Dual 0.02% chlorhexidine digluconate - 0.1% disodium EDTA loaded thermosensitive ocular gel for Acanthamoeba keratitis treatment.

Poor bioavailability and low residence time limit the efficiency of conventional biguanide-based eye drops against Acanthamoeba keratitis. The aim of this work was to formulate an original anti-amoebic thermoreversible ocular gel combining biguanide and metalloproteases inhibitor - chelating agent. Chlorhexidine digluconate (CHX)-ethylenediaminetetraacetic acid disodium salt (Na2EDTA) were compounded in poloxamer 407 saline solution. 0.02% CHX - 0.1% Na2EDTA loaded thermosensitive ocular gel exhibited appropriate pH (5.73 ±â€¯0.06), iso-osmolality (314 ±â€¯5 mOsm/kg), viscosity (ranged between 15 and 25 mPa.s) and thermal gelation (26.5 °C and 33 °C) properties. Bioadhesion of gel was successfully tested onto isolated bovine eyes as well as the assessment of CHX penetration into the cornea. Intracorneal CHX concentration was found greater than trophozoite minimum amoebicidal concentration and minimal cysticidal concentration after 15-min and 2-h ocular exposure, respectively, while any CHX permeation through the cornea was detected (<51 ng/cm2/h). Improvement of CHX ocular bioavailability was attributed to probable solubilization of tear film lipid layer by poloxamer. In vitro efficiency of CHX-Na2EDTA ocular gel was confirmed from the drastic reduction of trophozoite and cyst survival (to 25% and 2%, respectively), confirming the potential of the multicomponent pharmaceutical material strategy for the treatment of Acanthamoeba keratitis.

Enhancement of site specific delivery of diloxanide furoate as an antiamoebic drug.

The basic aim of the present research work is to deliver the diloxanide furoate (DF) at specific area using pectin microspheres. The microspheres were prepared by spray drying method and cross-linked by zinc acetate. Different concentrations of polymer (pectin 0.5-3%) and cross-linking agent (0-3% w/v in a mixture of ethanol:water) are taken to optimize the entrapment efficiency, swelling behavior, size and first 6h in-vitro release in simulated gastric fluids. Optimized formulation was characterized in the terms of in-vitro release, in-vivo drug disposition in various organs and in the blood of Sprague-Dawley albino rats and in-vivo gastrointestinal tract transit behavior using X-ray imaging method on albino rabbits. Findings suggested that microspheres containing a concentration of polymer (2% w/v) have average size of 100-500 µm, entrapment efficiency 85.82 ± 0.5 with swelling index 18.77 ± 5.21. In-vitro results and in-vivo gastric transit behavior (using X-ray imaging) have shown no release in first 3-6h that proved the colon specific delivery of DF. The results also suggested that the above approach have not only site specific delivery, but it improves the conversion of active drug by increasing the enzyme mediated hydrolytic degradation of DF due to the presence of polysaccharide polymer:water gel complex.

Assessment of blood-brain barrier penetration of miltefosine used to treat a fatal case of granulomatous amebic encephalitis possibly caused by an unusual Balamuthia mandrillaris strain.

Balamuthia mandrillaris, a free-living ameba, causes rare but frequently fatal granulomatous amebic encephalitis (GAE). Few patients have survived after receiving experimental drug combinations, with or without brain lesion excisions. Some GAE survivors have been treated with a multi-drug regimen including miltefosine, an investigational anti-leishmanial agent with in vitro amebacidal activity. Miltefosine dosing for GAE has been based on leishmaniasis dosing because no data exist in humans concerning its pharmacologic distribution in the central nervous system. We describe results of limited cerebrospinal fluid (CSF) and serum drug level testing performed during clinical management of a child with fatal GAE who was treated with a multiple drug regimen including miltefosine. Brain biopsy specimens, CSF, and sera were tested for B. mandrillaris using multiple techniques, including culture, real-time polymerase chain reaction, immunohistochemical techniques, and serology. CSF and serum miltefosine levels were determined using a liquid chromatography method coupled to tandem mass spectrometry. The CSF miltefosine concentration on hospital admission day 12 was 0.4 µg/mL. The serum miltefosine concentration on day 37, about 80 h post-miltefosine treatment, was 15.3 µg/mL. These are the first results confirming some blood-brain barrier penetration by miltefosine in a human, although with low-level CSF accumulation. Further evaluation of brain parenchyma penetration is required to determine optimal miltefosine dosing for Balamuthia GAE, balanced with the drug's toxicity profile. Additionally, the Balamuthia isolate was evaluated by real-time polymerase chain reaction (PCR), demonstrating genetic variability in 18S ribosomal RNA (18S rRNA) sequences and possibly signaling the first identification of multiple Balamuthia strains with varying pathogenicities.

