Concentrations Of Minocycline Research Articles

Evaluation of canine-specific minocycline and doxycycline susceptibility breakpoints for meticillin-resistant Staphylococcus pseudintermedius isolates from dogs.

Using the US Clinical and Laboratory Standards Institute (CLSI) human tetracycline breakpoints to predict minocycline and doxycycline susceptibility of Staphylococcus pseudintermedius (SP) isolates from dogs is not appropriate because they are too high to meet pharmacokinetic/pharmacodynamic data using a standard dose. New breakpoints have been approved for doxycycline and proposed for minocycline. Revised breakpoints are four dilutions lower than tetracycline breakpoints, providing a more conservative standard for classification of isolates. The objectives of this study were to measure minimum inhibitory concentrations (MICs) of minocycline and doxycycline of 100 canine meticillin-resistant SP clinical isolates, compare their susceptibilities to minocycline and doxycycline based on current and revised standards, and document their tetracycline resistance genes. E-test strips were used to determine MICs. PCR was used to identify tet genes. Using the human tetracycline breakpoint of MIC ≤ 4 μg/mL, 76 isolates were susceptible to minocycline and 36 isolates were susceptible to doxycycline. In contrast, using the proposed minocycline breakpoint (MIC ≤ 0.25 μg/mL) and approved doxycycline breakpoint (MIC ≤ 0.125 μg/mL), 31 isolates were susceptible to both minocycline and doxycycline. Thirty-one isolates carried no tet genes, two had tet(K) and 67 had tet(M). Use of the human tetracycline breakpoints misclassified 45 and five of the isolates as susceptible to minocycline and doxycycline, respectively. PCR analysis revealed that 43 and five of the isolates classified as susceptible to minocycline and doxycycline, respectively, possessed the tetracycline resistance gene, tet(M), known to confer resistance to both drugs. These results underscore the importance of utilizing the proposed minocycline and approved doxycycline canine breakpoints in place of human tetracycline breakpoints.

Resistance of Stenotrophomonas maltophilia to Fluoroquinolones: Prevalence in a University Hospital and Possible Mechanisms.

Objective: The purpose of this study was to investigate the clinical distribution and genotyping of Stenotrophomonas maltophilia, its resistance to antimicrobial agents, and the possible mechanisms of this drug resistance. Methods: S. maltophilia isolates were collected from clinical specimens in a university hospital in Northwestern China during the period between 2010 and 2012, and were identified to the species level with a fully automated microbiological system. Antimicrobial susceptibility testing was performed for S. maltophilia with the Kirby-Bauer disc diffusion method. The minimal inhibitory concentrations (MICs) of norfloxacin, ofloxacin, chloramphenicol, minocycline, ceftazidime, levofloxacin and ciprofloxacin against S. maltophilia were assessed using the agar dilution method, and changes in the MIC of norfloxacin, ciprofloxacin and ofloxacin were observed after the addition of reserpine, an efflux pump inhibitor. Fluoroquinolone resistance genes were detected in S. maltophilia using a polymerase chain reaction (PCR) assay, and the expression of efflux pump smeD and smeF genes was determined using a quantitative fluorescent (QF)-PCR assay. Pulsed-field gel electrophoresis (PFGE) was employed to genotype identified S. maltophilia isolates. Results: A total of 426 S. maltophilia strains were isolated from the university hospital from 2010 to 2012, consisting of 10.1% of total non-fermentative bacteria. The prevalence of norfloxacin, ciprofloxacin and ofloxacin resistance was 32.4%, 21.9% and 13.2% in the 114 S. maltophilia isolates collected from 2012, respectively. Following reserpine treatment, 19 S. maltophilia isolates positive for efflux pump were identified, and high expression of smeD and smeF genes was detected in two resistant isolates. gyrA, parC, smeD, smeE and smeF genes were detected in all 114 S. maltophilia isolates, while smqnr gene was found in 25.4% of total isolates. Glu-Lys mutation (GAA-AAA) was detected at the 151th amino acid of the gyrA gene, while Gly-Arg mutation (GGC-CGC) was found at the 37th amino acid of the parC gene. However, no significant difference was observed in the prevalence of gyrA or parC mutation between fluoroquinolone-resistant and -susceptible isolates (p> 0.05). The smqnr gene showed 92% to 99% heterogenicity among the 14 S. maltophilia clinical isolates. PFGE of 29 smqnr gene-positive S. maltophilia clinical isolates revealed 25 PFGE genotypes and 28 subgenotypes. Conclusions: Monitoring the clinical distribution and antimicrobial resistance of S. maltophilia is of great significance for the clinical therapy of bacterial infections. Reserpine is effective to inhibit the active efflux of norfloxacin, ciprofloxacin and ofloxacin on S. maltophilia and reduce MIC of fluoroquinolones against the bacteria. The expression of efflux pump smeD and smeF genes correlates with the resistance of S. maltophilia to fluoroquinolones.

