Population Pharmacokinetics of Difloxacin in Crucian Carp (Carassius auratus) after a Single Oral Administration.

This study aimed to investigate the population pharmacokinetics of difloxacin in crucian carp (Carassius auratus) orally provided a single dose of 20 mg/kg body weight (BW). To achieve this, fish were sampled at various intervals using a sparse sampling strategy, and plasma samples were analyzed using the high-performance liquid chromatography (HPLC) method. Subsequently, naïve average data were analyzed using a non-compartmental method, and a population model was developed based on the nonlinear mixed effects approach. The covariate of BW and the relationship between covariances were sequentially incorporated into the population model. However, it was found that only covariance and not BW affected the population parameters. Therefore, the covariance model was taken as the final population model, which revealed that the typical values of the absorption rate constant (tvKa), apparent volume of distribution per bioavailability (tvV), and clearance rate per bioavailability (tvCl) were 1.18 1/h, 14.18 L/kg, and 0.20 L/h/kg, respectively. Based on the calculated free AUC/MIC values, the current oral dose of difloxacin (20 mg/kg BW) cannot generate adequate plasma concentrations to inhibit pathogens with MIC values above 0.83 µg/mL. Further study should be carried out to collect the pathogens from crucian carp and determine the MIC data of difloxacin against them. Pharmacodynamic experiments must also be further carried out to determine the optimal therapeutic dose for the treatment of Aeromonas hydrophila infection.

Population Pharmacokinetics of Danofloxacin in Yellow River Carp (Cyprinus carpio haematopterus) After One Single Oral Dose.

This study aimed to determine the population pharmacokinetics of danofloxacin in healthy Yellow River carp (Cyprinus carpio Haematopterus) after single oral administration at 10 mg/kg body weight (BW). A sparse sampling was applied in this study and plasma samples were randomly collected from the tail veins of six carp at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 36, 48, 72, 96, 120 and 144 h after administration. A maximum of four plasma samples was collected from each carp. Then the concentrations of danofloxacin in plasma samples were determined through an HPLC method. Danofloxacin could be quantified in plasma up to 144 h after administration. The corresponding population pharmacokinetic modeling was developed according to the non-linear mixed effect method, including covariate and covariance models to explain some variations from unknown sources and improve the prediction ability. On the premise of sparse sampling, the typical values of the population (fixed effect) and inter-individual variation (random effect) were described by the current population pharmacokinetic model. The estimated typical values and coefficient of variation between individuals (CV%) of absorption rate constant (tvKa), apparent distribution volume (tvV) and clearance (tvCL) were 2.48 h-1 and 0.203%, 47.8 L/kg and 8.40%, 0.694 L/h/kg and 4.35%, respectively. The current danofloxacin oral dosing (10 mg/kg BW) can provide suitable plasma concentrations to inhibit those pathogens with MIC values below 0.016 µg/ml based on the calculated PK/PD indices of AUC/MIC or Cmax/MIC. Further studies are still needed to determine the in vitro and in vivo antibacterial efficacy of danofloxacin against pathogens isolated from Yellow River carp and finally draw a reasonable dosing regimen.

Exploring the Pharmacokinetics of Phenoxymethylpenicillin (Penicillin-V) in Adults: A Healthy Volunteer Study.

This healthy volunteer study aimed to explore phenoxymethylpenicillin (penicillin-V) pharmacokinetics (PK) to support the planning of large dosing studies in adults. Volunteers were dosed with penicillin-V at steady state. Total and unbound penicillin-V serum concentrations were determined, and a base population PK model was fitted to the data.

Selected Factors Affecting Oral Bioavailability of Nanoparticles Surface-Conjugated with Glycocholic Acid via Intestinal Lymphatic Pathway.

