Development, validation, and clinical application of a UPLC-MS/MS method for omadacycline determination in human serum.

BACKGROUND: Omadacycline is the first aminomethyl-tetracycline variety to successfully enter clinical applications. To support regular therapeutic drug monitoring (TDM) in clinical practice, an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method was developed that would allow omadacycline quantification in human serum. METHODS: Proteins were precipitated from serum samples using methanol. Tigecycline was used as the internal standard. Mobile phase A was formic acid in water (0.1% v/v) and mobile phase B was methanol. UPLC-MS/MS was performed for analyte separation using a gradient elution program at a flow rate of 0.3 mL/min and a total run time of 5 min. The chromatography column was a ZORBAX PRHD SB-Aq (3 × 50 mm, 1.8 µm, Agilent, USA). The multiple reaction monitoring transitions at m/z = 557.4/470.3 and 586.5/513.3 were selected for omadacycline and tigecycline in the positive mode, respectively. RESULTS: The validated curve ranges were 0.5-25.0 µg/mL. This method exhibited acceptable selectivity, matrix effects, and recovery. The inter- and intra-run accuracies ranged from 93.5% to 114.8%, and the inter- and intra-run precisions were between 1.29% and 5.55%. CONCLUSIONS: The LC-MS/MS method provided a simple, specific, and rapid quantification of omadacycline in the serum of patients with pulmonary infection.

Concentration-dependent photoluminescence carbon dots for visual recognition and detection of three tetracyclines.

Concentration-dependent photoluminescence carbon dots (CDs) have been successfully synthesized through the one-step hydrothermal treatment of o-phthalic acid and ethylenediamine. The CDs possessed higher fluorescence quantum yield, up to 39.22%, exhibiting distinguished optical property, water solubility, and stability. The CDs that emit strong blue-green fluorescence can visually identify and determine tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). TC quenched the fluorescence of CDs at 500 nm owing to the inner filter effect; OTC behaved similarly, but the emission wavelength of CDs was red-shifted to 515 nm. Inversely, once CTC was introduced to CDs solution, the fluorescence increased and the emission peak was blue-shifted to 450 nm. Bandgap transition and electrostatic interaction were proposed to be the mechanisms for the detection of OTC and CTC by CDs. Wide linear relationships were established for TC, OTC, and CTC with the limits of detection to be 50 nM, 36 nM, and 373 nM, respectively. Furthermore, the nanoscale probe constructed by this system has been applied to detect tetracyclines (TCs) in complex samples with satisfying recoveries (93.2-114%) and was designed as a portable test strip sensor for visually on-site TCs of honey sample screening. Accordingly, the preparation process of the nano fluorescent probe is simple and environmentally friendly, and the probe has a specific recognition ability for tetracyclines. The synthesized CDs in this work provide a new orientation for fast, effective, and visual real-time detection of tetracycline in actual samples.

Effect of surfactant coating of Fe3O4 nanoparticles on magnetic dispersive micro-solid phase extraction of tetracyclines from human serum.

A procedure for separation and preconcentration of tetracyclines from human serum samples involving magnetic dispersive micro-solid phase extraction was proposed. The extraction efficiency of different tetracyclines was improved with the use of the surfactant coated Fe3O4 magnetic nanoparticles. Sorption mechanism was presented, and the potential use of magnetic Fe3O4 nanoparticles coated with different surfactants for tetracyclines adsorption was demonstrated for the first time. The procedure involved nanoparticle floating in a liquid sample phase for analyte extraction followed by elution and determination by high performance liquid chromatography with diode array detection. Influence of the main involved parameters was studied, the system was dimensioned accordingly. The analytical curves were linear in the ranges of 0.25-10 mg L-1 for tetracycline and 0.10-10 mg L-1 for oxytetracycline or doxycycline. Limits of detection were estimated (IUPAC, 3 concept) as 0.08 mg L-1 for tetracycline, and 0.03 mg L-1 for oxytetracycline or doxycycline. The proposed procedure proved to be fast (10 min), simple (two stages), inexpensive (10 mg of nanoparticles) and was applied to human serum samples. Unlike previously synthesized nanoparticles for tetracyclines separation, the surfactant-coated Fe3O4 nanoparticles can be easily prepared with widely available and low-cost reagents. Moreover, elution of the analytes was accomplished in absence of organic solvents by an aqueous chelating agent solution.

