Pharmacokinetics of doxycycline hyclate in pigs with a new feed premix formulation.

This study aimed to evaluate the administration of doxycycline hyclate in a long-acting pharmaceutical preparation in pigs when administered either ad libitum as a feed medication or an oral bolus dose. In all instances, the studied dose was 20 mg/kg b.w. A total of 48 healthy crossbred, castrated male pigs (Landrace-Yorkshire) weighing 23 ± 4.3 kg were included in this trial. They were randomly assigned to six groups as follows: two groups for the experimental prototype 1 of doxycycline hyclate administering it ad libitum (Fad-lib) or as forced bolus (Fbolus); two groups for the experimental prototype 2 of doxycycline hyclate as for the former groups (FCad-lib and FCbolus), and two control groups receiving the same dose of doxycycline hyclate, but of a commercial premix, also as previously explained (Cbolus and Cad-lib). Statistical analysis of the mean pharmacokinetic values was carried out with Kruskal-Wallis and Dunn's tests. The relative bioavailability (Fr) of the best prototype, when administered ad libitum (FCad-lib), was five times larger than the reference group (Cadlib). These results allow the proposal that the referred differences achieved in the presented prototypes can mark a notable clinical difference, particularly in pathogens with some resistance.

Oral pharmacokinetics of a pharmaceutical preparation of florfenicol in broiler chickens.

Introduction: The use of florfenicol must follow particular pharmacokinetic/pharmacodynamic (PK/PD) ratios, i.e., it requires achieving serum concentrations at or slightly above the pathogen's minimum inhibitory concentration (MIC) during the dosing interval and that the ratio of area under the concentration vs. time curve (AUC)/MIC should be as high as possible (still undetermined for poultry). As an alternative to the standard soluble florfenicol that is administered to the flock through drinking water, florfenicol premix is often recommended as feed medication in Latin America. However, no particular pharmaceutical design has been proposed. Methods: This study compared the PK of two preparations of florfenicol in broiler chickens and pondered the possibility of each covering the referred PK-PD ratios as predictors of clinical efficacy. The preparations comprise a pharmaceutical form as FOLA pellets (F = bioavailability; O = optimum; and LA = long-acting) and the premix formulation. The former are small colored pellets with vehicles and absorption enhancers of florfenicol designed for long action, and the latter is the reference premix of the antibiotic. First, these two pharmaceutical forms of florfenicol were administered as oral boluses (30 mg/kg), aided by a probe. In a second trial of the dosing form, both pharmaceutical preparations of florfenicol were administered in feed and ad libitum (110 ppm; ~30 mg/kg). Results: In both cases, FOLA-florfenicol presented much higher relative bioavailability (3.27 times higher) and mean better residence time than florfenicol premix (two times high when forced as bolus dose). Consequently, FOLA-florfenicol possesses better PK/PD ratios than less sensitive pathogens, i.e., E. coli. It is proposed that if a metaphylactic treatment of a bacterial outbreak in poultry is implemented with florfenicol prepared as FOLA, better PK/PD ratios will be obtained than those of standard florfenicol premix. Discussion: Clinicians must confirm that feed consumption in the flock has not been affected by the particular disease if FOLA pellets of florfenicol are used.

Successful treatment of recurrent subclinical mastitis in cows caused by enrofloxacin resistant bacteria by means of the sequential intramammary infusion of enrofloxacin HCl-2H2O and ceftiofur HCl: a clinical trial.

BACKGROUND: Recurrent subclinical mastitis (RScM) due to resistant bacteria has low clinical and bacteriological cure rates, often requiring the culling of cows. The sequential intra-mammary administration of enrofloxacin hydrochloride-dihydrate (enro-C) followed by ceftiofur HCl may be useful for treating these cases. OBJECTIVES: This study assessed the bacteriological and clinical cure-efficacies of the sequentially intramammary administration of enro-C, followed by ceftiofur HCl to treat RScM in Holstein/Friesian cows. METHODS: This trial was conducted in a herd with a high prevalence of RScM, and 20 Holstein/Friesian cows were included: 45% suffering subclinical mastitis and 38.9% of the mammary quarters affected. Twenty-nine bacterial isolates in vitro resistant to enro-C were obtained (coagulase-negative Staphylococcus spp, 55.2%; Staphylococcus aureus, 27.6%; Escherichia coli, 6.9%; Streptococcus uberis, 6.9%; Corynebacterium bovis, 3.4%). Polymerase chain reaction-isolated the following genes linked to enro-C resistance: chromosomal (gyrA) and plasmid (aac(6')-lb-cr). The treatments were as follows: twice-daily intramammary infusions of enro-C (300 mg/10 mL) for 5 days. Cows clinically considered treatment failures were also treated with intramammary ceftiofur (125 mg/10 mL, twice daily for 5 days. The clinical and bacteriological cure rates were carried out when completing each treatment phase and at 14 and 21 days, aided by a California mastitis test, somatic cell count, and failure to identify the initially causative bacteria. RESULTS: Enro-C achieved 65% clinical and bacteriological cure rates, and 100% cure rates were obtained after the rescue treatment with ceftiofur HCl. CONCLUSIONS: Outstanding clinical and bacteriological cure rates in cows affected by RScM were achieved with the consecutive intramammary infusions of enro-C, followed by ceftiofur HCl.

