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.

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.

Distribution of systemic ciprofloxacin and doxycycline to gingiva and gingival crevicular fluid

BACKGROUND

Systemic fluoroquinolones and tetracyclines reach steady-state levels in gingival crevicular fluid (GCF) that are several-fold higher than their levels in serum. The mechanism by which this occurs is unclear, but gingival fibroblasts are known to accumulate these agents. Uptake by fibroblasts could enhance their distribution to gingiva. To test this hypothesis, steady-state levels of these agents were assayed in serum, gingival connective tissue (GCT), and GCF.

METHODS

Healthy subjects who needed resective periodontal surgery participated in the study. Approximately 78 hours prior to the surgical appointment, each subject began a 3-day regimen of ciprofloxacin or doxycycline. At the surgical appointment (scheduled approximately 6 hours after the last dose), samples of blood and GCT were collected. GCF samples were collected on paper strips and measured with an electronic device. Samples were extracted and analyzed by high performance liquid chromatography.

RESULTS

Mean ciprofloxacin levels in serum, GCT, and GCF were 0.40 microg/ml, 1.38 microg/g, and 1.66 microg/ml, respectively (P<0.001, N=9). For doxycycline, these levels were 1.11 microg/ml, 2.03 microg/g, and 2.41 microg/ml, respectively (P=0.002, N=8). For both agents, the GCT and GCF levels were significantly higher than serum levels (P<0.05), but not significantly different from each other.

CONCLUSIONS

Our findings suggest that fibroblasts could play an important role in the distribution of fluoroquinolones and tetracyclines to the gingiva. By accumulating these agents in GCT, fibroblasts could contribute to the relatively high levels they attain in GCF.

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.

Quantification of 6-deoxy-6-demethyl-4-dedimethylaminotetracycline (COL-3) in human plasma using liquid chromatography coupled with electrospray ionization tandem mass spectrometry

An accurate and reliable liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method has been developed and validated for the determination of 6-deoxy-6-demethyl-4-dedimethylaminotetracycline (COL-3) in human plasma. The assay used chrysin as an internal standard (I.S.). The analyte and the I.S. were extracted from acidified plasma by methyl-t-butyl ether. Separation was achieved on a YMCbasic column using acetonitrile-water-formic acid mobile phase. The MS-MS detection was by monitoring fragmentation 372.1-->326.2 (m/z) for COL-3 and 255.1-->153.1 (m/z) for the I.S. on a Sciex API 365 using a Turbo Ionspray in positive ion mode. The retention times were approximately 1.7 min for COL-3 and 1.8 min for the I.S. The validated dynamic range was 0.03-10.0 microg/ml using 0.25-ml plasma with correlation coefficients of >or=0.9985. The precision and accuracy for the calibration standards (n=3) were RSD<or=5.3% and RE<or=4.0%. The precision and accuracy for low-, mid- and high-concentration QC samples were RSD<or=2.8% and RE<or=5.1% for intra-batch (n=6) and RSD<or=2.3% and RE<o=3.4% for inter-batch (n=18), respectively. The extraction recoveries were 99% for COL-3 and 93% for I.S. The results showed that the quality control plasma samples were stable for at least 1 year if stored at approximately -70 degrees C. The presented method is simple, fast, specific and rugged. This method has been successfully used for supporting human pharmacokinetic studies.

Evidence for dissolution rate-limited absorption of COL-3, a matrix metalloproteinase inhibitor, leading to the irregular absorption profile in rats after oral administration

PURPOSE

This study was undertaken to elucidate the underlying mechanism of the irregular absorption profiles of COL-3, a matrix metalloproteinase inhibitor, with a double- or plateau-peak concentration after a single oral dose administration of COL-3 suspension to rats.

METHODS

The gastrointestinal absorption profiles of COL-3 in rats were assessed by comparing serum drug concentration curves after the following various modes of drug administration: oral and intraduodenal doses, oral doses of COL-3 in fine and coarse suspensions, intraduodenal dosing to the bile-duct intact and cannulated (BDC) rats, and oral doses with and without food. In addition, the biliary excretion of COL-3 in the BDC rats was examined.

RESULTS

Neither variable gastric emptying nor enterohepatic recycling was the source of the irregular gastrointestinal absorption of COL-3 in rats. Reduction in particle size, presence of food and endogenous bile emerged as the determinants of the oral absorption of COL-3 by enhancing the dissolution of the solid drug in the gastrointestinal fluids. Flip-flop of the absorption and elimination rate constants was noted only for COL-3 after intraduodenal administration of the coarse suspension to the BDC rats with the bile flow diverged out of the body.

CONCLUSIONS

Variability in dissolution rate-limited absorption was the main cause of the irregular absorption of COL-3 after oral administration of its solid dosage form.

Sensitive detection of tetracyclines using europium-sensitized fluorescence with EDTA as co-ligand and cetyltrimethylammonium chloride as surfactant

The determination of tetracyclines (TC) in aqueous solutions, based on europium-sensitized fluorescence, has been improved using EDTA as co-ligand and cetyltrimethylammonium chloride as surfactant. The method involves working in slightly alkaline solutions with the formation of a new chelate where the lanthanide ion is bound to the beta-diketone group. The method is about 6 times more sensitive than that with the Eu-TC-Triton system and LODs are 2.5 x 10(-10), 5 x 10(-10), 1.5 x 10(-9) and 2 x 10(-9) mol l-1 for TC, oxytetracycline, chlortetracycline and doxycycline, respectively. The method has been applied to the determination of TC in calf serum without sample pretreatment. The mean recovery was close to 102% and the lowest concentration attainable in serum samples was better than 0.1 microgram ml-1.