Sarecycline Review.

Objective: Sarecycline is a new oral tetracycline antibiotic recently approved by the US Food and Drug Administration. The aim of this article was to evaluate the data from published clinical trials of sarecycline in the treatment of acne, review the drug's pharmacology, and understand how this new medication may apply to clinical practice. Data Sources: A systematic literature review was performed using the terms sarecycline (Seysara), P005672, and WC-3035 in the MEDLINE and EMBASE databases. ClinicalTrials.gov was searched to identify ongoing or nonpublished studies. Study Selection and Data Extraction: Articles in English between January 2000 and April 2019 relating to clinical trials, pharmacology, safety, and microbiological profile were evaluated. Data Synthesis: In a phase 3 clinical trial (SC1401), absolute change from baseline in facial inflammatory lesion count at week 12 was -15.3 for the sarecycline arm and -10.1 for placebo (P < 0.01). In another phase 3 clinical trial (SC1402), the absolute change in this category was -15.7 for sarecycline and -10.7 for placebo (P < 0.01). Mean percentage change in facial inflammatory lesion count was higher in the sarecycline group than in the placebo group in both studies (P < 0.01). Relevance to Patient Care and Clinical Practice: The 1.5-mg/kg sarecycline dose has efficacy in reducing inflammatory lesions, is well tolerated, and has more targeted antimicrobial activity, which may help reduce the risk of developing antibiotic resistance. Conclusions: This novel, once-daily treatment may represent a useful treatment for patients with moderate to severe acne.

Omadacycline: A Review of the Clinical Pharmacokinetics and Pharmacodynamics.

Omadacycline is a novel aminomethylcycline antibiotic (antibacterial). Omadacycline has had chemical structure modifications at the C9 and C7 positions of the core tetracycline rings that allow stability in the efflux pump and ribosomal protection protein mechanisms of tetracycline resistance. The systemic exposure (i.e., maximum plasma concentrations [Cmax] and area under the plasma concentration-time curve [AUC]) after intravenous (IV) administration were linear and predictable over the dose range of 25 and 600 mg in healthy subjects. The oral bioavailability of omadacycline was 34.5% under fasted conditions (no food intake 6 h before and 4 h after dosing). Both AUC and Cmax values significantly decreased (41-61%) when a high-fat meal, with and without dairy, were administered 2 h before oral dosing of omadacycline. Similar to other tetracyclines, it is advisable to avoid concurrent administration of divalent- or trivalent cation-containing products (e.g., antacids and iron-containing preparations) for at least 4 h after oral administration of omadacycline. Omadacycline has a large volume of distribution (190 L) and low plasma protein binding (21.3%) that was concentration independent. Systemic exposure of omadacycline in epithelial lining fluid (ELF) and alveolar macrophages was greater than in plasma in healthy adult subjects. Omadacycline is excreted unchanged in the feces (81.1%) and urine (14.4%), and has a low potential for drug-drug interactions since it was not a substrate, inhibitor, or inducer of major cytochrome-metabolizing enzymes or organic anion transporters (OATs). No clinically significant differences in the pharmacokinetics of omadacycline have been observed for age, sex, and renal or hepatic impairment. Pharmacokinetic-pharmacodynamic studies have confirmed that the AUC from time zero to 24 h (AUC24)/minimum inhibitory concentration (MIC) ratio was the best index for correlating unbound plasma and total-drug ELF concentrations with the efficacy of omadacycline. A population pharmacokinetic model was developed with data from healthy subjects and infected patients and used to establish interpretive criteria for in vitro susceptibility testing and dosing regimens of omadacycline for treating acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia.

Challenges in the bioanalysis of tetracyclines: Epimerisation and chelation with metals.

