Plasma pharmacokinetics of oral chlortetracycline in group fed, ruminating, Holstein steers in a feedlot setting

The Assessment of the Phototoxic Action of Chlortetracycline and Doxycycline as a Potential Treatment of Melanotic Melanoma-Biochemical and Molecular Studies on COLO 829 and G-361 Cell Lines

Melanoma is still one of the most dangerous cancers. New methods of treatment are sought due to its high aggressiveness and the relatively low effectiveness of therapies. Tetracyclines are drugs exhibiting anticancer activity. Previous studies have also shown their activity against melanoma cells. The possibility of tetracycline accumulation in pigmented tissues and the increase in their toxicity under the influence of UVA radiation creates the possibility of developing a new anti-melanoma therapy. This study aimed to analyze the phototoxic effect of doxycycline and chlortetracycline on melanotic melanoma cells COLO 829 and G-361. The results indicated that tetracycline-induced phototoxicity significantly decreased the number of live cells by cell cycle arrest as well as a decrease in cell viability. The simultaneous exposure of cells to drugs and UVA caused the depolarization of mitochondria as well as inducing oxidative stress and apoptosis. It was found that the combined treatment activated initiator and effector caspases, caused DNA fragmentation and elevated p53 level. Finally, it was concluded that doxycycline demonstrated a stronger cytotoxic and phototoxic effect. UVA irradiation of melanoma cells treated with doxycycline and chlortetracycline allows for the reduction of therapeutic drug concentrations and increases the effectiveness of tested tetracyclines.

Florfenicol/Chlortetracycline Effect on Pharmacodynamic Indices for Mutant Selection of Riemerella anatipestifer in Ducks

Riemerella anatipestifer can cause septicemia and death in ducks and geese, leading to significant economic losses to animal farms. The emergence of resistance of R. anatipestifer to commonly used antibiotics increases the difficulty of treating R. anatipestifer infection. The aim of this study was to evaluate the utility of antibiotic combination to restrict mutant selection of multidrug-resistant (MDR) R. anatipestifer isolates. Pharmacokinetics of florfenicol and chlortetracycline in Pekin ducks were evaluated using both noncompartmental analysis and population pharmacokinetic models. The areas under the curve of florfenicol and chlortetracycline after single 20 and 10 mg/kg oral administration were 49.3 and 6.84 mg*h/L, respectively. Chlortetracycline exhibited high apparent clearance and low systemic exposure. Minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values of the two antibiotics were determined in 10 and 2 MDR R. anatipestifer isolates, respectively, to derive fT_MSW (the fraction of time over 24 hours wherein the free drug concentration was within the mutant selection window [MSW]) and fT_>MPC (the fraction of time that the free drug concentration was above the MPC). Both fT_MSW and fT_>MPC were estimated from simulated concentration-time profiles relative to MIC and MPC. Florfenicol and chlortetracycline combination have additive activities against R. anatipestifer in majority of isolates and could significantly decrease monotherapy MPC of florfenicol and chlortetracycline, as well as optimize both fT_MSW and fT_>MPC parameters, provided that the bioavailability of chlortetracycline is improved. The application of pharmacokinetic/pharmacodynamic analyses to MPC concepts to restrict selection of mutant bacterial strains can help improve short- and long-term outcomes of antibiotic treatment in animal farms.

Failure to Eliminate Persistent Anaplasma marginale Infection from Cattle Using Labeled Doses of Chlortetracycline and Oxytetracycline Antimicrobials

Bovine anaplasmosis, caused by the intracellular rickettsial pathogen Anaplasma marginale, is the most prevalent tick-transmitted disease of cattle worldwide. In the U.S., tetracycline antimicrobials are commonly used to treat and control anaplasmosis. Oxytetracycline, administered by injection, is indicated for treatment of clinical anaplasmosis in beef and dairy cattle and calves. Chlortetracycline, administered orally, is indicated for control of active anaplasmosis infection in beef and nonlactating dairy cattle. Tetracyclines have been demonstrated to be effective for treating active anaplasmosis, but their ability to eliminate A. marginale at currently approved therapeutic doses or dosing regimens remains unclear. In the absence of approved dosing regimens for A. marginale clearance, a study was conducted to determine the effect of approved oxytetracycline and chlortetracycline indications on A. marginale bacteremia. Fifteen animals with persistent anaplasmosis were enrolled and divided into three treatment groups. Group 1 (n = 6) received oral chlortetracycline (1.1 mg/kg bodyweight) administered via hand-fed medicated feed for 60 consecutive days. Group 2 (n = 6) received injectable oxytetracycline administered subcutaneously at 19.8 mg/kg bodyweight three times in 3-week intervals. Group 3 (n = 3) served as an untreated control. After 60 days, bacteremia failed to permanently decrease in response to treatment. This result indicates that clearance of A. marginale is unlikely to be reliably achieved using currently approved tetracycline-based regimens to manage anaplasmosis.

