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PubMed2000

Hepatic disposition of fexofenadine: influence of the transport inhibitors erythromycin and dibromosulphothalein.

PURPOSE: To examine the disposition of fexofenadine in the isolated perfused rat liver and the influence of erythromycin and dibromosulphthalein (DBSP) on the hepatic uptake and biliary excretion of fexofenadine. METHODS: Livers from four groups of rats were perfused in a recirculatory manner with fexofenadine HCl added as a bolus (125, 250, 500, or 1000 microg) to perfusate. Livers from another three groups of rats were perfused with 250 microg of fexofenadine HCl. With one group as control, erythromycin (4.0 microg/ml) or DBSP (136 microg/ml) was added to the perfusate of the other groups. In all experiments, perfusate and bile were collected for 60 min; in addition, livers from the second experiment were retained for assay. Fexofenadine was determined in perfusate, bile, and homogenized liver by HPLC. RESULTS: The area under the curve (AUC) of fexofenadine was linearly related to concentration. It was unchanged from control (12,800 +/- 200 ng x h/ml) by erythromycin (14,400 +/- 2000 ng x h/ml), but was increased 95% by DBSP (25,000 +/- 2600 ng x h/ml, P <0.001). The ratios of the concentrations of fexofenadine in liver/perfusate were decreased significantly by DBSP; those for bile/liver were increased by erythromycin. CONCLUSIONS: Erythromycin reduced the canalicular transport of fexofenadine into bile, whereas DBSP reduced uptake across the sinusoidal membrane.

Animals↗
PubMed2002

Hyperglycemia attenuates erythromycin-induced acceleration of liquid-phase gastric emptying of hypertonic liquids in healthy subjects.

Acute hyperglycemia has been associated with delayed gastric emptying in healthy controls. Erythromycin has recently been found to be a gastrointestinal prokinetic agent in both solids and hypertonic liquids. Our aim was to examine whether the acute steady-state hyperglycemia reduces the erythromycin-induced acceleration of gastric emptying of hypertonic liquids after a fasted state of the stomach in healthy subjects. In 12 healthy subjects scintigraphic measurement of gastric emptying of a hypertonic radiolabeled liquid meal, during normoglycemia (5-8.9 mmol/l glucose) or induced hyperglycemia (16-19 mmol/liter glucose) by intravenous glucose infusion after giving either placebo or 200 mg intravenous erythromycin, was performed on four separate days in random order. In the hyperglycemic state compared with normoglycemia, either after placebo administration or erythromycin, the gastric emptying of the hypertonic liquid was reduced. The lag-phase duration was significantly increased (17.5 +/- 5.5 min, and 7.2 +/- 4.5 min vs 10.5 +/- 3.4 min, and 3.5 +/- 2.5 min, respectively, P < 0.0001) as were the overall T1/2 (gastric emptying time of the half meal) (52.5 +/- 13 min and 24.5 +/- 5.5 min vs 42 +/- 10.5 min, and 16 +/- 6 min, respectively, P < 0.0001) and the percentage of liquid meal retained in the stomach at 60 and 100 min postprandially (P < 0.001). In conclusion, hyperglycaemia attenuates the acceleration effect of erythromycin and decreases the overall gastric emptying rate of hypertonic liquids in healthy subjects.

Adult↗
PubMed1991

Bioavailability of erythromycin acistrate from hard gelatin capsules containing sodium bicarbonate.

Erythromycin acistrate is a new prodrug of erythromycin. Its bioavailability from hard gelatin capsules containing the drug with or without sodium bicarbonate was studied in healthy volunteers. The plasma levels of erythromycin, anhydroerythromycin, and acetylerythromycin were measured using an HPLC method. Addition of sodium bicarbonate to the capsule markedly enhanced the plasma level of the microbiologically active substance, erythromycin, doubling the Cmax and AUC values (P less than 0.05). At the same time, the lag time in the absorption curve was shortened to one-third. No changes in the plasma levels of the inactive metabolite anhydroerythromycin were noted. It is concluded that adding sodium bicarbonate to an erythromycin acistrate formulation enhances its bioavailability.

Adult↗
PubMed2001

Effects of erythromycin on stretch-induced contractile activity of isolated myometrium from pregnant women.