Tetracyclines (TCs) are important broad spectrum antibiotics which are active against gram-positive and gram-negative bacteria. TCs readily form epimers, especially under weakly acidic conditions. The epimers are reported to have different antibacterial and toxicological properties and pose a significant challenge for selective bioanalysis, being isobaric with the parent drug and possessing very similar physicochemical properties. During the development, validation and use of bioanalytical methods for minocycline in plasma, urine and renal dialysate there were two unexpected findings. The first was that the analyte and the internal standard, tetracycline, were found to be unexpectedly stable and resistant towards epimerisation in the presence of the deproteinising agent, trichloroacetic acid (TCA). The second was that keeping minocycline spiked dialysate in a freezer led to significant losses which were worse for low concentrations at lower storage temperatures. Investigations into the stability of tetracycline, minocycline, omadacycline and tigecycline in aqueous acidic solutions, under typical analytical conditions, revealed that TCA acts as a stabiliser with respect to both epimerisation and other degradation pathways for these TCs. This gives the rarely used TCA a significant advantage over the commonly used deproteinising agents such as acetonitrile when analysing TCs. Studies of the recoveries of tetracycline and tigecycline from frozen renal dialysis buffer demonstrated similar losses to those for minocycline. These were assigned to deposition of insoluble Mg2+ or Ca2+ complexes on freezing, as pre-storage treatment of the samples by incubation in EDTA coated tubes at room temperature prevented the losses. Minocycline was stable in renal dialysis buffer samples when frozen, for up to ca. 3 months, when this treatment was employed. The TCs were analysed using LC-MS/MS based methods developed in-house using the assay that was originally developed for minocycline in plasma, urine and dialysate as a template.

A highly fluorescent lanthanide metal-organic framework as dual-mode visual sensor for berberine hydrochloride and tetracycline.

A microscale highly fluorescent Eu metal-organic framework (Eu-MOF) was synthesized with terephthalic acid and 1H-1,2,4-triazole-3,5-diamine by one-pot hydrothermal method. And it was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, powder X-ray diffraction, fluorescence spectroscopy, thermogravimetric analysis, and energy dispersive X-ray mapping. The prepared Eu-MOF has high quantum yield of 30.99%, excellent water dispersibility, good fluorescence stability, and favorable thermal stability. Based on the distinctly different fluorescence responses of different emission, the prepared Eu-MOF was used as dual-mode visual sensor for the sensitive detection of berberine hydrochloride and tetracycline. The limits of detection are 78 nM and 17 nM, respectively. The sensing mechanism was also discussed. Moreover, a filter paper sensor has been designed for sensing tetracycline with a notable fluorescence color change from blue to red. The prepared Eu-MOF is promising to be developed as a multi-mode luminescent sensor for visual detection in biochemical analysis. Graphical abstract Illustration of the synthesis of Eu-MOF and its sensing applications for berberine hydrochloride and tetracycline.

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

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

Comparison of Omadacycline and Tigecycline Pharmacokinetics in the Plasma, Epithelial Lining Fluid, and Alveolar Cells of Healthy Adult Subjects.

The steady-state concentrations of omadacycline and tigecycline in the plasma, epithelial lining fluid (ELF), and alveolar cells (AC) of 58 healthy adult subjects were obtained. Subjects were administered either omadacycline at 100 mg intravenously (i.v.) every 12 h for two doses followed by 100 mg i.v. every 24 h for three doses or tigecycline at an initial dose of 100 mg i.v. followed by 50 mg i.v. every 12 h for six doses. A bronchoscopy and bronchoalveolar lavage were performed once in each subject following the start of the fifth dose of omadacycline at 0.5, 1, 2, 4, 8, 12, or 24 h and after the start of the seventh dose of tigecycline at 2, 4, 6, or 12 h. The value of the area under the concentration-time curve (AUC) from time zero to 24 h postdosing (AUC0-24) (based on mean concentrations) in ELF and the ratio of the ELF to total plasma omadacycline concentration based on AUC0-24 values were 17.23 mg · h/liter and 1.47, respectively. The AUC0-24 value in AC was 302.46 mg · h/liter, and the ratio of the AC to total plasma omadacycline concentration was 25.8. In comparison, the values of the AUC from time zero to 12 h postdosing (AUC0-12) based on the mean concentrations of tigecycline in ELF and AC were 3.16 and 38.50 mg · h/liter, respectively. The ratio of the ELF and AC to total plasma concentrations of tigecycline based on AUC0-12 values were 1.71 and 20.8, respectively. The pharmacokinetic advantages of higher and sustained concentrations of omadacycline compared to those of tigecycline in plasma, ELF, and AC suggest that omadacycline is a promising antibacterial agent for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens.

