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QT interval prolongation and torsades de pointes due to erythromycin lactobionate.

STUDY OBJECTIVES: To discern the frequency of torsades de pointes and QT prolongation in patients receiving intravenous erythromycin lactobionate; to examine the degree of QT prolongation and QT dispersion due to intravenous erythromycin in a typical clinical setting; and to identify any concurrent factors that might predispose patients to excessive QT prolongation or torsades de pointes while receiving intravenous erythromycin. DESIGN: Retrospective cohort trial. SETTING: A university teaching hospital. PATIENTS: All inpatients who received intravenous erythromycin lactobionate during a 1-year period. MEASUREMENTS AND MAIN RESULTS: The records of 278 consecutive patients were analyzed, of whom 49 had 12-lead electrocardiograms while receiving and not receiving erythromycin. The dosages of erythromycin ranged from 18-83 (42 +/- 18) mg/kg/day. Of the 49 patients, the baseline QTc was 432 +/- 39 msec, compared with 483 +/- 62 msec during erythromycin therapy (p < 0.01). In 30 of 49 patients with heart disease, the increase in QTc due to erythromycin was 15 +/- 11%, compared with 8.6 +/- 10% in the 19 patients without heart disease (p < 0.05). The degree of QTc dispersion was 34 +/- 16 msec at baseline, compared with 80 +/- 35 msec with erythromycin (p < 0.01). Overall, 19 (39%) of 49 patients had a moderate to severe delay in ventricular repolarization (QTc > or = 500 msec). Of the 278 patients prescribed intravenous erythromycin over the year, it caused torsades de pointes in just one (< or = 0.4%). CONCLUSION: Erythromycin lactobionate-induced torsades de pointes is rare, although QT prolongation is common. Some patients may be at risk for suffering torsades de pointes due to this agent, particularly if heart disease or other factors that may further delay ventricular repolarization are present.

Adult↗

Effect of treatment with erythromycin on bronchoalveolar lavage fluid cell populations in foals.

OBJECTIVE: To determine whether oral administration of erythromycin alters the inflammatory response to bronchoalveolar lavage (BAL) in young horses. ANIMALS: 12 healthy, unweaned, mixed-breed foals of either sex, between 2 and 4 months old. PROCEDURE: BAL was performed; 250 ml of phosphate-buffered saline solution (300 mOsm, pH 7.4) was administered in 50-ml aliquots. Foals were carefully monitored for 4 days, then erythromycin base (25 mg/kg of body weight, PO, q 12 h) was given to foals of the treated group. After 4 days, foals were reanesthetized, and the same lung was relavaged. Cytologic examination was performed on BAL fluid (BALF) samples from both groups of foals. At 12 hours after administration of the final dose, erythromycin A and anhydroerythromycin A concentrations were determined in plasma of treated foals. RESULTS: In the second BALF sample from the same lung of control foals, percentage of neutrophils was significantly increased (53 +/- 38.0%) [corrected], compared with that from erythromycin-treated foals (4.88 +/- 3.66%, P < 0.05), and was associated with apparent decrease in the ability of BALF cells from erythromycin-treated foals to migrate toward a chemoattractant source. Significantly fewer BALF cells adhered to a cell culture substratum after erythromycin treatment of foals. Erythromycin A was not detected in plasma of any treated foal at the time of the second BAL; anhydroerythromycin A, a degradation product of erythromycin, was detected in plasma of 5 of 6 foals (mean concentration, 0.2 +/- 0.06 micrograms/ml). CONCLUSION AND CLINICAL RELEVANCE: Bal induces neutrophilic inflammation, which persists for at least 4 days in the lungs of young horses. Erythromycin [corrected] (25 mg/kg, PO q 12 h) diminishes this inflammatory response through a mechanism that may involve alteration of BALF cell function. Degradation of erythromycin to biologically active products or presence of parent drug in pulmonary secretions may be responsible for alterations in pulmonary lavage cell chemotaxis and adherence. Erythromycin administered orally to foals at clinically relevant doses appears to have nonantimicrobial effects that may interfere with host cell metabolism and decrease inflammatory responses in airways.

Administration, Oral↗

Pharmacokinetic advantages of erythromycin estolate over ethylsuccinate as determined by high-pressure liquid chromatography.

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.

Administration, Oral↗

A proteomic analysis of erythromycin resistance in Streptococcus pneumoniae.