Assessment of minocycline and polymyxin B combination against Acinetobacter baumannii.

Antimicrobial resistance among Acinetobacter baumannii is increasing worldwide, often necessitating combination therapy. The clinical utility of using minocycline with polymyxin B is not well established. In this study, we investigated the activity of minocycline and polymyxin B against 1 laboratory isolate and 3 clinical isolates of A. baumannii. Minocycline susceptibility testing was performed with and without an efflux pump inhibitor, phenylalanine-arginine β-naphthylamide (PAβN). The intracellular minocycline concentration was determined with and without polymyxin B (0.5 μg/ml). Time-kill studies were performed over 24 h using approximately 10(6) CFU/ml of each strain with clinically relevant minocycline concentrations (2 μg/ml and 8 μg/ml), with and without polymyxin B (0.5 μg/ml). The in vivo efficacy of the combination was assessed in a neutropenic murine pneumonia model. Infected animals were administered minocycline (50 mg/kg), polymyxin B (10 mg/kg), or both to achieve clinically equivalent exposures in humans. A reduction in the minocycline MIC (≥ 4×) was observed in the presence of PAβN. The intracellular concentration and in vitro bactericidal effect of minocycline were both enhanced by polymyxin B. With 2 minocycline-susceptible strains, the bacterial burden in lung tissue at 24 h was considerably reduced by the combination compared to monotherapy with minocycline or polymyxin B. In addition, the combination prolonged survival of animals infected with a minocycline-susceptible strain. Polymyxin B increased the intracellular concentration of minocycline in bacterial cells and enhanced the bactericidal activity of minocycline, presumably due to efflux pump disruption. The clinical utility of this combination should be further investigated.

Striking Growth-inhibitory Effects of Minocycline on Human Prostate Cancer Cell Lines

To elucidate a hypothetical link between retinoic acid (RA) signaling and minocycline for targeting prostate carcinoma (PCA). RA signaling has been implicated in growth-inhibition of malignant PCA, and intracellular RA homeostasis has been investigated as a potential therapeutic target. Minocycline is a tetracycline antibiotic with pleiotropic actions in many tissues and reaches comparably high levels in human prostate tissue. Interestingly, minocycline exhibits the rare side effect of a pseudotumor cerebri, which is otherwise known to occur from vitamin A intoxication or in retinoid therapy. Therefore, we hypothesized minocycline to putatively interact with intracellular RA homeostasis in PCA. Using LN-CAP, DU-145, and PC-3 cell lines, effects of minocycline on microsomal RA metabolism and on cell growth were assessed in vitro. Minocycline was identified to potently inhibit cell growth, at concentrations within the range of tissue levels readily reached under standard therapeutic conditions. In vitro inhibition experiments revealed inhibition of RA breakdown, yet only at comparably high concentrations of minocycline. Using all trans-RA, RA metabolism inhibitor liarozole, and different retinoid receptor antagonists, the putative RA-dependent effects of minocycline were further evaluated and confirmed to be independent of RA signaling. Our findings add to the growing body of evidence for the many pleiotropic actions of minocycline. In view of the striking effects of minocycline on cell growth in PCA cell lines in vitro and its relatively safe side effect profile, the use of minocycline for targeting PCA should be timely clinically evaluated.