Evaluation of a Tasteless Enrofloxacin Pharmaceutical Preparation for Cats. Naive Pooled-Sample Approach to Study Its Pharmacokinetics.

Available pharmaceutical preparations of enrofloxacin injected SC or IM to cats are likely to cause adverse tissue reactions in the injection sites (pH of the drug preparations is ≥10.4). Tablets often induce abundant ptyalism and vomiting, casting doubt on the efficacy of the drug administration maneuver. In addition, the reported oral bioavailability is very low. In this trial, the oral pharmacokinetics of dried alginate beads of enrofloxacin (DABE) administered by concealing them in the cat's moist food or morsels, is described. A naïve polled sampling approach was chosen with fourteen adult healthy cats. Neither their housing nor their feeding habits were altered. A single pharmacokinetic profile was obtained with 5 samples per designated bleeding time, sampling each cat 2-3 times only. None of the cats rejected their medicated food or morsels. Plasma profile of enrofloxacin exhibited an AUC0-24 value of 12.4 µg·h/mL and an AUC0-∞ value of 19.2 µg·h/mL, which are comparatively greater than values previously referred for kittens. In contrast, λ and elimination t½ were almost identical (0.12 1/h and 6.1 h). Pharmacokinetics/pharmacodynamics ratios taking the breakpoint of Staphylococcus epidermidis as a surrogate (0.5 µg/mL), can be regarded as borderline or low, but perhaps adequate in cats, as higher concentrations may be linked to toxicity (AUC0-24/MIC = 24.8; Cmax/MIC = 4.6).

Comparative bioavailability of enrofloxacin in dogs when concealed in noncommercial morsels, either as tablet or as enrofloxacin-alginate dried beads.

Administration of enrofloxacin tablets concealed in improvised morsels to elude the unpleasant flavor of this drug is likely to diminish maximum plasma concentrations (Cmax ) reached by this drug, jeopardizing treatment efficacy. To avoid this, the hypothesis that alginate dried beads containing enrofloxacin (ADBE) could modify the pharmacokinetics of enrofloxacin in dogs was tested. ADBE were manufactured and pharmaceutically defined as having high entrapment efficiency (>90%) and a drug loading capacity of 56%-67%. Based on the hydrophilic nature of alginate and its interaction with the anionic charge of the amino groups of enrofloxacin, a novel modified release system was obtained in which ADBE give place to both a rapid diffusion releasing of enrofloxacin and a maintained release. The ADBE concealed in a sausage (ADBEs) achieved both the highest Cmax (5.1 µg/ml ± 0.3 SD) and the area under the concentration versus time (AUC0-24 ) (41.2 µg hr-1  ml-1  ± 6.9 SD). The tablet administered alone had a Cmax of 1.9 µg/ml ± 0.3 SD and an AUC0-24  = 16.5 µg h-1  ml-1  ± 3.5 SD, while the tablet concealed in a sausage reached a Cmax of 1.2 µg/ml ± 0.3 SD with an AUC0-24  = 12.3 µg hr-1  ml-1  ± 3.8 SD (p < .05 in both cases when confronting ADBEs vs. tablets). Consequently, Cmax /MIC and AUC0-24 /MIC ratios are higher for ADBEs. Other PK parameters were statistically indistinguishable, and other morsels containing enrofloxacin as a tablet or as ADBE rendered less favorable PK parameters. Due to ease of administration and favorable PK for ADBE concealed in a sausage, this pharmaceutical design can be regarded as PK/PD consistent and worthy of clinical studies.

A non-inferiority study evaluating a new extended-release preparation of tilmicosin injected subcutaneously vs. ceftiofur administered intramammary, as dry-cow therapy in Holstein Friesian cows.