BACKGROUND: Despite the fact that preterm labor and birth account for the vast majority of neonatal morbidity and mortality the currently available treatment options are still far from satisfactory. The aim of this study was to investigate the effects of erythromycin on stretch-induced contractions of pregnant human myometrial strips, obtained at cesarean section. METHOD: Myometrial strips were suspended in an organ bath under 3 g tension and the effects of erythromycin (0.1, 0.2, 0.5, 1.0 mM) on stretch-induced isometric contractions were evaluated. Results were statistically analyzed using Kruskal Wallis analysis of variance and Wilcoxon Rank tests where appropriate. RESULTS: Erythromycin caused a significant decrease in the peak amplitude, while causing an increase in frequency of stretch-induced myometrial contractions in a dose dependent manner in vitro. CONCLUSIONS: Results from this preliminary study suggest that erythromycin may have additional beneficial effects in infection related preterm labor cases, however, further studies are needed for clarifying the usefulness of erythromycin as a tocolytic agent.

Erythromycin↗
PubMed1989

Inhibition of alfentanil metabolism by erythromycin.

To investigate a possible connection between erythromycin administration and reduced elimination of alfentanil, a controlled crossover study of alfentanil pharmacokinetics was undertaken. Six subjects were monitored for alfentanil plasma levels for 8 hours after alfentanil was administered. These measurements were obtained after a 0-, 1-, and 7-day course of erythromycin. Elimination half-life increased significantly (p less than 0.01) after 7 days from the control value of 84.0 +/- 8.2 minutes to 131.4 +/- 43.5 minutes. Clearance was decreased significantly (p less than 0.05) from 3.9 +/- 0.8 ml/kg/min to 2.9 +/- 1.2 ml/kg/min after 7 days. Values after 1 day were intermediate. Distribution volume did not change significantly. Subjects differed sharply in their sensitivity to erythromycin. Because of the interaction between erythromycin and alfentanil, we recommend that patients who are receiving erythromycin should be given alfentanil in reduced amounts or should avoid the drug completely.

Adult↗
PubMed1990

Pharmacokinetic evaluation of erythromycin and caffeine administered with bromocriptine.

A study was performed to determine if the pharmacokinetics of bromocriptine is altered by factors that have been shown to interact with other ergot compounds. The effects on bromocriptine plasma concentrations by bromocriptine coadministration with caffeine and erythromycin were evaluated in five male volunteers. Serial blood samples were obtained during a 12-hour period after a single 5 mg oral dose of bromocriptine (alone and after 4-day treatments of either erythromycin estolate, 250 mg four times/day, or caffeine, 200 mg four times/day). There were no significant alterations of bromocriptine pharmacokinetic parameters after caffeine, although statistical power was very low. With the use of erythromycin, the bromocriptine area under the concentration-time curve standardized to body weight increased significantly by 268%, whereas peak bromocriptine plasma concentration (Cmax) increased to 4.6 times the Cmax from bromocriptine alone. Time to achieve Cmax was not altered by erythromycin. We conclude that erythromycin can markedly increase the systemic bioavailability of bromocriptine, which can lead to increased therapeutic or adverse effects, whereas the effects of caffeine require further study.

Adult↗
PubMed1997

Cisapride and erythromycin prokinetic effects in gastroparesis due to type 1 (insulin-dependent) diabetes mellitus.

BACKGROUND: Erythromycin, a macrolide antibiotic, has been shown to have gastric prokinetic effects and has been proposed as an alternative therapeutic option for diabetic gastroparesis. However, its efficacy has not yet been compared with that of other prokinetic drugs. AIMS: The purpose of the present study was to compare the effects of erythromycin (250 mg 60 min before meals) and cisapride (10 mg 30 min before meals) on gastric emptying of healthy subjects and insulin-dependent diabetics. PATIENTS AND METHODS: Six type 1 diabetic patients with a previous scintigraphic demonstration of gastroparesis and five healthy subjects were recruited for the study. Gastric emptying was scintigraphically studied by labelling the solid component of a standard test meal. Three scintigraphic studies, spaced at least 3 days apart, were carried out on each subject, basally and after erythromycin or cisapride. RESULTS: Cisapride significantly accelerated gastric emptying in both the healthy subjects and the diabetic patients without any significant effect on the lag-time, whereas erythromycin in addition to a significant improvement of the overall gastric emptying also showed a pronounced effect on the lag-time in both groups (controls 25 +/- 5 vs. 37 +/- 8 min, P < or = 0.04; diabetics 65 +/- 11 vs. 112 +/- 16 min, P < 0.03). CONCLUSIONS: Erythromycin may represent an effective therapeutic alternative to more established forms of treatment in patients with diabetic gastroparesis, especially when other drugs have failed.