Nd:YAG Laser Irradiation of the Tooth Root Surface Inhibits Demineralization and Root Surface Softening Caused by Minocycline Application

The aim of this study was to investigate the effect of laser irradiation on root surface demineralization caused by local drug delivery systems (DDS), and to evaluate the effect of sealing on drug retention. The duration of supportive periodontal treatment (SPT) has increased with increasing life expectancy. Repeated root planing and DDS application during SPT should be reconsidered with regard to their effects on the root surface. Extracted human teeth were collected, cut into 3 × 3 × 2 mm root dentin specimens, and divided randomly into eight groups with various combinations of Nd:YAG laser power (0, 0.5, 1, and 2 W), with and without DDS (minocycline HCl). Specimen microhardness and calcium (Ca) solubility were measured after treatment. The specimens (control and laser and DDS groups) were examined by scanning electron microscopy. Forty SPT patients were recruited, to assess the effect of periodontal pocket sealing on drug retention. Laser irradiation increased the microhardness of root specimens in an energy-dependent manner. Calcium solubilities decreased from the 0 W+DDS group to the 2.0 W+DDS group. The mean Ca solubilities in the 1.0 W+DDS and 2.0 W+DDS groups were significantly lower than in the 0 W+DDS group (p<0.01, p<0.001, respectively). Laser irradiation counteracted the softening effect of DDS. Morphologic change was observed in the 2 W+DDS group; however, no morphologic changes were observed in the control and the 1 W+DDS groups. The mean concentration of minocycline in the periodontal pocket 24 h after application was 252.79 ± 67.50 μg/mL. Laser irradiation of the root surface inhibited the softening and decalcification caused by minocycline HCl. Sealing the periodontal pockets effectively improved drug retention. These results suggest that the combination of laser irradiation and DDS could benefit patients receiving repeated SPT.

Prolonged Minocycline Treatment Impairs Motor Neuronal Survival and Glial Function in Organotypic Rat Spinal Cord Cultures

BackgroundMinocycline, a second-generation tetracycline antibiotic, exhibits anti-inflammatory and neuroprotective effects in various experimental models of neurological diseases, such as stroke, Alzheimer’s disease, amyotrophic lateral sclerosis and spinal cord injury. However, conflicting results have prompted a debate regarding the beneficial effects of minocycline.MethodsIn this study, we analyzed minocycline treatment in organotypic spinal cord cultures of neonatal rats as a model of motor neuron survival and regeneration after injury. Minocycline was administered in 2 different concentrations (10 and 100 µM) at various time points in culture and fixed after 1 week.ResultsProlonged minocycline administration decreased the survival of motor neurons in the organotypic cultures. This effect was strongly enhanced with higher concentrations of minocycline. High concentrations of minocycline reduced the number of DAPI-positive cell nuclei in organotypic cultures and simultaneously inhibited microglial activation. Astrocytes, which covered the surface of the control organotypic cultures, revealed a peripheral distribution after early minocycline treatment. Thus, we further analyzed the effects of 100 µM minocycline on the viability and migration ability of dispersed primary glial cell cultures. We found that minocycline reduced cell viability, delayed wound closure in a scratch migration assay and increased connexin 43 protein levels in these cultures.ConclusionsThe administration of high doses of minocycline was deleterious for motor neuron survival. In addition, it inhibited microglial activation and impaired glial viability and migration. These data suggest that especially high doses of minocycline might have undesired affects in treatment of spinal cord injury. Further experiments are required to determine the conditions for the safe clinical administration of minocycline in spinal cord injured patients.

Cytoprotective activity of minocycline includes improvement of mitochondrial coupling: the importance of minocycline concentration and the presence of VDAC

Available data indicate that minocycline, an antibiotic of the tetracycline family, has cytoprotective properties due to a direct interaction with mitochondria. Yet, the data in the case of isolated mitochondria suggest discrepant or even detrimental effect(s) of the interaction. We have studied the cytoprotective activity displayed by minocycline in the case of the yeast Saccharomyces cerevisiae cells pretreated with H₂O₂. We demonstrated that the activity of minocycline required the presence of VDAC (voltage-dependent anion-selective channel) and provided distinct improvement of mitochondrial coupling. In the case of isolated mitochondria, we verified that minocycline exhibited uncoupler activity when applied in micromolar concentrations. However, when added in nanomolar concentrations, minocycline was able to improve the level of coupling for isolated mitochondria. The coupling improvement effect was observed in mitochondria containing VDAC but not in Δpor1 mitochondria (depleted of VDAC1, termed here VDAC) and in both types of mitoplasts. Thus, properly low concentrations of minocycline within the cell in the vicinity of VDAC-containing mitochondria enable the improvement of energy coupling of mitochondria that contributes to cytoprotective activity of minocycline.

