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]

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.

[Roxithromycin passage in the cervix mucus]

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.

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.

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.

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.

[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.

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.

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.

[Microbiological, pharmacokinetic and clinical studies of rokitamycin dry syrup in the pediatric field]

Rokitamycin (RKM), a newly developed macrolide antibiotic with a 16-membered ring, dissolves well under acidic conditions. It has been improved over other macrolides to minimize individual variations in its absorbability. We measured, using the GA-test, variations in gastric acidities of 43 children with ages between 1 to 14 years, and investigated the relationship between gastric acidities and pharmacokinetic values. Also activities (expressed in MICs) of antimicrobial agents were studied against clinically isolated 229 bacterial strains using an inoculum size of 10(6) cells/ml. Tested organisms included Streptococcus pyogenes (77 strains), Streptococcus agalactiae (29), Streptococcus pneumoniae (2), as Gram-positive cocci, and Haemophilus influenzae (1), Haemophilus parainfluenzae (1), Bordetella pertussis (12), Salmonella sp. (4) and Campylobacter jejuni (103) as Gram-negative bacilli. Against stock strains of bacteria, MICs of 10 drugs (RKM, erythromycin (EM), josamycin (JM), midecamycin (MDM), midecamycin acetate (MOM), clindamycin (CLDM), amoxicillin (AMPC), cefaclor (CCL), minocycline, ofloxacin (OFLX] were determined. Against isolates from patients who underwent treatment with RKM, MICs of only 4 drugs (RKM, EM, JM, MOM) were determined. Measurements were made on plasma and urinary concentrations of RKM and its urinary recovery rates after patients including 6 boys with ages between 5 years 1 month and 11 years 6 months were administered with RKM (dry syrup). Two groups of 6 boys were administered between meals with RKM at dose levels of 5 and 10 mg/kg, respectively. Clinical and bacteriological effects of RKM were evaluated for 175 patients including 5 cases of pharyngitis, 3 tonsillitis, 32 pneumonia, 17 mycoplasmal pneumonia, 34 atypical pneumonia, 28 streptococcal infections, 29 Campylobacter enteritis, 4 Salmonella gastroenteritis, and 23 enteritis due to unknown organisms. Five drop-out cases were excluded from the evaluations. In the evaluable cases, an average dose level used was 31.8 mg/kg/day, with a daily dose divided into 3 to 4 administrations and with an average treatment duration of 9 days. Adverse reactions of RKM and its effects on laboratory test values were investigated in these patients including the drop out cases. Obtained results of these studies are summarized below. 1. The GA-test produced pH values indicating that amounts of gastric acid were mostly either normal or high in 42 of the 43 subjects tested (97.7%), and only one low acid case (2.3%) was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

The spiramycin paradox

Spiramycin has been found to be effective in a variety of clinical and experimental infections despite modest in-vitro activity. In animal models of infection, spiramycin has been found to be as effective as or more effective than erythromycin despite inferior in-vitro activity. These paradoxical results are explained in part by spiramycin's ability to achieve intra-cellular and tissue concentrations that exceed serum concentrations by a factor of ten or more. Furthermore, spiramycin clearance from these sites is much lower resulting in sustained tissue and intracellular concentrations. Finally, spiramycin appears to produce a substantial post-antibiotic effect and, possibly, subinhibitory effects that may further enhance its in-vivo activity.

Spiramycin uptake by alveolar macrophages

The in-vitro and in-vivo uptake of spiramycin by human and animal alveolar macrophages was studied. In-vitro penetration was studied in guinea pig and human alveolar macrophages incubated in medium 199 at 37 degrees C containing spiramycin at various concentrations. Results were expressed as the cellular/extracellular concentration ratio (C/E). The in-vivo study was performed in patients receiving 500 or 1000 mg spiramycin every 8 h as a 1-h infusion on day 1. A single infusion was given on day 2, 2 h before serum and bronchoalveolar lavage (BAL) sampling. Spiramycin was assayed by HPLC, and by a microbiological assay. In guinea pig alveolar macrophages, the C/E ratio of spiramycin after 60 min at 37 degrees C was 20.3 +/- 6.5 when the concentration was 10 mg/l. In human alveolar macrophages, the C/E ratio was 21.3 +/- 8.7 at 5 mg/l spiramycin and 23.8 +/- 8.7 at 50 mg/l. The accumulated spiramycin was slowly released when the cells (guinea pig alveolar macrophages) were washed and re-incubated in antibiotic free medium. Spiramycin was able to penetrate the alveolar space. In BAL supernatant, spiramycin levels were about 24-fold the serum level (n = 6 patients), when the BAL/serum glucose ratios were used as the dilution estimate. Alveolar macrophage levels ranged from 17 to 210 mg/l (n = 6 patients receiving 500 mg spiramycin infusion). These results are consistent with the in-vitro data.

