-3-amino-2-oxazolidinone (furazolidone) in intact cells were investigated in the human intestinal cell line Caco-2. One-electron reduction of furazolidone led to the formation of a free radical intermediate that could be monitored in dense cell suspensions by noninvasive electron spin resonance spectroscopy. The effects of enzyme inhibitors on the kinetics of radical production and decay were used to estimate the relative contribution of different enzymes to the reductive activation of the drug. Although many enzymes are known to reduce nitrofurans in vitro (e.g., xanthine oxidase, aldehyde oxidase, DT-diaphorase, mitochondrial redox chain components), their contributions were insignificant in living Caco-2 cells. The first reducing equivalent required for the formation of the nitroanion derivative of furazolidone appeared to be provided essentially by the microsomal cytochrome P450 reductase. This was confirmed through studies of the NADPH-dependent radical formation by microsomes. Differentiated Caco-2 cells, an established enterocyte model, showed only modestly increased radical formation and the same enzyme-specificity pattern as undifferentiated cells. Consistently, only a small increase in P450 reductase activity was found in differentiated cells, in contrast to the 10-fold increase seen in typical differentiation marker enzymes. With the electron spin resonance method that we describe, it is possible to distinguish between sites of bioactivation of redox active drugs in intact cells.

Comparative killing kinetics of methicillin-resistant Staphylococcus aureus by bacitracin or mupirocin

The in vitro activities of bacitracin and mupirocin were compared for seven different strains of methicillin-resistant Staphylococcus aureus. Six of seven strains showed bacitracin minimum inhibitory concentrations (MICs) of 0.5 to 1.0 units/mL, and all seven had mupirocin MICs of 0.5 to 2 micrograms/mL. Time-kill studies revealed 2.6- to 4.5-log reduction in 24 hours with strains susceptible to bacitracin (4 units/mL) and 0 to 2.2 reduction with mupirocin (16 micrograms/mL). Bacitracin should be considered further for in vivo studies because of enhanced bacteriocidal effect and lower cost.

Effect on neonatal thyroid function of povidone-iodine used on mothers during perinatal period

OBJECTIVE

Our objective was to evaluate the effect on the neonatal thyroid function of povidone-iodine (PVP-I) used on mothers during the perinatal period.

METHODS

Eight consecutive-term pregnant women were randomly separated into 4 groups. Either PVP-1 or benzethonium chloride (BC) was used to disinfect both maternal skin during labor and vaginal lacerations after delivery in Group I and IV; and PVP-1 or BC was supplied to either skin or lacerations in Groups II and III. On day 5, we measured the iodide concentration in breast milk and random urine of neonates, and the levels of neonatal thyroid-stimulating hormone (TSH) and free thyroxine.

RESULTS

The TSH levels in Group I and the breast-milk iodide concentrations in Groups I and II were significantly higher than those in Group IV (p < 0.05). Dietary iodide intake from breast milk correlated significantly with urinary iodide concentrations (r = 0.52, p < 0.001). In our clinic, the recall rate at the time of screening for congenital hypothyroidism was significantly decreased by discontinuing the use of PVP-I (4.47% vs 0.74%, p < 0.001).

CONCLUSIONS

These findings suggest that the use of PVP-I on mothers is associated with transient neonatal hyperthyrotropinemia, in which breast milk might play an important role. Therefore, we recommend that the use of PVP-I be avoided during labor.