Effects of minocycline on endogenous neural stem cells after experimental stroke

Minocycline has been reported to reduce infarct size after focal cerebral ischemia, due to an attenuation of microglia activation and prevention of secondary damage from stroke-induced neuroinflammation. We here investigated the effects of minocycline on endogenous neural stem cells (NSCs) in vitro and in a rat stroke model.Primary cultures of fetal rat NSCs were exposed to minocycline to characterize its effects on cell survival and proliferation. To assess these effects in vivo, permanent cerebral ischemia was induced in adult rats, treated systemically with minocycline or placebo. Imaging 7days after ischemia comprised (i) Magnetic Resonance Imaging (MRI), assessing the extent of infarcts, (ii) Positron Emission Tomography (PET) with [11C]PK11195, characterizing neuroinflammation, and (iii) PET with 3’-deoxy-3’-[18F]fluoro-L-thymidine ([18F]FLT), detecting proliferating endogenous NSCs. Immunohistochemistry was used to verify ischemic damage and characterize cellular inflammatory and repair processes in more detail.In vitro, specific concentrations of minocycline significantly increased NSC numbers without increasing their proliferation, indicating a positive effect of minocycline on NSC survival. In vivo, endogenous NSC activation in the subventricular zone (SVZ) measured by [18F]FLT PET correlated well with infarct volumes. Similar to in vitro findings, minocycline led to a specific increase in endogenous NSC activity in both the SVZ as well as the hippocampus. [11C]PK11195 PET detected neuroinflammation in the infarct core as well as in peri-infarct regions, with both its extent and location independent of the infarct size. The data did not reveal an effect of minocycline on stroke-induced neuroinflammation.We show that multimodal PET imaging can be used to characterize and quantify complex cellular processes occurring after stroke, as well as their modulation by therapeutic agents. We found minocycline, previously implied in attenuating microglial activation, to have positive effects on endogenous NSC survival. These findings hold promise for the development of novel treatments in stroke therapy.

Delivering Minocycline into Brain Endothelial Cells with Liposome-Based Technology

Minocycline has been proposed as a way to blunt neurovascular injury from matrix metalloproteinases (MMPs) during stroke. However, recent clinical trials suggest that high levels of minocycline may have deleterious side-effects. Here, we showed that very high minocycline concentrations damage endothelial cells via calpain/caspase pathways. To alleviate this potential cytotoxicity, we encapsulated minocycline in liposomes. Low concentrations of minocycline could not reduce tumor necrosis factor α (TNFα)-induced MMP-9 release from endothelial cells. But low concentrations of minocycline-loaded liposomes significantly reduced TNFα-induced MMP-9 release. This study provides proof-of-concept that liposomes may be used to deliver lower levels of minocycline for targeting MMPs in cerebral endothelium.

The Two Different Effects of the Potential Neuroprotective Compound Minocycline on AMPA-Type Glutamate Receptors

Background: Minocycline has demonstrated neuroprotective effects in experimental neurodegenerative diseases. The aim of this study was to investigate if there is any direct interaction between minocycline and the AMPA-type receptor channels, and to elucidate the underlying molecular pharmacological mechanisms. Methods: The patch-clamp technique was used combined with an ultrafast solution exchange system to investigate the interaction of minocycline with recombinant AMPA-type glutamate receptor channels (homomeric GluR2flipGQ or nondesensitizing GluR2L504Y). Results: Dose-dependent decreases in the relative peak current amplitude (rAmp) and the relative steady-state current (rC_des) were found in coapplication experiments with GluR2L504Y receptors, but not in preincubation experiments. Furthermore, coapplication of 1 or 3 mmol/l minocycline showed a decrease in the fast time constant of current decay, and reopening currents were observed. But in the test with GluR2flipGQ receptors, rAmp, relative area under the curve and rC_des increased with increasing concentrations of minocycline, and the steady-state time constant also increased when 3 µmol/l glutamate were used as agonist. Conclusion: Minocycline modulates AMPA-type receptor channels in a combination of a weaker open-channel block effect and a stronger potentiation effect, and the latter effect arises mainly from attenuating the extent of receptor desensitization.

