On the mechanism of action of 9-O-arylalkyloxime derivatives of 6-O-mycaminosyltylonolide, a new class of 16-membered macrolide antibiotics.

New 16-membered 9-aryl-alkyl oxime derivatives of 5-O-mycaminosyl-tylonolid (OMT) have recently been prepared and were found to exhibit high activity against macrolide-resistant strains. In this study, we show that these compounds do not affect the binding of tRNAs to ribosomes in a cell-free system derived from Escherichia coli and that they cannot inhibit peptidyltransferase, peptidyl-tRNA translocation, or poly(U)-dependent poly(Phe) synthesis. However, they severely inhibit poly(A)-dependent poly(Lys) synthesis and compete with erythromycin or tylosin for binding to common or partially overlapping sites in the ribosome. According to footprinting analysis, the lactone ring of these compounds seems to occupy the classic binding site of macrolides that is located at the entrance of the exit tunnel, whereas the extending alkyl-aryl side chain seems to penetrate deeper in the tunnel, where it protects nucleoside A752 in domain II of 23S rRNA. In addition, this side chain causes an increased affinity for mutant ribosomes that may be responsible for their effectiveness against macrolide resistant strains. As revealed by detailed kinetic analysis, these compounds behave as slow-binding ligands interacting with functional ribosomal complexes through a one-step mechanism. This type of inhibitor has several attractive features and offers many chances in designing new potent drugs.

Inactivation of the macrolide antibiotics erythromycin, midecamycin, and rokitamycin by pathogenic Nocardia species.

A survey of five Nocardia spp. with respect to susceptibility towards three macrolides (erythromycin, rokitamycin, and midecamycin) showed that the Nocardia spp. have different susceptibility profiles. Most of the resistance was due to the inactivation of the macrolides by phosphorylation, glycosylation, reduction, deacylation, or a combination thereof.

[Use of oral macrolide and azalide antibiotics in children with bronchopulmonary diseases]. / Primenenie peroral'nykh makrolidnykh i azalidnykh antibiotikov pri bronkholegochnoi patologii u detei.

The therapeutic efficacy of oral macrolides (erythromycin base and midekamycin, macropen) and azalides (azithromycin, sumamed) in the treatment of children with acute and chronic (during the aggravation) bronchopulmonary diseases was studied. The main etiological factors of acute and chronic pneumonia were Streptococcus pneumoniae and Haemophilus influenzae. The proportion of Staphylococcus aureus was high in infants with acute pleuropulmonary inflammations. The susceptibility of the isolates to the antibiotics was found to be high. The results of the trials showed that erythromycin, macropen and azithromycin were efficient in the treatment of acute and chronic pneumonia. The foci of acute pneumonia dissolved after oral administration of the drugs within the same periods as after the use of other parenteral antibiotics. The comparative estimation of the drug efficacy revealed that azithromycin was more active. The ease of the azithromycin administration (in the form of a suspension) in infants and children once a day for a shorter treatment course up to 5 days, high efficacy and no adverse reactions permitted to consider the antibiotic as the most promising antibacterial agent for the treatment of respiratory infections in children in hospitals and outpatient departments.

Pharmacokinetics of a new macrolide, roxithromycin, in infants and children.

The pharmacokinetics of roxithromycin was investigated after oral administration of 2.5 mg/kg doses given 12 hours apart during 6 days in infants and children. These 18 subjects suffering from a respiratory tract infection were divided into three age groups: group I less than 18 months, group II less than 5 years, group III less than 13 years. At day 6, the elimination plasma half-life had an average value (mean +/- SD) of 19.8 +/- 9.7 h (group I), 21.0 +/- 9.4 h (group II) and 20.8 +/- 6.9 h (group III), respectively. The maximum concentration of roxithromycin (Cmax) was attained between 1 and 2 hours after dosing with mean values of 10.1 +/- 3.0 mg/l (group I), 8.7 +/- 4.9 mg/l (group II), 8.8 +/- 7.0 mg/l (group III). All the calculated pharmacokinetic parameters did not significantly differ from one group to another. The kinetics of roxithromycin in infants and children seemed to be age independent and showed no accumulation after repeated doses. During 12 hours, the plasma concentrations were above MIC of microorganisms generally present in respiratory tract infections. Two daily doses of 2.5 mg/kg of roxithromycin 12 hours apart may be proposed in infants and children.