BACKGROUND: A new, extended long-acting tilmicosin (TLAe) preparation was tested against intramammary ceftiofur (CEF) using a non-inferiority trial model during dry-cow therapy (DCT) in a farm with high bovine population density and deficient hygiene application. OBJECTIVES: To evaluate the possibility that TLAe administered parenterally can achieve non-inferiority status compared to CEF administered intramammary for DCT. METHODS: Cows were randomly assigned to TLAe (20 mg/kg subcutaneous; n = 53) or CEF (CEF-HCl, 125 mg/quarter; n = 38 cows) treatment groups. California mastitis testing, colony-forming unit assessment (CFU/mL), and number of cases positive for Staphylococcus aureus were quantified before DCT and 7 d after calving. A complete cure was defined as no bacteria isolated; partial cure when CFU/mL ranged from 150 to 700, and cure-failure when CFU/mL was above 700. RESULTS: TLAe and CEF had overall cure rates of 57% and 53% (p > 0.05) and S. aureus cure rates of 77.7% and 25%, respectively (p < 0.05). The pathogens detected at DCT and 7 days after calving were S. aureus (62.71% and 35.55%), Staphylococcus spp. (22.03% and 35.55%), Streptococcus uberis (10.16% and 13.33%), and Escherichia coli (5.08% and 15.55%). Non-inferiority and binary logistic regression analyses revealed a lack of difference in overall efficacies of TLAe and CEF. Apart from S. aureus, S. uberis was the predominant pathogen found in both groups. CONCLUSIONS: This study is the first successful report of parenteral DCT showing comparable efficacy as CEF, the gold-standard. The extended long-term pharmacokinetic activity of TLAe explains these results.

Higher Bioavailability of Calcium in Chickens With a Novel In-Feed Pharmaceutical Formulation.

Egg production and egg shell quality decrease toward the end of the first laying cycle in hens (approximately by week 80). Even so, farmers often choose to work a second cycle with them. Defective egg shell production has been mainly linked to a decrease in gastrointestinal absorption of calcium. Here we studied pharmaceutically-designed modified-release small pellets (FOLAs) containing calcium to improve calcium bioavailability (F). The influence of FOLA alone or with capsicum-oleoresin was studied in a total of 400 Bovans-White hens randomly divided into four groups of 20 laying hens each and with five replicates per group (n = 100) as follows: (1) control group (GC) receiving a diet containing basal levels of 4.1% of calcium-carbonate; (2) group GF treated as GC but with the same dose of calcium-carbonate in FOLA; (3) group GFc5 was treated as GF but with 6 ppm of capsicum-oleoresin (500,000 Scoville Heat Units [SHU]); and (4) group GFc10 treated as GFc5 but with 1,000,000 SHU capsicum-oleoresin. Plasma concentrations of calcium were determined during 5 days at predetermined times sampling more often on days 1 and 5 for blood plasma kinetics of calcium. Relative bioavailability (Fr) values based on the area under the serum calcium concentration vs. time curve (AUC) were obtained and compared to GC. The AUC was statistically different among all groups (P < 0.5), but the GFc10 had the greatest Fr (194%), with serum calcium concentrations ranging from 25.37 to 31.2 µg/dL. Calcium residence time (RT) between GC and GF showed no statistical differences while GFc5 and GFc10 had statistically superior RT values. Simultaneously, the number of shell-less eggs per group and their thickness was evaluated by utilizing the same groups but with 150 hens per group on 6 days. Shell-less eggs decreased to zero in Group GFc10 and produced eggs with the greatest shell thickness from day 2 onwards. The inclusion of calcium-carbonate in the pharmaceutical form FOLA induced higher serum calcium concentrations (GF, GFc5, and GFc10) particularly during the night-phase of the hen's cycle-this coincides with the time at which egg shell formation occurs.

Oral Plus Topical Administration of Enrofloxacin-Hydrochloride-Dihydrate for the Treatment of Unresponsive Canine Pyoderma. A Clinical Trial.