Pharmacokinetics, Distribution, Metabolism, and Excretion of Omadacycline following a Single Intravenous or Oral Dose of 14C-Omadacycline in Rats.

The absorption, distribution, metabolism, and excretion (ADME) of omadacycline, a first-in-class aminomethylcycline antibiotic with a broad spectrum of activity against Gram-positive, Gram-negative, anaerobic, and atypical bacteria, were evaluated in rats. Tissue distribution was investigated by quantitative whole-body autoradiography in male Long-Evans Hooded (LEH) rats. Following an intravenous (i.v.) dose of 5 mg/kg of body weight, radioactivity widely and rapidly distributed into most tissues. The highest tissue-to-blood concentration ratios (t/b) were observed in bone mineral, thyroid gland, and Harderian gland at 24 h post-i.v. dose. There was no evidence of stable accumulation in uveal tract tissue, suggesting the absence of a stable binding interaction with melanin. Following a 90 mg/kg oral dose in LEH rats, the highest t/b were observed in bone mineral, Harderian gland, liver, spleen, and salivary gland. The plasma protein binding levels were 26% in the rat and 15% to 21% in other species. Omadacycline plasma clearance was 1.2 liters/h/kg, and its half-life was 4.6 h; the steady-state volume of distribution (Vss) was 6.89 liters/kg. Major circulating components in plasma were intact omadacycline and its epimer. Consistent with observations in human, approximately 80% of the dose was excreted into the feces as unchanged omadacycline after i.v. administration. Fecal excretion was primarily the result of biliary excretion (∼40%) and direct gastrointestinal secretion (∼30%). However, urinary excretion (∼30%) was equally prominent after i.v. dosing.

Designed miniaturization of microfluidic biosensor platforms using the stop-flow technique.

Here, we present a novel approach to increase the degree of miniaturization as well as the sensitivity of biosensor platforms by the optimization of microfluidic stop-flow techniques independent of the applied detection technique (e.g. electrochemical or optical). The readout of the labeled bioassays, immobilized in a microfluidic channel, under stop-flow conditions leads to a rectangular shaped peak signal. Data evaluation using the peak height allows for a high level miniaturization of the channel geometries. To study the main advantages and limitations of this method by numerical simulations, a universally applicable model system is introduced for the first time. Consequently, proof-of-principle experiments were successfully performed with standard and miniaturized versions of an electrochemical biosensor platform utilizing a repressor protein-based assay for tetracycline antibiotics. Herein, the measured current peak heights are the same despite the sextuple reduction of the channel dimensions. Thus, this results in a 22-fold signal amplification compared to the constant flow measurements in the case of the miniaturized version.

Randomized, Open-Label Study of the Pharmacokinetics and Safety of Oral and Intravenous Administration of Omadacycline to Healthy Subjects.

Omadacycline is a first-in-class aminomethylcycline antibiotic with microbiological activity against Gram-positive and Gram-negative aerobes and anaerobes and atypical bacteria that is being developed for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). The bioavailability of a phase 3 tablet formulation relative to that obtained via intravenous (i.v.) administration (and of other oral formulations relative to that of the phase 3 tablet) was investigated in an open-label, randomized, four-period, crossover study with healthy subjects age 18 to 50 years. Subjects received omadacycline at 100 mg i.v., 300 mg orally as two different tablet formulations with different dissolution profiles, and 300 mg as an oral solution. Plasma omadacycline concentrations were determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Twenty of 24 subjects completed all treatment periods. The two tablet formulations produced equivalent total exposures. The phase 3 tablet produced an exposure equivalent to that of the 100-mg i.v. dose, with a geometric mean ratio (90% confidence intervals [CI]) for area under the concentration-time curve from 0 h to infinity [AUC∞]) of 1.00 (0.93, 1.07). The absolute bioavailability of the tablets was approximately 34.5%. Intersubject variability was consistent among the oral formulations (∼20 to 25%). Single oral and i.v. doses of omadacycline were well tolerated; three subjects experienced mild adverse events (dizziness, nausea, and vomiting) that resolved without intervention. A 300-mg dose of the tablet formulation of omadacycline intended for use in phase 3 studies produced a total exposure equivalent to that of a 100-mg i.v. dose.

