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In a crossover design study, we compared the plasma bactericidal activities of erythromycin estolate (500 mg) and erythromycin ethylsuccinate (600 mg) after administration of a single oral dose to 12 healthy volunteers. Both erythromycin esters displayed very good plasma bactericidal activities against Streptococcus pneumoniae. The median bactericidal titers produced in plasma against Streptococcus pyogenes and Streptococcus pneumoniae were significantly higher with erythromycin estolate than with the ethylsuccinate ester at both 2 and 8 h after dosing (P less than 0.05 by Student's t test). Both erythromycin esters showed rather weak bactericidal activity against Branhamella catarrhalis; a further look at these results indicated that erythromycin estolate presented 50% of the plasma samples at 2 h with bactericidal titers superior or equal to 1:8, versus 11% for the ethylsuccinate ester. Of the 60 plasma bactericidal activity tests performed against Staphylococcus aureus, only 6 (10%) and 3 (5%) exhibited titers of 1:8 or greater for erythromycin estolate and erythromycin ethylsuccinate, respectively. Clinical trials are warranted in which these products are compared in infections other than Streptococcus pyogenes pharyngitis, for which the clinical superiority of erythromycin estolate has been demonstrated.
Relative bioavailability of erythromycin was determined after multiple-dose administration of erythromycin estolate in comparison to erythromycin ethylsuccinate both given as oral suspensions to twelve healthy volunteers. The daily erythromycin dose of erythromycin ethylsuccinate was 50% higher than the respective dose of erythromycin estolate; the dosage interval tau was 12 h for erythromycin estolate and 8 h for erythromycin ethylsuccinate. This scheme was planned in accordance to advices of the respective manufactures. Results of the study confirm the differences in extent of bioavailability of both erythromycin derivatives known from single-dose investigations. Furthermore, the experimental data show that a twice daily administration of 1000 mg erythromycin as erythromycin estolat resulted in sufficiently high plasma concentration of the active compound.
Chang liver cells and isolated rat hepatocytes were exposed to medium containing different concentrations of erythromycin estolate or erythromycin base for 1-5 h. Hepatotoxicity was quantitated by measuring leakage of enzymes from cells into surrounding medium and the damage to the plasma cell membrane seen under surface scanning electron microscopy. Only the cells exposed to erythromycin estolate showed significantly greater enzyme leakage than controls and appeared severely affected by cytopathic changes when observed under scanning electron microscopy.
Two patients experienced hepatotoxicity associated with erythromycin estolate (Ilosone) usage, followed 13 and 15 years later by an hepatotoxic reaction with administration of erythromycin ethylsuccinate (E.E.S.). These cases provide further evidence for erythromycin ethylsuccinate-associated hepatotoxicity and demonstrate erythromycin cross-sensitivity after previous erythromycin estolate liver injury. Hepatotoxicity to both sensitivity after previous erythromycin estolate liver injury. Hepatotoxicity to both estolate and ethylsuccinate preparations of erythromycin stimulates speculation regarding the potentially hepatotoxic moiety of the erythromycin molecule. Furthermore, these cases suggest that all erythromycin preparations should be avoided or used only with careful monitoring in patients with previous erythromycin-associated liver injury.
In an open randomized multicenter study 190 culture-positive pediatric ambulatory pertussis patients were treated for 14 days with either erythromycin estolate (EST) (n = 93; 40 mg/kg/day divided in 2 doses) or erythromycin ethylsuccinate (ETH) (n = 97; 60 mg/kg/day divided in 3 doses). On day 14 Bordetella pertussis was recovered from cultures of 2 patients (2.2%) treated with EST and 1 patient (1.0%) treated with ETH. Despite the fact that 151 patients (79.4%) had reached the early paroxysmal stage at initiation of antimicrobial therapy, clinical improvement was seen in the majority (reduced frequency and severity of coughing: EST, 77.4 and 67.7%; ETH, 74.2 and 63.9%, respectively). Drug-related side effects were noted in 11 patients (11.8%) treated with EST and 16 patients (16.5%) treated with ETH (P greater than 0.05) and consisted mainly of minor gastrointestinal complaints. Erythromycin estolate in a lower dose administered only twice a day was equivalent to erythromycin ethylsuccinate in all aspects and proved to be adequate antimicrobial treatment for pertussis patients.
The pharmacokinetics of erythromycin and erythromycin 2'-propanoate were studied in healthy male volunteers following single and repeated doses of erythromycin stearate tablets, erythromycin estolate capsules, and a suspension. Estolate dosages gave rise to higher plasma levels of total drug than the stearate. However, the stearate yielded higher plasma levels of erythromycin base. Absorption of all dosage forms, except the suspension, was delayed, and pharmacokinetic interpretation of both single- and multiple-dose data required incorporation of an absorption lag time. The absorption of erythromycin stearate was inhibited by food and also by low fluid volumes in fasted subjects. Absorption of erythromycin estolate was increased in the presence of food and was not greatly affected by fluid volume. Although single-dose data poorly predicted circulating levels of erythromycin following repeated doses, trends observed after single doses were maintained during chronic treatment.