Lipidomic-based investigation into the therapeutic effects of polyene phosphatidylcholine and Babao Dan on rats with non-alcoholic fatty liver disease

In recent years, with the improvement of people's living standards, non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in the world. In this paper, the metabolic disorders in Sprague Dawley (SD) rats were induced by a choline-deficient, l-amino acid-defined (CDAA) diet. The therapeutic effects of polyene phosphatidylcholine (PPC) and Babao Dan (BBD) on NAFLD were observed. Lipidomic analysis was performed using ultra-high-performance liquid chromatography-Orbitrap MS, and data analysis and lipid identification were performed using the software LipidSearch. Both PPC and BBD can reduce lipid accumulation in the liver and improve abnormal biochemical indicators in rats, including reduction of triglycerides, total cholesterol, alanine transaminase and aspartate transaminase in serum. In addition, lipids in rat serum were systematically analyzed by lipidomics. The lipidomic results showed that the most obvious lipids with abnormal metabolism in CDAA diet-induced rats were glycerides (triglycerides and diacylglycerols), phospholipids and cholesterol esters. Both BBD and PPC partly reversed the disturbance to lipids induced by the CDAA diet. PPC may be more effective than BBD in alleviating NAFLD because it has a better effect on inhibiting the abnormal accumulation of lipids and reducing the inflammatory reaction in the body.

Determination of plasma-chlortetracycline (CTC) concentrations in grazing beef cattle fed one of four FDA approved free-choice CTC-medicated minerals

Control of active bovine anaplasmosis in the United States is predicated on the use of chlortetracycline (CTC)-medicated feed throughout the vector season. However, data describing population pharmacokinetics of chlortetracycline in cows, on pasture, having free-choice access to CTC-medicated mineral for consecutive months is lacking. This study documented plasma-CTC concentrations in grazing cows during peak vector season in an anaplasmosis endemic herd. Each pasture was administered one of the four Food and Drug Administration approved CTC-medicated mineral formulations and were assigned as follows: 0.77 g/kg, Aureo Anaplaz C700 Pressed (Sweetlix Livestock Supplements, Mankato, MN); 5.5 g/kg, Purina Anaplasmosis Block (Purina Animal Nutrition, Gray Summit, MO); 6.6 g/kg, Stockmaster Aureo FC C6000 Mineral (Hubbard Feeds, Mankato, MN); 8.8 g/kg, MoorMan's Special Range Minerals AU 168XFE (ADM Animal Nutrition, Quincy, IL). Blood samples were collected monthly for determining plasma drug concentration by Ultra performance liquid chromatography (UPLC) and mass spectrometry. Continued plasma-CTC monitoring allowed for characterization of trends between treatment groups (pastures), age groups (<3 yr or >4 yr), and sampling times (June to October). Results indicate formulation (pasture) and time were significant factors affecting concentrations of CTC in plasma. Cows exposed to 5.5 g/kg block formulation recorded higher CTC plasma concentrations compared with other pasture groups (P = 0.037). Plasma-CTC concentrations increased over time (month of measurement; P = 0.0005). Specifically, concentrations measured after 5 months of continuous CTC treatment were higher than those measured in earlier months.

Chlortetracycline and melanin biopolymer - The risk of accumulation and implications for phototoxicity: An in vitro study on normal human melanocytes

Tetracyclines belong to antimicrobial classes with the highest consumption in veterinary medicine and agriculture, which leads to the contamination of the environment and food products, as well as to antibiotic resistance and adverse drug reactions. Chloro-derivatives of tetracyclines are thought to be relatively more phototoxic than others and belong to the most frequently cited drugs as photosensitizers. Melanins are heterogenous biopolymers determining skin, hair and eye colour. They are biosynthesized in a multistep process in melanocytes. Melanins, besides photoprotective and antioxidant properties, may also contribute to adverse skin drug reactions, which involve e.g. hyperpigmentation disorders and phototoxic reactions. Furthermore, they have the ability to form a drug-melanin complex, which leads to deposition of the drug or its metabolites in pigmented tissues. The aim of the study was to examine the ability of chlortetracycline to form a complex with melanin, as well as the effect of the drug on viability, antioxidant defence system and melanogenesis in normal human epidermal melanocytes exposed to the UVA radiation. The obtained results show for the first time that chlortetracycline forms a complex with melanin polymers, which creates a possibility of the drug accumulation in pigmented tissues. A simultaneous exposition of normal melanocytes to chlortetracycline and to the UVA radiation decreases cell viability, proportionally to the drug concentration and the irradiation time. The phototoxic effect appears to be related to the induction of oxidative stress in melanocytes, mainly through an increase of SOD and a decrease of the CAT activity. Chlortetracycline itself does not influence the melanin content or the activity of tyrosinase. The UVA radiation appeared to be a conditioning factor stimulating melanogenesis, whereas the presence of the drug augmented this effect.