19-Deformyl-4'-deoxydesmycosin (TMC-016): synthesis and biological properties of a unique 16-membered macrolide antibiotic.

19-Deformyl-4'-deoxydesmycosin was synthesized by the following synthetic route: 19-Deformylation of desmycosin, 3,2',4''-tri-O-trimethylsilylation, 4'-O-sulfonylation, 4'-iodination, reductive deiodination and 3,2',4''-tri-O-detrimethylsilylation. Deformylation of the aldehyde group at the C-19 position was achieved by two different methods: A) A simple one-step deformylation using Wilkinson's catalyst ((Ph3P)3RhCl). B) Reductive decarboxylation of the 19-carboxyl derivative following NaClO2 oxidation of the aldehyde. 19-Deformyl-4'-deoxydesmycosin showed very strong antimicrobial activity in vitro and in vivo.

[Pharmacokinetics of ponsinomycin administered in a syrup form in single 400-800 and 1200 mg doses in healthy volunteers]. / Pharmacocinétique de la ponsinomycine administrée sous forme de sirop en prises uniques aux doses de 400-800 et 1,200 mg chez le volontaire sain.

Ponsinomycin is a new macrolide. Its pharmacokinetics is characterized by an extensive metabolism. Following oral dosing in human, unchanged ponsinomycin is not found in blood, but 3 main metabolites: Mb12, Mb6 and Mb9a can be assayed. Twelve young healthy volunteers received ponsinomycin orally, at doses equal to 400, 800 and 1,200 mg on 3 separate occasions, according to a cross-over design. Metabolites Mb12, Mb6 and Mb9a were measured in plasma by HPLC. The pharmacokinetics of Mb12 was linear in the range of doses administered. A dose-dependent effect leading to a reduction of the apparent elimination rate when dose increased was observed with Mb9a and more importantly with Mb6.

[Roxithromycin passage in the cervix mucus]. / Passage de la roxithromycine dans la glaire cervicale.

We studied the diffusion of roxithromycin in the cervix mucus of fifteen healthy normal women, aged 24 to 44 (median 37). They were consulting physician to have an IUD. After this intervention (between the 4 to 7 days of menstrual cycle) they received an antibiotic treatment with the standard dose of roxithromycin: 150 mg bd for a week. At the end of this treatment the cervix mucus was taken 1 to 12 hours after the last antibiotic dose. We dose the roxithromycin by a microbial assay (Bacillus subtilis ATCC 6633, antibiotic medium 1, pH 8) and the acid alpha-1-glycoprotein by an immunodiffusion assay. All women had drug measurable with levels from 0.45 to 2.07 mg/l (median: 0.80 mg/l). The acid alpha-1-glycoprotein levels were quite constant (median: 0.19 mg/l). The antibiotic concentrations observed are above the MIC of the major genital pathogens, mainly C. trachomatis, G. vaginalis, H. ducreyi and U. urealyticum, but lower than the MIC ov N. gonorrhoeae and M. hominis.

Solid phase extraction and HPLC determination of spiramycin in plasma and vitreous concentrations.

A method for extracting spiramycin by an octadecylsilica cartridge is described for plasma or vitreous samples. The macrolide antibiotic is then measured by reversed-phase HPLC with UV detection. The limit of detection is estimated to be 50 ng/mL. The coefficient of variation for the procedure is 6.1% and 5.2% for the range of concentrations 0.2 micrograms/mL and 10 micrograms/mL respectively. By this method, pharmacokinetic profiles were performed for five adult patients. Spiramycin could be accurately measured in the vitreous humour, allowing the determination of antibiotic at its site of action.