[Hygienic substantiation of using new antibiotic preparations, tylosin phosphate and vitagrin as food additives]

Hygienic regulation of the use of the agents studied in animal experiments as food additives has been validated with respect to the dose level, regimen of addition and the period of waiting for slaughter. It is recommended that tylosin-phosphate should be included into the animals' ration as a food additive in a dose of 60 mg/kg for a short time (2-3 days), the period of waiting for slaughter being not less than 6-7 days. Addition of vitagrin has been recommended for young growing animals in a dose of 400-500 g/ton of feed. The dose of vitagrin should be reduced to 200-300 g/ton of feed one-two months before slaughter, with a 10-day period of waiting for slaughter.

Spiramycin concentrations in the human respiratory tract: a review

Spiramycin has exceptionally good distribution properties, especially in respiratory tract tissues and fluids. Three hours after a single oral dose of 3 g spiramycin, the serum concentration ranged from 1.6 to 2.8 mg/l and the reported half-life was approximately 8 h. Studies of lung tissue concentrations showed that high pulmonary levels were achieved after a loading dose of 3 g; the levels were higher after multiple doses and reached approximately 30 to 45 mg/kg in lung tissue and 6.5 to 36 mg/kg in bronchial mucosa; in bronchial secretions and in sputum the concentrations of spiramycin ranged from 1.5 to 7.3 mg/l (after 1 g, multiple doses). In upper respiratory tract tissues and fluids, high levels of spiramycin were reached as well: 8 to 13 mg/kg in sinus mucosa; 15 to 29.5 mg/kg in tonsils or adenoids.

[Studies on the metabolic fate of 14C-rokitamycin. Absorption, distribution, metabolism and excretion in infant rats]

14C-Rokitamycin (RKM) at the dose of 200 mg/kg was administered orally to fasted infant rats to study the absorption, distribution, metabolism and excretion in infant animals. The mean blood level of 14C-RKM reached its peak of 20.25 micrograms/ml in 30 minutes. The mean area under the curve was 93.23 micrograms.hr/ml. In vivo plasma protein binding rates of 14C-RKM were about 30% in both infant and adult rats. 14C-RKM was distributed at high concentrations into liver, kidney, lung, spleen, pancreas, bone marrow, submaxillary gland and some other tissues. Major metabolites detected in plasma, urine and bile were 10"-OH-RKM, leucomycin A7, leucomycin V and 14-OH-leucomycin V. In excretion studies, about 97% of the administered radioactivity was recovered in urine and feces within 144 hours. After intraduodenal administration to rats with cannulated bile ducts, 7.42% and 25.66% of the radioactivity were excreted within 24 hours in the urine and bile, respectively.

[Laboratory and clinical studies of rokitamycin dry syrup in the field of pediatrics]

Laboratory and clinical studies on rokitamycin (RKM) dry syrup, a new macrolide antibiotic, were carried out in the field of pediatrics. The results are summarized as follows. 1. Plasma concentrations and urinary recovery rates after oral administration on fasting of RKM dry syrup at doses of 10 mg/kg and 20 mg/kg to 2 and 1 cases, respectively, were determined. Peak plasma levels were obtained in 30 minutes after administration of both dosages with half-lives of 1.5 to 2.2 hours. A clear-cut dose response was observed. Urinary recovery rates in the first 6 hours after administration ranged from 1.75 to 2.26%. 2. The MICs of RKM against 80 clinical isolates (Streptococcus pyogenes 9, Streptococcus pneumoniae 14, Branhamella catarrhalis 4, Haemophilus influenzae 27, Haemophilus parainfluenzae 9, Haemophilus haemolyticus 2, Haemophilus parahaemolyticus 14 and Campylobacter jejuni 1) were compared with MICs of midecamycin acetate (MOM), josamycin (JM) and erythromycin (EM). The antibacterial activity of RKM was superior to those of MOM and JM and slightly inferior to that of EM. 3. Twenty-eight pediatric patients with acute infectious diseases (acute tonsillitis 4, streptococcal infection 4, acute bronchitis 9, pneumonia 4, mycoplasmal pneumonia 2 and Campylobacter enteritis 5) were treated with RKM dry syrup at a daily dose of 12-42.9 mg/kg t.i.d. as a rule. Efficacy rates were 92.9% clinically and 58.6% bacteriologically. 4. No adverse reactions were observed. Abnormal laboratory findings were mild; thrombocytosis in 2 and eosinophilia in 1. 5. The taste and the odor of RKM dry syrup preparation were sufficiently tolerable for the pediatric patients to accept it.