Monte Carlo Simulations Suggest Current Chlortetracycline Drug-Residue Based Withdrawal Periods Would Not Control Antimicrobial Resistance Dissemination from Feedlot to Slaughterhouse

Antimicrobial use in beef cattle can increase antimicrobial resistance prevalence in their enteric bacteria, including potential pathogens such as Escherichia coli. These bacteria can contaminate animal products at slaughterhouses and cause food-borne illness, which can be difficult to treat if it is due to antimicrobial resistant bacteria. One potential intervention to reduce the dissemination of resistant bacteria from feedlot to consumer is to impose a withdrawal period after antimicrobial use, similar to the current withdrawal period designed to prevent drug residues in edible animal meat. We investigated tetracycline resistance in generic E. coli in the bovine large intestine during and after antimicrobial treatment by building a mathematical model of oral chlortetracycline pharmacokinetics-pharmacodynamics and E. coli population dynamics. We tracked three E. coli subpopulations (susceptible, intermediate, and resistant) during and after treatment with each of three United States chlortetracycline indications (liver abscess reduction, disease control, disease treatment). We compared the proportion of resistant E. coli before antimicrobial use to that at several time points after treatment and found a greater proportion of resistant enteric E. coli after the current withdrawal periods than prior to treatment. In order for the proportion of resistant E. coli in the median beef steer to return to the pre-treatment level, withdrawal periods of 15 days after liver abscess reduction dosing (70 mg daily), 31 days after disease control dosing (350 mg daily), and 36 days after disease treatment dosing (22 mg/kg bodyweight for 5 days) are required in this model. These antimicrobial resistance withdrawal periods would be substantially longer than the current U.S. withdrawals of 0–2 days or Canadian withdrawals of 5–10 days. One published field study found similar time periods necessary to reduce the proportion of resistant E. coli following chlortetracycline disease treatment to those suggested by this model, but additional carefully designed field studies are necessary to confirm the model results. This model is limited to biological processes within the cattle and does not include resistance selection in the feedlot environment or co-selection of chlortetracycline resistance following other antimicrobial use.

Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes

The objectives of this study were to determine plasma concentrations and pharmacokinetic parameters of feed-grade chlortetracycline (CTC) in sheep after oral administration of 80 or 500 mg/head daily, divided into two equal doses given at 12-h intervals for 8 days. These are the approved, and commonly used but unapproved, feed additive doses, respectively, in the United States for the prevention of ovine infectious abortion. Blood samples were collected just prior to dosing at 0, 12, 24, 72, 96, and 192 h, as well as 4, 8, 12, 24, and 36 h after the last dose, and noncompartmental pharmacokinetic analysis was performed to estimate elimination half-life and area under the plasma concentration-time curve (AUC). Mean observed maximum CTC concentrations (Cmax ) were 20.0 ng/mL (80 mg dose) and 101 ng/mL (500 mg dose). Mean apparent elimination half-life was 18 h (80 mg dose) and 20 h (500 mg dose). Although published data do not exist to estimate plasma CTC concentrations necessary for the prevention of ovine infectious abortion, concentrations reached in our study suggest that either the FDA-approved and FDA-unapproved dosages are not high enough or that the pharmacodynamic parameter relating preventive dose to pathogen minimum inhibitory concentrations is yet to be determined.

Immunization-induced Anaplasma marginale-specific T-lymphocyte responses impaired by A. marginale infection are restored after eliminating infection with tetracycline

Infection of cattle with Anaplasma marginale fails to prime sustained effector/memory T-cell responses, and high bacterial load may induce antigen-specific CD4 T exhaustion and deletion. We tested the hypothesis that clearance of persistent infection restores the exhausted T-cell response. We show that infection-induced T-cell exhaustion, characterized as loss of antigen-specific proliferation, and gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) production are partially restored in cattle following clearance of persistent infection with tetracycline.