Development of a liquid chromatographic method for the quantification of paromomycin. Application to in vitro release and ex vivo permeation studies.

We have developed a reversed phase high performance liquid chromatography pulsed amperometric detection (RPHPLC-PAD) method for the determination of paromomycin. It is sensitive, repeatable, and selective without the pretreatment step. Trifluoroacetic acid-water was utilized as the eluent and detected by PAD under NaOH alkaline conditions. The paromomycin detection limit (S/N=3.3) was 2µgmL(-1) and the quantification limit (S/N=10) was 6µgmL(-1). Coefficients of linear regression were higher than 0.99 for concentrations between 6.25 and 200µgmL(-1). The intra and inter-day precision (RSD) was less than 6.5%. The average recoveries were 97.53-102.01%. The proposed HPLC-PAD method presented advantageous performance characteristics and it can be considered suitable for the evaluation of paromomycin loaded nanogel formulation in ex vivo permeation and in vitro release studies.

Bioanalytical method development, pharmacokinetics, and toxicity studies of paromomycin and paromomycin loaded in albumin microspheres.

Intracellular location of leishmania parasite in macrophages protects them from both hosts defence system as well as from antibiotics like paromomycin (PM) acting against them, thus there is a need of a formulation targeting intracellular parasites. Considering this, PM-loaded albumin microspheres (PM-MS) were prepared to target PM to macrophages where leishmania parasites resides and evaluated for their safety profile. A new bioanalytical method for quantitative determination of PM in rat plasma was developed by pre-column derivatization with 9-fluorenylmethyl chloroformate. The developed bioanalytical method was validated and applied for pharmacokinetic studies of PM administered by intramuscular and intravenous routes as well as for developed PM-MS which were administered by intravenous route. Comparative acute and subacute toxicity studies were also carried out for these formulations. The developed method was found to be very sensitive with a quantification limit of 40 ng/ml. Pharmacokinetic studies demonstrated nearly 80% reduction in C(max) of PM when administered as PM-MS, compared to other formulations at equivalent dose. Toxicity studies indicated increased level of blood urea and blood urea nitrogen in PM intramuscular injection at 90 mg/kg dose, whereas at the same dose level PM-MS showed no symptoms of toxicity. Results obtained suggest that developed PM-MS formulation is a promising alternative to the presently marketed PM intramuscular injection for the treatment of visceral leishmaniasis.

Evaluation of the pharmacokinetic profile of artesunate, artemether and their metabolites in sheep naturally infected with Fasciola hepatica.

The pharmacokinetic (PK) parameters of artesunate, artemether and their metabolites dihydroartemisinin (DHA) and dihydroartemisinin-glucuronide (DHA-glucuronide) were determined in sheep naturally infected with Fasciola hepatica. Sheep were treated either with artesunate (intramuscular (i.m.): 40 and 60 mg/kg) or artemether (i.m.: 40 and 160 mg/kg; oral: 80 mg/kg). Blood samples were withdrawn at selected time points post treatment and the artemisinins were quantified in plasma by liquid chromatography and tandem mass spectrometry (LC-MS/MS). The in vitro effect of the metabolites against F. hepatica was investigated using a phenotype-based assay and scanning electron microscopy (SEM). Following artesunate applications (40 and 60 mg/kg), comparable C(max) (maximal plasma concentration) and AUCs (area under the plasma concentration-time curve) were observed for artesunate (C(max): 8.4×10(3) and 9.4×10(3)ng/ml; AUC: 6.9×10(5) and 9.7×10(5) ng min/ml), DHA (C(max): both 2.4×10(3)ng/ml; AUC: 3.7×10(5) and 5.0×10(5) ng min/ml), and DHA-glucuronide (C(max): 1.7×10(4) and 1.6×10(4)ng/ml; AUC: 2.6×10(6) and 3.3×10(6) ng min/ml). Mean elimination half-lifes (t(1/2)) of artesunate, DHA and DHA-glucuronide ranged between 58 and 63 min, 94 and 113min, and 89 and 98 min, respectively. The i.m. oil-based drug formulation liberated artemether slowly and constant levels of artemether and its metabolites were observed during the entire sampling period (24 h). The AUCs of all analytes were significantly higher for the i.m. 160 mg/kg dose compared to i.m. 40 and oral 80 mg/kg doses (P=0.018). Mean C(max) of artemether (2126 and 426 ng/ml) and DHA-glucuronide (3477 and 1587 ng/ml) were higher following oral compared to i.m. (160 mg/kg) treatments (P>0.068), whereas C(max) of DHA was significantly higher following i.m. applications (P=0.0062). DHA rapidly reduced the viability of F. hepatica in vitro, whereas DHA-glucuronide showed no activity. SEM observations revealed only minor and focal tegumental alterations in few of the DHA treated worms. The calculated PK parameters reflect the anthelmintic activity of artesunate and artemether following different routes of application and will aid in the design of future studies with these drugs.