Effect of urinary alkalinisation and acidification on the tissue distribution of hexachlorophene in rats

1. Urinary alkalinisation may be helpful in treating acute poisoning with uncouplers of oxidative phosphorylation containing a phenolic hydroxyl (pKa 4-6) or other acidic moiety. 2. We studied the effects of urine alkalinisation and acidification on the tissue distribution of hexachlorophene (HCP, pKa 5.7) in male Sprague Dawley rats (10 rats/group). 3. Ammonium chloride (10 mL kg-1, 2% m/v) or sodium bicarbonate (10 mL kg-1, 2% m/v) were administered by gavage on three occasions over 24 h, prior to a single gavage dose of HCP (180 mg kg-1). Controls received aqueous sodium chloride (10 mL kg-1, 0.9% m/v) followed by either HCP (180 mg kg-1) or vehicle alone. 4. Urine pH, body mass and body temperature were monitored during the study and, at the conclusion of the experiment (12 h post-HCP dose), organ mass (liver, kidney, brain), and plasma, urine and tissue HCP concentrations were measured. 5. No clinical features of toxicity were observed in any group. However, sodium bicarbonate significantly reduced median HCP in liver--median plasma and kidney HCP concentrations were also reduced but not significantly. Conversely, ammonium chloride significantly increased median HCP concentrations in liver and kidney--median plasma HCP was also increased but not significantly. 6. The results provide some support for the hypothesis that blood pH influences the tissue distribution of uncouplers of oxidative phosphorylation containing an acidic moiety. Urinary alkalinisation may be useful in treating acute poisoning with these compounds.

Simultaneous determination of malachite green and its metabolite leucomalachite green in eel plasma using post-column oxidation

A rapid HPLC method with solid-phase extraction (SPE) clean-up for malachite green (MG) and leucomalachite green (LMG) in eel plasma was developed. MG and LMG were extracted with a buffered methanolic solution. The extract was subjected to aromatic sulphonic acid SPE. MG and LMG were eluted from the SPE column with methanol after a treatment with ammonia gas. The reconstituted eluate was analyzed on a Chromspher B column with acetonitrile-ion-pair buffer (pH 4.0) (6:4, v/v) as the mobile phase and detection at 610 nm after post-column oxidation with PbO2. The average recoveries for MG and LMG over the linear range of applicability (20-2500 ng/ml) were 82 +/- 1% and 83 +/- 1%, respectively. The limits of quantification were 5.0 micrograms/l for MG and 0.9 micrograms/l for LMG.

Primary interactions of three quaternary ammonium compounds with blastospores of Candida albicans (MEN strain)

The absorption of three quaternary ammonium compounds (QAC), cetylpyridinium chloride, cetrimide and benzalkonium chloride, onto the surface of blastospores of Candida albicans (MEN strain) was examined at room temperature. Equilibrium uptake occurred in less than 30 seconds for cetylpyridinium chloride and cetrimide whereas 5 min contact time was required for benzalkonium chloride. The adsorption of all three agents may be mathematically described as Langmuirian and hence a concentration-dependent formation of drug-monolayer on the surface of the blastospore occurred. From this the number of molecules adsorbed onto the surface of a single blastospore was calculated to be 1.33 x 10(12), 3.17 x 10(12) and 2.32 x 10(12) for cetylpyridinium chloride, cetrimide and benzalkonium chloride, respectively. These dissimilarities are most likely due to differences in the orientations of both the cationic nitrogen atom and the accompanying lipophilic portions of each QAC at the blastospore surface. Relating these observations to the known antiadherence effects of cetylpyridinium chloride and cetrimide, it can be concluded that monolayer coverage of the blastospore surface with QAC does not account for the observed reduced adherence. This suggests that the anti-adherence effects are due to either direct interaction with, or steric blockade of, adhesions on the blastospore surface.

Gingival absorption of triclosan following topical mouthrinse application

This study assessed the gingival uptake and urinary excretion of triclosan in dogs following topical applications of a mouthrinse containing 0.03% of triclosan. Five different phases were conducted to define the time course of plasma concentration. The effect of plaque on gingival absorption was also measured. Phase I: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-2 hours. Phase II: Plaque was not removed from the animals' teeth. Blood sampling time was 0-2 hours. Phase III: Plaque was not removed from the animals' teeth. Blood sampling time was 0-6 hours. Phase IV: Plaque was not removed from the animals' teeth. Blood sampling time was 0-12 hours. Phase V: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-12 hours. The test substance was administered to 1 male and 1 female dog in Phases I, II, IV and V, and to 1 male dog in Phase III. The same animals were used in each phase. On the first day of each phase, the animals were treated with distilled water for a 15-minute period. The animals were exposed daily to the test material for a 15-minute period during the remaining 7 days of each phase. The test material was administered using custom-made acrylic applicator trays to enclose the maxillar premolars and molars and gingiva of one-half of the upper jaw. A leak-proof seal along the mucogingival junction and palatal mucosa was established and maintained during the exposure period.(ABSTRACT TRUNCATED AT 250 WORDS)