Adult↗
PubMed1999

Clinical efficacy and safety of a topical combination of retinaldehyde 0.1% with erythromycin 4% in acne vulgaris.

The objective of this randomized, controlled, multicentre study was to assess the efficacy and safety of a topically applied retinaldehyde 0.1% gel in combination with a topical erythromycin 4% lotion for the treatment of acne vulgaris. Treatment consisted of applying either retinaldehyde or its vehicle every morning and erythromycin every evening for 8 weeks. Efficacy parameters were sequential lesion counts for papules and pustules, and a 6-point semiquantitative scale for comedones and microcysts. Safety parameters were local tolerance and adverse events. Of 74 recruited patients, 73 were appraisable for efficacy and safety. In both treatment groups, papules and pustules were reduced significantly at the end of treatment (P < 0.001), and no statistical difference was observed between the groups. Comedones and microcysts were significantly improved with retinaldehyde combined with erythromycin (P = 0.005), but not with erythromycin alone. However, no statistical difference between the groups could be demonstrated (test power, 50%). Local tolerance of the combined treatment group was very satisfactory, as only a few patients experienced local irritation. In conclusion, retinaldehyde combined with erythromycin appears to be a valuable topical therapy in polymorphic acne.

Acne Vulgaris↗
PubMed2000

Biosynthesis of the anti-parasitic agent megalomicin: transformation of erythromycin to megalomicin in Saccharopolyspora erythraea.

Megalomicin is a therapeutically diverse compound which possesses antiparasitic, antiviral and antibacterial properties. It is produced by Micromonospora megalomicea and differs from the well-known macrolide antibiotic erythromycin by the addition of a unique deoxyamino sugar, megosamine, to the C-6 hydroxyl. We have cloned and sequenced a 48 kb segment of the megalomicin (meg) biosynthetic gene cluster which contains the modular polyketide synthase (PKS) and the complete pathway for megosamine biosynthesis. The similarities and distinctions between the related megalomicin and erythromycin gene clusters are discussed. Heterologous expression of the megalomicin PKS in Streptomyces lividans led to production of 6-deoxyerythronolide B, the same macrolactone intermediate for erythromycin. A 12 kb fragment harbouring the putative megosamine pathway was expressed in Saccharopolyspora erythraea, resulting in the conversion of erythromycin to megalomicin. Considering the extensive knowledge surrounding the genetic engineering of the erythromycin PKS and the familiarity with genetic manipulation and fermentation of S. erythraea, the ability to produce megalomicin in this strain should allow the engineering of novel megalomicin analogues with potentially improved therapeutic activities.

Anti-Bacterial Agents↗
PubMed2001

New erythromycin derivatives from Saccharopolyspora erythraea using sugar O-methyltransferases from the spinosyn biosynthetic gene cluster.

Using a previously developed expression system based on the erythromycin-producing strain of Saccharopolyspora erythraea, O-methyltransferases from the spinosyn biosynthetic gene cluster of Saccharopolyspora spinosa have been shown to modify a rhamnosyl sugar attached to a 14-membered polyketide macrolactone. The spnI, spnK and spnH methyltransferase genes were expressed individually in the S. erythraea mutant SGT2, which is blocked both in endogenous macrolide biosynthesis and in ery glycosyltransferases eryBV and eryCIII. Exogenous 3-O-rhamnosyl-erythronolide B was efficiently converted into 3-O-(2'-O-methylrhamnosyl)-erythronolide B by the S. erythraea SGT2 (spnI) strain only. When 3-O-(2'-O-methylrhamnosyl)-erythronolide B was, in turn, fed to a culture of S. erythraea SGT2 (spnK), 3-O-(2',3'-bis-O-methylrhamnosyl)-erythronolide B was identified in the culture supernatant, whereas S. erythraea SGT2 (spnH) was without effect. These results confirm the identity of the 2'- and 3'-O-methyltransferases, and the specific sequence in which they act, and they demonstrate that these methyltransferases may be used to methylate rhamnose units in other polyketide natural products with the same specificity as in the spinosyn pathway. In contrast, 3-O-(2',3'-bis-O-methylrhamnosyl)-erythronolide B was found not to be a substrate for the 4'-O-methyltransferase SpnH. Although rhamnosylerythromycins did not serve directly as substrates for the spinosyn methyltransferases, methylrhamnosyl-erythromycins were obtained by subsequent conversion of the corresponding methylrhamnosyl-erythronolide precursors using the S. erythraea strain SGT2 housing EryCIII, the desosaminyltransferase of the erythromycin pathway. 3-O-(2'-O-methylrhamnosyl)-erythromycin D was tested and found to be significantly active against a strain of erythromycin-sensitive Bacillus subtilis.