[Studies on the absorption and excretion of rokitamycin in infant beagle dogs. Comparison with adult beagle dogs]

Absorption and excretion of rokitamycin (RKM) were studied after oral administration of 50 mg/kg to fasted infant and adult Beagle dogs. In infant Beagle dogs, the mean plasma level of RKM reached its peak of 6.53 micrograms/ml in 15 minutes after administration. The area under the curve (AUC) value was 11.04 micrograms.hr/ml. In adult Beagle dogs, the mean plasma level of RKM reached its peak of 8.62 micrograms/ml in 30 minutes after administration. The AUC value was 18.25 micrograms.hr/ml. Ratios of Cmax and AUC value in infant Beagle dogs to those in adults were about 75% and 60%, respectively. In infant Beagle dogs, urinary excretion of RKM was 2.55% of the dose within 24 hours. In adult Beagle dogs, urinary excretion of RKM was 3.03% of the dose within the same period. The excretion ratio of RKM in infant Beagle dogs was about 85% of the adults' value.

Rokitamycin uptake by alveolar macrophages

The ability of antibiotics to enter cells, especially phagocytic cells, may be an important factor affecting therapy for infections caused by organisms which survive and proliferate intracellularly. It is well known that macrolides and clindamycin have high intracellular penetration ability. We studied the uptake of rokitamycin (RKM), a new oral macrolide, using rabbit alveolar macrophages and 2 other macrolides for comparison. Intracellular concentrations of erythromycin and josamycin were, respectively, approximately 20 and 40 times higher than extracellular concentrations when they were incubated at an initial extracellular concentration of 5 micrograms/ml (I/E = 20.1 +/- 2.6, 40.8 +/- 7.4). In comparison to these 2 macrolides, the uptake of RKM was massive and very rapid. The cellular concentration of RKM was approximately 120 times higher than the extracellular concentration. Uptake of the 3 macrolides by rabbit alveolar macrophages at 4 degrees C was approximately 10% of that at 37 degrees C. This study demonstrated that RKM was rapidly and massively accumulated by alveolar macrophages, and that the drug accumulation depends on temperature. These observations suggest that RKM therapy may be very effective for the treatment of some infectious diseases.

[Clinical study of rokitamycin dry syrup in pediatrics]

A total of 22 patients with acute pediatric infections was treated with rokitamycin (TMS-19-Q, RKM) dry syrup, a new macrolide antibiotic developed by Toyo Jozo Co., Ltd., Ohhito, Japan, to investigate its clinical efficacy. 1. A girl of an age 4 years 2 months (weighing 16.5 kg) was administered orally 10 mg/kg of RKM, and a boy of an age 8 years 7 months (weighing 24.5 kg), 15 mg/kg, and blood concentrations of RKM in these subjects were measured to investigate its absorption and excretion. Blood concentrations of the drug reached a peak of 0.84 microgram/ml in an hour after the administration in the girl, 0.72 microgram/ml in 30 minutes in the boy, with T1/2 of 0.86 and 1.82 hours, respectively. Their 6-hour cumulative urinary recovery rates were 2.79 and 2.13%, respectively. 2. A total of 20 patients was treated with RKM dry syrup. These patients included 3 with acute pharyngitis, one with acute tonsillitis, 4 with hemolytic streptococcal infections, 7 with acute bronchitis, 2 with pneumonia, another 2 with pertussis, and one with Campylobacter enteritis. The treatment was effective in 18 of them with a clinical efficacy of 90.0%. 3. Bacteriological responses to RKM dry syrup were as follows: eradication of pathogens in 5, pathogens decreased in 3, and no changes were observed in 3 of 12 patients from whom pathogens had been isolated prior to the treatment, thus the eradication rate was 45.5% with the exception of 1 patient whose bacteriological response was unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical studies of rokitamycin dry syrup in the field of pediatrics]

We studied the absorption and excretion as well as the clinical effect of rokitamycin (RKM, TMS-19-Q) dry syrup. The results we found are summarized as follows: 1. When 3 pediatric patients were medicated orally with a single dose of 10 mg/kg of the drug, its peak concentrations of 0.75 and 0.51 microgram/ml appeared in the blood in 30 minutes after administration in 2 patients, and of 0.21 microgram/ml in 1 hour in the other patient. At 4 hours after administration, its concentration in the blood was 0.07-0.08 microgram/ml in all of the patient, and at 6 hours, it was undetectable. T1/2 values were 1.05-2.08 hours. First 6-hour urinary recovery rates of the drug in the first 2 patients were 1.52 and 1.11%, respectively. 2. Twenty-four patients with 25 diseases were medicated with 7.14-12.5 mg/kg of the drug 3-4 times daily for 4-10 days. The patients consisted of 12 with tonsillitis, 7 with bronchitis, 3 with colitis, one each with Haemophilus influenzae pneumonia, mycoplasmal pneumonia, and pertussis. Clinical responses to the treatment were excellent in 7, good in 13, and poor in 5, with an efficacy rate of 80.0%. Bacteriologically, of 17 isolates whose changes were followed, 8 were eradicated, 1 decreased, and 8 remained unchanged, with an eradication rate of 47.1%. 3. No adverse reactions to the drug were observed in any of these patients, while abnormal laboratory test values observed were slight eosinophilia and also slight elevations of S-GOT and S-GPT in one of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

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%.