Enzyme-linked immunosorbent assay for screening the plasma residues of tetracycline antibiotics in pigs

The recommended therapeutic doses of three kinds of tetracyclines, oxytetracycline (OTC, withdrawal period, 10 days), chlortetracycline (CTC, withdrawal period, 5 days) and tetracycline (TC, withdrawal period, 5 days), were each administered to a group of 15 pigs. Blood was sampled before drug administration and during the withdrawal period. The concentration of tetracyclines in plasma, determined by semi-quantitative ELISA, was compared with that of internal standard (10 ppb as oxytetracycline). The absorbance ratio of internal standard to sample (B/Bs) was employed as an index to determine the tissue residues in pigs. All 45 plasma samples from nontreated pigs showed negative in the residue of any of three tetracycline antibiotics. OTC was detected in plasma of pigs treated until the 8th day, CTC until the 4th day, and TC was detected until the 3rd day of its withdrawal period. The present study showed that the semi-quantitative ELISA easily be adopted in predicting tissue residues for tetracycline antibiotics in live pigs.

Biodistribution of radiolabeled [(3)H] CMT-3 in rats

CMT-3 is a NON-ANTIMICROBIAL tetracycline (TC), chemically modified to enhance its collagenase-inhibitory property. This property is therapeutically useful in treating diseases such as periodontitis, cancer and arthritis. CMT-3 was labeled with tritium [(3)H] at Carbon 7. Four adult male Sprague-Dawley rats (350--400 g body weight) were gavaged once with a mixture of cold CMT-3 and [(3)H] CMT-3 (750 microCi). An additional four rats were gavaged for 2 days with cold CMT-3(15 mg/Kg/day) and on the third day the rats were gavaged with a mixture of cold and [(2)H] CMT-3 (750 microCi); and all 8 rats were placed in the metabolic cages. Blood samples were collected from the tail at multiple intervals from 1--14 hr after [(3)H] CMT-3 administration. At 14 hr, the rats were anesthetized, euthanized and various tissues including visceral organs were removed and weighed. The contents of GI tracts were emptied and added to the fecal pellets and weighed. The urine samples were collected and volume measured. Each tissue or organ was minced finely with scissors and 100 mg of tissue was digested in 1 ml of Tissue-solv (Packard Lab), for 4 hrs at 37 degrees C and each sample was diluted up to 10 ml of distilled water. A 100 microl aliquot was taken and diluted with an equal volume of glacial acetic acid, 10 ml of Atom-lite was added and counted for radioactivity in a liquid scintillation spectrometer. This biodistribution study revealed that over 14 hrs, 54% and 3% of [(3)H] CMT-3 were excreted in the feces and urine, respectively. The serum [(3)H] CMT-3 count reached its maximum value at about 12 hours. The tissues retained the CMTs as follow: muscle (23%); skin (2.41%); bone (1.72%); and the brain retained 0.21% of the label. The radioactive CMT-3 in the visceral organs is as follows: GI tract - its contents (8.9%); heart (0.41%), testis (0.41%); lungs >(0.16%); spleen (0.08%); liver (0.03%); kidneys > (0.02%).

A combination of subtherapeutic doses of chemically modified doxycycline (CMT-8) and a bisphosphonate (clodronate) inhibits bone loss in the ovariectomized rat: a dynamic histomorphometric and gene expression study

Recent studies have demonstrated that tetracyclines can reduce bone loss in the ovariectomized (OVX) rat model of osteoporosis. In the current study, a non-antimicrobial, chemically modified doxycycline (CMT-8), alone or in combination with a bisphosphonate (Clodronate), was evaluated in this model. Forty-two, 6month old, female rats were randomly assigned to the following groups, (6/ group): a) sham/vehicle, b) OVX/vehicle; c) OVX/1 mg/day CMT-8; d) OVX/2 mg/day CMT-8, e) OVX/1 mg/week Clodronate; and f) OVX/1 mg/day CMT-8 + 1 mg/week Clodronate, CMT-8 was administered by oral gavage, Clodronate injected S/C. Following sham surgery or OVX, the rats were treated for 90 days with CMT-8 or vehicle alone, injected at three different times with fluorochrome labels, the rats were sacrificed, and the tibiae excised for analysis by dynamic bone histomorphometry. Femurs were aseptically removed and analyzed for collagen, collagenase and osteopontin mRNAs by Northern and dot blot analysis. As expected, OVX decreased trabecular bone volume (BV/TV by 73.8% vs. sham p<.01), and also reduced trabecular thickness, numbers, and increased spacing. Bone loss in the OVX animals was partially prevented with either 2 mg/day CMT-8 or 1 mg/wk Clodronate (p<.01), while the 1 mg/day CMT-8 had no effect. Interestingly, the efficacy of the combination therapy of CMT-8 and Clodronate was significantly better than either treatment by itself, maintaining bone mass and structural indices at levels identical to sham values. OVX rats mRNA for collagen, collagenase and osteopontin were elevated indicating high-turnover bone loss. Only COMBO therapy significantly reduced the collagenase and osteopontin mRNA. In summary, CMT-8 mono-therapy (2 mg) alone partially inhibited bone loss in this animal model of osteoporosis. However, 1 mg/day (CMT-8) monotherapy had no effect on bone loss or bone mRNA levels and when combined with Clodronate, interacted to increase efficacy. Thus, a combination of a suboptimal dose of CMT-8 and a bisphosphonate appears to increase the amount of bone by suppressing resorption in a model of osteoporosis.