Anti-Bacterial Agents↗
PubMed1995

Reduced incidence of preterm delivery with metronidazole and erythromycin in women with bacterial vaginosis.

BACKGROUND: Pregnant women with bacterial vaginosis may be at increased risk for preterm delivery. We investigated whether treatment with metronidazole and erythromycin during the second trimester would lower the incidence of delivery before 37 weeks' gestation. METHODS: In 624 pregnant women at risk for delivering prematurely, vaginal and cervical cultures and other laboratory tests for bacterial vaginosis were performed at a mean of 22.9 weeks' gestation. We then performed a 2:1 double-blind randomization to treatment with metronidazole and erythromycin (433 women) or placebo (191 women). After treatment, the vaginal and cervical tests were repeated and a second course of treatment was given to women who had bacterial vaginosis at that time (a mean of 27.6 weeks' gestation). RESULTS: A total of 178 women (29 percent) delivered infants at less than 37 weeks' gestation. Eight women were lost to follow-up. In the remaining population, 110 of the 426 women assigned to metronidazole and erythromycin (26 percent) delivered prematurely, as compared with 68 of the 190 assigned to placebo (36 percent, P = 0.01). However, the association between the study treatment and lower rates of prematurity was observed only among the 258 women who had bacterial vaginosis (rate of preterm delivery, 31 percent with treatment vs. 49 percent with placebo; P = 0.006). Of the 358 women who did not have bacterial vaginosis when initially examined, 22 percent of those assigned to metronidazole and erythromycin and 25 percent of those assigned to placebo delivered prematurely (P = 0.55). The lower rate of preterm delivery among the women with bacterial vaginosis who were assigned to the study treatment was observed both in women at risk because of previous preterm delivery (preterm delivery in the treatment group, 39 percent; and in the placebo group, 57 percent; P = 0.02) and in women who weighed less than 50 kg before pregnancy (preterm delivery in the treatment group, 14 percent; and in the placebo group, 33 percent; P = 0.04). CONCLUSIONS: Treatment with metronidazole and erythromycin reduced rates of premature delivery in women with bacterial vaginosis and an increased risk for preterm delivery.

Adult↗
PubMed1997

The effect of changes in the consumption of macrolide antibiotics on erythromycin resistance in group A streptococci in Finland. Finnish Study Group for Antimicrobial Resistance.

BACKGROUND: In the early 1990s there was an increase in erythromycin resistance among group A streptococci in Finland. In response, policies regarding outpatient antibiotic therapy were changed, and nationwide recommendations were issued that called for reductions in the use of macrolide antibiotics for respiratory and skin infections in outpatients. We studied the effect of this policy on the pattern of erythromycin resistance throughout Finland. METHODS: From 1991 through 1996, a total of 39,247 group A streptococcal isolates from throat swabs (82 percent of the isolates) and pus samples (18 percent) and 290 isolates from blood cultures were studied in regional microbiology laboratories. The susceptibility of the isolates to erythromycin was tested by the disk-diffusion or the screening-plate method. RESULTS: Consumption of macrolide antibiotics decreased from 2.40 defined daily doses per 1000 inhabitants per day in 1991 to 1.38 in 1992 (P=0.007) and remained near the lower level during the study period. The change in consumption was followed by a steady decrease in the frequency of erythromycin resistance among group A streptococcal isolates from throat swabs and pus samples, from 16.5 percent in 1992 to 8.6 percent in 1996 (odds ratio for 1996 as compared with 1992, 0.5; 95 percent confidence interval, 0.4 to 0.5). CONCLUSIONS: In Finland, after nationwide reductions in the use of macrolide antibiotics for outpatient therapy, there was a significant decline in the frequency of erythromycin resistance among group A streptococci isolated from throat swabs and pus samples.

Anti-Bacterial Agents↗
PubMed1979

Cytoplasmic inheritance of erythromycin resistance in human cells.