Delivery of antiplaque agents from dentifrices, gels, and mouthwashes

Antiplaque agents delivered from toothpastes, gels, or mouthrinses can augment mechanical oral hygiene procedures to control the formation of supragingival plaque and the development of early periodontal disease. Clinically effective antiplaque agents are characterized by a combination of intrinsic antibacterial activity and good oral retention properties. The overall oral retention of an antiplaque agent is determined by the strength and rate of association of the agent with its receptor sites and the accessibility of these sites. The substantivity of an antiplaque agent and its clearance from the oral cavity are determined by the rate of dissociation of the agent from the receptor sites and the salivary composition and flow rate. Positively charged and non-charged organic molecules, metal ions, enzymes, and surface-active agents have all been considered as antiplaque agents. To exert clinical antiplaque activity, an antimicrobial agent must be formulated in a chemically compatible delivery vehicle to give optimal release and uptake to the sites of action in a biologically active form during its time of application. In principle, antiplaque activity may be enhanced by combining antimicrobial agents with broadly similar, but complementary, modes of action. Alternatively, the activity of a single agent may be increased by use of a retention aid to enhance oral substantivity. Substantial evidence exists to demonstrate the validity of the first approach. However, there are few data, as yet, to support the effectiveness of the second. The oral mucosa is the bulk retention site for all clinically proven antiplaque agents. Plaque, the pellicle-coated tooth surface, and saliva are probably all sites of biological action. A detailed understanding of the interactions between agents and the various receptor sites, and of the importance of these receptor sites to biological activity, is generally lacking.

Pharmacokinetic and metabolic disposition of p-chloro-m-xylenol (PCMX) in dogs

The pharmacokinetic and metabolic profile of p-chloro-m-xylenol (PCMX) was studied in healthy mongrel dogs after intravenous and oral administration of single doses of 200 and 2000 mg of PCMX, respectively. Calculation of pharmacokinetic parameters was based on compartmental and noncompartmental methods. The mean pharmacokinetic parameters of elimination half-life and mean residence time were 1.84 and 1.69 hr, respectively. The apparent volume of distribution at steady state was estimated to be 22.4 liters, and the plasma clearance was 14.6 liters/hr. The bioavailability of PCMX was 21%, indicating low absorption for this drug. PCMX's metabolite data show that a presystemic elimination process (first-pass effect) is also occurring. PCMX plasma concentrations after intravenous administration of 500-, 200-, and 100-mg doses were found to be proportional to the dose given, demonstrating that the pharmacokinetic profile of PCMX is linear over the dose range studied. Biotransformation studies showed that urinary excretion was not the major route for rapid elimination of unchanged PCMX and almost all material excreted in urine was associated with the conjugated species (glucuronides and sulfates). Statistical significant differences were not found (P greater than 0.05) between the percentages excreted in urine of PCMX and its conjugated metabolites after intravenous and oral administration. The percentages excreted in urine after iv and oral doses of unchanged PCMX were, respectively, 0.45 and 0.37; total conjugates, 46.3 and 43.3; sulfates, 38.1 and 33.2; and glucuronides, 8.2 and 10.2.