Streptococcus pneumoniae is a significant human pathogen which is an important cause of pneumonia and bacteraemia. Over the past few years the incidence of antibiotic resistance among clinical isolates of S. pneumoniae has increased. Penicillin resistance is now widespread and the frequency of isolates that are resistant to erythromycin has risen. Erythromycin resistance in S. pneumoniae follows two basic patterns. The MLS erythromycin-resistant phenotype is due to the enzymatic methylation of ribosomal RNA that blocks erythromycin binding to the ribosome. Alternatively, in isolates of the M phenotype, a more recently documented mechanism, resistance is associated with an active efflux process that reduces intracellular levels of erythromycin. We used two-dimensional electrophoresis to examine the proteins synthesised by erythromycin-susceptible and -resistant S. pneumoniae. Erythromycin-resistant S. pneumoniae with the M phenotype showed a significantly increased synthesis of a 38,500 Dalton (pI 6.27) protein compared to susceptible isolates. Peptide mass mapping was used to identify the 38,500 Dalton protein as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). It was demonstrated that S. pneumoniae synthesised at least three forms of GAPDH that differed in their isoelectric points. The form of GAPDH possessing the most basic pI showed the increased synthesis in the erythromycin-resistant S. pneumoniae isolates. Alterations in the synthesis of GAPDH were only found for those erythromycin-resistant isolates possessing the M phenotype. S. pneumoniae isolates with the MLS phenotype were indistinguishable from the susceptible strains using the analytical conditions employed for the current study. The possible role of GAPDH in erythromycin resistance of S. pneumoniae is considered.

Anti-Bacterial Agents↗

Effect of loxiglumide and atropine on erythromycin-induced reduction in gallbladder volume in human subjects.

This study was undertaken to investigate the effect of erythromycin, a motilin agonist with prokinetic activity, on fasting gallbladder volume. To evaluate the mechanism of action of erythromycin on gallbladder motility, erythromycin (3.5 mg/kg.20 min, intravenously) was infused on three separate occasions: during cholinergic blockage with atropine (0.005 mg/kg.hr), during cholecystokinin receptor blockade with loxiglumide (10 mg/kg.hr) and during saline solution infusion (control). Atropine, loxiglumide and saline solution infusions were started 3 hr before administration of erythromycin and were continued for 3 hr thereafter. Gallbladder volumes (measured by ultrasonography), plasma cholecystokinin levels (radioimmunoassay) and plasma pancreatic polypeptide levels (radioimmunoassay) were determined at regular intervals for 6 hr in six healthy volunteers. During the 3-hr infusion before administration of erythromycin, both loxiglumide and atropine significantly increased gallbladder volumes--from 18 +/- 2 to 37 +/- 3 cm3 (p less than 0.05) and from 17 +/- 3 to 24 +/- 2 cm3 (p less than 0.05), respectively--whereas saline solution did not significantly affect gallbladder volume. During control saline solution infusion, erythromycin induced prolonged gallbladder contraction that was significant (p less than 0.05) between 60 and 180 min and reached a maximum of 45% +/- 8% at 150 min. Plasma cholecystokinin levels were not affected by erythromycin. Erythromycin induced a significant (p less than 0.05) increase in plasma pancreatic polypeptide levels, from 12 +/- 1 pmol/L to 34 +/- 3 pmol/L. Loxiglumide did not prevent the erythromycin-induced reduction in gallbladder volume. Atropine markedly reduced the effect of erythromycin, causing slight but significant (p less than 0.05) gallbladder volume reductions (18% +/- 4%) between 150 and 180 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Binding of erythromycin to the 50S ribosomal subunit is affected by alterations in the 30S ribosomal subunit.