To investigate the mechanisms of erythromycin cholestasis, the effects of erythromycin estolate (EE) on the excretory function of the isolated perfused rat liver and on liver plasma membrane (LM) preparations were studied and compared to those of erythromycin base (EB) and lauryl sulfate (LS), added alone or in combination. EE (at 125 to 200 microM) caused dose-dependent reductions of bile and perfusate flows, bile acid (BA) excretion, and biliary BA concentration. The alterations of the excretory function were only in part due to the decreased perfusate flow. In contrast, both 200 and 300 microM concentrations of EB elicited similar choleretic responses, which were presumably related to the osmotic activity of the drug excreted in the bile. LS did not affect hepatic excretory functions. However, the simultaneous addition of EB and LS resulted in a rate of bile flow lower than that observed with EB alone. EE, but not EB, increased canalicular permeability to [14C]sucrose as measured by bile to plasma (B:P) ratio. Neither drugs altered [14C]erythritol B:P ratio. In LM preparations both Na+,K+- and Mg2+-ATPase activities were inhibited in a dose-dependent manner by EE, but not by EB. The data suggest that EE could affect bile flow by inhibiting cotransport of Na+ and BA and by altering LM permeability and support the view that the effect of erythromycins on the liver may be related to their surface activity.
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Erythromycin and some other macrolide antibiotics can first induce a cytochrome P-450 isozyme similar to the one induced in rats by pregnenolone-16 alpha-carbonitrile and then inhibit it by forming a stable cytochrome P-450-metabolite complex. The purpose of this study was to compare azithromycin, a novel 15-membered ring azalide, and erythromycin estolate for the potential to cause hepatic microsomal enzyme induction and inhibition in Sprague-Dawley rats. The daily oral administration of 800 mg of erythromycin estolate per kg for 7 days resulted in statistically significant elevations of NADPH-cytochrome c reductase, erythromycin N-demethylase (3.2-fold), and total cytochrome P-450 content. Approximately 40% of cytochrome P-450 was complexed with erythromycin metabolite. In contrast, the daily administration of 200 mg of azithromycin per kg for 7 days caused significant elevations of N-demethylase (2.5-fold) only and did not produce any increases in total cytochrome P-450 content or NADPH-cytochrome c reductase. No complexed cytochrome P-450 was detected in the azithromycin-dosed rats despite liver concentrations of azithromycin that were 118 times greater than the liver concentrations of erythromycin estolate in erythromycin estolate-dosed rats. Although the short-term oral administration of azithromycin produced hepatic accumulation of the drug and elevated azithromycin demethylase activity, there was no other evidence of hepatic cytochrome P-450 induction or inactivation via cytochrome-metabolite complex formation. In contrast to erythromycin estolate, azithromycin is not expected to inhibit its own metabolism or that of other drugs via this pathway.
A randomized crossover study in 16 healthy volunteers given multiple doses of erythromycin base enteric-coated tablets or erythromycin estolate capsules revealed essentially no difference in the resultant plasma concentration of bioactive erythromycin. This similarity in bioactivity persisted despite the fact that total eryghromycin levels (bioactive erythromycin base plus bioinactive erythromycin propionate) were at least three times higher after administration of the estolate than after administration of the base.
The effects of erythromycin estolate, a well known hepatotoxic macrolide antibiotic, on isolated rat hepatocyte viability and on subcellular Ca2+ transport have been investigated. Erythromycin estolate (0.5 mM), but not erythromycin base and erythromycin ethylsuccinate, induced 100% cell death after 60 min incubation, and caused maximal inhibition of mitochondrial and microsomal Ca2+ sequestration activities at 0.1 mM concentration. Sodium lauryl sulphate, which is the surfactant moiety of the erythromycin estolate molecule, caused effects similar to those exhibited by erythromycin estolate. Disorders of the intracellular calcium homeostasis seem to play a role in the lauryl sulphate-mediated hepatotoxic action of erythromycin estolate.
The pharmacokinetics of erythromycin estolate (500 mg) and erythromycin ethylsuccinate (600 mg) were compared in 12 healthy volunteers after single doses and after repeated oral doses (every 8 h). High-pressure liquid chromatography with electrochemical detection was used to determine concentrations in plasma and urine of estolate, ethylsuccinate, and erythromycin base. The maximum concentration of drug in the serum, the half-life, and the area under the curve for erythromycin estolate were significantly greater than those of erythromycin ethylsuccinate after both regimens. After single and multiple doses, the respective areas under the curve of erythromycin base generated by estolate formulation were 3 and 1.6 times greater (P less than 0.05) than those of ethylsuccinate. The lower percentage of hydrolysis of erythromycin estolate (41 versus 69%) combined with its longer half-life (5.47 versus 2.72 h) and its larger area under the curve (30.61 versus 4.68 micrograms/h/ml, after multiple doses) could explain these differences. This study underscores the need for a specific high-pressure liquid chromatography assay and the importance of wide variability, rate-limited processes, changes with multiple doses, and the appearance of a second peak when one studies the pharmacokinetics of erythromycin esters. The pharmacokinetic data presented in this study reinforce the clinical advantages of erythromycin estolate over erythromycin ethylsuccinate.