Here, we describe the absorption pathways of nanoparticles whose surface is modified with bile acid and present environmental factors that influence oral bioavailability (BA) from the gastrointestinal tract (GIT). The approach utilized 100 nm sized fluorescence-labeled, carboxylated polystyrene nanoparticles (CPN) conjugated with glycocholic acid (G/CPN) to exclude potential artifacts, if existing, and instability issues in evaluating the transit of G/CPN in the GIT and measuring BA. The in vitro study using SK-BR-3 that expresses the apical sodium bile acid transporter showed that once G/CPN is internalized, it stayed 2.9 times longer in the cells than CPN, indirectly suggesting that G/CPN takes intracellular trafficking pathways different from CPN in SK-BR-3 cells. In a Caco-2 cell monolayer, G/CPN passed through the monolayer without damaging the tight junction. G/CPN, when administered orally in rodents, showed sustained transit time in the GIT for at least 4 h and was absorbed into the intestinal lymphatic system and circulated into the blood. Ingestion of food before and after oral administration delays G/CPN absorption and decreases BA. A decrease in gastrointestinal motility by anesthetic condition increased the relative BA of G/CPN by up to 74%. Thus, the oral BA of G/CPN can be optimized by taking food ingestion and gastrointestinal motility into account.

Pharmacodynamic dose effects of oral cannabis ingestion in healthy adults who infrequently use cannabis.

BACKGROUND: Prior controlled cannabis research has mostly focused on smoked cannabis and predominantly included frequent cannabis users. Oral cannabis products ("edibles") make up a large and growing segment of the retail cannabis market. This study sought to characterize the pharmacodynamic effects of oral cannabis among infrequent cannabis users. METHODS: Seventeen healthy adults who had not used cannabis for at least 60 days completed four experimental sessions in which they consumed a cannabis-infused brownie that contained 0, 10, 25, or 50 mg THC. Subjective effects, vital signs, cognitive/psychomotor performance, and blood THC concentrations were assessed before and for 8 h after dosing. RESULTS: Relative to placebo, the 10 mg THC dose produced discriminable subjective drug effects and elevated heart rate but did not alter cognitive/psychomotor performance. The 25 and 50 mg THC doses elicited pronounced subjective effects and markedly impaired cognitive and psychomotor functioning compared with placebo. For all active doses, pharmacodynamic effects did not manifest until 30-60 min after ingestion, and peak effects occurred 1.5-3 h post-administration. Blood THC levels were significantly correlated with some pharmacodynamic drug effects, but were substantially lower than what is typically observed after cannabis inhalation. CONCLUSION: Ingestion of oral cannabis dose-dependently altered subjective drug effects and impaired cognitive performance. Unlike inhaled forms of cannabis for which acute effects occur almost immediately, effects of oral cannabis were considerably delayed. In an era of legalization, education about the time course of drug effects for cannabis edibles is needed to facilitate dose titration and reduce acute overdose incidents.

Safety and Pharmacokinetics of the Aminomethylcycline Antibiotic Omadacycline Administered to Healthy Subjects in Oral Multiple-Dose Regimens.

Omadacycline, a first-in-class aminomethylcycline antibiotic, is related to tetracyclines but is structurally modified to circumvent mechanisms of resistance to tetracyclines. Omadacycline demonstrates potent activity against a broad range of pathogens, including drug-resistant strains, and is in late-stage development for treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. Previous studies support an intravenous-to-oral transition regimen with 300-mg once-daily oral dosing. This phase 1 study investigated the pharmacokinetics and safety/tolerability of multiple oral omadacycline doses higher than 300 mg. Using a 3-period crossover design, healthy adults were randomized to receive oral omadacycline at 300, 450, and 600 mg in variable sequence (n = 26) or placebo (n = 7) once daily for 5 consecutive days per period. In plasma, omadacycline maximum concentration and total exposure increased with increasing dose but were less than dose proportional. The kinetics of omadacycline plasma accumulation were similar between dose levels; exposure on day 5 was ∼50% higher than that on day 1. Omadacycline plasma concentrations on day 1 of 450-mg dosing were similar to those on day 5 of 300-mg dosing. All doses were generally well tolerated, but the 600-mg dose was associated with more gastrointestinal adverse events.