Expression of resistance to erythromycin in Escherichia coli, caused by an altered L4 protein in the 50S ribosomal subunit, can be masked when two additional ribosomal mutations affecting the 30S proteins S5 and S12 are introduced into the strain (Saltzman, Brown, and Apriion, 1974). Ribosomes from such strains bind erythromycin to the same extent as ribosomes from erythromycin sensitive parental strains (Apirion and Saltzman, 1974). Among mutants isolated for the reappearance of erythromycin resistance, kasugamycin resistant mutants were found. One such mutant was analysed and found to be due to undermethylation of the rRNA. The ribosomes of this strain do not bind erythromycin, thus there is a complete correlation between phenotype of cells with respect to erythromycin resistance and binding of erythromycin to ribosomes. Furthermore, by separating the ribosomal subunits we showed that 50S ribosomes bind or do not bind erythromycin according to their L4 protein; 50S with normal L4 bind and 50S with altered L4 do not bind erythromycin. However, the 30S ribosomes with altered S5 and S12 can restore binding in resistant 50S ribosomes while the 30S ribosomes in which the rRNA also became undermethylated did not allow erythromycin binding to occur. Thus, evidence for an intimate functional relationship between 30S and 50S ribosomal elements in the function of the ribosome could be demonstrated. These functional interrelationships concerns four ribosomal components, two proteins from the 30S ribosomal subunit, S5, and S12, one protein from the 50S subunit L4, and 16S rRNA.

Aminoglycosides↗

Blockade of the human cardiac K+ channel Kv1.5 by the antibiotic erythromycin.

Erythromycin administration has been associated with a prolongation of cardiac repolarization in certain clinical settings. This could be due to blockade of voltage-dependent K+ channels in the human heart. For this reason we examined the effects of erythromycin on a rapidly activating delayed rectifier K+ channel (Kv1.5) cloned from human heart and stably expressed in human embryonic kidney cells. When examined using the whole-cell patch clamp technique, erythromycin (100 microM) blocked Kv1.5 current in a time-dependent manner but required prolonged exposure to do so. However, when we examined Kv1.5 current using inside-out macro-patches, erythromycin applied to the cytoplasmic surface rapidly (within 1-2 min) inhibited Kv1.5 current with an IC50 value of 2.6 x 10(-5)M (1.7 - 3.9 x 10(-5)M, 95% C.L.). The main effect of erythromycin was to accelerate the rate of Kv1.5 current decay thereby reducing the current at the end of a prolonged voltage-clamp pulse. Erythromycin also blocked Kv1.5 current in both a voltage- and frequency-dependent manner but had little effect on the activation kinetics, deactivation kinetics, or the steady-state inactivation properties of Kv1.5. These data suggest that erythromycin acts as a blocker of an activated state of the Kv1.5 channel and that it may access its binding site from the intracellular face of the channel. This study is the first to examine the effects of erythromycin on a cloned human cardiac K+ channel. It is concluded that erythromycin blocks Kv1.5 at clinically relevant concentrations. Blockade of voltage-dependent K+ channels in the heart could contribute to the alterations in cardiac repolarization that have been observed with erythromycin.

Cell Line↗

Erythromycin ameliorates renal injury via anti-inflammatory effects in experimental diabetic rats.

AIMS/HYPOTHESIS: Recent studies have shown that the inflammatory process is involved in the pathogenesis of diabetic nephropathy. Fourteen-membered ring macrolides, including erythromycin, have anti-inflammatory, as well as antibacterial effects. The aim of this study was to investigate the renoprotective effects of erythromycin in streptozotocin (STZ)-induced diabetic rats. METHODS: STZ-induced diabetic rats were treated orally with erythromycin (5 mg/kg body weight) or vehicle every day for 8 weeks. To evaluate the effect of erythromycin treatment, we measured urinary albumin excretion, and examined the following in the kidney: histological changes, the expression of intercellular adhesion molecule-1 (ICAM-1), macrophage infiltration, and nuclear factor-kappa B (NF-kappaB) activity. RESULTS: Erythromycin significantly reduced urinary albumin excretion without affecting blood glucose levels and blood pressure. Erythromycin also attenuated glomerular hypertrophy, mesangial expansion, macrophage infiltration and ICAM-1 expression in renal tissues. The expression of the gene encoding TGFB1 (also known as TGF-beta1), type IV collagen protein production and NF-kappaB activity in renal tissues were increased in diabetic rats and reduced by erythromycin treatment. CONCLUSIONS/INTERPRETATION: Erythromycin prevented renal injuries without changes of blood glucose levels and blood pressure in experimental diabetic rats. These results suggest that the renoprotective effects of erythromycin are based on its anti-inflammatory effect via suppression of NF-kappaB activation. Modulation of microinflammation with erythromycin may provide a new approach for diabetic nephropathy.

Albuminuria↗

Erythromycin improves glycaemic control in patients with Type II diabetes mellitus.