The toxicology of Clioquinol.

5-Chloro-7-iodo-quinolin-8-ol (Clioquinol) is a halogenated 8-hydroxyquinoline that was used in 1950-1970s as an oral anti-parasitic agent for the treatment and prevention of intestinal amebiasis. However in the 1970s oral Clioquinol was withdrawn from the market due to reports of neurotoxicity in Japanese patients. Recently, reports have demonstrated that Clioquinol has activities beyond its use as an antimicrobial. For example, Clioquinol inhibits the function of the proteasome and displays preclinical efficacy in the treatment of malignancy. In addition, due to its ability to bind copper and dissolve beta-amyloid plaques in the brain, Clioquinol has been investigated for the treatment of Alzheimer's disease. As such, efforts are underway to repurpose Clioquinol. In light of the reemergence of oral Clioquinol, we review the toxicology of this compound in animals and humans with an emphasis on its neurotoxicity. Such information will aid in the design of clinical trials of oral Clioquinol for new indications such as cancer therapy.

Con-A conjugated mucoadhesive microspheres for the colonic delivery of diloxanide furoate.

The aim of the research work was to develop cyst-targeted novel concanavalin-A (Con-A) conjugated mucoadhesive microspheres of diloxanide furoate (DF) for the effective treatment of amoebiasis. Eudragit microspheres of DF were prepared using emulsification-solvent evaporation method. Formulations were characterized for particle size and size distribution, % drug entrapment, surface morphology and in vitro drug release in simulated gastrointestinal (GI) fluids. Eudragit microspheres of DF were conjugated with Con-A. IR spectroscopy and DSC were used to confirm successful conjugation of Con-A to Eudragit microspheres while Con-A conjugated microspheres were further characterized using the parameters of zeta potential, mucoadhesiveness to colonic mucosa and Con-A conjugation efficiency with microspheres. IR studies confirmed the attachment of Con-A with Eudragit microspheres. All the microsphere formulations showed good % drug entrapment (78+/-5%). Zeta potential of Eudragit microspheres and Con-A conjugated Eudragit microspheres were found to be 3.12+/-0.7mV and 16.12+/-0.5mV, respectively. Attachment of lectin to the Eudragit microspheres significantly increases the mucoadhesiveness and also controls the release of DF in simulated GI fluids. Gamma scintigraphy study suggested that Eudragit S100 coated gelatin capsule retarded the release of Con-A conjugated microspheres at low pH and released microspheres slowly at pH 7.4 in the colon.

Effect of ketoconazole on the pharmacokinetics of ornidazole--a possible role of p-glycoprotein and CYP3A.

The influence of ketoconazole, a modulator of P-glycoprotein (P-gp), on the exsorption of ornidazole from everted sacs of rat intestine (duodenum, jejunum and ileum) was investigated. The effect of ketoconazole pretreatment on the pharmacokinetics of ornidazole was also studied in eight healthy human volunteers. After overnight fasting ornidazole 500 mg was administered before and after pretreatment with ketoconazole 200 mg once daily for 7 days. Serum samples were analyzed by reversed phase HPLC. Significant differences were observed in pharmacokinetic parameters C(max), AUC(0-t), AUC(0-infinity), T(max) and clearance. Ornidazole is believed to be metabolized through CYP3A and it has considerable intestinal efflux, which was observed from the in vitro study. The altered pharmacokinetic parameters can be attributed to ornidazole efflux from the blood to the intestine and its metabolism by CYP3A in the intestine.