Optimal timing for the oral administration of Da-Cheng-Qi decoction based on the pharmacokinetic and pharmacodynamic targeting of the pancreas in rats with acute pancreatitis.

AIM: To identify the optimal oral dosing time of Da-Cheng-Qi decoction (DCQD) in rats with acute pancreatitis (AP) based on the pharmacokinetic and pharmacodynamic parameters. METHODS: First, 24 male Sprague-Dawley rats were divided into a sham-operated group [NG(a)] and three model groups [4hG(a), 12hG(a) and 24hG(a)]. The NG(a) and model groups were administered DCQD (10 g/kg.BW) intragastrically at 4 h, 4 h, 12 h and 24 h, respectively, after AP models induced by 3% sodium taurocholate. Plasma samples were collected from the tails at 10 min, 20 min, 40 min, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h after a single dosing with DCQD. Plasma and pancreatic tissue concentrations of the major components of DCQD were determined by high-performance liquid chromatography tandem mass spectroscopy. The pharmacokinetic parameters and serum amylase were detected and compared. Second, rats were divided into a sham-operated group [NG(b)] and three treatment groups [4hG(b), 12hG(b) and 24hG(b)] with three corresponding control groups [MG(b)s]. Blood and pancreatic tissues were collected 24 h after a single dosing with DCQD. Serum amylase, inflammatory cytokines and pathological scores of pancreatic tissues were detected and compared. RESULTS: The concentrations of emodin, naringin, honokiol, naringenin, aloe-emodin, chrysophanol and rheochrysidin in the 12hG(a) group were higher than those in the 4hG(a) group in the pancreatic tissues (P < 0.05). The area under the plasma concentration-time curve from time 0 to the time of the last measurable concentration values (AUC0→t) for rhein, chrysophanol, magnolol and naringin in the 12hG(a) group were larger than those in the 4hG(a) or 24hG(a) groups. The 12hG(a) group had a higher Cmax than the other two model groups. The IL-10 levels in the 12hG(b) and 24hG(b) groups were higher than in the MG(b)s (96.55 ± 7.84 vs 77.46 ± 7.42, 251.22 ± 16.15 vs 99.72 ± 4.7 respectively, P < 0.05), while in the 24hG(b) group, the IL-10 level was higher than in the other two treatment groups (251.22 ± 16.15 vs 154.41 ± 12.09/96.55 ± 7.84, P < 0.05). The IL-6 levels displayed a decrease in the 4hG(b) and 12hG(b) groups compared to the MG(b)s (89.99 ± 4.61 vs 147.91 ± 4.36, 90.82 ± 5.34 vs 171.44 ± 13.43, P < 0.05). CONCLUSION: Late-time dosing may have higher concentrations of the most major components of DCQD, with better pharmacokinetics and pharmacodynamics of anti-inflammation than early-time dosing, which showed the late time to be the optimal dosing time of DCQD for AP.

Whole-Body Distribution of Donepezil as an Acetylcholinesterase Inhibitor after Oral Administration in Normal Human Subjects: A 11C-donepezil PET Study.