AIMS/HYPOTHESIS: Erythromycin mimics the effect of the gastrointestinal hormone motilin by binding to its receptor and acting as a motilin agonist. We recently found that motilin stimulates insulin secretion at lower doses than doses required to stimulate gastric contractile activity. We studied the effects of erythromycin on insulin secretion and glycaemic control in patients with diabetes mellitus. METHODS: Inpatients (n = 34) with Type II (non-insulin-dependent) diabetes mellitus were randomly assigned to receive either erythromycin (400 mg orally three times a day, n = 19) or a placebo (n = 15) for 1 week (first study). Another 34 outpatients with Type II diabetes were also treated with erythromycin (200 mg orally three times a day, n = 17) or a placebo (n = 17) for 4 weeks (second study). Finally, nine inpatients with Type II diabetes and eight normal control subjects received intravenous erythromycin (10 mg x kg(-1) x h(-1)) or saline infusion and insulin secretion was examined (third study). RESULTS: Erythromycin lowered fasting blood glucose and fructosamine concentrations (p < 0.01) and increased basal as well as glucose-stimulated insulin secretion (p <0.05-0.01) (first study). Low doses of erythromycin treatment for 4 weeks also significantly improved glycaemic control in Type II diabetic patients (second study). Erythromycin infusion significantly increased plasma insulin and decreased glucose concentrations in Type II diabetic and control subjects and greatly potentiated glucose-induced insulin secretion in the latter (third study). CONCLUSION/INTERPRETATION: These results indicate that erythromycin given orally has an antidiabetogenic effect and therefore erythromycin derivatives that lack the antibacterial activity could have a therapeutic value in Type II diabetic patients.

Blood Glucose↗

Erythromycin enhances fasting and postprandial proximal gastric tone in humans.

BACKGROUND & AIMS: Low doses of erythromycin induce antral contractions and accelerate gastric emptying. However, the effect of erythromycin on the proximal stomach remains unknown. The aim of this study was to assess the effect and mechanism(s) of action of erythromycin on proximal gastric tone in humans. METHODS: Gastric tone was measured using an electronic barostat in two groups of 6 subjects both in the fasting state and after a 200-kcal meal. On different occasions, subjects received saline, atropine alone (6 micrograms.kg-1.h-1 for 30 minutes), erythromycin alone (1.5 mg/kg in the fasting state and 1.5 and 3.0 mg/kg in the postprandial state), and erythromycin plus atropine. RESULTS: Low-dose (1.5 mg/kg) erythromycin enhanced fasting gastric tone, but only the 3.0-mg/kg dose reduced the duration of meal-induced relaxation (37 +/- 14 vs. 105 +/- 20 minutes; P < 0.01). Atropine did not change the fasting or postprandial gastric tone as well as the erythromycin-induced responses. Plasma motilin levels were unaffected by erythromycin infusion. No correlation was observed between gastric tone and plasma motilin or erythromycin levels. CONCLUSIONS: Erythromycin enhances fasting and postprandial proximal gastric tone in humans by a mechanism that does not seem to involve endogenous motilin release or a cholinergic pathway.

Adult↗

Erythromycin-felodipine interaction: magnitude, mechanism, and comparison with grapefruit juice.

OBJECTIVE: To investigate a potentially marked effect by erythromycin on felodipine pharmacokinetics, to characterize the mechanism, and to compare the interaction with that between grapefruit juice and felodipine. METHODS: Felodipine, 10 mg extended release, was administered with 250 ml water, 250 mg erythromycin, or 250 ml grapefruit juice in a randomized crossover study of 12 healthy men. Erythromycin base, 250 mg four times a day, was started the day before and continued on that study day. Pharmacokinetic values of felodipine, the primary metabolite dehydrofelodipine, and the major secondary derivative M3 metabolite were studied. RESULTS: Compared with water, erythromycin produced severalfold higher felodipine area under the plasma drug concentration-time profile (AUC), plasma peak drug concentration (Cmax), and apparent elimination half-life (t1/2); however, the effect was variable among individuals. Erythromycin augmented dehydrofelodipine AUC, Cmax, and t1/2 but decreased dehydrofelodipine/felodipine ratios. The AUC of the M3 metabolite and the M3 metabolite/dehydrofelodipine ratios were reduced. These findings support inhibition of both metabolic pathways likely mediated by CYP3A4. Grapefruit juice produced similar mean effects but did not prolong felodipine or dehydrofelodipine t1/2. Individually, felodipine AUC with erythromycin was greater than or similar to that with grapefruit juice. Relative felodipine AUC (erythromycin compared with grapefruit juice) correlated with relative felodipine Cmax but not with relative felodipine t1/2, suggesting felodipine AUC differed between these treatments, mainly from factors affecting presystemic drug elimination. CONCLUSIONS: Erythromycin produced an important pharmacokinetic interaction with felodipine by inhibition of drug metabolism. Although erythromycin and grapefruit juice shared a common mechanism, erythromycin likely reduced felodipine biotransformation at the gut wall and liver, whereas single-dose grapefruit juice had an effect mainly at the gut wall.