The lipophilicity, pharmacokinetics, and cellular uptake of different chemically-modified tetracyclines (CMTs)

CMTs are analogs of tetracyclines, which are chemically modified to eliminate their antimicrobial efficacy but which retain their inhibitory activity against matrix metalloproteinases. These compounds have been found to inhibit connective tissue breakdown in animal models of diseases such as periodontitis, arthritis and cancer. Because CMTs exhibit different in vivo efficacy in these various models of disease, the current study compared their pharmacokinetics and other properties as follows: Adult male Sprague-Dawley rats were administered by oral gavage a single dose of 5mg of different CMTs suspended in 1 ml 2% carboxymethyl-cellulose, and blood samples were collected from 1-48 hours after dosing. The sera were extracted, then analyzed by HPLC using a C-18 reverse-phase column. The results showed that the peak concentrations (C(max)) in rat sera 1-12 hours after oral administration of CMTs -1, -2,-3, -4,-5,-6,-7,-8 and doxycycline were 5.5, 0.7, 4.6, 6.2, 0.8, 0.7, 9.0 (note: the 3 peaks detected for CMT-7 were combined), 15.0 and 0.9 microg/ml, respectively. Their in vivo half-lives (t(1/2)) were 11, 5, 22, 11, 32, 15, 37, 38, and 17 hours, respectively. Of the anticollagenase CMTs tested, CMT-8 showed the greatest C(max) and t(1/2)values, followed by CMTs-3, -1, -4, and perhaps -7; CMTs-2, -5, and -6 exhibited much lower levels in serum. The relative lipophilicities of the 8 CMTs and doxycycline were tested by examining their extractability in octanol. The results showed that CMT-2, -5, and -6 had the lowest partition coefficients using this organic solvent, while CMT-3 was the most lipophilic. The lipophilicity of the different CMTs was also positively correlated (r(2)=0.767, P<0.05) to peak serum concentrations (C(max)), but not to their serum half-lives (r(2)=0.25,P=0.49). This property of the different CMTs was also found to be positively correlated to their ability to enter into human whole blood cells in vitro (r2=0.95, P<0.001). Since CMT-8, as well as CMTs-3 and -1, consistently exhibited the greatest in vivo efficacy in animal models of tissue breakdown, this may reflect, at least in part, their favorable pharmacokinetics and tissue uptake.

Concentration of 3 tetracyclines in plasma, gingival crevice fluid and saliva

BACKGROUND

Systemically-administered tetracyclines have been used widely for treatment of periodontal diseases with little understanding of their delivery characteristics to periodontal tissues. This study was designed to measure concentrations of 3 tetracyclines in gingival crevice fluid (GCF), plasma and saliva of following systemic administration.

METHOD

The concentration of tetracycline (TC), minocycline (MN) and doxycycline (DX) was measured in gingival crevice fluid (GCF), plasma and saliva of 20 subjects following single sequential standard oral systemic doses. Gingival crevice fluid concentration was measured at 4 sites (2 shallow and 2 deep) before administration, and at 1 h and 2 h following administration. Plasma and saliva concentrations were measured from in samples at the same time points. No antibacterial activity was detected before administration. The highest concentrations were measured 2 h after administration.

RESULTS

The average concentrations at 2 h were highest in plasma (TC = 1.02, MN=2.18, DX=2.35 microg/ml). Intermediate concentrations were measured in GCF (TC=0.61, MN= 1.49, DX= 1.65 microg/ml). Saliva concentrations (TC=0.09 MN=0.31, DX=0.47 microg/ml) were the lowest of the 3 fluids monitored. Data are presented indicating that the average GCF concentration of systemically administered tetracyclines is less than the that of plasma concentration. The concentration of tetracyclines in GCF was strongly associated with plasma concentration, indicating a primary role of drug absorption in the delivery of these systemically administered antibiotics to the site of action in periodontal therapy. The average GCF concentration in individuals varied widely (between 0 and 8 microg/ml) with approximately 50% of samples not achieving levels of 1 microg/ml.

CONCLUSION

These observations suggest that poor absorption of orally-administered tetracyclines in many individuals may account for much of the variability in clinical response to antibiotics observed in practice.