An outpatient clinical trial on unresponsive deep-bacterial canine pyoderma (UDCP), without a control group, is presented. The chosen treatment was implemented with a new crystal-solvate of enrofloxacin (enrofloxacin HCl-2H2O or enro-C), in a dual scheme, i.e., 10 mg/kg/day PO, plus its topical administration, prepared as 0.5% in an alginate gel, thrice per day. Fifty-five cases that were unsuccessfully treated previously with another antibacterial drug, were selected and then classified as severe or very severe, according to a clinical score tailored for this trial. Aerobic bacteriological cultures of skin lesions and antibacterial sensitivity tests, were performed. Hematological status, liver, and kidney functions were determined before and after treatment. A complete success was obtained in 32 severe and 23 very severe, cases. The main bacterial isolates were: Staphylococcus intermedius (19/99), Staphylococcus pseudintermedius (16/99), Staphylococcus epidermidis (15/99), Staphylococcus pyogenes (14/99), Staphylococcus saprophyticus, Streptococcus sp., and others including Pseudomonas aeruginosa (6/99). The average duration of treatment was 8.03 days ± 2.1 SD and 12.0 ± 2.4 days, for dogs with severe or very severe UDCP, respectively. The adverse effects caused by enro-C were inconsequential and the hematological tests showed no deviations from normality. The use of enro-C administered dually to treat UDCP, is considered safe and highly effective.

Outpatient Clinical Trial in Dogs With Leptospirosis Treated With Enrofloxacin Hydrochloride-Dihydrate (ENRO-C).

Pharmacokinetics of enrofloxacin HCl-2H2O (enro-C) in dogs and Monte-Carlo simulations against Leptospira spp. prompted a clinical study to treat the clinically apparent phase of this disease. Leptospirosis was diagnosed by real-time PCR from blood, micro-agglutination titers (MAT), clinical signs and blood parameters of the liver and kidney. In order to determine the clinical ability of the participants to diagnose leptospirosis on the first exam and establish an early treatment to avoid excessive organ damage, patients were clinically classified as: high-risk or medium-risk. Forty-five dogs were included in this trial (from 2017 to early 2019). The treatment consisted of IM injections of a 5% aqueous enro-C suspension (10 mg/kg/day) for 10 days, and subsequently enro-C was administered orally for another 7 days in gelatin capsules. Thirty-four high-risk and 11 medium-risk dogs were treated, including 6 puppies (4 high-risk with ages between 6 to 10 months and 2 medium-risk dogs with an average age of 6 and 7 months). Other ages ranged from 1 to 5 years. Fifteen cases had a history of having received prior treatment with other antibiotics, including all puppies. The clinical diagnostic error was 13.5% (7/52 cases), and only one of the misdiagnosed dogs had been classified as a high-risk patient. Three to 5 days after finishing treatment with enro-C, 82.2% of the dogs were negative to real-time PCR from urine samples and 100% negativity was observed on day 30 after treatment, when antibody titrations dropped to 1:100-1:200. Based on the absence of clinical signs, real-time PCR, and MAT titers, all treated dogs were considered as successful treatments. Within 6-24 months of clinical follow-up, no relapses were recorded. Adverse effects were inconsequential. This study represents the first report of a successful treatment of canine leptospirosis using a fluoroquinolone, and due to its efficacy, it is suggested that enro-C be considered as a viable option for the treatment of this disease.

Pharmacokinetics of enrofloxacin HCl-2H2 O (ENRO-C), PK/PD, and Monte Carlo modeling vs. Leptospira spp. in cows.

The pharmacokinetics, PK/PD ratios, and Monte Carlo modeling of enrofloxacin HCl-2H2 O (Enro-C) and its reference preparation (Enro-R) were determined in cows. Fifty-four Jersey cows were randomly assigned to six groups receiving a single IM dose of 10, 15, or 20 mg/kg of Enro-C (Enro-C10 , Enro-C15 , Enro-C20 ) or Enro-R. Serial serum samples were collected and enrofloxacin concentrations quantified. A composite set of minimum inhibitory concentrations (MIC) of Leptospira spp. was utilized to calculate PK/PD ratios: maximum serum concentration/MIC (Cmax /MIC90 ) and area under the serum vs. time concentration of enrofloxacin/MIC (AUC0-24 /MIC90 ). Monte Carlo simulations targeted Cmax /MIC = 10 and AUC0-24 /MIC = 125. Mean Cmax obtained were 6.17 and 2.46 µg/ml; 8.75 and 3.54 µg/ml; and 13.89 and 4.25 µg/ml, respectively for Enro-C and Enro-R. Cmax /MIC90 ratios were 6.17 and 2.46, 8.75 and 3.54, and 13.89 and 4.25 for Enro-C and Enro-R, respectively. Monte Carlo simulations based on Cmax /MIC90  = 10 indicate that only Enro-C15 and Enro-C20 may be useful to treat leptospirosis in cows, predicting a success rate ≥95% when MIC50  = 0.5 µg/ml, and ≥80% when MIC90  = 1.0 µg/ml. Although Enro-C15 and Enro-C20 may be useful to treat leptospirosis in cattle, clinical trials are necessary to confirm this proposal.