Adolescent↗

Cellular and ionic mechanisms underlying erythromycin-induced long QT intervals and torsade de pointes.

OBJECTIVES: This study sought to elucidate the cellular and ionic basts for erythromycin-induced long QT syndrome. BACKGROUND: Erythromycin is known to produce long QTU intervals on the electrocardiogram (ECG) and to be associated with the development of torsade de pointes (TdP). The mechanisms responsible for the adverse effects of this widely used antibiotic are not well defined. METHODS: The present study used microelectrode and whole-cell patch-clamp techniques to assess the effects of erythromycin on epicardial, endocardial and M cells in transmural strips, arterially perfused wedges and single myocytes isolated from the canine left ventricle. RESULTS: In isolated strips, erythromycin (10 to 100 micrograms/ml) produced a much more pronounced prolongation of the action potential duration (APD) in M cells than in endocardial and epicardial cells, resulting in the development of a large dispersion of repolarization across the ventricular wall at slow stimulation rates. Erythromycin (50 to 100 micrograms/ml) induced early after depolarizations (EADs) in cells in the M (20%) but not epicardial or endocardial regions in transmural strips of ventricular free wall. Erythromycin (100 micrograms/ml) also caused APD prolongation and a transmural dispersion of repolarization, but not EADs, in intact arterially perfused wedges of canine left ventricle. These changes were attended by the development of a long QT interval on the transmural ECG. A polymorphic ventricular tachycardia closely resembling TdP was readily and reproducibly induced after erythromycin but not before. Whole-cell patch-clamp techniques, used to examine the effects of erythromycin on myocytes isolated from the M region, showed a potent effect of the drug to inhibit the rapidly activating component (IK(r)) but not the slowly activating component (IKs) of the delayed rectifier potassium current (IK). The inward rectifier current (IK1) was unaffected. CONCLUSIONS: Our data demonstrate a preferential response of M cells to the class III actions of erythromycin, due principally to the effect of the drug to inhibit IK(r) in a population of cells largely devoid of IKs. Our findings indicate that erythromycin thus produces long QT intervals as well as a prominent dispersion of repolarization across the ventricular wall, setting the stage for induction of TdP-like tachyarrhythmias displaying characteristics typical of reentry.

Action Potentials↗

Anaphylaxis to erythromycin.

BACKGROUND: Erythromycin and its salts belong to the larger class of macrolides. Erythromycin is well tolerated. The most common side effects are gastrointestinal distress, nausea, and vomiting, which are dose related. Allergic and pseudoallergic reactions due to macrolide antibiotics are uncommon. Anaphylaxis and acute respiratory distress appear in the literature as case reports. METHODS: We report a 24-year-old man who presented 12 years ago a systemic allergic reaction to penicillin, confirmed by skin tests and detection of specific IgE (RAST). Since then he had tolerated erythromycin on several occasions. Nine months ago, his general practitioner prescribed erythromycin orally as treatment for a respiratory infection. Thirty minutes after taking the first dose, 500 mg, he developed an anaphylactic reaction. The episode subsided with treatment with high dose corticosteroids, antihistamines, and epinephrine. Skin prick tests and intradermal tests were performed with erythromycin at different concentrations. We also measured total IgE and specific IgE to erythromycin by CAP and Phadezym RAST (Pharmacia, Uppsala, Sweden), respectively. We also performed a Prausnitz-Küstner test (PK test), and oral challenge test. RESULTS: Skin testing to erythromycin was not helpful because of cutaneous hyperreactiviness. No significant levels of specific IgE to erythromycin were detected. The oral challenge and the Prausnitz-Küstner test were positive. CONCLUSIONS: The positive history and oral challenge test suggested an anaphylactic reaction to erythromycin. The positive Prausnitz-Küstner test demonstrated the presence of specific IgE to erythromycin.