An erythromycin-resistant mutant, ERY2301, was isolated from ethidium bromide-treated HeLa cells in the presence of erythromycin at 300 micrograms/ml. ERY2301 cells were enucleated and the anucleate cytoplasts were fused with D98/AH-2, a hypoxanthine phosphoribosyltransferase-deficient variant of HeLa cells. The resultant cybrids were isolated in a double selective medium containing erythromycin and 6-thioguanine. Cybrid formation occurred at a frequency of 10(-3) to 10(-4). In vitro protein synthesis by intact and Triton X-100 treated mitochondria isolated from ERY2301 was resistant to the macrolide antibiotics erythromycin and carbomycin, but was sensitive to chloramphenicol. These results suggest that the site of erythromycin resistance in ERY2301 may be at the level of mitochondrial protein synthesis and indicate that this trait is cytoplasmically inherited and, therefore, presumably encoded in the mitochondrial genome.

Cell Division↗
PubMed1980

Posttranscriptional modification of mRNA conformation: mechanism that regulates erythromycin-induced resistance.

The nucleotide sequence of a gene in plasmid pE194 responsible for erythromycin-induced resistance, including regulation of the resistance phenotype, is reported. A DNA fragment from plasmid pE194, obtained by digestion with Taq I restriction endonuclease, was cloned in Bacillus subtilis by using pC194 as the plasmid cloning vector. Erythromycin-resistant, inducible transformant clones containing the Taq I fragment A were obtained in which the expression of resistance was similar to that found in the original pE194 background; an interpretative model of the regulation of the erythromycin-resistance determinant is proposed based on the sequence of the Taq I A fragment. The cloned Taq I A fragment consists of 1442 base pairs and has open reading frames capable of coding for a peptide and a protein containing 19 and 243 amino acids, respectively, referred to as the "leader peptide" and "29,000 protein." Between the putative transcriptional start site and the ribosome binding site for 29,000-protein synthesis, the promoter region contains four complementary inverted repeat sequences named "1, 2, 3, and 4," respectively, in which 1 is complementary to 2, 2 is complementary to 3, and 3 is complementary to 4. Sequence 1 encodes the COOH-terminal half of the leader peptide, whereas the ribosome binding site for synthesis of 29,000 protein is sequestered in a loop formed by the association of 3 and 4. The 29,000-protein promoter region does not appear to contain any transcription stop signal. We propose a model for regulation of erythromycin resistance according to which ribosomes engaged in leader peptide synthesis are partially inhibited by optimal inducing (i.e., subinhibitory) concentrations of erythromycin that, in turn, cause an accumulation of these partially inhibited ("stalled") ribosomes in sequence 1. During induction, the translationally inactive states of association of the inverted repeats, postulated to be 1 plus 2 and 3 plus 4, respectively, are perturbed by a high level of stalled ribosome occupancy in sequence 1, and in the resultant redistribution, 2 associates with 3, freeing 4 and thereby freeing the ribosome binding site sequestered by the association of 3 and 4. Sequence alterations at the 5' end of the 29,000-protein coding region associated with mutation to constitutive expression have been localized to the inverted complementary repeats, and determination of base changes in eight mutants are all capable of reducing the stability of the postulated stems in a manner consistent with predictions made by the model.

Drug Resistance, Microbial↗
PubMed1981

Erythromycin. New indications and toxicities.

Although erythromycin was introduced into clinical medicine more than 28 years ago, the indications for its use continue to expand. This antibiotic has emerged as appropriate therapy for Legionnaires' disease, chronic bacterial prostatitis caused by Escherichia coli, Klebsiella pneumoniae, and Proteus species, enteritis and colitis produced by Campylobacter fetus, and soft tissue and pleuropulmonary anaerobic infections in which Bacteroides fragilis plays no role. In combination with an aminoglycoside, erythromycin has proven to be effective for perioperative antibiotic prophylaxis in patients undergoing elective colon surgery. Additional therapeutic indications continue to be explored. The renewed interest in erythromycin has resulted in a closer examination of its potential for toxicity. New untoward events attributed to erythromycin administration have been described. This antibiotic has produced both reversible hearing loss and pseudomembranous colitis. Erythromycin also possesses the ability to inhibit the degradation of theophylline.

Enterocolitis, Pseudomembranous↗
PubMed2006

A randomized controlled trial of adjunctive erythromycin in women with idiopathic preterm labor.