Spiramycin concentrations in female pelvic tissues, determined by HPLC: a preliminary report

An automated high performance liquid chromatographic method with remote controlled column switching was used to measure the concentration of spiramycin in pelvic tissues and plasma after oral administration of the antibiotic. Three oral doses of 2 g spiramycin were given to patients scheduled for elective gynaecological surgery over the 14 h before 6 a.m. on the day of surgery. Spiramycin concentrations in serum ranged from 7.4 to 12.5 mg/l between 3 h 20 min and 9 h 20 min after the last dose of spiramycin. Spiramycin pelvic tissue concentrations were determined in five of the eleven females and ranged from 4.4 to 33.3 mg/kg. The highest concentrations were observed in the Fallopian tube. These preliminary results suggest that spiramycin has good diffusion into female pelvic tissues.

Spiramycin concentrations in lung tissue

Spiramycin concentrations in lung tissue were studied in patients undergoing pulmonary surgical procedures. The first group of six patients received 500 mg spiramycin iv 16 h before surgery and 500 mg at anaesthetic induction (total 1 g). The second group of six patients received three doses of 500 mg spiramycin iv 24, 16 and 8 h before surgery, and 500 mg at anaesthetic induction (total 2 g). Samples were taken from lung tissue, pleura, fat tissue and muscle. In group 1, the mean lung tissue concentration of spiramycin was 1.15 +/- 0.14 mg/kg and 7.99 +/- 2.02 mg/kg in group 2 (P less than 0.02). The differences in concentration in pleura, fat tissue and muscle samples between treatment groups 1 and 2 were not statistically significant.

3H-spiramycin penetration into fibrin vegetations in an experimental model of streptococcal endocarditis

In-vivo diffusion of labelled spiramycin into fibrin was investigated in a rabbit model of left sided subacute endocarditis caused by a nutritionally variant streptococcus that produces large fibrin vegetations. Animals received one 30 min infusion of different doses of 3H spiramycin alone (73.4 +/- 3.5 microCi and 846 microCi) or 57.5 +/- 3.5 microCi in combination with 50 mg/kg 'cold' spiramycin. Thirty minutes after the end of infusion (T30) these vegetation/blood and vegetation/muscle ratios were between 1 and 2 and the vegetation/plasma ratio was between 2 and 4 for the three doses tested. Autoradiography showed that 3H spiramycin was homogeneously distributed throughout the vegetation in comparison with some other drugs. On the other hand, there were considerable differences in antibiotic concentration among different vegetations in a single animal.

Pharmacokinetics of spiramycin in man

The pharmacokinetics of spiramycin were studied after single and repeated administration by iv and oral routes. Following iv administration of a 500-mg dose in a one-hour infusion, peak serum concentrations were 1.54-3.10 mg/l. These concentrations are higher than MICs of spiramycin for various infectious agents. Eight hours after the end of infusion, the mean serum concentration was close to 0.25 mg/l. Spiramycin is rapidly and widely distributed throughout the body and achieves high ratios of tissue to serum concentrations in bucco-dental, pulmonary and prostatic tissues and skin. The distribution half-life of spiramycin was 10 min. The steady-state volume of distribution (Vdss) and the tissue distribution volume were 5.6 and 4.5 l/kg. The absolute bioavailability of spiramycin was 36% (S.D. +/- 14). Oral doses of spiramycin between 1 and 2 g resulted in linear increase in the peak serum levels and areas under the serum concentration-time curve. Spiramycin does not appear to undergo important metabolic conversion and is mainly excreted via the biliary route. Indeed, in man, the urinary excretion of active compounds represents only 7.6 to 20% of the administered dose. Spiramycin had a terminal elimination half-life of approximately 5 h. Renal clearance (144 ml/min) was much lower than non-renal clearance (887 ml/min). The total body clearance of spiramycin in young adults was 1.42 l/min (S.D. +/- 0.5) but only 0.53 l/min (S.D. +/- 14) in elderly subjects. During repeated iv administration (500 mg tid), steady state was achieved after four doses. Cmax and Cmin were 3.0 and 0.5 mg/l in young adults and 4.5 and 1.75 mg/l in elderly patients. Spiramycin's kinetics differ in several important respects from erythromycin's, notably the larger volume of distribution of spiramycin which reflects the higher tissue concentration. The reduced spiramycin clearance in elderly subjects requires further investigation.