Determination of 5-chloro-7-iodo-8-quinolinol (clioquinol) in plasma and tissues of hamsters by high-performance liquid chromatography and electrochemical detection.

This paper describes a method of determining clioquinol levels in hamster plasma and tissue by means of HPLC and electrochemical detection. Clioquinol was separated on a Nucleosil C18 300 mm x 3.9 mm i.d. 7 microm column at 1 ml/min using a phosphate/citrate buffer 0.1M (400 ml) with 600 ml of a methanol:acetonitrile (1:1, v/v) mobile phase. The retention times of clioquinol and the IS were, respectively, 11.6 and 8.1 min; the quantitation limit (CV>8%) was 5 ng/ml in plasma and 10 ng/ml in tissues. The intra- and inter-assay accuracies of the method were more than 95%, with coefficients of variation between 3.0 and 7.7%, and plasma and tissue recovery rates of 72-77%. There was a linear response to clioquinol 5-2000 ng/ml in plasma, and 10-1000 ng/g in tissues. The method is highly sensitive and selective, makes it possible to study the pharmacokinetics of plasma clioquinol after oral administration and the distribution of clioquinol in tissues, and could be used to monitor plasma clioquinol levels in humans.

Resistance, biguanide sorption and biguanide-induced pentose leakage during encystment of Acanthamoeba castellanii.

AIMS: This study investigates the effects of biguanides during encystment of Acanthamoeba castellanii. METHODS AND RESULTS: A non-nutrient encystment system was used to investigate the changes in the levels of sorption (uptake) of three non-cysticidal concentrations (10, 20 and 50 microg ml(-1)) of chlorhexidine diacetate (CHA) and polyhexamethylene biguanide (PHMB) as well as their effects on viability and leakage of pentose sugars during the first 36 h of encystment. Trophozoites treated with CHA or PHMB were more sensitive and generally sorbed more of each biocide than cysts. During encystment, the largest increases in resistance developed between 18 and 36 h for both biguanides with the resistance emerging to biguanide concentrations of 10 or 20 microg ml(-1) between 18 and 24 h. At 50 microg ml(-1) resistance emerged between 24 and 36 h. There was a general decrease in biocide sorption during encystment between 0-24 and 0-21 h for CHA and PHMB, respectively, at a concentration of 50 microg ml(-1). The greatest decline in biguanide-induced pentose leakage was between 0 and 12 h. CONCLUSIONS: The results suggest that during encystment some of the changes in the susceptibility to CHA or PHMB may be related to decreases in the levels of biocide sorption, which is limited by the developing cyst wall. SIGNIFICANCE AND IMPACT OF THE STUDY: During encystation, changes occur in biguanide sensitivity. The physical barrier of the cyst wall may be an important factor in limiting biocide sorption.

Disposition of antimony and aminosidine combination after multiple subcutaneous injections in dogs.

The disposition of a combination of antimony (Sbv) (12.8 mg/kg) and aminosidine (AM) (10 mg/kg) in 10 healthy Beagle dogs after multiple subcutaneous injections is described. Sbvplasma concentrations were determined by atomic absorption spectrometry, and AM by ion-pair liquid chromatography, using a fluorimetric detector. Sbvreached Cmaxat 60 min, and for about 1 h plasma levels were homogeneously stabilized between 10.78 and 11.76 microgram/mL; by 12 h, Sbvplasma concentrations were close to the detection limit (0.3 microgram/mL). AM Cmaxvalues were recorded after 1 h (30.6+/-3.11 microgram/mL, mean +/- SD), and plasma levels reached values close to the detection limit (0.15 microgram/mL) between 7 and 8 h after injection. Sbvkinetic parameters did not appear modified by the presence of AM. Moreover, repeated injections of the combination did not modify the kinetic behaviour of the two drugs and did not alter the renal function of the animals. The superimposition analysis of the Sbvdata suggests that a twice daily injection of the metal at a dose of 12.8 mg/kg would be sufficient to maintain inhibitory Sbvconcentrations similar to those recorded in humans.

[SMON and pharmacokinetics of chinoform with special reference to animal species difference].