OBJECTIVE: Our purpose was to determine the effects of erythromycin among hospitalized women with idiopathic preterm labor who were treated with tocolytics. METHODS: This prospective randomized trial was conducted in patients with preterm labor of no clinically identifiable cause between 26 and 34 weeks of gestation, who were receiving magnesium sulfate. A total of 136 patients were screened. Of these, 80 eligible, consenting patients were randomized to receive either 400 mg erythromycin or placebo orally every 6 hours for 10 days. Necessary statistical comparisons were preformed using unpaired two-tailed Student's t-test and Chi-square analysis. RESULTS: In comparing the 38 erythromycin and 42 placebo patients there was improvement in the treatment-to-delivery interval (33.33 +/- 18.36 versus 26.88 +/- 13.9 days, respectively), mean gestational age at delivery (36.11 +/- 2.33 versus 34.36 +/- 2.33 weeks, respectively), mean birth weight (2722.31 +/- 511.65 versus 2419.41 +/- 513.54 g, respectively), and reduced neonatal admission to NICU (36.8% versus 60.19%) in the erythromycin group. CONCLUSION: In patients with idiopathic preterm labor the adjunctive use of erythromycin therapy appeared safe and well tolerated and resulted in a statistically significant delay from admission to delivery and improved gestational age at delivery, mean birth weight and neonatal outcome.

Adult↗
PubMed1998

Clonal spread of group A streptococcus with the new type of erythromycin resistance. Finnish Study Group for Antimicrobial Resistance.

In 1990, a new type of erythromycin resistance phenotype, designated NR, was found in group A streptococcus (GAS) in Finland. In the present study, the distribution of GAS isolates with this and other erythromycin-resistance phenotypes was surveyed in Finland, and the clonality of the isolates was explored. Of 4179 GAS isolates collected from all over Finland, 695 (17%) were resistant to erythromycin, and 82% of these had the NR phenotype. Of a group of 96 isolates with the NR phenotype from different areas, 91% was T4 serotype, opacity factor-positive. The majority of these isolates were studied further: All were M4 serotype and 88% were of one clonal origin in genetic analyses. Thus, one single clone predominates among erythromycin-resistant GAS in Finland. This clone is of T4M4 serotype and mediates the new type of erythromycin resistance, characterized by the NR phenotype.

Bacterial Typing Techniques↗
PubMed1992

Azithromycin and clarithromycin: overview and comparison with erythromycin.

Azithromycin and clarithromycin are erythromycin analogues that have recently been approved by the FDA. These drugs inhibit protein synthesis in susceptible organisms by binding to the 50S ribosomal subunit. Alteration in this binding site confers simultaneous resistance to all macrolide antibiotics. Clarithromycin is several-fold more active in vitro than erythromycin against gram-positive organisms, while azithromycin is 2- to 4-fold less potent. Azithromycin has excellent in vitro activity against H influenzae (MIC90 0.5 microgram/ml), whereas clarithromycin, although less active against H influenzae (MIC90 4.0 micrograms/ml) by standard in vitro testing, is metabolized into an active compound with twice the in vitro activity of the parent drug. Both azithromycin and clarithromycin are equivalent to standard oral therapies against respiratory tract and soft tissue infections caused by susceptible organisms, including S aureus, S pneumoniae, S pyogenes, H influenzae, and M catarrhalis. Clarithromycin is more active in vitro against the atypical respiratory pathogens (e.g., Legionella), although insufficient in vivo data are available to demonstrate a clinical difference between azithromycin and clarithromycin. Superior pharmacodynamic properties separate the new macrolides from the prototype, erythromycin. Azithromycin has a large volume of distribution, and, although serum concentrations remain low, it concentrates readily within tissues, demonstrating a tissue half-life of approximately three days. These properties allow novel dosing schemes for azithromycin, because a five-day course will provide therapeutic tissue concentrations for at least ten days. Clarithromycin has a longer serum half-life and better tissue penetration than erythromycin, allowing twice-a-day dosing for most common infections. Azithromycin pharmacokinetics permit a five-day, single daily dose regimen for respiratory tract and soft tissue infections, and a single 1 g dose of azithromycin effectively treats C trachomatis genital infections; these more convenient dosing schedules improve patient compliance. Azithromycin and clarithromycin also are active against some unexpected pathogens (e.g., B burgdorferi, T gondii, M avium complex, and M leprae). Clarithromycin, thus far, appears the most active against atypical mycobacteria, giving new hope to what has become a difficult group of infections to treat. Gastrointestinal distress, a well known and major obstacle to patient compliance with erythromycin, is relatively uncommon with the new macrolides. Further clinical data and experiences may better define and expand the role of these new macrolides in the treatment of infectious diseases.

Azithromycin↗