The combination of chloroquine and minocycline, a therapeutic option in cerebrospinal infection of Whipple's disease refractory to treatment with ceftriaxone, meropenem and co-trimoxazole

Sir, Whipple’s disease is a chronic infection caused by Tropheryma whipplei. In a prospective study, the CNS was found to be involved in 38.5% of the cases. Treatment is not always successful. – 6 Co-trimoxazole (trimethoprim/sulfamethoxazole) has been reported to be significantly more effective than tetracycline; however, resistance to co-trimoxazole has also been observed. – 6 More recently, there have even been reports describing resistance of CNS infections to treatment with ceftriaxone, a bactericidal antibiotic penetrating the blood–brain barrier. In 2002, a patient presented with diarrhoea, weight loss to 64 kg, anaemia (8.4 g/dL haemoglobin) and erythrocyte sedimentation rate of 33 mm/h. The medical history revealed relapsing arthritis since 1991 and pericarditis necessitating pericardial resection in 1993. Gastrointestinal biopsies disclosed periodic acid-Schiff (PAS)-positive macrophages typical of untreated Whipple’s disease in the mucosa of the duodenum and the ileum and in the submucosa of the colon. The patient had no cerebral symptoms. However, microscopic examination of centrifuged CSF obtained by spinal puncture showed a PAS-positive macrophage typical of Whipple’s disease (histopathology carried out by Dr Reinhard Golz, Wuppertal), and the PCR to T. whipplei in the CSF was positive. The patient was admitted to a prospective treatment trial, as reported in Feurle et al. He was randomized to 2 g of ceftriaxone infused intravenously once daily for 2 weeks, followed by oral co-trimoxazole at a dosage of 160/300 mg twice daily for 12 months. While the patient recovered from all signs and symptoms of Whipple’s disease, the PCR for T. whipplei remained positive in the CSF for 5.5 years despite additional treatment with 1 g of meropenem infused intravenously thrice daily for 2 weeks followed by cotrimoxazole for another year. After a further year of cotrimoxazole, the CSF was still positive in the T. whipplei PCR, while the patient was receiving this treatment. PAS-positive macrophages in duodenal mucosal biopsies and in the CSF had disappeared. CT and magnetic resonance imaging of the brain did not reveal any structural abnormality. At this time, the patient had no symptoms of systemic or cerebral Whipple’s disease. The presence of T. whipplei in the CSF was confirmed by sequence analysis of the amplification product, and the viability was established by culture in MRC5 fibroblasts and in axenic medium. In vitro susceptibility of the cultured strain to ceftriaxone, meropenem, tetracyclines and co-trimoxazole is shown in Table 1. The risk of this patient developing symptomatic cerebral disease seemed unpredictable. After obtaining written informed consent for an individual treatment attempt, this patient was treated with chloroquine and tetracycline, a combination suggested previously. Chloroquine (or hydroxychloroquine) enhances antimicrobial activity of tetracyclines by raising the pH of the phagolysosomes within macrophages. Minocycline was selected as the tetracycline in this case as this compound has been reported to cross the blood–brain barrier well. Pollock et al., taking advantage of this pharmacokinetic property, were probably the first to treat a patient with cerebral Whipple’s disease with minocycline. They did not combine it with chloroquine. Others prefer the combination of doxycycline and chloroquine. In the present study, the dosage of chloroquine, based on a body weight of 83 kg, was 1725 mg of chloroquine phosphate in divided doses orally on day 1, and 575 mg on the second to the fourth day, followed by one 250 mg chloroquine phosphate tablet once daily for 45 days. A serum concentration of 165 mg/ L chloroquine (therapeutic range 20 to 200 mg/L) was obtained. Minocycline was given at a dosage of one 100 mg minocycline tablet twice daily for 45 days. This dosage had to be reduced to 100 mg daily from day 5 to day 8 because of vertigo. Vestibular toxicity manifesting as dizziness, ataxia and nausea is a common side effect of this tetracycline. The plasma concentration of minocycline, determined by HPLC, was 2.1 mg/L. The serum and respective plasma concentrations were determined 5 weeks after onset of treatment and 14 h after the last medication. The PCR for T. whipplei in the CSF was negative, both 12 and 24 months later. The patient has been asymptomatic now for more than 9 years after the initial examination and treatment. Obviously, this new treatment option, found to be efficacious in a single patient, should be evaluated in a prospective trial. The regimen is attractive as the combination of minocycline and chloroquine can be given orally. However, vestibular side effects (occurring in .70% of women taking 100 mg of minocycline every 12 h) will render any study difficult. Our male patient had to reduce the dose of minocycline for several days.