The experimental reproduction of SMON using several kinds of animals given a prolonged administration of chinoform has been carried out by many investigators because of the importance to solve the problem of etiology in the SMON. In these experiments, it is demonstrated that a marked species difference was observed in the relationship between the doses given to animals and the frequency of the onset of neurologic symptoms. Although dogs were accepted as the most suitable animal model for SMON, pathological changes in the peripheral nerve of the dog were not observed. The blood level or tissue distribution of chinoform after oral, intravenous or intraperitoneal administration of the drug differed in the animal species. Thus, it is considered that the species difference in the onset of neurologic symptoms is principally caused by the difference in pharmacokinetics of chinoform in each animal. Moreover, for the onset of neurologic symptoms in animals, perhaps it is necessary to maintain the level of unconjugated chinoform in the nerve tissues around several to over ten micrograms/ml for three or four weeks as well as that in SMON patients while the neurologic symptoms or pathological changes do not appear in some kinds of animals at these levels. In a study on the cellular toxicity of chinoform, many other problems remain to be solved although degeneration or uncoupling on oxidative phosphorylation in mitochondria of the axons by chinoform and lipid peroxidation of the membrane by chinoform-ferric chelate have been already shown.

Comparative pharmacokinetics and amoebicidal activity of metronidazole and satranidazole in the golden hamster, Mesocricetus auratus.

The pharmacokinetic properties of metronidazole and satranidazole were studied in the golden hamster (Mesocricetus auratus), at a dose of 80 mg/kg po. Blood and liver samples were collected at frequent time intervals and assayed for metronidazole and satranidazole by HPLC. Satranidazole exhibited significantly higher plasma concentrations than metronidazole at 1 and 2 h post-dose, but the comparative Cmax values were not significantly different. The satranidazole plasma elimination half-life of 1.01 h was significantly shorter than the corresponding metronidazole half-life of 3.62 h. The comparative liver pharmacokinetic parameters Cmax, Tmax and T1/2 did not differ significantly. Satranidazole however exhibited significantly higher liver concentrations at 1 h post-dose and Cmax and AUC0-infinity values were approximately 35% higher. The in-vivo amoebicidal activity of both compounds was evaluated in the acute hamster hepatic model of amoebiasis. Both metronidazole and satranidazole were administered as single graded doses po, and their dose-response profiles were characterized. Satranidazole demonstrated significantly greater amoebicidal activity than metronidazole with an ED50 value of 19.5 mg/kg, compared to an ED50 value of 45 mg/kg for metronidazole. These data suggest that higher plasma and liver concentrations of satranidazole and greater intrinsic potency probably contribute to superior amoebicidal activity in the hamster model of hepatic infection.

Pharmacokinetics and amoebicidal activity of (+-)-(E)-3-(4- methylsulphinylstyryl)-1,2,4-oxadiazole (BTI 2286E) and its sulphone metabolite (BTI 2571E) in the golden hamster, Mesocricetus auratus.

BTI 2286E is a 1,2,4-oxadiazole with amoebicidal activity. Three groups of golden hamsters received single doses of BTI 2286E or its sulphone metabolite BTI 2571E as either BTI 2286E 60 mg/kg po or BTI 2571E 60 mg/kg po or BTI 2571E 60 mg/kg ip. Blood samples were collected up to 8 h post-dose and plasma concentrations of BTI 2286E and BTI 2571E were assayed by HPLC. BTI 2286E was rapidly absorbed, extensively metabolized during first pass and rapidly eliminated with a plasma elimination half-life of 1.32 h. Conversion to BTI 2571E was the major pathway of elimination. BTI 2571E had approximately 40% bioavailability after oral administration. After intraperitoneal administration its absorption was slow and prolonged, with an apparent elimination half-life of 2.77 h, considerably longer than the elimination half-life of 0.67 h observed when BTI 2571E was formed as a metabolite, in vivo. The amoebicidal activity of both the compounds was evaluated in the acute hamster hepatic model of amoebiasis. Both BTI 2286E and BTI 2571E were administered as single graded po or ip dose, and their dose-response profiles were characterized. BTI 2571E exhibited poor activity after oral administration (ED50 70 mg/kg) probably due to poor bioavailability, but after intraperitoneal administration its activity (ED50 40 mg/kg) was comparable to that of BTI 2286E after po or ip administration.