Effects of chlorhexidine gluconate douche on normal vaginal flora

The effects of a 0.5% aqueous chlorhexidine gluconate (CHG) douche on the normal vaginal flora of twenty healthy nonpregnant volunteers were investigated. The douche was applied in a premeasured 180-ml quantity daily for 7 consecutive days. Specimens for aerobic and anaerobic culture of the vaginal flora were obtained on 3 occasions from each volunteer, once before and twice after CHG use. The culture results were analyzed qualitatively and quantitatively. A blood sample was also collected within 24 h of the last CHG application to determine serum CHG concentration. Lactobacillus spp., Gardnerella vaginalis and Staphylococcus epidermidis were the most prevalent aerobic bacteria at all phases of the study and Bacteroides spp. were the most prevalent anaerobes. The composition of the normal flora was essentially the same 30 days after the last dose as the pretreatment flora. Small amounts of CHG were detected in the serum of all but one subject. No untoward effects on the participants were observed. Candida albicans counts were slightly higher, but prevalence was not significantly increased at the end of the study.

[Tomicide adsorption on bacterial cells]

The capacity of the bacteriocin-like factor of tomicid being adsorbed on microbial cells, depending on the sensitivity of test microorganisms to the preparation, its form and concentration, the duration of the contact of microbial cells with tomicid, the temperature and pH of the incubation medium, was studied. The bacteriocin-like factor of tomicid was found to be capable of nonspecific sorption on microbial cells (in an amount of 64-128 units per mg of dried cell mass). The decrease of the temperature of the incubation medium to 0 degrees C and its pH to 4.8 and 5.4 inhibited the process of binding this bacteriocin-like factor by microbial cells. The presence of the substance with lysozyme properties in the preparation influenced the process of the adsorption of the main antibacterial component on microbial cells sensitive to lysozyme.

In vitro skin permeation and bioassay of chlorhexidine phosphanilate, a new antimicrobial agent

An in vitro technique was developed to study the permeation and antimicrobial activity of graded concentrations of a new antibacterial agent, chlorhexidine phosphanilate (CHP), in cream formulations using Franz diffusion cells. Formulations containing from 0.2 to 2% CHP were quantitatively applied to intact excised skin and to skin from which the stratum corneum and partial epidermis had been enzymatically removed. Receptor fluids from diffusion cells were sampled over time and assayed by HPLC methods for chlorhexidine and phosphanilic acid; 24- and 48-hr samples of the diffusate from studies with damaged skin were also bioassayed using clinical isolates of appropriate microbial species. Through intact skin almost no permeation of CHP was observed over 48 hr. The failure of CHP to penetrate intact human skin suggests that normal stratum corneum is the rate-limiting barrier to penetration by this antimicrobial agent. In damaged skin lacking stratum corneum barrier, the release of CHP from the formulation becomes the rate-determining step. Coincident with penetrating damaged skin, CHP dissociates, and the molar ratio of the chlorhexidine and phosphanilate moities in the diffusate changes to favor phosphanilic acid. The extent of changes in the permeation rates of both moieties of CHP was directly related to the CHP concentration in cream. Both CHP moieties were found to reach equilibrium in the dermis within 24 hr after application. It was also observed that CHP creams down to 0.2% concentration yielded diffusates with activity exceeding the minimum inhibitory concentration of all test microorganisms within 24 hr.

Increased survival rates by topical treatment of burns with cerium nitrate

In experiments on mice we were able to show that the negative effects attributed to burn toxins could almost completely be prevented by one single early treatment of the burned skin with a 0.04 M solution of cerium nitrate [Ce(NO3)3]. The survival rate was 10% for animals which were grafted with burned skin. Treatment with Ce(NO3)3 increased the survival rate to 74%. A reflection of this protective effect was the prevention of the burn-induced disturbance of the acceptor control ratio in isolated liver cell mitochondria. Repeated use of Ce(NO3)3 showed adverse effects due to an increased absorption. An effective treatment of burns with Ce(NO3)3 is without problems and can be done in any hospital.