Adult↗

Direct inhibitory effect of erythromycin on the gallbladder muscle.

Erythromycin, a macrolide antibiotic, stimulates motor activity in various parts of the gastrointestinal tract in humans and animals. This effect of erythromycin resembles that of motilin, a gastrointestinal hormone, in evoking contractions similar to phase 3 activity of the migrating motor complex. Motilin induces contractions in the canine gallbladder but fails to evoke any response, either in vivo or in vitro, in the human gallbladder. Surprisingly, erythromycin stimulates human gallbladder emptying in healthy volunteers and in persons with diabetic autonomic neuropathy. In the present study we examined the effect of erythromycin on chemically and electrically evoked contractions of isolated gallbladders from guinea pigs and humans by use of isometric force measurements. Carbachol, a muscarinic cholinergic agonist, evoked gallbladder contractions that were diminished by erythromycin in a concentration-dependent manner: at 200 micromol/L the contractions were 86% +/- 20% of the control response, at 500 micromol/L they were 63% +/- 21% of control, and at 1000 micromol/L they were 41% +/- 20% of control (P <0.05, N = 10, mean +/- standard deviation). Electrically evoked gallbladder contractions were reduced to 68% +/- 18% of the control response with the addition of 500 micromol/L of erythromycin and to 56% +/- 19% of control after the addition of 1000 micromol/L (P <0.05, N = 8). Guinea pig but not human gallbladders contracted after stimulation with the alpha-adrenergic agonist phenylephrine. Erythromycin reduced these contractions in a concentration-dependent manner but had no effect on gallbladder contractions induced by bradykinin. In human gallbladder strips, erythromycin at 500 micromol/L reduced the contractile response to electrical stimulation to 71% +/- 16% of the control value (N = 10 [5 patients], P <0.01) and the carbachol-evoked contractions to 53% +/- 24% (P <0.01, N = 32). The inhibitory effect of erythromycin persisted in the presence of the nerve blocker tetrodotoxin at 1 micromol/L. It is concluded that erythromycin has a direct inhibitory effect on guinea pig and human gallbladder contractions.

Adrenergic alpha-Agonists↗

Design, synthesis, and evaluation of stable and taste-free erythromycin proprodrugs.

Erythromycin A is normally formulated for children as its 2'-ethyl succinate, a taste-free prodrug. Unfortunately, the prodrug hydrolyzes at a measurable rate in the medicine bottle, leading to the vile-tasting erythromycin. We have prepared derivatives of erythromycin B as putative paediatric prodrugs, taking advantage of the much improved acid stability of erythromycin B relative to erythromycin A. Thus, erythromycin B enol ether ethyl succinate is very poorly soluble in water, and its hydrolysis is undetectable in conditions resembling the medicine bottle. In acid, however, it converts rapidly to erythromycin B 2'-ethyl succinate, and this is in turn hydrolyzed to erythromycin B in neutral and basic conditions. Derivatives of erythromycin B enol ether are therefore proposed as taste-free proprodrugs of erythromycin B.

Anti-Bacterial Agents↗

Gallbladder fasting volume is reduced and gallbladder postprandial emptying is enhanced by intravenous erythromycin.

It has been recently shown that erythromycin, a macrolide antibiotic, exhibits prokinetic properties, by enhancing gastric emptying in health and disease and by inducing gallbladder contraction. The aim of the study was to further investigate the effect of intravenous erythromycin on gallbladder motility during fasting and postprandial states. In 10 healthy male subjects gallbladder emptying was assessed by ultrasonography on three different occasions, each in a random sequence, as follows: (1) after giving 300 ml of fresh milk and infusing normal saline as placebo (postprandial emptying), (2) after infusing 200 mg of erythromycin during the fasting state, and (3) after infusing 200 mg of erythromycin along with ingestion of 300 ml of fresh milk. Infusion of erythromycin and placebo lasted 10 min. From the emptying curves, the duration of the lag phase of emptying, the ejection fraction of emptying, and the time by which maximal emptying was achieved were calculated. Infusion of erythromycin induced an immediate contraction [lag phase (+/-SD): 1.3+/-2.6 SD min] of the gallbladder by 42.1+/-22% of its initial volume. Infusion of erythromycin during the postprandial state significantly decreased the duration of the lag phase (1.3+/-3.5 min after erythromycin plus test meal versus 3.6+/-4.2 min after test meal only, P < 0.04) and significantly increased the ejection fraction (78+/-8.5% after erythromycin plus test meal versus 60.6+/-8.5% after test meal only, P < 0.0008). It is concluded that intravenously given erythromycin induces contraction of the gallbladder during the fasting state and enhances postprandial gallbladder emptying by accelerating the initiation and increasing the extent of emptying.