Administration of doxycycline hydrochloride via drinking water to turkeys under laboratory and field conditions

A series of experiments were carried out in order to determine doxycycline hydrochloride (DoxHCl) plasma levels in 6-wk-old turkeys medicated via drinking water containing DoxHCl at a concentration of 250 mg/L under laboratory and field conditions. Maximal plasma concentration (Cmax) values of 5.7 (+/-1.0) microgram/mL and 4.9 (+/-1.4) micrograms/mL obtained after DoxHCl administration during 2 and 7 d, respectively, were not significantly different. A significant difference was found between the area under the plasma concentration-time profile, calculated between 0 and 168 h (AUC(0-168)), Cmax, and the minimal plasma concentration (Cmin) values obtained after medication with a DoxHCl solution at a concentration of 250 mg/L (431.9 +/- 96.6 micrograms.h/mL, 4.9 +/- 1.4 micrograms/mL and 0.7 +/- 0.3 microgram/mL) and after medication with a DoxHCl solution at a concentration of 750 mg/L (1,176.5 +/- 201.8 micrograms.h/mL, 12.5 +/- 2.7 micrograms/mL and 2.9 +/- 0.4 micrograms/mL), respectively. The increase in body weight was also significantly higher for turkeys medicated with a DoxHCl solution at a concentration of 750 mg/L (83.7 g/d) than for the lower concentration (35.6 g/d). The DoxHCl solution uptake significantly decreased with the increase of DoxHCl concentration. A Cmax value of 1.7 +/- 0.6 micrograms/mL and a Cmin value of 0.5 +/- 0.1 microgram/mL were observed during the field experiment. Water consumption under laboratory conditions was followed for tap water (70 +/- 50 mL/kg.d) and for a DoxHCl solution at a concentration of 250 mg/L supplemented with 1 g anhydrous citric acid/L (119 +/- 6 mL/kg.d) and revealed to be not significantly different. The variability was significantly higher for tap water than for the DoxHCl solution. The stability of the DoxHCl solution containing 1 g citric acid/L over 24 h was 99% expressed as the percentage of the initial concentration.

Use of metal complexation in non-aqueous capillary electrophoresis systems for the separation and improved detection of tetracyclines

Metal complexation in non-aqueous capillary electrophoresis systems was evaluated for the separation and improved detection of tetracycline antibiotics using laser-induced fluorescence detection. It was found that three factors were important for the choice of complexing agent: (i) it should be soluble in the organic solvent used for the separation, (ii) it should have a sufficient fast complexing rate so as not to invalidate the electrophoretic separation and, (iii) it should give a large increase in the fluorescence intensity. Mg2+ ions were found to be the most suitable ions for the separation of the tetracyclines as the acetate salt of magnesium is very soluble in organic solvents and only a relatively low current was generated during electrophoresis making it possible to use high concentrations of the complexing metal ion. Metal complexation strongly intensified the fluorescence of tetracyclines and all organic solvents investigated further intensified the fluorescence, e.g. dimethylformamide improved the fluorescence of the oxytetracycline metal complex by a factor of 34 compared to water. However, magnesium acetate was not sufficiently soluble in dimethylformamide and therefore N-methylformamide, improving the fluorescence intensity by only a factor of 9, was used. It was demonstrated that the method can be used for the detection of tetracyclines at the ppb level in milk and plasma.

Rapid determination of tetracycline antibiotics in serum by reversed-phase high-performance liquid chromatography with fluorescence detection

A rapid and accurate determination of tetracycline antibiotics in human serum by reversed-phase high-performance liquid chromatography with fluorescence detection has been developed, based on protein precipitation in serum. Various reagents for precipitation were investigated, and 24% trichloroacetic acid in methanolic solution gave the maximum recovery (at least 94.3%) and interference-free chromatograms of different three tetracyclines. At a concentration of 0.5 micrograms/ml, the precision (relative standard deviation) ranged from 1.12 to 1.94%. In the range 0.04-10.0 micrograms/ml for oxytetracycline and chlorotetracycline and 0.01-10.0 micrograms/ml for tetracycline, linear responses were observed. The detection limits of this method were 10-35 ng/ml for all three antibiotics. The proposed method was applied to the determination of serum concentrations in subjects receiving tetracycline antibiotics.

Spectrofluorimetric determination of tetracycline and anhydrotetracycline in serum and urine

A spectrofluorimetric method, involving alkaline degradation and formation of a magnesium complex, is described for the determination of tetracycline (TC) and anhydrotetracycline (ATC) in their mixed solution. Tetracycline is degraded and determined in alkaline solution. This treatment of ATC produces almost no fluorescence, but a fluorescent magnesium complex forms at pH 7.5. Several synthetic samples of TC and ATC, with TC:ATC ratios ranging from 50:1 to 1:50, were analysed. The recoveries of TC and ATC are about 71-76 and 61-63% in serum, respectively, and are all about 100% in urine.

In vitro and in vivo characterization of novel 8-methoxy derivatives of chlortetracycline

The in vitro activities of three new 8-methoxychlortetracyclines, Sch 36969, 33256 and 34164 were compared to tetracycline, minocycline and doxycycline. Against aerobic Gram-negative rods Sch 36969 had a geometric mean MIC (GMM) of 4.2 micrograms/ml, about 8-fold more potent than Sch 33256, and similar to all the other compounds. Sch 36969 also had good activity against methicillin-resistant (GMM, 0.21 micrograms/ml) and -susceptible Staphylococci (GMM, 0.14 micrograms/ml), Streptococci (GMM, 0.06 micrograms/ml), and most anaerobic bacteria (GMM, less than 0.5 micrograms/ml). In general, Sch 36969 was similar to, or more potent than, all the other compounds tested. Serum levels of Sch 36969 in squirrel monkeys were 4-fold lower (AUC, 4.5 micrograms.hours/ml) than those of chlortetracycline (AUC, 16.1 micrograms.hours/ml). In mouse protection tests (PD50s) against various strains of bacteria, Sch 36969 was similar in activity to tetracycline, but up to 6-fold less active than chlortetracycline. The structure activity relationships for these new chlortetracyclines are described.