The inter- and intrapersonal variability in the absorption and disposition of erythromycin estolate in humans was assessed by comparing total erythromycin serum concentrations in five subjects who each received a single erythromycin estolate tablet on three separate occasions under identical experimental conditions. Coefficients of variation for the pharmacokinetic parameters Cmax, Tmax, AUC0-12, MRT, and t1/2 were of a similar magnitude when calculated between subjects in any one administration phase or between phases. In addition, serum concentrations of both erythromycin base (active component) and erythromycin propionate were selectively determined in the same subjects only during the final two phases of the study. Comparison of AUC0-12 values showed that the percentage of the total area (base and ester components) present as erythromycin base remained relatively constant between administrations (mean values of 14.5 and 11.2%), with low coefficients of variation between subjects (10.8 and 11.6%). Discrepancy value calculations revealed that the variability in serum concentration-time profiles between the three phases of the study fell into the "small"-to-"moderate" classification. From these data it is apparent that intrapersonal variations in the absorption and disposition of erythromycin estolate are of a similar magnitude to interpersonal variations and should be borne in mind in the design and interpretation of comparative bioavailability studies involving similar formulations of this compound. The relative proportions of erythromycin base and propionate did, however, remain fairly constant both between treatments and between subjects.
Women in the second half of pregnancy, who were infected with genital mycoplasmas and who gave written informed consent, were randomly assigned to receive capsules of identical appearance containing erythromycin estolate, clindamycin hydrochloride, or a placebo for 6 weeks. Levels of serum glutamic oxalacetic transaminase (SGOT) were determined before and during treatment by a fluorometric method. All pretreatment levels of SGOT were normal (<41 units). Participants who received erythromycin estolate had significantly more abnormally elevated levels of SGOT (16/161, 9.9%) than did those who received clindamycin (4/168, 2.4%, P < 0.01) or those who received placebo (3/165, 1.8%, P < 0.01). Elevated levels of SGOT ranged from 44 to 130 U. Serum bilirubin levels were normal. Gamma-glutamyl transpeptidase activity was abnormal in six of six participants who had abnormal levels of SGOT while receiving erythromycin estolate. There were few associated symptoms, and all levels of SGOT returned to normal after cessation of treatment. The treatment of pregnant women with erythromycin estolate may be inadvisable.
Erythromycin estolate (EE) added to perfusing medium of isolated rat liver caused a dose-dependent decrease of both perfusate and bile flows. Biliary bile acid analysis showed that EE decreased both bile acid excretion rate and concentration. This suggests that EE interferes with the formation of bile acid dependent fraction of bile. EE is known to cause, in some individuals a reversible cholestatic hepatic injury. Our data if applicable to clinical setting indicate that an intrinsic toxicity of EE may contribute to the development of hepatic damage.
Using prescription-event monitoring to determine whether erythromycin estolate was a more frequent cause of jaundice than erythromycin stearate or tetracycline 12 208 patients, for whom 5343 doctors had prescribed one of the three drugs, were identified by the Prescription Pricing Authority. Of the questionnaires sent to general practitioners about the possible occurrence of jaundice, 76% were returned. There were 16 reports of jaundice, of which four were attributable to gall stones, three to cancer, six to viral hepatitis, and only three were possibly related to an antibiotic. All three patients, in whom the antibiotic was a possible cause, had been treated with erythromycin stearate. No case was attributable to the estolate which had previously been suspected of being a more frequent cause of jaundice. Although the incidence is unknown, it is very unlikely to be more than one in 100.
A method is described for the determination of erythromycin estolate by liquid chromatography. A C18 reversed-phase column (25 x 0.46 cm i.d.) was used with acetonitrile-tetrabutylammonium sulphate (pH 6.5, 0.2 M)-phosphate buffer (pH 6.5, 0.2 M)-water [x:5:5:(90-x), v/v/v/v] as mobile phase. The proportion of acetonitrile (x) has to be adapted to the type of stationary phase used. For RSil C18 LL 42.5% (v/v) was used. The column was heated at 35 degrees C, the flow rate was 1.5 ml min-1 and UV detection was performed at 215 nm. The main component, erythromycin A propionate, was separated from all other components which were present in commercial samples. The impurities most frequently observed were the propionate ester of erythromycin C and the amide N-propionyl-N-demethyl-erythromycin A. Erythromycin A was shown to be present in specialties.