OBJECTIVES: It is difficult to investigate the whole-body distribution of an orally administered drug by means of positron emission tomography (PET), owing to the short physical half-life of radionuclides, especially when 11C-labeled compounds are tested. Therefore, we aimed to examine the whole-body distribution of donepezil (DNP) as an acetylcholinesterase inhibitor by means of 11C-DNP PET imaging, combined with the oral administration of pharmacological doses of DNP. METHODS: We studied 14 healthy volunteers, divided into group A (n=4) and group B (n=10). At first, we studied four females (mean age: 57.3±4.5 y), three of whom underwent 11C-DNP PET scan at 2.5 h after the oral administration of 1 mg and 30 µg of DNP, respectively, while one patient was scanned following the oral administration of 30 µg of DNP (group A). Then, we studied five females and five males (48.3±6.1 y), who underwent 11C-DNP PET scan, without the oral administration of DNP (group B). Plasma DNP concentration upon scanning was measured by tandem mass spectrometry. Arterialized venous blood samples were collected periodically to measure plasma radioactivity and metabolites. In group A, 11C-DNP PET scan of the brain and whole body continued for 60 and 20 min, respectively. Subjects in group B underwent sequential whole-body scan for 60 min. The regional uptake of 11C-DNP was analyzed by measuring the standard uptake value (SUV) through setting regions of interest on major organs with reference CT. RESULTS: In group A, plasma DNP concentration was significantly correlated with the orally administered dose of DNP. The mean plasma concentration was 2.00 nM (n=3) after 1 mg oral administration and 0.06 nM (n=4) after 30 µg oral administration. No significant difference in plasma radioactivity or fraction of metabolites was found between groups A and B. High 11C-DNP accumulation was found in the liver, stomach, pancreas, brain, salivary glands, bone marrow, and myocardium in groups A and B, in this order. No significant difference in SUV value was found among 11C-DNP PET studies after the oral administration of 1 mg of DNP, 30 µg of DNP, or no DNP. CONCLUSION: The present study demonstrated that the whole-body distribution of DNP after the oral administration of pharmacological doses could be evaluated by 11C-DNP PET studies, combined with the oral administration of DNP.

Serum toxicokinetics after intravenous and oral dosing of larkspur toxins in goats.

Poisoning of cattle by larkspur plants (Delphinium spp.) is a concern for cattle ranchers in western North America. Previous research studies have evaluated the toxicokinetic profile of multiple larkspur toxins in several livestock species. However, those studies were all performed by orally dosing plant material. Consequently some toxicokinetic parameters could not be definitively determined. In this study, we compared the serum toxicokinetic profile of the larkspur alkaloids methyllycaconitine (MLA) and deltaline in goats dosed both IV and via oral gavage. The results from this study indicate that the toxic alkaloids in larkspurs undergo flip-flop kinetics, meaning the rate of absorption of the alkaloids is slower than the rate of elimination. The implications of flip-flop kinetics in treating animals poisoned by larkspur is discussed.

Results of daily oral dosing with up to 60,000 international units (iu) of vitamin D3 for 2 to 6 years in 3 adult males.

In the 1930's and 1940's, vitamin D was reported to be an effective treatment for a number of diseases, including asthma, psoriasis, rheumatoid arthritis, rickets and tuberculosis. High doses were used, 60,000 to 300,000 IU a day for asthma, and 200,000 to 600,000 IU a day for rheumatoid arthritis. Toxicity from hypercalcemia occurred after prolonged oral dosing with these supraphysiologic doses. Assays for measuring vitamin D in the blood were not available, and blood levels of vitamin D associated with hypercalcemia were unknown. A 2011 report on vitamin D toxicity showed that hypercalcemia resolved when 25-hydroxyvitamin D (25OHD) blood levels dropped below 400ng/ml in 2 patients with blood levels ranging from 645ng/ml to 1220ng/ml after accidental ingestion of massive doses of vitamin D. We now know that vitamin D is made in the skin in amounts ranging up to 25,000 IU a day with exposure to UVB radiation. There is little data on the safety and blood levels of 25OHD and calcium after prolonged daily intake of amounts of vitamin D in this range. In this report, one subject took increasing daily doses of vitamin D3 for 6 years starting in April 2009: 6500 IU for 6 months; increasing to 10,000 IU for 13 months; 20,000 IU for 24 months; 40,000 IU for 12 months; 50,000 IU for 10 months, and 60,000 IU since October 2014. 25OHD blood levels were 28, 81, 204, 216, 225, 166, and 218ng/ml. Subject 2 began 10,000 IU in Nov 2011, increased to 20,000 IU in Feb 2014, 25,000 IU in June 2014, and 30,000 IU in Oct 2014, and then decreased to 20,000 IU in June 2015. 25OHD blood levels were 96.6, 161.1 and 106.9ng/ml. He reported marked clinical improvement in his asthma. Subject 3 started on daily 10,000 IU in Sept 2013, increasing to 20,000 IU on Nov 2013. 25OHD blood levels were 31.4, 102, 164, 148, and 143ng/ml. No one developed hypercalcemia or any adverse events. The major finding of this case series is prolonged daily dosing of vitamin D3 with doses of 10,000 to 60,000 IU was safely tolerated.