Roxithromycin. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy.

Roxithromycin is an acid-stable orally administered antibacterial macrolide structurally related to erythromycin. It has an in vitro antibacterial profile similar to that of erythromycin, with activity against Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, S. pyogenes, Branhamella catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila, Chlamydia trachomatis, Gardnerella vaginalis, Haemophilus ducreyi, some anaerobes and other less common pathogens. Roxithromycin has a pharmacokinetic profile that is characterised by excellent enteral absorption achieving high concentrations in most tissues and body fluids. The results of clinical studies with roxithromycin have confirmed the potential for its use in a variety of infections, which was suggested by its antibacterial activity in vitro and pharmacokinetic profile. Clinical efficacy has been confirmed in the treatment of respiratory tract infections, including community-acquired and atypical pneumonias, ear, nose and throat infections, genitourinary tract infections, and skin and soft tissue infections. In a relatively small number of patients roxithromycin has generally been shown to be as effective as erythromycin and other appropriate antibacterial drugs in some of the above indications. Roxithromycin is well tolerated and has less potential than erythromycin to produce clinically significant drug interactions. Thus, roxithromycin is an orally active drug which should prove a useful alternative when selecting antibacterial therapy for indications where macrolides are appropriate.

Data acquisition and processing system for drug release characterization by thin layer chromatography.

Samples of an antibiotic released from an ocular insert in an in vitro test are characterized by thin layer chromatography (TLC). Conventional characterization methods include cutting and weighing strip chart paper peak profiles obtained with a scanning densitometer for spotted TLC plates, and relating peaks for unknowns to peaks for standards on the basis of relative weights. A data collection and processing system is described in which the data collection and processing is highly automated utilizing a specially developed software program. A Kontes densitometer (Model 800) and a personal computer (IBM PC-AT or Zenith-248) are interfaced using a Keithley 570 data acquisition system. Two BASIC software programs were developed to provide quantitative evaluation of chromatograms of an antibiotic (tylosin tartrate); the first program generates chromatograms on the computer screen through initiating controlled operation of a scanning densitometer for TLC plate analysis, and the second program processes the data providing quantitative analysis of the spectral output through a peak detection and peak integration routine. The approach represents a new general, versatile, quick and effective method to characterize TLC samples for various numbers of peaks for unknowns and standards for different concentration levels.

Miokamycin penetration into oral cavity tissues and crevicular fluid.

Diffusion of miokamycin into gum, maxillary-mandibular bone and crevicular fluid was studied in human beings. The antibiotic concentrations were determined in specimens at different times after oral administration of 600 mg in a single dose of miokamycin. Peak serum levels (2.32 +/- 0.67 mcg/ml) were found at the first hour after dosage. In healthy gum tissue the highest antibiotic levels (1.44 +/- 0.34 mcg/gr) were observed at the second hour, while in the inflamed gum miokamycin penetrates more rapidly, being, as in serum at the highest levels detectable during the first hour. In the bone of the maxilla or mandible the highest levels of miokamycin (0.88 +/- 0.13 mcg/gr) were detected at the second hour after treatment. In the crevicular fluid miokamycin showed a similar profile as that in serum, since the peak levels were reached at the first hour (2.4 +/- 0.88 mcg/ml, but the decrease of the antibiotic occurred more slowly than in serum. Miokamycin rapidly penetrates into tissues and fluids of oral cavity. A single oral dose of 600 mg guarantees antibacterial levels against susceptible bacteria over six hours.

High-performance liquid chromatographic analysis of josamycin in serum and urine.