Pharmacokinetics of enrofloxacin HCl-2H2O (Enro-C) in dogs and pharmacokinetic/pharmacodynamic Monte Carlo simulations against Leptospira spp.

Pharmacokinetic/pharmacodynamic (PK/PD) ratios of reference enrofloxacin (Enro-R) and enrofloxacin as HCl-2H2O (Enro-C), as well as Monte Carlo simulations based on composite MIC50 and MIC90 (MIC, minimum inhibitory concentration) vs. Leptospira spp., were carried out in dogs after their intramuscular (IM) or oral administration (10 mg/kg). Plasma determination of enrofloxacin was achieved by means of high-performance liquid chromatography. Maximum plasma concentration values after oral administration were 1.47 ± 0.19 µg/mL and 5.3 ± 0.84 µg/mL for Enro-R and Enro-C, respectively, and 1.6 ± 0.12 µg/mL and 7.6 ± 0.93 µg/mL, respectively, after IM administration. Areas under the plasma vs. time concentration curve in 24 h (AUC0-24) were 8.02 µg/mL/h and 36.2 µg/mL/h for Enro-Roral and Enro-Coral, respectively, and 8.55 ± 0.85 µg/mL/h and 56.4 ± 6.21 µg/mL/h after IM administration of Enro-R and Enro-C, respectively. The PK/PD ratios and Monte Carlo simulations obtained with Enro-C, not Enro-R, indicated that its IM administration to dogs will result in therapeutic concentrations appropriate for treating leptospirosis. This is the first time enrofloxacin has been recommended to treat this disease in dogs.

Efficacy of a New Recrystallized Enrofloxacin Hydrochloride-Dihydrate against Leptospirosis in a Hamster Model.

A trial on Syrian hamsters (Mesocricetus auratus) infected with Leptospira interrogans serovar Canicola was established to compare treatment efficacies of daily intramuscular (i.m.) injections of either 10 mg/kg of 5% enrofloxacin (Baytril [BE]; Bayer Animal Health, Mexico) or the same dose of enrofloxacin hydrochloride-dihydrate (enro-C). Hamsters were experimentally infected via the oral submucosa with 400 microorganisms/animal, in a sequential time schedule aligned to the initial treatment day, and were treated in groups as follows: a group treated with 5% enrofloxacin daily for 7 days after 24 h of infection (group BE24); a group treated as described for group BE24 but with enro-C (enro-C24); a group also treated with 5% enrofloxacin but starting at 72 h after infection (BE74); a group treated as described for group BE74 but with injection of enro-C (enro-C74). An untreated-uninfected control group (group CG-) and an infected-untreated control group (group CG+) were assembled (n = 18 in all groups). Weights and temperatures of the hamsters were monitored daily for 28 days. After hamsters were euthanatized or following death, necropsy, histopathology, macroscopic agglutination tests (MAT), bacterial culture, and PCR were performed. The mortality rates were 38.8% in group BE24 and 100% in group BE74 No mortality was observed in group enro-C24, and 11.1% mortality was recorded in group enro-C74 The mortality rates in groups CG+ and CG- were 100% and zero, respectively. Combined necropsy and histopathologic findings revealed signs of septicemia and organ damage in groups BE24, BE72, and CG+ Groups enro-C24 and CG- showed no lesions. Moderated lesions were registered in 3 hamsters in group enro-C72 MAT results were positive in 83.3% of BE24 hamsters (83.3%) and 100% of BE72 and CG+ hamsters; MAT results were positive in 16.7% in group Enro-C24 and 38.9% in group enro-C72 Only 4/18 were PCR positive in group enro-C72 and only 1 in group enro-C24 (P < 0.05). It can be concluded that enro-C may be a viable option to treat leptospirosis in hamsters and that this may be the case in other species.

Efficacy of nitazoxanide to treat natural Giardia infections in dogs.