ASP5878, a selective FGFR inhibitor, to treat FGFR3-dependent urothelial cancer with or without chemoresistance.

FGF/FGFR gene aberrations such as amplification, mutation and fusion are associated with many types of human cancers including urothelial cancer. FGFR kinase inhibitors are expected to be a targeted therapy for urothelial cancer harboring FGFR3 gene alternations. ASP5878, a selective inhibitor of FGFR1, 2, 3 and 4 under clinical investigation, selectively inhibited cell proliferation of urothelial cancer cell lines harboring FGFR3 point mutation or fusion (UM-UC-14, RT-112, RT4 and SW 780) among 23 urothelial cancer cell lines. Furthermore, ASP5878 inhibited cell proliferation of adriamycin-resistant UM-UC-14 cell line harboring MDR1 overexpression and gemcitabine-resistant RT-112 cell line. The protein expression of c-MYC, an oncoprotein, in gemcitabine-resistant RT-112 cell line was higher than that in RT-112 parental cell line and ASP5878 decreased the c-MYC expression in both RT-112 parental and gemcitabine-resistant RT-112 cell lines. Once-daily oral administration of ASP5878 exerted potent antitumor activities in UM-UC-14, RT-112 and gemcitabine-resistant RT-112 xenograft models without affecting body weight. These findings suggest that ASP5878 has the potential to be an oral targeted therapy against urothelial cancer harboring FGFR3 fusion or FGFR3 point mutation after the acquisition of gemcitabine- or adriamycin-resistance.

Tissue distribution of organochlorine pesticides in largemouth bass (Micropterus salmoides) from laboratory exposure and a contaminated lake.

Tissue concentrations of persistent organochlorine pesticides in laboratory-exposed largemouth bass (Micropterus salmoides) and in bass collected from Lake Apopka, FL were determined by both total mass and lipid normalized mass to better understand the bioaccumulation pathways of contaminants. In the laboratory study, male bass were orally administered a single dose of a mixture of two pesticides (p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and dieldrin) and then fed uncontaminated food for 28 days. Gastrointestinal tract, liver, brain, gonad, kidney, spleen, and muscle were collected for chemical analysis. Different profiles were observed by total contaminant mass in tissues compared to lipid normalized mass. On a lipid normalized basis, p,p'-DDE was highest in the gastrointestinal tract followed by the liver, gonad, spleen, muscle, kidney and then brain. Dieldrin, on the other hand, was highest in the gastrointestinal tract and spleen and then followed by the gonad, muscle, liver, kidney, and brain. Distribution of the chemicals among the organs differed by their log KOW values and generally followed the blood flow path after the gastrointestinal tract. The low contaminant levels found in kidney and brain suggest insufficient time for equilibration into these tissues, especially into the brain where the blood-brain barrier may be slow to traverse. In Lake Apopka fish, dichlorodiphenyltrichloroethanes (DDXs, sum of p,p'-DDE, p,p'-DDD, and p,p'-DDT), Drins (sum of aldrin, dieldrin, and endrin), and hexachlorocyclohexanes (HCHs) were found. For DDXs, the lipid normalized concentrations in each tissue were about the same, as predicted from theory. For Drins and HCHs, the lipid normalized concentrations were similar for kidney, spleen, brain, gonad and muscle, but much lower in the gastrointestinal tract and liver, probably because of metabolism occurring in those tissues.

Effective multiple oral administration of reverse genetics engineered infectious bursal disease virus in mice in the presence of neutralizing antibodies.