Eravacycline Pharmacokinetics and Challenges in Defining Humanized Exposure In Vivo.

We assessed the pharmacokinetic profile of eravacycline, a novel antibiotic of the tetracycline class, and determined the dose in an immunocompetent murine thigh infection model that would provide free-drug exposure similar to that observed in humans after the administration of 1 mg/kg intravenously (i.v.) every 12 h (q12h). Eravacycline demonstrated a nonlinear protein-binding profile. The 2.5-mg/kg i.v. q12h dose in mice resulted in an area under the concentration-time curve for the free, unbound fraction of the drug of 1.64 mg · h/liter, which closely resembles the human exposure level.

A novel M-shape electrochemical aptasensor for ultrasensitive detection of tetracyclines.

Analytical techniques for detection and quantitation of tetracyclines in food products are greatly in demand. In this study, a novel electrochemical aptasensor was designed for ultrasensitive and selective detection of tetracyclines, based on M-shape structure of aptamer (Apt)-complementary strands of aptamer (CSs) complex, exonuclease I (Exo I) and gold electrode. The aptasensor was developed to make a noticeable electrochemical difference in the absence and presence of tetracycline. In the absence of tetracycline, the M-shape structure, which acts as a gate and barrier for the access of redox probe to the surface of gold electrode remains intact, leading to a weak electrochemical signal. Upon addition of tetracycline, Apt leaves CSs, resulting in disassembly of M-shape structure and following the addition of Exo I, a strong electrochemical signal was observed. The developed analytical assay indicated high selectivity toward tetracycline with a limit of detection (LOD) as low as 450 pM. Moreover, the designed aptasensor was effectively used for the detection of tetracycline in milk and serum samples with LODs of 740 and 710 pM, respectively.

Phase I, open-label, safety and pharmacokinetic study to assess bronchopulmonary disposition of intravenous eravacycline in healthy men and women.

This study evaluated the pulmonary disposition of eravacycline in 20 healthy adult volunteers receiving 1.0 mg of eravacycline/kg intravenously every 12 h for a total of seven doses over 4 days. Plasma samples were collected at 0, 1, 2, 4, 6, and 12 h on day 4, with each subject randomized to undergo a single bronchoalveolar lavage (BAL) at 2, 4, 6, or 12 h. Drug concentrations in plasma, BAL fluid, and alveolar macrophages (AM) were determined by liquid chromatography-tandem mass spectrometry, and the urea correction method was used to calculate epithelial lining fluid (ELF) concentrations. Pharmacokinetic parameters were estimated by noncompartmental methods. Penetration for ELF and AM was calculated by using a ratio of the area under the concentration time curve (AUC0-12) for each respective parameter against free drug AUC (fAUC0-12) in plasma. The total AUC0-12 in plasma was 4.56±0.94 µg·h/ml with a mean fAUC0-12 of 0.77±0.14 µg·h/ml. The eravacycline concentrations in ELF and AM at 2, 4, 6, and 12 h were means±the standard deviations (µg/ml) of 0.70±0.30, 0.57±0.20, 0.34±0.16, and 0.25±0.13 with a penetration ratio of 6.44 and 8.25±4.55, 5.15±1.25, 1.77±0.64, and 1.42±1.45 with a penetration ratio of 51.63, respectively. The eravacycline concentrations in the ELF and AM achieved greater levels than plasma by 6- and 50-fold, respectively, supporting further study of eravacycline for patients with respiratory infections.

Sensitive determination of four tetracycline antibiotics in pig plasma by field-amplified sample stacking open-tubular capillary electrochromatography with dimethylethanolamine aminated polychloromethyl styrene nano-latex coated capillary column.