BACKGROUND: Giardia parasites cause gastrointestinal disease in humans, dogs, and many other animals worldwide. The treatment of dogs for giardiasis requires further investigation to ascertain levels of drug efficacy and the possibility of adverse side effects. Nitazoxanide (NTZ) has shown good clinical anti-Giardia activity in humans, yet it has not been evaluated for the treatment of giardiasis in dogs. METHODS: Thirty-five dogs, naturally infected with Giardia were divided into five groups (n = 7): dogs in group NTZ1, NTZ2, and NTZ3 were treated with a single oral dose of 37.5 mg/kg, 75 mg/kg, and 150 mg/kg, respectively, of NTZ on days 0 and 14. The fourth group was treated with a commercially available regimen that includes a combination of pyrantel, praziquantel, and febantel (FEB) administered orally for three consecutive days. Additionally, an untreated control group was established. Giardia cysts from the stool of each dog were quantified on days -3, 0, 5, 7, 9, 11, 14, 18, 25, and 28. Biochemical parameters were evaluated in all dogs, before the first treatment and after concluding the experiment. RESULTS: Shedding of Giardia cysts was reduced in all treated groups when compared to untreated controls (P < 0.01). However, NTZ2, NTZ3, and FEB had a lower risk during the study. Furthermore, NTZ was also effective against another protozoan, Cryptosporidium spp. at doses of 75 mg/kg and 150 mg/kg, in contrast to the combination of febantel + pyrantel + praziquantel. Biochemical parameters of treated animals, namely, aspartate transaminase and alanine transaminase enzymes, remained within physiological ranges. CONCLUSIONS: Based on these results, the implementation of NTZ as a treatment for giardiasis in dogs is proposed. The administration of a single dose is an important advantage of NTZ because it reduces workload, particularly in animals placed in shelters and kennels, where handling of large numbers of animals is required, and personnel is frequently scarce.

Enrofloxacin hydro-chloride dihydrate.

The asymmetric unit of the title compound, C19H23FN3O3 (+)·Cl(-)·2H2O [systematic name: 4-(3-carb-oxy-1-cyclo-propyl-6-fluoro-4-oxo-1,4-di-hydro-quin-o-lin-7-yl)-1-ethyl-piperazin-1-ium chloride dihydrate], consists of two independent monocations of the protonated enrofloxacin, two chloride anions and four water mol-ecules. In the cations, the piperazinium rings adopt chair conformations and the dihedral angles between the cyclo-propyl ring and the 10-membered quinoline ring system are 56.55 (2) and 51.11 (2)°. An intra-molecular O-H⋯O hydrogen bond is observed in each cation. In the crystal, the components are connected via O-H⋯Cl, N-H⋯Cl and O-H⋯O hydrogen bonds, and a π-π inter-action between the benzene rings [centroid-centroid distance = 3.6726 (13) Å], resulting in a three-dimensional array.

Efficacy of a pharmaceutical preparation based on glycyrrhizic acid in a challenge study of white spot syndrome in white shrimp (Litopenaeus vannamei).

There is a lack of preventive and therapeutic drug-based treatments for the shrimp viral disease known as white spot syndrome (WSSV). Thus a challenge study inducing WSSV in juvenile white shrimp (Litopenaeus vannamei) was established, setting 4 groups: challenged - not treated and unchallenged, untreated control groups and two experimental ones (E1 and E2) both treated with diammonium glycyrrhizic acid, extracted from licorice with added vitamins and oligoelements, and as in-feed medication. Group E1 received diammonium glycyrrhizic acid included in their daily feed, starting 17 days before challenge with WSSV and maintaining the treatment for further 5 days after the end of the trial, which was set on day 18. Group E2 received this medication as group E1 throughout the trial, but starting 1 day before the challenge with WSSV. The group with highest surviving median values was E1, amounting two times the survival median in comparison with the control groups (P = 0.007). Also a statistical difference was found in terms of survival means in favor of group E1 as compared to group E2. Macroscopic and histopathological findings revealed lesions compatible with WSSV and similar mortality in the challenged untreated group. These findings were highly reduced or inexistent in mortality analyzed from groups E1 as well as in the unchallenged - untreated control group and greatly reduced in group E2. Considering the apparent high efficacy observed and that glycyrrhizic acid and mineral and vitamin components added as treatment, and taking as an advantage that this preparation has been regarded as nutraceuticals, it is here proposed that large scale trials should be conducted to evaluate the effects here observed in commercial and larger scale shrimp farms.

Pharmacokinetics of a peroral single dose of two long-acting formulations and an aqueous formulation of doxycycline hyclate in horses.