Simultaneous liquid chromatographic determination of some tetracyclines in serum

A sensitive liquid chromatographic method has been developed for the simultaneous determination of oxytetracycline, minocycline, tetracycline, and doxycycline in serum. A serum sample is vortex-mixed with a solution of mobile phase for tetracyclines and 2% (v/v) phosphoric acid. The mixture is filtered using a 30,000 molecular weight cutoff microseparation tube which separates high-molecular-weight solutes following low-speed centrifugation. Tetracyclines are separated from other serum components by reverse phase liquid chromatography (LC) with buffered methanol mobile phase. Ultraviolet absorbance of the column effluent is monitored at 267 nm. Concentrations as low as 0.2 micrograms/mL of tetracyclines in serum are quantitatable, with recoveries from 76.2 to 102.6% and coefficients of variation from 2.69 to 5.36%. The method has been tested in bovine, porcine, equine, caprine, ovine, canine, feline, and avian (turkey) serum.

Determination of tetracycline antibiotics in tissues and blood serum of cattle and swine by high-performance liquid chromatography

Tissue homogenates and blood serum were acidified with hydrochloric acid and deproteinized with acetonitrile. Tetracyclines were partitioned into water and concentrated by solid-phase absorption on the analytical column form 0.01 M phosphoric acid-methanol (80:20). Tetracyclines were eluted with an acetonitrile gradient. An all-organic polymeric column (Polymer Labs. PLRP-S) was used. Similar results were obtained on a bonded reversed-phase column after addition of tetramethyl-ammonium chloride to the mobile phase. Recoveries were near 100% from blood serum, 83-94% from muscle, and 80-100% from liver and kidney with sensitivities of 0.1 ppm or less for muscle and blood serum.

Pharmacokinetics of minocycline hydrochloride in clinically normal and hypoproteinemic sheep

Eight adult sheep were given 2.2 mg of minocycline hydrochloride/kg of body weight IV before and after blood was collected to induce hypoproteinemia. The blood collection produced a significant (P less than 0.01) reduction in PCV, hemoglobin, and total serum protein values. Pharmacokinetic evaluation of the serum drug concentration vs time data was performed, using a noncompartmental model based on statistical moment theory. Pharmacokinetic values obtained from the sheep with normal serum protein were 5.94 +/- 1.78 ml/kg/min for clearance, 1.32 +/- 0.16 L/kg for the steady-state volume of distribution, and 3.89 +/- 0.80 hours for mean residence time. Significant differences were not found in these values obtained from the sheep when they were hypoproteinemic. The effective half-life, reported as the harmonic mean, increased from 2.57 hours in sheep before blood collection to 2.91 hours in sheep when they were hypoproteinemic. The 2.2 mg of minocycline/kg administered once or twice daily would not be expected to produce adequate serum concentrations for most susceptible microorganisms. Some evidence that minocycline disposition may follow zero-order kinetics is presented.

High-performance liquid chromatography of tetracyclines

The possibilities of two non-ionogenic resins (XAD-2 and PRP-1) in the chromatography of tetracyclines and their degradation products are described. It appears that, in contrast to silica-based materials, this type of column material produces linear calibration curves, even in the low nanogram range. Two different methods of sample pretreatment in bioanalysis of tetracyclines and their degradation products are compared with respect to selectivity towards the matrix background and recovery.

Treatment of nonpulmonary infections due to Mycobacterium fortuitum and Mycobacterium chelonei on the basis of in vitro susceptibilities

One hundred twenty-three patients with nonpulmonary infections due to Mycobacterium fortuitum or Mycobacterium chelonei were treated by wound debridement and with chemotherapy on the basis of in vitro susceptibilities of the organism. Of 76 patients with infections caused by M. fortuitum, 13 required no therapy or were adequately treated with surgery alone. Patients with active localized disease received single drug therapy (usually with a sulfonamide) for a mean period of 10.6 weeks for cellulitis and seven months for osteomyelitis. Patients with extensive disease received amikacin or amikacin plus cefoxitin (mean, four weeks) followed by a sulfonamide (mean, six months). The 47 patients with infections caused by M. chelonei received no therapy or were treated with surgery alone (6); with amikacin (10), erythromycin (6), doxycycline (3), or cefoxitin (1); or with amikacin plus cefoxitin followed by cefoxitin alone for a total of 10-12 weeks (20); or other multiple-drug regimens (1). Surgery was performed on 74 (60%) patients. Schlichter tests or serum drug levels were determined for 81 (66%) patients. Response to therapy was excellent; 68 (90%) infections with M. fortuitum and 34 (72%) with M. chelonei were successfully treated. Cultures became negative within six weeks of chemotherapy, except for sternal osteomyelitis, for which cultures were not negative until up to 14 weeks. Follow-up for a mean period of 12 months following therapy was possible in 80% of cases. Relapses were rare except in patients with disseminated disease, and drug resistance developed in only one patient. These studies demonstrate the value of routine susceptibility testing of these mycobacterial species and the benefit of chemotherapy on the basis of in vitro susceptibilities.