This paper described the preparation and application of a new dimethylethanolamine aminated polychloromethyl styrene nano-latex (DMEAPL) coated capillary column (ccc-DMEAPL) in the determination of four tetracycline antibiotics (TCA) including tetracycline (TC), oxytetracycline (OTC), doxycycline (DC) and chlorotetracycline (CTC) in pig plasma. The ccc-DMEAPL column was characterized with steady EOF values of ca. 1.5-5.2×10(-5)cm(2)/Vs at pH 1.8-6.3. The optimized conditions for field-amplified sample stacking open-tubular capillary electrochromatography (FASS-OT-CEC) were as following: background electrolyte, 10mmol/L Na2HPO4+15mmol/L citric acid (pH 3.2); ccc-DMEAPL, 50µm i.d.×50cm (effective length 41.5cm), separation voltage, 18kV; column temperature, 25°C; UV detection wavelength, 270nm; water-plug injection: 30mbar×10s; sample electrokinetic injection, 10kV×20s. The four TCA were extracted with the solution of 10mmol/L Na2HPO4+15mmol/L citric acid+4g/L EDTA-2Na (pH 3.2). The FASS-OT-CEC method was validated in terms of linearity, sensitivity, selectivity, precision and accuracy. The LODs ranged from 3 to 7ng/mL, the recoveries for the four TCA were all more than 80%. The developed method was successfully applied for the determination of TCs in the actual pig plasma samples.

Improved nonaqueous capillary electrophoresis for tetracyclines at subparts per billion level.

A NACE method with laser-induced fluorescence detection was modified for sensitive detection of 4 tetracyclines (TCs) in biological samples and feeds. The changes in injection mode, injection times, id of capillary, excitation wavelength, and the use of surfactant and sample stacking technique all contributed to improved LODs of TCs to sub-ng/mL level. With the optimized conditions, the instrumental LODs could reach 1.33 ng/mL for chlorotetracycline (CTC) and 13.3 ng/mL for TC, oxytetracycline (OTC), and doxycycline (DC), an improvement of 10-100-fold over past studies. A simple SPE procedure was further developed for the extraction and concentration of TCs in plasma, urine, feed, and milk. Taken together, the instrumental LOD and feasible SPE concentration factors the overall LODs for CTC could reach 65 pg/mL in feed and milk and 260 pg/mL in plasma and urine. Detection limits for TC, OTC, and DC at sub-ng/mL level were also achieved. The modified CE-LIF method was found to be less complicated and more sensitive than the best current methods using UV or LIF detection, and has been applied successfully to assess oral absorption of DC in swine and chickens and to confirm suspected TC-positive bovine serum samples.

Pharmacokinetics and pharmacodynamics of the tetracyclines including glycylcyclines.

The pharmacokinetics of tetracyclines and glycylcyclines are described in three groups. Group 1, the oldest group, represented by tetracycline, oxytetracycline, chlortetracycline, demeclocycline, lymecycline, methacycline and rolitetracycline is characterized by poor absorption after food. Group 2, represented by doxycycline and minocycline, is more reliably absorbed orally, while group 3, represented by the glycylcycline tigecycline, is injectable only, with an improved antibacterial spectrum compared with the tetracyclines. Though incompletely understood, the pharmacodynamic properties of the tetracyclines and glycylcyclines are summarized.

A sensitive method for determination of COL-3, a chemically modified tetracycline, in human plasma using high-performance liquid chromatography and ultraviolet detection.

COL-3, 6-deoxy-6-desmethyl-4-desdimethylamino-tetracycline, is a matrix metalloproteinase inhibitor currently in clinical development. A HPLC-UV method to quantitate COL-3 in human plasma was developed. COL-3 was extracted from plasma using solid-phase extraction cartridges. COL-3 is separated on a Waters Symmetry Shield RP8 (3.9 mm x150 mm, 5 microm) column with EDTA (0.001 M) in sodium acetate (0.01 M, pH 3.5)-acetonitrile mobile phase using a gradient profile at a flow rate of 1 ml/min for 22 min. Carryover was eliminated by using an extended needle wash of methanol:acetonitrile:dichloromethane (1:1:1, v/v/v). Detection of COL-3 and the internal standard, chrysin, was observed at 350 nm. COL-3 and chrysin elute at 8.9 and 9.9 min, respectively. The lower limit of quantitation in human plasma of COL-3 was 75 ng/ml, linearity was observed from 75 to 10,000 ng/ml. A 30,000 ng/ml sample that was diluted 1:50 with plasma was accurately quantitated. This method is rapid, widely applicable, and suitable for quantifying COL-3 in patient samples enabling further clinical pharmacology characterization of COL-3.