BACKGROUND: Doxycyline (Dox) is a semisynthetic antibacterial drug with pharmacological advantages over its parent drug (tetracycline) in the treatment of various bacterial diseases in horses. Yet, at present a horse-customized pharmaceutical formulation is not available. Based on its pharmacokinetic/pharmacodynamic (PK/PD) ratio, Dox is considered a time-dependent antibacterial drug and ideally expected to achieve sustained plasma drug concentrations both at or slightly above the minimal inhibitory concentration (MIC) level for as long as possible between dosing intervals. Hence, the objective of this study was to formulate two long-acting (LA) doxycyline hyclate (Dox-h) formulations for oral administration and define their pharmacokinetics in non-fasted adult horses to obtain better bioavailability and longer mean residence time, features needed to comply better with its pharmacokinetic/pharmacodynamic (PK/PD) ratios. RESULTS: Pharmacokinetic parameters were determined after the oral administration of a single 10 mg/kg bolus dose of two 20% Dox-h formulations: one based on a ß cyclodextrin (Dox-ß) matrix and a second one on a poloxamer (Dox-pol) matrix. The results were compared with the pharmacokinetics of a single 10 mg/kg bolus oral dose of a freshly made aqueous Dox-h solution (Dox-a). Dox-pol showed the greatest values for relative bioavailability (548%); maximum serum concentration (Cmax) value was 1.3 ± 0.7 µg/mL with time to reach the Cmax (Tmax) of 5.9 ± 1.7 h, area under the curve (AUC) of 17.0 ± 2.2 µg h/ml and elimination half-life (T½ ß) of 4.9 ± 1.0 h. CONCLUSIONS: Considering a minimal inhibitory concentration MIC of 0.25 µg/mL, clinically effective plasma concentrations might be obtained for up to 24 h administering Dox-pol. This is an oral paste formulation that might optimize the use of Dox-h in horses in terms of PK/PD ratio congruency, and it is likely that it may also improve prescription compliance due to its ease of administration.

Pharmacokinetics of an injectable long-acting formulation of doxycycline hyclate in dogs.

Based on its PK/PD ratios, doxycycline hyclate (DOX-h), a time-dependant antibacterial, is ideally expected to achieve both sustained plasma drug concentrations at or slightly above the MIC level for as long as possible between dosing intervals. Pursuing this end, a poloxamer-based matrix was used to produce a long-acting injectable preparation (DOX-h-LA) and its serum concentrations vs. time profile investigated after its SC injection to dogs (≤ 0.3 mL per injection site), and results compared with the oral (PO) and IV pharmacokinetics of DOX-h, prepared as tablet or as freshly made solution. A crossover (4 x 4 x 4) study design was employed with 12 Mongrel dogs, with washout periods of 21 days, and at dose of 10 mg/kg in all cases. DOX-h-LA showed the greatest values for bioavailability (199.48%); maximum serum concentration (Cmax) value was 2.8 ± 0.3 with a time to reach Cmax (Tmax) of 2.11 ± 0.12 h and an elimination half-life of 133.61 ± 6.32 h. Considering minimum effective serum concentration of 0.5 µg/mL, a dose-interval of at least 1 week h can be achieved for DOX-h-LA, and only 48 h and 24 h after the IV or PO administration of DOX-h as a solution or as tablets, respectively. A non-painful small bulge, apparently non-inflammatory could be distinguished at injection sites. These lumps dissipated completely in 30 days in all cases.

Bioequivalencia de dos formulaciones de amoxicilina-ácido clavulánico para uso oral en perros / Bioequivalence of two amoxicillin-potassium clavulanate oral preparations in dogs

The aim of this trial was to carry out a bioequivalence (BE) study in dogs using a generic preparation of amoxicillin-potassium clavulanate vs a commercially available reference preparation, both claiming to achieve plasma concentrations that allow a 12 h dosing interval after oral administration. The oral pharmacokinetic profiles of a single dose of each preparation were carried out in 12 adult mongrel dogs in a crossover model with a 10 day washout period at a dose of 12.5 mg/kg of trihydrate amoxicillin and potassium clavulanate as tablets. A composite determination of amoxicillin-potassium clavulanate concentration in each sample of plasma was carried out in triplicate, using a microbiological agar diffusion analysis. Pharmacokinetic analysis was carried out with a non-compartmental model. Statistical analysis of pharmacokinetic variables was carried out by ANOVA and Bonferroni t test, setting a P < 0.05. In accordance with international standards, it was found that the generic preparation failed to be bioequivalent, i.e: AUC0-∞ 9.08 ± 0.26 μg h/ml and Cmax 5.48 ± 0.19 μg/ml for the generic preparation vs AUC0-∞ 13.28 ± 0. 30 μg h/ml and Cmax 2.9 ± 0.17 μg/ml for the reference one. A 0.25 μg/ml breakpoint can be set as minimum effective plasma concentration for amoxicillin; hence the generic preparation requires a dose interval of eight h.