BACKGROUND: Despite spectacular successes in hepatitis B and C therapies, severe hepatic impairment is still a major treatment problem. The clinically tested infectious bursal disease virus (IBDV) superinfection therapy promises an innovative, interferon-free solution to this great unmet need, provided that a consistent manufacturing process preventing mutations or reversions to virulent strains is obtained. METHODS: To address safety concerns, a tissue culture adapted IBDV vaccine strain V903/78 was cloned into cDNA plasmids ensuring reproducible production of a reverse engineered virus R903/78. The therapeutic drug candidate was characterized by immunocytochemistry assay, virus particle determination and immunoblot analysis. The biodistribution and potential immunogenicity of the IBDV agent was determined in mice, which is not a natural host of this virus, by quantitative detection of IBDV RNA by a quantitative reverse transcriptase-polymerase chain reaction and virus neutralization test, respectively. RESULTS: Several human cell lines supported IBDV propagation in the absence of visible cytopathic effect. The virus was stable from pH 8 to pH 6 and demonstrated significant resistance to low pH and also proved to be highly resistant to high temperatures. No pathological effects were observed in mice. Single and multiple oral administration of IBDV elicited antibodies with neutralizing activities in vitro. CONCLUSIONS: Repeat oral administration of R903/78 was successful despite the presence of neutralizing antibodies. Single oral and intravenous administration indicated that IBDV does not replicate in mammalian liver alleviating some safety related concerns. These data supports the development of an orally delivered anti-hepatitis B virus/ anti-hepatitis C virus viral agent for human use.

Clinical efficacy and safety of monthly oral ibandronate 100 mg versus monthly intravenous ibandronate 1 mg in Japanese patients with primary osteoporosis.

UNLABELLED: The MOVEST study evaluated the efficacy and safety of monthly oral ibandronate versus licensed monthly IV ibandronate in Japanese osteoporotic patients. Relative BMD gains after 12 months were 5.22 % oral and 5.34 % IV, showing non-inferiority of oral to IV ibandronate (primary endpoint). No new safety concerns were identified. INTRODUCTION: The randomized, phase 3, double-blind MOVEST (Monthly Oral VErsus intravenouS ibandronaTe) study evaluated the efficacy and safety of monthly oral ibandronate versus the licensed monthly intravenous (IV) ibandronate regimen in Japanese patients with osteoporosis. METHODS: Ambulatory patients aged ≥ 55 years with primary osteoporosis were randomized to receive oral ibandronate 100 mg/month plus monthly IV placebo, or IV ibandronate 1 mg/month plus monthly oral placebo. The primary endpoint was non-inferiority of oral versus IV ibandronate with respect to bone mineral density (BMD) gains at the lumbar spine after 12 months of treatment. RESULTS: Four hundred twenty-two patients were enrolled with 372 patients in the per-protocol set (183 and 189 in the oral and IV ibandronate groups, respectively). The relative change from baseline in lumbar spine BMD values for the oral and IV ibandronate groups, respectively, was 5.22 % (95 % confidence interval [CI] 4.65, 5.80) and 5.34 % (95 % CI 4.78, 5.90). The least squares mean difference between the two groups was -0.23 % (95 % CI -0.97, 0.51), showing non-inferiority of oral ibandronate to IV ibandronate (non-inferiority limit = -1.60). Changes in BMD values at other sites, and bone turnover marker levels in the oral ibandronate group, were comparable with those of the IV group. The safety profile was similar to that previously demonstrated; no new safety concerns were identified. CONCLUSIONS: This study demonstrated the non-inferiority of oral ibandronate 100 mg/month to IV ibandronate 1 mg/month (licensed dose in Japan) in increasing lumbar spine BMD in Japanese patients with primary osteoporosis.

Identification of new oral dosing regimens for the neuraminidase inhibitor oseltamivir in patients with moderate and severe renal impairment.