Absorption of minocycline hydrochloride and tetracycline hydrochloride. Effect of food, milk, and iron

Serum concentrations of tetracycline hydrochloride and minocycline hydrochloride were compared when administered with water, milk, a meal, and 300 mg ferrous sulfate in two groups of eight volunteers. Absorption of both antibiotics was significantly decreased by administration with iron (77% inhibition with minocycline and 81% with tetracycline), milk (27% inhibition with minocycline, 65% with tetracycline), and food (13% inhibition with minocycline and 46% with tetracycline). The inhibitory effect on absorption with food and milk was significantly greater for tetracycline than for minocycline.

Effect of intrauterine administration of tetracyclines on cynomolgus monkeys

Cynomolgus monkeys were used to screen for chemicals which potentially could be used as tubal occluding agents. Intrauterine administrations of solution or pellets of tetracycline and its analogues (100 mg doses) were tested for their effects on morphologic changes in the reproductive tract of monkeys. These effects were compared to monkeys receiving intrauterine administration of quinacrine pellets (36 mg) since quinacrine has been used successfully in the clinical setting. Blood levels of drugs, blood chemistry and hematology determinations and liver and kidney pathology data were also obtained as indices for toxicity. Morphologic damage to the uterine lining and intramural section of the tube (including necrosis, inflammation or scarring) was elicited by intrauterine tetracycline and doxycycline in the same frequency and severity as quinacrine. In contrast, saline or sham control monkeys showed no morphological damage of the tube or uterus. Although all drugs could be detected in the blood 4 hours after intrauterine administration, levels were near or below the limit of detection by one week. No evidence was found for toxicity of tetracycline or its analogues for the dosage given. Because of these results and the extensive literature on tetracycline toxicity, further studies should be directed toward the use of tetracycline as a sterilizing agent in women.

Measurement of tetracycline levels in parakeets

Parakeets were fed hulled millet seed containing 0.5% chlortetracycline (CTC) or minocycline. Blood concentrations of more than 1 micrograms CTC/ml and more than 5 micrograms minocycline/ml were obtained. Equivalent drug assay results were obtained from blood specimens collected by venipuncture or by use of treated filter-paper discs. The latter is a fairly simple method for assaying CTC concentrations in blood of treated psittacines.

[Tetracycline penetration into human peripheral blood leukocytes and their intracellular distribution]

The studies showed that the tetracyclines tested (morphocycline, tetracycline and methacycline) penetrated into leucocytes of the human peripheral blood. Agranulocyte absorbed the drugs more actively than granulocytes. Pinocytosis was suggested to be involved in the penetration. On interaction with intracellular structures the tetracyclines reversibly bound to the organoid cells lost their biological activity to a significant degree. Progressive dissociation of organoid-drug complexes and the egress of tetracyclines from the cells were likely to occur as their contents in the extracellular environment decreased. The penetration capacity and subcellular structure affinity of methacycline were the highest among the drugs tested. It is suggested that penetration of the tetracyclines through the cytoplasmic membranes and their distribution inside the cells are reciprocal.

Plasma concentration and disposition of antimicrobial agents in the dog

Although there is sufficient information on the pharmacology and therapeutic application of the antimicrobial drugs to permit their effective use, they are still often misused in canine practice. This paper collates the data on drug dose rate/plasma concentration relationships observed in dogs after the administration of specific members of the major antimicrobial drug groups and on the possible impact of drug disposition (distribution and elimination) on therapeutic effect. Some information gleaned from studies in other animal species is added.

Antibiotic treatment of acute salpingitis. A study of plasma concentrations of two tetracyclines (doxycycline and lymecycline)

A group of 782 patients with a diagnosis of acute salpingitis (a few of the patients because of other infection in the pelvis) were treated with the recommended oral dose of doxycycline (200 mg the first day and 100 mg once daily for at least the following 9-12 days) in combination with 1 g benzyl penicillin and 0.6 g procaine penicillin twice daily intramuscularly for 5-7 days. The plasma concentrations of doxycycline were determined on the third day of treatment before the next dose was given. In 26.5% of the patients the concentrations were below 1 microgram/ml plasma, considered as the minimum therapeutic level. The dose of doxycycline was increased to 200 mg a day in these patients and the plasma concentrations increased accordingly. In another group of 80 patients, 40 were treated with the standard doxycycline dose, and the other 40 patients with the standard lymecycline dose (300 mg twice a day). The plasma concentrations, determined before the dose on the third day, were below 1 microgram/ml in 35% of the patients treated with doxycycline, and in 5% of those treated with lymecycline. Since acute salpingitis in most cases is a serious complication to a lower genital tract infection, often a sexually transmitted disease caused by tetracycline-sensitive organisms, the importance of achieving and determining the therapeutic plasma concentrations of tetracyclines is stressed.