Pharmacokinetics and distribution of minocycline in mature horses after oral administration of multiple doses and comparison with minimum inhibitory concentrations

Minocycline holds great potential for use in horses not only for its antimicrobial effects but also for its anti-inflammatory and neuroprotective properties. However, there are no pharmacokinetic or safety data available regarding the use of oral minocycline in horses. To determine pharmacokinetics, safety and penetration into plasma, synovial fluid, aqueous humour (AH) and cerebral spinal fluid (CSF) of minocycline after oral administration of multiple doses in horses and to determine the minimum inhibitory concentrations (MIC) of minocycline for equine pathogenic bacteria. Six horses received minocycline (4 mg/kg bwt q. 12 h for 5 doses). Thirty-three blood and 9 synovial fluid samples were collected over 96 h. Aqueous humour and CSF samples were collected 1 h after the final dose. Minocycline concentrations were measured using high pressure liquid chromatography. The MIC values of minocycline for equine bacterial isolates were determined. At steady state, the mean ± s.d. peak concentration of minocycline in the plasma was 0.67 ± 0.26 µg/ml and the mean half-life was 11.48 ± 3.23 h. The highest trough synovial fluid minocycline concentration was 0.33 ± 0.12 µg/ml. The AH concentration of minocycline was 0.09 ± 0.03 µg/ml in normal eyes and 0.11 ± 0.04 µg/ml in blood aqueous barrier-disrupted eyes. The mean CSF concentration of minocycline was 0.38 ± 0.09 µg/ml. The MIC values were determined for 301 isolates. Minocycline concentrations were above the MIC(50) and MIC(90) for many gram-positive equine pathogens. This study supports the use of orally administered minocycline at a dose of 4 mg/kg bwt every 12 h for the treatment of nonocular infections caused by susceptible (MIC ≤ 0.25 µg/ml) organisms in horses. Further studies are required to determine the dose that would be effective for the treatment of ocular infections.

Neuroprotection by Minocycline Caused by Direct and Specific Scavenging of Peroxynitrite

Minocycline prevents oxidative protein modifications and damage in disease models associated with inflammatory glial activation and oxidative stress. Although the drug has been assumed to act by preventing the up-regulation of proinflammatory enzymes, we probed here its direct chemical interaction with reactive oxygen species. The antibiotic did not react with superoxide or (•)NO radicals, but peroxynitrite (PON) was scavenged in the range of ∼1 μm minocycline and below. The interaction of pharmacologically relevant minocycline concentrations with PON was corroborated in several assay systems and significantly exceeded the efficacy of other antibiotics. Minocycline was degraded during the reaction with PON, and the resultant products lacked antioxidant properties. The antioxidant activity of minocycline extended to cellular systems, because it prevented neuronal mitochondrial DNA damage and glutathione depletion. Maintenance of neuronal viability under PON stress was shown to be solely dependent on direct chemical scavenging by minocycline. We chose α-synuclein (ASYN), known from Parkinsonian pathology as a biologically relevant target in chemical and cellular nitration reactions. Submicromolar concentrations of minocycline prevented tyrosine nitration of ASYN by PON. Mass spectrometric analysis revealed that minocycline impeded nitrations more effectively than methionine oxidations and dimerizations of ASYN, which are secondary reactions under PON stress. Thus, PON scavenging at low concentrations is a novel feature of minocycline and may help to explain its pharmacological activity.

Bioequivalence Study of Two Minocycline Capsule Formulations in Healthy Subjects

The purpose of this study was to find out whether the bioavailability of 100 mg minocycline capsule manufactured by Y.S.P. Industries (M) Sdn. Bhd. was equivalent to that produced by Apotex Canada (Apo-Minocycline ® 100 mg). The pharmacokinetic parameters assessed in this study were area under the plasma concentration-time curve from time zero to the last observed quantifiable concentration (AUC t ), area under the plasma concentration-time curve from time zero to infinity (AUC inf ), the peak plasma concentration of the drug (C max ), time needed to achieve the peak plasma concentration (t max ), and the elimination half life (t 1/2 ). These parameters were determined on plasma concentrations of minocycline. This was a randomized, single blind, two-period, two-sequence crossover study which included 20 healthy adult male and female subjects under fasting conditions. In each of the two study periods (separated by a washout of one week) single dose of test or reference drug was administered. Blood samples were taken up to 60 h post dose, the plasma was separated and the concentration of minocycline were determined by HPLC-UV method. In this study, the mean (SD) AUC t, AUC inf , C max , and t ½ of minocycline from the test drug were 17272.46 (3316.80) ng.h.mL -1 , 19438.68 (3862.36) ng.h.mL -1 , 938.75 (192.92) ng/mL, and 19.46 (4.90) h, respectively, with the median (range) t max of minocycline from the test drug was 2.00 (0.67 – 3.00) h. The mean (SD) AUC t , AUC inf , C max , and t ½ of minocycline from the reference drug were 16999.33 (3103.27) ng.h.mL -1 , 19078.66 (3401.97) ng.h.mL -1 , 944.19 (188.56) ng/mL, and 18.90 (4.84) h, respectively, with the median (range) t max of minocycline from the reference drug was 2.00 (1.00 – 3.00) h. The geometric mean ratios (90% C.I.) of the test drug/reference drug for minocycline were 101.36% (97.85 – 105.00%) for AUC t, 101.53% (98.31 – 104.85%) for AUC inf , and 99.22% (95.92 – 102.63%) for C max , respectively. Based on this study, it can be concluded that the two minocycline capsules (test and drug reference drug) were bioequivalent in term of the rate and extent of absorption.