Topical iodine-containing antiseptics and neonatal hypothyroidism in very-low-birthweight infants

The thyroid function of very-low-birthweight (VLBW; below 1500 g) infants admitted to neonatal intensive-care units was studied at two hospitals; one routinely used topical iodinated antiseptic agents and the other used chlorhexidine-containing antiseptics. Serial monitoring of urinary iodine excretion and serum thyrotropin and thyroxine levels was undertaken from birth for the first 4 weeks of life. Urinary iodine excretion rose dramatically in the 54 iodine-exposed infants and was up to fifty times greater than in the 29 non-exposed infants. Within 14 days, 25% (9 of 36) of the infants exposed to iodine had serum thyrotropin levels above 20 mIU/l, compared with none of the control group. The mean serum thyroxine level in these 9 infants (44.1 nmol/l) was significantly lower than that in exposed infants with normal thyrotropin levels (83.1 nmol/l) and in the non-exposed control group (83.0 nmol/l); thyroxine levels fell before serum thyrotropin rose. These disturbances in thyroid function correlated positively with urinary iodine excretion and hence iodine absorption. Thyroid function had returned to normal by the time of discharge from hospital. It is concluded that iodine absorption, from topical iodine-containing antiseptics, may cause hypothyroidism during a critical period of neurological development in the newborn infant. The routine use of iodine antisepsis in VLBW infants should be avoided because of this effect.

The round window as access route for agents injurious to the inner ear

The ototoxicity of 50% propylene glycol, 70% isopropyl alcohol, 2% acetic acid, Otic Domeboro solution (Miles Pharmaceuticals, West Haven, CT), 1% Gentian violet (Purepac Pharmaceutical, Elizabeth, NJ), Vosol Otic solution (Wallace Laboratories, Cranbury, NJ), Genoptic Ophthalmic solution (Allergan Pharmaceuticals, Irvine, CA), Cortisporin Otic suspension (Burroughs Wellcome, Greenville, NC), Coly-Mycin S Otic (Parke-Davis, Rochester, MI), and Pyocidin Otic (Berlex Laboratories, Cedar Knolls, NJ) was studied in rats according to their effect on the latencies of the second peak of the auditory brainstem responses (ABR) at different sound pressure levels. The substances were instilled into the round window (RW) niches of rats, and the ABR to 1-kHz and 6-kHz tonebursts were obtained, 30 minutes, two hours, and 1 week after exposure. For all substances except isopropyl alcohol and propylene glycol, which evidently quickly penetrated the RW, approximately two hours of exposure were required before inner ear function was affected. The ototoxic effect of the antibiotic drugs was to some degree reversed with time, whereas the recorded potentials for antiseptics such as 1% Gentian violet, 2% acetic acid, and Otic Domeboro indicate that they caused severe damage to inner ear function. Some increases in latencies were also noted after exposure to propylene glycol and isopropyl alcohol, except when the latter was quickly withdrawn from the RW niche.

Topical antimicrobial agents and antibiotics for the eye

Antibiotics for eye infection can be given topically, by subconjunctival or intravitreous injection, or systemically. The bacteria responsible are reviewed and pharmacokinetics influencing topical concentration are discussed. An approach to treatment by the primary care specialist is suggested.

Percutaneous drug absorption in the newborn: hazards and uses

The newborn infant's skin is not a complete barrier to the absorption of externally applied agents, particularly if it is damaged, diseased, or immature. Immaturity is the most important factor that determines percutaneous absorption. Very immature infants in the early neonatal period have a poorly developed epidermis, which is readily permeable to drugs. The main consequences of percutaneous absorption are hazardous. Topically applied agents are absorbed, causing toxic systemic effects that may result in illness and even death without the cause being recognized. No drug or antiseptic agent should be applied to the premature infant's skin without consideration of the effects that might result from percutaneous absorption. On a more optimistic note, the relatively permeable skin could be an advantage to the preterm infant by providing an alternative method of drug administration. The drug theophylline for example can be absorbed and produce therapeutic blood levels for up to 3 days after a single topical application. There is a need for the development of transdermal drug delivery systems for the newborn infant similar to those currently used for therapy in adults.