[Studies of rokitamycin in pediatrics]

Pharmacokinetic, bacteriological and clinical studies on a new macrolide antibiotic, rokitamycin (RKM) dry syrup for pediatric use, were done, and results as summarized below were observed: 1. Five children with ages between 6 and 10 years were administered orally with RKM at a dose level of 10 mg/kg either at 30 minutes before or 30 minutes after meal on a crossover design, and plasma concentrations and urinary excretion rates of the drug were measured. Plasma concentrations of RKM following the administration before meal were 0.50 microgram/ml at 1/2 hour, 0.43 microgram/ml at 1 hour, 0.15 microgram/ml at 2 hours, 0.03 microgram/ml at 4 hours, and not detectable at 6 hours. Plasma concentrations following the administration after meal were 0.11 microgram/ml at 1/2 hour, 0.15 microgram/ml at 1 hour, 0.09 microgram/ml at 2 hours, 0.03 microgram/ml at 4 hours, and not detectable at 6 hours. The 0-6 hour urinary recovery rates were 1.41% following the administration before meal, and 0.93% following the administration after meal. These results suggested that the drug might be absorbed more rapidly, giving a higher plasma concentration, when administered before meal than when administered after meal. Changes in plasma concentrations of RKM following the administration of 10 mg/kg before meal were similar to those of two 100 mg RKM tablets (TMS-19-Q.GC tablets) to adult patients. Therefore, it seemed optimal to administer 10 mg/kg 3 times daily at fasting to children as a rule.(ABSTRACT TRUNCATED AT 250 WORDS)

[Laboratory and clinical studies of rokitamycin in pediatric fields]

We have carried out laboratory and clinical studies on rokitamycin (RKM, TMS-19-Q). The results are summarized as follows. Serum and urinary concentrations of RKM were determined in 6 children with ages between 6 and 12 years given single oral doses of 5, 10 and 15 mg/kg. Mean serum concentrations peaked at 30 minutes after administration of 5, 10 and 15 mg/kg, and respective peak values were 0.30 microgram/ml, 0.79 microgram/ml and 1.32 micrograms/ml. Biological half-lives for 5, 10 and 15 mg/kg were 2.0 hours, 1.65 hours and 1.36 hours. The 6-hour urinary recovery ranged from 1.11% to 2.58% after administration of 5 mg/kg, and the mean 6-hour urinary recoveries were 1.35% after administration of 10 mg/kg and 2.28% after administration of 15 mg/kg. Therapeutic responses were recorded as excellent or good in 22 (73.3%) of the children, comprising 6 with tonsillitis, 2 with pharyngitis, 4 with bronchitis, 1 with bronchopneumonia, 1 with Mycoplasma pneumonia, 2 with whooping cough, 5 with streptococcal infections, 5 with Campylobacter enteritis, 3 with impetigo and 1 with SSSS. The microbiological effectiveness of RKM on identified pathogens comprising 4 strains of Staphylococcus aureus, 1 strain of Streptococcus pneumoniae, 6 strains of Streptococcus pyogenes, 4 strains of Haemophilus influenzae and 5 strains of Campylobacter spp. was not so satisfactory as evidenced by a eradication rate of 50.0%. No significant side effect due to the drug was observed in any cases. In conclusion, RKM was found to be efficacious and safe for the treatment of bacterial infections in children.

[Clinical and pharmacokinetic evaluation of a +rokitamycin dry syrup in children]

Twenty five children were treated with rokitamycin (RKM) and its clinical efficacy and side effects were evaluated. Ages of the patients ranged from 13 days to 10 years. Doses of RKM ranged 17.1-39.3 mg/kg/day for 2.3 to 17.7 days. Twenty four patients including 8 Mycoplasma pneumonia, 5 bronchopneumonia, 6 bronchitis, 2 streptococcosis, 1 otitis media, 1 tonsillitis and 1 Chlamydia conjunctivitis were evaluated for clinical efficacy. Results were excellent in 7, good in 12, fair in 4, and poor in 1 patient. One patient was excluded from the evaluation, because the patient was treated with erythromycin before entering this study. Out of the 25 patients, 3 cases showed eosinophilia, 2 cases showed elevated GOT and GPT but no adverse clinical signs due to RKM were observed. The pharmacokinetics of RKM was studied in 5 patients whose ages ranged from 8 to 12 years. Plasma peak concentrations of RKM in 2 patients were 0.14 and 0.16 micrograms/ml at 30 minutes after doses of 5 mg/kg. Peak concentrations in 3 patients ranged from 0.32 to 1.02 micrograms/ml after doses of 10 mg/kg. Portions of the drug excreted into urine within 6 hours were 0.49 and 1.03% in 2 patients each of whom was given doses of 5 mg/kg, and ranged from 1.16 to 1.30% in 3 patients, each given 10 mg/kg. Metabolic products in urine within 4 hours after doses of 5 to 10 mg/kg were studied in 4 patients. Leucomycin A7 and leucomycin V accounted for almost 90% of all the related compounds excreted.