El objetivo de este trabajo fue determinar la bioequivalencia entre dos preparados comerciales de amoxicilina-ácido clavulánico disponibles en forma de tableta para uso oral en perros, y cuyo intervalo de dosificación indicado por los fabricantes es de 12 horas. Se calculó el perfil farmacocinético de cada preparado, a una dosis oral de 12.5 mg/kg de amoxicilina y ácido clavulánico en doce perros adultos mediante un modelo cruzado. Se determinó la concentración activa de la combinación de ambos fármacos en cada muestra de plasma, utilizando un método de análisis microbiológico por difusión en agar. El cálculo farmacocinético se llevó a cabo con un modelo no compartamental y los valores obtenidos se analizaron mediante un ANDEVA y prueba T de Bonferroni, con una P < 0.05. Tomando en cuenta las pautas internacionales, la formulación genérica resultó no ser bioequivalente a la de referencia. Esto es, se obtuvieron valores de AUC0-∞ 9.08 ± 0.26 μg h/ml y Cmax 5.48 ± 0.19 μg/ml para el genérico vs AUC0-∞ 13.28 ± 0. 30 μg h/ml y Cmax 2.9 ± 0.17 μg/ml para el de referencia. Si se considera un punto de inflexión para bacterias susceptibles, de 0.25 μg/ml, el preparado genérico requiere un intervalo de dosificación de ocho horas.

Pharmacokinetics of doxycycline and tissue concentrations of an experimental long-acting parenteral formulation of doxycycline in Wistar rats.

Doxycycline hyclate (CAS 24390-14-5, doxycycline-h), an antibacterial with time-dependent action, was formulated as a non-irritating long-acting parenteral formulation based on a beta-cyclodextrin: poloxamer-based matrix (doxycycline-h-LA). Tissue and serum concentrations vs time profile were investigated after its subcutaneous injection to Wistar rats. Serum concentration profiles and key pharmacokinetic (PK) variables of doxycycline-h-LA were compared to the corresponding profiles and PK values obtained with an aqueous formulation of doxycycline-h administered either intramuscularly, orally or intravenously to Wistar rats. In all groups, the dose was 10 mg/kg. Doxycycline-h-LA showed outstanding bioavailability (951% or 477% if a correction formula is considered), as compared to the one obtained with an aqueous formulation (106-82%, respectively). Corresponding values for maximum serum concentration were 3.19 microg/ml and 3.00 microg/ml, respectively, and elimination half-lives were completely different: 42.49 h and 2.77 h for doxycycline-h-LA and the aqueous formulation, respectively. Considering minimal inhibitory concentrations of doxycycline for sensitive and resistant bacteria (from < or = 0.5 to > or =1.5 microg/ml), doxycycline-h-LA could be injected every 2 or 3 days, while aqueous doxycycline-h would require a dosing interval from 7.5 to 11 h. But if tissue concentrations are taken as braking points, the dosing interval will vary from 48 to 94 h. For doxycycline-h-LA, mean tissue:serum ratios were 2:1 for lungs, 9.8:1 for kidneys and 2.2:1 for intestine homogenates. These values are in close agreement with those found for the distribution of doxycycline in other species.

Pharmacokinetics after administration of an injectable experimental long-acting parenteral formulation of doxycycline hyclate in goats.

OBJECTIVE: To determine the pharmacokinetics after SC administration of an experimental, long-acting parenteral formulation of doxycycline hyclate in a poloxamer-based matrix and after IV and IM administration of an aqueous formulation of doxycycline hyclate in goats. ANIMALS: 30 clinically normal adult goats. PROCEDURES: Goats were allocated to 3 groups (10 goats/group). One group of goats received doxycycline hyclate (10 mg/kg) IM, a second group received the same dosage of doxycycline hyclate IV, and the third group received the long-acting parenteral formulation of doxycycline hyclate SC. Serum concentrations of doxycycline were determined before and at various intervals after administration. RESULTS: The long-acting parenteral formulation of doxycycline hyclate had the greatest bioavailability (545%); mean +/- SD maximum serum concentration was 2.4 +/- 0.95 microg/mL, peak time to maximum concentration was 19.23 +/- 2.03 hours, and elimination half-life was 40.92 +/- 4.25 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the long-acting parenteral formulation of doxycycline hyclate distributed quickly and widely throughout the body after a single dose administered SC, and there was a prolonged half-life. Bioavailability of the longacting parenteral formulation of doxycycline hyclate after SC administration was excellent, compared with bioavailability after IV and IM administration of an aqueous formulation of doxycycline hyclate. Although no local tissue irritation and adverse effects were detected, clinical assessment of drug-residues and toxicologic evaluations are warranted before this long-acting parenteral formulation of doxycycline hyclate can be considered for use in goats with bacterial infections.