A high-performance liquid chromatographic assay for the analysis of josamycin in human serum and urine is presented. The assay involves a simple solid-phase extraction procedure coupled with a phase separation step, separation on a reversed-phase C18 column with UV detection by a multi-wavelength programmable detector. The mobile phase was acetonitrile-0.015 M phosphate buffer, pH 6.0 (5:2) at a flow-rate of 1.2 ml/min. The column temperature was maintained at 35 degrees C. Linear calibration curves over the concentration ranges 0.1-2.0 mg/l (serum) and 0.5-5 mg/l (urine) were obtained with correlation coefficients of 0.9983 and 1.0000, respectively. The relative standard deviations of five replicate samples at the upper and lower limits of each calibration curve were below 7%. The recoveries at the upper and lower ends of the calibration range for serum were 77% and 70%, respectively, and those for urine were 76% and 80%, respectively.

Toxicity, uptake, and subcellular distribution in rat hepatocytes of roxithromycin, a new semisynthetic macrolide, and erythromycin base.

Rat hepatocytes were used to study the toxicity of a new semisynthetic macrolide, roxithromycin, in comparison with erythromycin base and erythromycin estolate. Roxithromycin caused lactate dehydrogenase leakage close to that of erythromycin estolate and higher than erythromycin base after 21 h of exposure to the drugs. This effect was, at least in part, explained by the higher uptake: roxithromycin was two to three times more concentrated by liver cells than erythromycin base. For both roxithromycin and erythromycin base, the uptake depended on time, temperature, and extracellular antibiotic concentration. The accumulated macrolides egressed rapidly when cells were incubated in antibiotic-free medium. No uptake and no loss of accumulated drugs were observed at 4 degrees C. After accumulation by hepatocytes, roxithromycin and erythromycin base underwent similar subcellular distribution, mostly concentrating in cytosol and lysosomes. The small amount accumulated in the other particulate fractions followed the order mitochondria much greater than nuclei greater than microsomes. Roxithromycin, however, was less concentrated than erythromycin base in the microsomes.

No effect of roxithromycin on pharmacokinetic or pharmacodynamic properties of warfarin and its enantiomers.

The macrolide antibiotics are metabolized by cytochrome P-450 enzymes in the liver and interactions with similarly metabolized compounds have been described. Simultaneous treatment with erythromycin and warfarin is known to decrease warfarin clearance and prolong prothrombin time. Roxithromycin (RU 28965), a new erythromycin derivative with improved pharmacokinetic properties, might then, because of structure similarity, be expected to interact with warfarin. In 21 healthy volunteers, the effect of orally administered roxithromycin (150 mg b.i.d.) on warfarin steady-state kinetics, and the effects of warfarin on roxithromycin kinetics, were investigated in a double-blind, randomized study versus placebo. Since the warfarin enantiomers, R- and S-warfarin have both different potency and different metabolism, the ratio between the enantiomers with and without roxithromycin, was also determined. In this study, mean AUC for warfarin increased slightly from day 14 of warfarin treatment to day 28, but no difference was found between the roxithromycin group and the placebo group, and no change appeared in the ratio between the warfarin enantiomers. A moderate increase in dosage was needed to maintain hypocoagulability during warfarin medication, but there was no difference between the roxithromycin group and the placebo groups, respectively. In addition, roxithromycin kinetics appeared to be unaffected by warfarin treatment.

[Clinical studies of rokitamycin dry syrup on Chlamydia trachomatis infections in the neonate and infant].

A dry syrup preparation for infants and children of a newly developed 16-membered macrolide antibiotic, rokitamycin, was administered to 5 neonates and low birth weight infants of 6 to 25 days after births at a dose level of 10 mg/kg on an empty stomach then plasma drug levels were determined. The dry syrup preparation was also given to a total of 19 Chlamydia trachomatis infection cases of 7 days to 8 months old neonates, low birth weight infants and infants including 12 cases of pneumonia, 2 cases of conjunctivitis and 5 non-symptomatic carriers at an average daily dose level of 48.1 mg/kg in 2 to 4 doses for an average of 19 days and its clinical effects, bacteriological effectiveness, side effects and effects on laboratory test values were examined. The obtained results are summarized as follows. 1. Because the test subjects were neonates and premature infants, obtainable amounts of blood samples were limited, thus it was not possible to determine time courses of plasma drug levels to reach their peaks. Peak plasma levels, however, were speculated to be similar to those in children. Plasma half-lives of the drug were also not determinable, but they seemed to be somewhat longer than those in children. 2. Clinical efficacies were determinable in the 2 cases of conjunctivitis and 10 of the 12 cases of pneumonia, with excellent or good results in both cases of the former and with excellent or good results in 9 of the 10 determinable cases of the latter. Thus, the overall efficacy rate was high, 91.7%. 3. Bacteriological efficacies were determinable in 18 cases including non-symptomatic carriers. C. trachomatis was eradicated in 16 of the cases with an overall efficacy rate of 88.9%. 4. Diarrhea was observed in 2 cases, which were suspected as side effects of the drug. 5. No abnormalities were observed in the laboratory test results. Judging from the above results, this drug appears to be useful for the treatment of C. trachomatis infections of neonates, low birth weight infants and infants.