Development and application of a radioimmunoassay for tetracycline

Antiserum against tetracycline was produced in rabbits immunized with a tetracycline hapten conjugated to bovine serum albumin. The antiserum was used to develop a radioimmunoassay for tetracycline. As little was 1 ng of tetracycline can be detected in one sample. The antitetracycline antiserum showed a considerable degree of specificity since it cross-reacted only with chlortetracycline (70%). However, its cross-reactivity with oxytetracycline, doxycycline, demeclocycline, methacycline and rolitetracycline was only negligible. The radioimmunoassay of tetracycline was used to measure the systemic bioavailability of orally administered tetracycline (25 mg/kg) to a group of mongrel dogs. Detectable levels of tetracycline were exhibited within 30 min and maximum plasma concentrations of the drug occurred within 3 to 4 hr after dose administration.

Fluorometric determination of tetracyclines in small blood and tissue samples

A reported fluorometric method to determine tetracycline in biological material was modified to determine low levels of the antibiotics when using only small amounts of starting material. The method is applicable to tissue distribution studies in small experimental animals and also can be used for serial determinations in blood samples of these animals and for biopsy material. The tetracyclines are extracted in the presence of ethylenediaminetetraacetic acid, and the phosphate precipitation steps are omitted. This omission makes the procedures considerably less time consuming. The recoveries of the tetracyclines, oxytetracycline and doxycycline, are approximately 80-100%. The values obtained by this method were consistent with those from microbiological assays, and its reliability was shown further in a comparison with the fate of radioactive tetracycline.

Liquid chromatographic determination of minocycline in human serum

A rapid, specific, and sensitive liquid chromatographic assay for minocycline in human serum is described. The drug and an internal standard (oxytetracycline) were extracted into ethyl acetate from 0.5 ml of buffered serum (pH 6.5). Chromatographic separation was achieved on a 10-micrometer Lichrospher 100 CH 8 column with acetonitrile--citric acid (0.1 M) as the eluent. The column effluent was monitored at 352 nm. The assay was linear up to 3 micrograms/ml with a mean coefficient of variation of 3.3% (n = 6). An extraction recovery of 89.4 +/- 3.2% (mean +/- SD, n = 17) was obtained over the 0.5--2.6 micrograms/ml range. The detection limit averaged 50 ng/ml. A serum concentration-time profile in humans after oral intake is presented.

Improved high-performance liquid chromatographic procedure for the determination of tetracyclines in plasma, urine and tissues

An improved extraction procedure for the determination of oxytetracycline, tetracycline and chlortetracycline in urine, plasma and tissues by high-performance liquid chromatography is described. The addition of phenylbutazone (3,5-dioxo-1,2-diphenyl-4-n-butylpyrazolidine) to water, urine or plasma enhances the extraction of these compounds by ethyl acetate. The recovery of oxytetracycline from plasma is increased six fold and the need for two separate extractions of urine and plasma is eliminated. The formation of phenylbutazone-tetracycline ion pairs and their role in the extraction process is discussed.

Cetocycline, tetracycline analog: in vitro studies of antimicrobial activity, serum binding, lipid solubility, and uptake by bacteria

Cetocycline (formerly chelocardin or cetotetrine) is structurally related to the tetracyclines. It was found to be more active than tetracycline against many clinical isolates of aerobic gram-negative bacilli, but is less active against staphylococci, and has no activity against Pseudomonas. It is bactericidal against susceptible enteric gram-negative bacteria at concentrations two to four times higher than the minimal inhibiting concentrations. The drug is highly lipid soluble; more than 80% is bound to serum, and it is more avidly taken up by susceptible bacteria than tetracycline. A direct correlation between drug uptake and susceptibility of bacteria was not noted, except with a strain of Proteus vulgaris.

Effects of serum lipid content on the binding of minocycline

Minocycline was added to normal and hyperlipemic serum samples in concentrations of 1 approximately 10 mcg/ml. These specimens had similar protein contents. Chemically extractable minocycline was quantitated fluorometrically. Hyperlipemic serum (cholesterol 480 mg/100 ml; triglycerides 321 mg/100 ml) yielded an average of 50% less minocycline than did normal serum (cholesterol 170 mg/100 ml; triglycerides 114 mg/100 ml). When ultrafiltrates of serum containing 6, 12 and 20 mcg/ml minocycline were assayed microbiologically, it was evident that variations in serum triglyceride and cholesterol levels did not alter the ratio of bound to free drug. Minocycline appears to be reversibly associated with, and/or soluble in, triglyceride-cholesterol components of serum.

Reversed-phase high-performance liquid chromatographic determination of tetracyclines in urine and plasma

The high-performance liquid chromatographic separation and quantitative analysis of oxytetracycline, tetracycline, and chlortetracycline from urine and plasma were effected on an octadecylsilane reversed-phase packing. The calcium complexes of the tetracyclines were extracted from urine and plasma with ethylacetate and then reextracted into hydrochloric acid. Following the injection of the hydrochloric acid extracts onto the column, the individual tetracyclines were eluted isocratically and quantitated spectrophotometrically. Concentrations of less than 1 microng/ml in urine and 1.5 microng/ml in plasms were quantitatively determined with a relative standard deviation of less than 5%.