Availability of lower-dose oseltamivir capsules, an increased pharmacokinetic database, and a desire to align drug exposure across the spectrum of renal function prompted reassessment of oral dosing in patients with renal impairment. The data set comprised 128 subjects (71 with varying degrees of renal impairment) from 8 studies, which included single and multiple doses of 20-1000 mg. Pharmacokinetic profiles of oseltamivir phosphate (OP) and oseltamivir carboxylate (OC) were modeled simultaneously in NONMEM. Exposure metrics of OP and OC (AUC48 h , Cmax , Cmin ) after administration of various dosing regimens were simulated for renal impairment subgroups and compared with exposures in patients with normal renal function receiving approved regimens. For influenza treatment, 30 mg once-daily and twice-daily regimens were selected for severe and moderate impairment, respectively. These regimens provided OC exposures similar or above those of the approved 75-mg twice-daily treatment regimen in subjects with normal renal function. For influenza prophylaxis, 30 mg once every other day and once-daily regimens were selected for severe and moderate impairment, respectively. No dosing adjustments were required for mild impairment. This analysis supported revised labeling in the United States and Europe for oral oseltamivir dosing in patients with moderate and severe renal impairment.

Alternative method of oral administration by peanut butter pellet formulation results in target engagement of BACE1 and attenuation of gavage-induced stress responses in mice.

Development of novel therapeutic agents aimed at treating neurodegenerative disorders such as Alzheimer's and Parkinson's diseases require chronic and preferentially oral dosing in appropriate preclinical rodent models. Since many of these disease models involve transgenic mice that are frequently aged and fragile, the commonly used oro-gastric gavage method of drug administration often confounds measured outcomes due to repeated stress and high attrition rates caused by esophageal complications. We employed a novel drug formulation in a peanut butter (PB) pellet readily consumed by mice and compared the stress response as measured by plasma corticosterone levels relative to oral administration via traditional gavage. Acute gavage produced significant elevations in plasma corticosterone comparable to those observed in mice subjected to stress-induced hyperthermia. In contrast, corticosterone levels following consumption of PB pellets were similar to levels in naive mice and significantly lower than in mice subjected to traditional gavage. Following sub-chronic administration, corticosterone levels remained significantly higher in mice subjected to gavage, relative to mice administered PB pellets or naive controls. Furthermore, chronic 30day dosing of a BACE inhibitor administered via PB pellets to PSAPP mice resulted in expected plasma drug exposure and Aß40 lowering consistent with drug treatment demonstrating target engagement. Taken together, this alternative method of oral administration by drug formulated in PB pellets results in the expected pharmacokinetics and pharmacodynamics with attenuated stress levels, and is devoid of the detrimental effects of repetitive oral gavage.

Optimization and validation of Mycobacterium marinum-induced adult zebrafish model for evaluation of oral anti-tuberculosis drugs.

INTRODUCTION: Mycobacterium marinum has emerged as a suitable species for induction of tuberculosis-like disease in zebrafish, and various zebrafish models (larval and adult) for drug screening have been proposed in the literature. It is believed that an adult zebrafish model is more useful in drug screening because, apart from assessment of efficacy, one can obtain data on dosage, pharmacokinetics and overall health improvement. This study suggests a simple, cost-effective and resource-efficient protocol for screening of anti-tuberculosis drugs. METHODS: The parameters used for assessment of infection as well as anti-bacterial response were: (a) bacterial count; and (b) body weight change. An optimization study was conducted to establish the concentration of bacteria required to produce a reproducible phenotype of tuberculosis (TB). A negative control (Amoxicillin) and anti-mycobacterial drugs (Isoniazid, Rifampicin, Moxifloxacin, Ethambutol and Isoniazid+Rifampicin) were used for validation of the protocol. All the drugs were administered orally. RESULTS: An intra-peritoneal inoculation of 0.75million bacteria/fish was optimized for the model. All the anti-tuberculosis drugs showed efficacy in this model, whereas the negative control did not show any signs of reversing the parameters of M. marinum infection. DISCUSSION: Adult zebrafish model of M. marinum-induced tuberculosis has not been fully exploited as a drug screening tool. In the present report, a protocol is suggested that is simple, reproducible and resource-efficient for screening of anti-tuberculosis agents. This protocol is an attempt to refine the published protocols and use this model as a surrogate model of human TB for the purpose of drug screening.