Adult↗

Resistance to erythromycin in group A streptococci.

BACKGROUND: The use of erythromycin in Finland nearly tripled from 1979 to 1989. In 1988, we observed an unusually high frequency of resistance to erythromycin in group A streptococci in one geographic region. Because routine testing does not detect the sensitivity of these organisms to antibiotics, we initiated a national study to evaluate the extent of this resistance. METHODS: We studied 272 isolates of group A streptococci obtained from blood cultures from 1988 through 1990. In 1990 we collected from six regional laboratories 3087 consecutive isolates from throat swabs and 1349 isolates from pus samples. Resistance was indicated by growth on blood agar containing 2 micrograms of erythromycin per milliliter after incubation in 5 percent carbon dioxide. We also evaluated the clinical importance of erythromycin resistance in a retrospective study of consecutive patients with pharyngitis. RESULTS: The frequency of resistance to erythromycin in group A streptococci from blood cultures increased from 4 percent in 1988 to 24 percent in 1990. From January to December 1990, the frequency of resistance in isolates from throat swabs increased from 7 percent to 20 percent, and resistance in isolates from pus increased from 11 percent to 31 percent. In four communities within 50 km of each other, the frequency of erythromycin resistance ranged from 2 to 5 percent to 26 to 44 percent. Several distinct DNA restriction profiles and serotypes were found among resistant isolates from the same area, suggesting a multiclonal origin. The treatment of pharyngitis with erythromycin failed in 9 of 19 patients infected with erythromycin-resistant group A streptococci, as compared with 1 of 26 patients with erythromycin-susceptible isolates (47 percent vs. 4 percent, P = 0.008). CONCLUSIONS: In Finland since 1988 there has been a rapid and substantial increase in resistance to erythromycin in group A streptococci. The extent of this resistance is particularly serious since there are only a few alternative antibiotics available for peroral treatment of group A streptococcal infections.

Blood↗

The effect of erythromycin on Pseudomonas aeruginosa and neutrophil mediated epithelial damage.

Erythromycin therapy for long periods may benefit patients with chronic bronchial sepsis colonized by Pseudomonas aeruginosa despite the lack of antibacterial activity. We have investigated the effect of filtrates of 24 h P. aeruginosa cultures (CF) with or without erythromycin 0.5, 5, 20 mg/L on human nasal epithelium in the absence or presence of polymorphonuclear leucocytes (PMN). Ciliary beat frequency (CBF) and epithelium integrity were examined for 4 h. Erythromycin (20 mg/L) alone did not affect epithelium. CF without erythromycin slowed CBF by 63.5% of control at 4 h, and caused disruption of surface integrity in 80% of the epithelium. Addition of erythromycin to CF did not inhibit these effects. Erythromycin did not affect growth of P. aeruginosa. Filtrates of P. aeruginosa cultured with erythromycin (5 and 20 mg/L) caused less CBF slowing (37.2% and 19.2% of control, respectively) and epithelial disruption (4.2% and 6.7%, respectively). Unstimulated PMN (10(7)/mL) slowed CBF by 13% of control at 4 h but did not cause epithelial disruption. PMN and CF together slowed CBF (95.4% of control) and damaged epithelium (93.3% of epithelium disrupted) synergically. Pre-incubation of PMN with erythromycin did not inhibit these effects. PMN and filtrates of P. aeruginosa cultured with erythromycin (5 and 20 mg/L) caused less CBF slowing (58.0% and 33.6% of control, respectively) and epithelial disruption (40.0% and 13.3%, respectively). Erythromycin may benefit patients by reducing P. aeruginosa production of factors which damage epithelium and stimulate neutrophil mediated cytotoxicity.

Bacterial Toxins↗