Rapid fluorimetric assay of minocycline in plasma or serum: comparison with microbiological assay

1. Plasma concentrations of minocycline were assayed by measuring the fluorescence emission of an aluminum-minocycline chelate in a spectrofluorimeter. 2. The assay gives reproducible results over the concentration range 0.05-5.0 mug ml-1, and compared favourably with results achieved using a conventional large plate agar diffusion microbiological assay in a double-blind comparison of the two methods. 3. Fluorimetric assay of minocycline in plasma was found to correlate closely with antibiotic activity (r = 0.95). The method is easy and economical to perform, results being obtained in 1 h.

Sodium aurothiomalate, gold keratinate, and various tetracyclines in mycoplasma-induced arthritis of rodents

Sodium aurothiomalate (ATM), gold keratinate and five different tetracyclines were investigated for activity against M. arthritidis strain ATCC 14124 and M. pulmonis strain JB, both in vitro and in rodents with arthritis caused by these mycoplasmas. In vitro, ATM had only slight activity against M. arthritidis and M. pulmonis, while gold keratinate was virtually inactive against M. pulmonis. In contrast, the tetracyclines were highly active against both mycoplasmas. The tetracyclines and the gold salts were both predominantly mycoplasmastatic. In both rats and mice, parenteral administration of ATM, begun shortly before or after infection of rodents with mycoplasmas, prevented the development of arthritis. ATM or gold keratinate, given subcutaneously to mice already arthritic from infection with M. pulmonis, reduced the severity of the arthritis, even although gold keratinate was inactive aganist this mycoplasma in vitro. Moreover, direct testing of serum, collected from mice treated with gold keratinate, failed to demonstrate antimycoplasmal activity in vitro. These results suggest that the action of gold-containing drugs in mycoplasmal arthritis is due to biological properties of gold other than antimycoplasmal activity. Tetracyclines were also found to be effective in preventing arthritis in rats and mice when given subcutaneously. With high doses, subcutaneous, but not oral, therapy significantly reduced the severity of established arthritis in mice infected with M. pulmonis. The blood levels achieved with the different tetracyclines, when related to their therapeutic activity, indicated that good antimycoplasmal activity and adequate absorption from the gut were not the only properties needed for optimal effectiveness. The results are discussed in relation to treatment of rheumatoid patients with tetracycline HCl.

Determination of beta-cetotetrine in plasma and urine using high-performance liquid chromatography with electrochemical detection

A sensitive and specific method for the determination of beta-cetotetrine in biological fluids has been developed using reversed-phase high-performance liquid chromatography and thin-layer electrochemical detection. The limit of detection for beta-cetotetrine was less than 0.25 pmoles, or approx. 100 pg injected on-column. beta-Cetotetrin could be analyzed in plasma at concentrations of 25ng/ml. Linear responses were observed up to 2.5 mug/ml, and the relative standard deviation of the procedure was +/-5%. The method was also employed for the determination of similar levels of beta-cetotetrine in urine.

[Interaction of morphocycline with beryllium ions]

Behaviour of morphocycline (H5R) and its complex with beryllium ions in acqueous solutions was studied fluorimetrically. The ionization constants of H5R were estimated at pH 1.5-15 according to the data of fluorimetric determination with respect to OH-group: pK1 6.40, pK2 8.25, pK3 10.65, pK4 11.30. Two constants characterizing the deprotonization process with respect to the carbonylic group and nitrogen were also estimated: pK01--1.0 (greater than C = 0) and pK02 4.75 (--N=). Formation of an intensively fluorescing compound less than [Be3(OH)3(H2O2)5]2HR greater than 2+ was observed at pH 6.0-7.0. The cause of such intensive fluorescence was deformation of ion [Be3(OH)3(H2O)6]3+ because of its exclusion from the coordinating sphere of one molecule of water during the complex formation and decreasing of level H comes from II as compared to the morphocycline level II comes from n. A procedure for detecting morphocycline in the blood of humans and animals was developed.

Fluorimetric assay of tetracycline mixtures

A simple and precise fluorimetric method is described for the simultaneous assay in plasma of a mixture containing chlortetracycline, demethylchlortetracycline and tetracycline. Assay within the therapeutic ranges of 0-5 mg litre(-1) is achieved by formation of strongly fluorescent aluminum/tetracycline complexes, without prior extraction or separation of the individual antibiotics. This is performed by determinations at the peak excitation and fluorescence emission wavelengths of each tetracycline chelate. The method can be similarly applied to the assay of oxytetracycline, rolitetracycline and minocycline.

Displacement of albumin-bound antimicrobial agents by bilirubin

The ability of bilirubin to displace antimicrobial agents from their binding sites on albumin was studied in vitro by equilibrium dialysis. Sulfonamides, tetracyclines, penicillins and cephalosporins of different degrees of protein binding were tested. It was found that bilirubin reduced the protein binding of all four classes of antimicrobial agents, although by varying degrees. This effect was most pronounced with the compounds which had the highest degree of protein binding, such as cloxacillin, cephazolin, methacycline and sulfisoxazole, all of which are bound greater than 80% by albumin. On the other hand, the drugs with less than 25% binding, such as ampicillin, cephalexine and tetracycline were not ostensibly displaced by bilirubin. Scatchard plots of the binding of sulfamethoxazole to albumin in the presence of 400 mumol/1 of bilirubin, showed that bilirubin almost completely displaced the sulfonamide molecule from the high affinity site on the albumin molecule. Reduced protein binding of drugs in hyperbilirubinemic infants may have pharmacokinetic significance.