Antibiotic susceptibility of Propionibacterium acnes isolated from acne vulgaris in Korea

Propionibacterium acnes plays an important role in the development of acne, and inflammatory lesions are improved by antibiotics. Long-term use of antibiotics may result in development of resistant strains and treatment failure. The aim of the present study was to investigate the isolation rate of P. acnes and to evaluate its antibiotic susceptibility to widely used antibiotics in acne in Korea. Among 46 patients, 31 P. acnes strains were cultured. Isolated P. acnes was measured for minimum inhibitory concentration (MIC) of tetracycline, doxycycline, minocycline, erythromycin and clindamycin using an Epsilometer test. Age, disease duration and previous history of antibiotic therapy for acne were compared in relation to the MIC. The mean MIC of tetracycline, minocyclines, doxycycline, clindamycin and erythromycin were all below the breakpoint of antibiotic resistance. The patients with acne vulgaris with disease duration of more than 2 years documented higher MIC values in doxycycline, erythromycin, and clindamycin than those of less than 2 years. The patients who were previously treated with topical or systemic antibiotics showed higher MIC in doxycycline. Antibiotic resistance of P. acnes is still low in Korea, but at this point, there is an increasing trend of MIC. Caution and acknowledgement of increased risk of antibiotic resistant P. acnes should be advised in acne antibiotic treatment to minimize and avoid the emergence of the resistant strain.

Pharmacokinetics and tissue distribution of minocycline hydrochloride in horses

To determine the pharmacokinetics and tissue distribution of minocycline in horses. 5 healthy Thoroughbred mares for the pharmacokinetic experiment and 6 healthy Thoroughbred mares for the tissue distribution experiment. Each mare was given 2.2 mg of minocycline hydrochloride/kg, IV. Blood samples were collected once before minocycline administration (0 hours) and 10 times within 48 hours after administration in the pharmacokinetics study, and 24 tissue samples were obtained at 0.5 and 3 hours in the distribution study. No adverse effects were observed in any of the mares after minocycline administration. The mean+/-SD elimination half-life was 7.70+/-1.91 hours. The total body clearance was 0.16+/-0.04 L/h/kg, and the volume of distribution at steady state was 1.53+/-0.09 L/kg. The percentage of plasma protein binding was 68.1+/-2.6%. Plasma concentration of free minocycline was 0.12 microg/mL at 12 hours. Minocycline was not detected in brain tissue, CSF or aqueous humor at 0.5 hours; however, it was found in all tissues, except in the aqueous humor, at 3 hours. Clearance of minocycline in healthy mares was greater than that reported for humans. For effective treatment of infections with common equine pathogens, it will be necessary to administer minocycline at a dosage of 2.2 mg/kg, IV, every 12 hours. This drug could be useful for infections in many tissues, including the CNS. The pharmacokinetic and tissue distribution data should aid in the appropriate use of minocycline in horses.