[Bacteriological, pharmacokinetic and clinical studies on a rokitamycin dry syrup in the pediatric field]

Bacteriological, pharmacokinetic and clinical studies were done on the effect of rokitamycin (RKM, TMS-19-Q) in the field of pediatrics. The results are summarized below. 1. Antibacterial activities Antibacterial activities of RKM against Staphylococcus aureus (including 50 methicillin-sensitive and 50 methicillin-resistant strains), 18 strains of Haemophilus influenzae and 50 strains of Campylobacter jejuni were studied comparatively with activities of josamycin (JM), midecamycin (MDM), erythromycin (EM) and cefaclor (CCL) or ampicillin. Minimum inhibitory concentrations (MICs) of the 5 antibiotics against methicillin-sensitive S. aureus showed a wide variation but RKM was somewhat superior among them. MIC80 of those antibiotics tested against methicillin-sensitive S. aureus were as follows; RKM 1.56, JM 12.5, MDM 12.5, EM 6.25, and CCL 3.13 micrograms/ml. Among methicillin-resistant S. aureus (MRSA), ratios of strains highly resistant to these antibiotics (MIC greater than or equal to 100 micrograms/ml) to total number of strains tested were: 18% to RKM, and 26%, 34% and 48% to JM, MDM and EM, respectively, again showing the superiority of RKM and the proliferation of resistant organisms to EM. MICs of RKM against H. influenzae were distributed in a range between 0.78 and 12.5 micrograms/ml, which were similar to MIC range of CCL, and approximately twice as high as that of EM, but 4 folds lower than those of JM and MDM. Against C. jejuni, the MIC range of RKM was quite broad, 0.10-12.5 micrograms/ml, with a peak value of 0.20 micrograms/ml. The cumulative number of strains vs. MIC curve was similar to that of EM, and RKM was approximately 4 to 8 folds more effective than the other 3 antibiotics. 2. Absorption and excretion The absorption and the excretion of RKM were studied with its dry syrup preparations. Dose levels examined were 5 mg/kg in 2 cases, 10 mg/kg in 7 cases, 15 mg/kg in 2 cases and 20 mg/kg in 1 case. Peak concentrations of RKM in blood were not dose-dependent and were 0.16-0.23, 0.29-0.91, 0.35-0.46 microgram/ml and 0.53 microgram/ml, respectively, for the 4 dose levels. Most of drug levels dropped below the detection limit in 4 hours after the administration when dose levels up to 10 mg/kg were used, and when dose levels were at or above 15 mg/kg, 0.07-0.09 microgram/ml of RKM was detected in blood at 6 hours after the administration. Urinary recovery rates in 6 hours were between 0.19 and 3.31%.(ABSTRACT TRUNCATED AT 400 WORDS)

[Appraisal of rokitamycin in the pediatric field]

In a study of rokitamycin (RKM) dry syrup for its usefulness in pediatric infections, the following results were obtained: 1. Frequencies of RKM-resistant strains among fresh isolates from sick children were very low, and 4.4% of 68 isolates of Staphylococcus aureus, 4.2% of 48 isolates of Streptococcus pneumoniae, and none of 96 isolates of Streptococcus pyogenes were found to be RKM-resistant. 2. Hypo- to achlorhydria was found in 2 (3.77%) of 53 children. 3. When children were administered once orally with 5, 10 and 15 mg/kg of RKM dry syrup at fasting, mean peak values of plasma concentration were 0.25, 0.55 and 0.74 micrograms/ml with a T1/2 (beta) of 2.18, 1.97 and 2.00 hours, respectively. Urinary recovery rates during the first 0-6 hours were quite low, and values were 1.21, 1.38 and 2.23%, respectively. 4. The clinical efficacy of RKM dry syrup was studied on children chiefly with acute pneumonia, mycoplasmal pneumonia and tonsillitis. Among 379 children from whom pathogens had been determined, responses to the treatment were excellent in 186, good in 144, fair in 24, poor in 20 and unknown in 5 patients, the overall efficacy rate being 88.2%. Among all 598 treated patients, including those with undetermined pathogens, responses were excellent in 247, good in 269, fair in 42, poor in 35 and unknown in 5 patients, the efficacy rate being 87.0%. 5. The clinical efficacy of the drug in treating Chlamydia infection in 12 patients including a Chlamydia carrier and the clinical efficacy in treating Campylobacter enteritis in 36 patients were studied. All the cases showed "good" responses. Among 66 patients with mycoplasmal pneumonia, responses were excellent in 33 and good in 27 patients, with an efficacy rate of 90.9%. 6. The optimal dose of RKM dry syrup seemed to be in the range between 20 and 40 mg/kg. It appeared, however, that a dose of about 40 mg/kg would be required to eradicate the pathogen from the pharynx in S. pyogenes infection. 7. Adverse reactions to RKM dry syrup were found in 9 (1.45%) of 622 patients. The reactions were gastrointestinal symptoms except eruption occurred in 1 patient, but they were all mild. Laboratory examinations revealed eosinophilia in 19 and abnormal hepatic enzyme activities in 8 of 455 patients studied, but such abnormalities were all transient and mild.