Use of pharmacokinetic modeling to assess antimicrobial pressure on enteric bacteria of beef cattle fed chlortetracycline for growth promotion, disease control, or treatment

Antimicrobial use in food animals may increase antimicrobial resistance in their enteric bacteria that can be transferred to human microbiome. Over 70% of U.S. beef feedlots use non-ionophore in-feed antimicrobials for animal disease control, treatment, or growth promotion. The fraction of feedlots feeding chlortetracycline (CTC), mostly for disease control but also for treatment, has increased since the mid-1990s to present. Quantitative information on the antimicrobial selective pressure on the enteric bacteria of cattle fed CTC is lacking. Hence, the purpose of this study was to develop a deterministic mathematical model of the pharmacokinetics of ingested CTC in a beef steer and estimate the concentration of antimicrobially active (undegraded) CTC in the animal's large intestine. To evaluate the fit of the model to existing data, we also estimated the CTC concentrations in the central circulation, and fresh and aging manure from the steer. The model accounted for CTC abiotic degradation while in the gastrointestinal tract, absorption into the central circulation and tissues, biliary and renal excretion, and removal from the intestine by defecation. The model included an increase in the large intestine volume as the steer grew. We estimated that during CTC feeding to a 300-kg steer for growth promotion, the maximal drug concentration in the large intestine was 0.3 μg/mL; during disease control it was 1.7 μg/mL; and during treatment it was 31.5 μg/mL. The estimated CTC concentrations in the central circulation and the steer's manure agreed reasonably well with published data.

Plasma disposition and tissue depletion of chlortetracycline in the food producing animals, chickens for fattening

Chickens were used to investigate plasma disposition of chlortetracycline after single IV (15 mg/kg) and multiple oral administration (60 mg/kg, 5 days) and residue depletion of chlortetracycline after multiple oral doses (60 mg/kg, 5 days). Plasma and tissue samples were analyzed by HPLC. Mean elimination half-lives in plasma were 7.96 and 13.15 h after IV and multiple oral administration. Maximum plasma concentration was 4.33 μg/ml and the interval from oral administration until maximal concentration was 1.79 h. Oral bioavailability was 17.76%. After multiple oral dose, mean kidney, liver and muscle tissue concentrations of chlortetracycline+4-epi-chlortetracycline of 835.3, 192.7, and 126.3 μg/kg, respectively, were measured 1 day after administration of the final dose of chlortetracycline. Chlortetracycline residues were detected in kidney and liver (205.4 and 81.7 μg/kg, respectively), but not in muscle, 3 days after the end of chlortetracycline treatment. The mean chlortetracycline+4-epi-chlortetracycline concentrations were below LOQ at 3 and 5 days after cessation of medication in muscle and liver, respectively. A withdrawal time of 3 days was necessary to ensure that the chlortetracycline residues were less than the maximal residue limits (MRLs) established by the European Union (100, 300, and 600 μg/kg in muscle, liver, and kidney, respectively).

The efficacy of three chlortetracycline regimens in the treatment of persistent Anaplasma marginale infection

Chemosterilization is reported in cattle fed chlortetracycline hydrochloride (CTC) at dosages ranging from 1.1mg/kg for 120 days to 11 mg/kg for 30-60 days. The relationship between plasma CTC drug concentration and carrier clearance has not been described. Chronic carrier status was established in 21 steers with a Virginia isolate of Anaplasma marginale and confirmed by cELISA and an A. marginale-specific RT-PCR. Four negative, splenectomized steers served as active disease transmission sentinels. Steers were randomized to receive 4.4 mg/kg/day (LD); 11 mg/kg/day (MD); or 22 mg/kg/day (HD) of oral chlortetracycline; or placebo (CONTROL) for 80 days. The LD, MD and HD treatment groups consisted of 5 infected steers and 1 splenectomized steer; CONTROL group had six infected steers and 1 splenectomized steer. The daily treatments and ration were divided equally and fed twice daily. Blood samples were collected semi-weekly for determining plasma drug concentration by ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry method and assessment of disease status by both cELISA and RT-PCR. Mean (CV%) chlortetracycline plasma drug concentrations in the LD, MD, and HD groups were 85.3 (28%), 214.5 (32%) and 518.9 (40%)ng/mL during days 4 through 53 of treatment. A negative RT-PCR assay result was confirmed in all CTC-treated groups within 49 days of treatment; however, cELISA required an additional 49 to 88 days before similar results. Subinoculation of splenectomized steers confirmed chemosterilization. These results are important for influencing future chemosterilization strategies and impacting free trade policy among countries and regions of contrasting endemicity.