Roxithromycin and controlled release theophylline, an interaction study.

A clinical trial, involving 16 male subjects affected by a relapse of chronic bronchitis, was performed in order to evaluate the possible interference of roxithromycin (RU 28965) with theophylline plasma levels. Theophylline was administered to patients as a controlled release formulation. Results did not show any clinically relevant change in theophylline blood levels, implying the conclusion that the new macrolide roxithromycin can be administered simultaneously with a controlled release theophylline.

Roxithromycin disposition in tonsils after single and repeated administrations.

Levels of roxithromycin in serum and tissue were investigated in 29 subjects undergoing tonsillectomy. A total of 13 subjects received a single oral dose of 300 mg, and 16 received four oral doses 12 h apart as follows: a 300-mg loading dose followed by three 150-mg doses. Measurable levels of roxithromycin were present in tonsil samples of 11 of 13 subjects in the first group. The mean levels in tonsils and serum were 0.8 microgram/g and 6.7 micrograms/ml, resulting in a mean tissue/serum ratio of 0.16. In the multiple-dose group, roxithromycin was found in 14 of 16 subjects at mean levels in tonsils and serum of 1.6 micrograms/g and 8.7 micrograms/ml, and the tissue/serum ratio was 0.23.

Synthesis and evaluation of tylosin-related macrolides modified at the aldehyde function: a new series of orally effective antibiotics.

Modification of the aldehyde group in tylosin and related macrolide antibiotics dramatically enhanced the oral efficacy of the derivatives against experimental infections caused by susceptible bacteria in laboratory animals. A large number and wide variety of aldehyde-modified macrolide derivatives were prepared, utilizing the Mitsunobu reaction and other chemical transformations. Evaluation of in vitro and in vivo antimicrobial activity indicated that derivatives of demycarosyltylosin (desmycosin) combined the broadest spectrum of antimicrobial activity with the best efficacy and bioavailability after oral administration.

A comparison of the pharmacokinetics and tissue penetration of spiramycin and erythromycin.

The pharmacokinetics of two orally administered macrolides, spiramycin and erythromycin, were compared in six healthy male volunteers in a single dose cross-over study. Penetration of these antimicrobial agents into inflammatory fluid was studied. Spiramycin was administered in a 2 g dose and erythromycin in a 500 mg dose. Spiramycin (Tmax = 3.3 h) and erythromycin (Tmax = 1.2 h) were well absorbed reaching mean plasma Cmax of 3.1 mg/l and 2.1 mg/l, respectively. The relative bioavailability of erythromycin compared to spiramycin appeared to be three- to four-fold greater. The mean plasma elimination half-life was 3.8 h for spiramycin and 1.6 h for erythromycin. The percentage penetration of the antibiotics into inflammatory fluid was good, being 66% for spiramycin and 54% for erythromycin. Both antimicrobial agents attained inflammatory fluid Cmax of 0.7 mg/l by 4-4.8 h. Spiramycin persisted in the inflammatory fluid with a mean elimination half-life of 7.7 h compared to 2.2 h for erythromycin. Twenty-four hour urinary recovery of the administered dose of each antimicrobial agent was less than 5%.