[Bacteriological, pharmacokinetic and clinical studies of a rokitamycin syrup in pediatrics]

Rokitamycin (RKM) dry syrup was administered to a group of pediatric patients. The results obtained are summarized as follows. 1. Of the recent isolates of Streptococcus pyogenes, fewer strains were highly resistant to RKM than to josamycin (JM), midecamycin (MDM), erythromycin and lincomycin. Also, macrolides (MLs)-resistant strains proved to be susceptible to RKM. 2. Recent isolates of Staphylococcus aureus, Streptococcus agalactiae, group G Streptococci, S. pyogenes, Streptococcus pneumoniae and Haemophilus influenzae were more susceptible to RKM than to midecamycin acetate and JM. Oral administrations of 10-15 mg/kg of the drug were followed by its peak concentrations of 0.07-0.77 micrograms/ml in the blood at 30 minutes in many patients, and by an undetectable level at 6 hours also in many of them. T1/2 values were 1.2-2.6 hours, and first 6-hour urinary excretion rates were 1.26-1.74%. 3. Fifty-two patients with acute upper and lower respiratory tract infections, Campylobacter enteritis, etc. were treated with RKM at about 20-40 mg/kg daily for 4-14 days, with an overall efficacy rate of 88.5%. 4. An eradication rate of 81.4% was achieved for 43 strains of 7 species isolated from the patients. 5. No abnormal laboratory test values were observed after treatment with drug 4 approximately 14 days. A side effect, stomach discomfort, was observed in 1 patient.

[Clinical and pharmacokinetic studies of rokitamycin in children]

Rokitamycin dry syrup (RKM), a new macrolide antibiotic preparation, was evaluated for its safety, efficacy and pharmacokinetics in 19 children. RKM was effective in mycoplasmal pneumonia, Chlamydia trachomatis pneumonitis and Campylobacter gastroenteritis. Efficacies of RKM in streptococcal pharyngitis and Haemophilus influenzae pneumonia, however, were insufficient. Pharmacokinetic observations seemed to indicate that RKM achieved higher blood concentrations than older macrolides, but a large individual variation was observed. Diarrhea which was the only type of side effect observed in our cases, was encountered in 2 of 17 evaluable cases. From these data, RKM seems to have a place in the treatment of pediatric infectious diseases.

Pharmacokinetics of roxithromycin (RU 965)

This report contains the findings of five studies performed to evaluate the pharmacokinetics of roxithromycin (RU 965), a new macrolide antibiotic. Roxithromycin was given as 150- and 300-mg film-coated tablets. The drug is rapidly absorbed after oral administration. Peak plasma levels following 150- and 300-mg doses occur within two hours. Steady state is reached within four days with doses of 150 mg twice a day or 300 mg once daily. The plasma half-life is approximately 12 hours. About 10% of the dose is excreted in urine. Although dose dependency was observed for the various pharmacokinetic parameters, dose proportionality could be demonstrated only in terms of the percentage of the dose excreted in urine. The rate of absorption is not affected by age. The rate of elimination and renal clearance are decreased in healthy elderly subjects, however, these differences should not be clinically meaningful. The bioavailability of the drug is not affected to a clinically meaningful extent when it is given with milk. Less than 0.05% of the administered dose is excreted in the breast milk of lactating women. Roxithromycin was safe and well tolerated with no clinically meaningful changes in any of the safety variables in any of the five studies reported.

The effect of antibiotics on the intracellular survival of bacteria in human phagocytic cells

[14C]-labeled josamycin (Wilprafen) readily enters several types of human phagocytic cells-polymorphonuclear leucocytes (PMNLs), adherent monocytes and alveolar macrophages - and is accumulated by these cells to a concentration about 20 times that in the extracellular medium. Similar studies using [14C]-benzyl penicillin revealed that the beta-lactam antibiotic penetrated these cells very poorly. Low concentrations of josamycin and the various phagocytes acted synergistically to inhibit the intracellular proliferation of L. pneumophila or H. influenzae. In contrast, penicillin G was not effective against legionellae ingested by PMNLs, monocytes or alveolar macrophages, even at high concentrations. The uptake of the antibiotics apparently correlates well with its efficacy against the intracellular survival of bacterial pathogens in human phagocytic cells.