Improving Outcomes of Neuroprotection by Minocycline: Guides from Cell Culture and Intracerebral Hemorrhage in Mice

Minocycline ameliorates deficits in models of acute and chronic neurological diseases, but many publications do not replicate these results. We tested the hypothesis that a key factor in achieving neurological benefits is the exposure of neural cells to local high concentrations of minocycline. This hypothesis was evaluated by using human neurons in culture and in a mouse model of intracerebral hemorrhage (ICH). In culture, neurons were very vulnerable to blood-induced toxicity, with 60% lost within 24 hours in an environment of 5% blood in culture medium. Minocycline reduced blood-induced neurotoxicity in a concentration-dependent manner. In vivo, the introduction of blood into the striatum of mice to simulate ICH resulted in a massive lesion by 24 hours. When minocycline was mixed with the blood used to inflict ICH, the resulting extent of neuropathology was significantly less than that achieved with intraperitoneal administration of medication. The combination of intracerebral and intraperitoneal minocycline improved neuroprotection compared with either alone. We then delayed minocycline treatment and injected it into the hematoma 1 hour after ICH. We found greater alleviation of brain damage and neuronal death with increasing concentrations of minocycline injected locally, which was reflected in limited behavioral and histological recovery. We conclude that the prospect of neuroprotection with minocycline is improved by high concentrations of minocycline delivered locally into the central nervous system with supplementation from systemic administration.

Synoviocytes are more sensitive than cartilage to the effects of minocycline and doxycycline on IL-1α and MMP-13-induced catabolic gene responses

The objective of this study was to determine the primary articular tissue target of doxycycline and minocycline. Synoviocytes-cartilage cocultures (n = 4) were treated with MMP-13 (25 ng/mL medium) or IL-1 (1.0 ng/mL medium) for 24 h. Doxycycline (4.3, 0.43, 0.043 microM) or minocycline (10, 1.0 or 0.1 microM) were then added and cultures were continued for 96 h. Cartilage and media were analyzed for GAG content. Quantitative PCR was used to measure cartilage MMP-3, MMP-13, aggrecan, COL2A1, ADAMTS-4, and ADAMTS-5 expression, and synoviocyte MMP-3, MMP-13, ADAMTS-4, and ADMATS-5 expression. Total and active MMP-3, MMP-13, and ADAMTS 4/5 enzymes were measured in culture medium. All concentrations of doxycycline and minocycline diminished GAG accumulation in the media. All concentrations of minocycline, but only the highest concentration of doxycycline decreased MMP-3 and MMP-13 expression in synoviocytes but not cartilage, and basal ADAMTS-5 mRNA levels in both synoviocytes and cartilage. Only minocycline decreased active MMP-13 protein in synoviocytes. In summary, the protective effects of tetracycline compounds are more pronounced in synoviocytes than cartilage, and following minocycline compared to doxycycline. Studies to determine the molecular mechanism of action of the tetracyclines in synoviocytes might lead to the design of targeted therapeutics for the treatment of OA or RA.

The antibiotics doxycycline and minocycline inhibit the inflammatory responses to the Lyme disease spirochete Borrelia burgdorferi.

Tetracyclines moderate inflammatory responses of various etiologies. We hypothesized that tetracyclines, in addition to their antimicrobial function, could exert control over the inflammation elicited by Borrelia burgdorferi. To model systemic effects, we used the human monocytic cell line THP-1; to model effects in the central nervous system, we used rhesus monkey brain astrocytes and microglia. Cells were stimulated with live or sonicated B. burgdorferi or with the lipoprotein outer surface protein A in the presence of increasing concentrations of doxycycline or minocycline. Both antibiotics significantly reduced the production of tumor necrosis factor-alpha, interleukin (IL)-6, and IL-8 in a dose-dependent manner in all cell types. Microarray analyses of the effect of doxycycline on gene transcription in spirochete-stimulated monocytes revealed that the NFKB and CHUK (alias, IKKA) genes were down-regulated. Functionally, phosphorylation of IkappaBalpha and binding of NF-kappaB to target DNA were both reduced in these cells. Our results suggest that tetracyclines may have a dual therapeutic effect in Lyme disease.

Rapid Determination of Minocycline in Pharmaceutical Formulations and Human Urine/Serum Samples Based on the Minocycline-Europium-Sodium Dodecylbenzene Sulfonate Luminescence System

A new luminescence method based on the minocycline (MNC)-europium (Eu3+)-sodium dodecylbenzene sulfonate (SDBS) system was developed for the determination of MNC. SDBS formed a ternary complex with MNC-Eu3+ and significantly enhanced the luminescence intensity of Eu3+. The enhanced luminescence intensity showed a good linear relationship with the concentration of MNC over the range of 4.0 × 10−7 ∼ 1.0 × 10−5 mol L−1 with a detection limit of 2.0 × 10−8 mol L−1. This method is rapid and sensitive, and has been successfully applied for the determination of MNC in capsules and human urine/serum samples. The luminescence mechanism is also studied.