Comparative efficacy of clindamycin, erythromycin and spiramycin against Staphylococcus aureus in the rat croton oil pouch model

Spiramycin, a macrolide antibiotic, has inferior in-vitro activity to erythromycin, but superior tissue penetration. Recent publications have suggested that the in-vivo activity of spiramycin should be re-assessed. The efficacy of clindamycin, erythromycin and spiramycin was compared against Staphylococcus aureus infections in the rat croton oil pouch model. The concentration of spiramycin in the pouch fluid was lower than the concentration of clindamycin or erythromycin after single or multiple intraperitoneal injections. In contrast, the concentration of spiramycin in the pouch wall (73.3 +/- 14.5 micrograms/g) was markedly higher than that of erythromycin (less than 7.5 micrograms/g). Multiple doses of spiramycin had no significant effect upon bacterial growth in the pouch, whereas clindamycin and erythromycin had a significant bactericidal effect. The results suggest that spiramycin is bound to tissues, diffuses poorly into tissue fluid and may therefore be ineffective against infections in large collections of tissue fluid.

Pharmacokinetics of roxithromycin in paediatrics

Macrolides are well known for their high lipid solubility and good tissue penetration. The pharmacokinetic properties of roxithromycin, a new semisynthetic macrolide, appear to be very interesting in healthy adult patients. Five paediatric pharmacokinetic studies are summarized and show that the pharmacokinetic properties of roxithromycin in paediatrics are very similar to those previously reported in adults and suggest that the same dose every 12 h is appropriate in paediatrics, 2.5 mg/kg. The diffusion of roxithromycin into upper respiratory tract tissues appears to be good in children.

Pharmacokinetics of roxithromycin in renal and hepatic failure and drug interactions

In patients with renal insufficiency roxithromycin pharmacokinetic parameters are significantly altered. In particular, the Cmax, the AUC and the T1/2 are increased and the Clr is reduced. In alcoholic cirrhotic patients the blood half-life is dosage higher than in normals. In spite of this, in these types of patients the usual roxithromycin dosage should not be modified. Potential pharmacokinetic drug interactions that involve roxithromycin are very few and concern only disopyramide and theophylline. Theophylline concentrations should be monitored if the pretreatment blood level is greater than 15 mg/l.

[New aspects of macrolides: contribution of roxithromycin]

Roxithromycin (RU 28965) is a new semi-synthetic derivative of erythromycin. Its antibacterial activity is of the same order as that of other macrolides, although its MIC's against Legionella pneumophila are lower. In double-blind comparative studies there was no significant difference in therapeutic effectiveness between roxithromycin and the reference antibiotics tested. However, this new macrolide exhibits exceptional pharmacological properties (prolonged half-life, excellent tissue penetration and intracellular activity), and it is very well tolerated both clinically and biochemically.

Tissue distribution of roxithromycin

As tissue distribution studies have become increasingly important aspects of the assessment of new antimicrobials, roxithromycin distribution has been evaluated in experimental models and in human tissues and body fluids. High levels were achieved in respiratory tract tissues and fluids and in the male and female genital tract. In most experiments the local concentrations of roxithromycin were as high as that in serum, reaching 4-6 mg/l (or mg/kg) or more. These high levels were generally stable and an equilibrium was reached between central and extra-vascular compartments. These data provide important information which may be clinically relevant.

Cellular uptake and subcellular distribution of roxithromycin and erythromycin in phagocytic cells

The intracellular accumulation and subcellular distribution of 14C-labelled roxithromycin and erythromycin has been studied in macrophages and polymorphonuclear neutrophils of both human and animal origin. Roxithromycin was consistently and significantly more accumulated than erythromycin, reaching intracellular/extracellular concentration ratios between 14 (in polymorphonuclear neutrophils) and 190 (in alveolar macrophages from smokers). Uptake was reversible, insensitive to anaerobiosis and to the presence of an aminoglycoside, but inhibited by acid pH. Upon subcellular fractionation by isopycnic centrifugation in sucrose gradients., half the roxithromycin or erythromycin recovered in cell homogenates was found associated with the lysosomes in macrophages, and about one third with azurophil granules in polymorphonuclear leucocytes. Inasmuch as cellular uptake is a necessary, albeit not sufficient, condition for antimicrobials to kill or inhibit the growth of intracellular bacteria the properties of roxithromycin may give it a distinct advantage over other antimicrobial agents.