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PubMed1996

Evaluation of the efficacy, safety and toleration of azithromycin vs. penicillin V in the treatment of acute streptococcal pharyngitis in children: results of a multicenter, open comparative study. The Swiss Tonsillopharyngitis Study Group.

BACKGROUND: For many years alternatives to penicillin have been studied for the management of pediatric group A beta-hemolytic Streptococcus (GABHS) pharyngitis. As a result of its pharmacokinetic profile azithromycin is unique among these alternative antimicrobials in allowing once daily dosing and shorter duration of treatment. However, the optimum dose (e.g. 10 or 12 mg/kg/day) and duration (e.g. 3 or 5 days) of azithromycin therapy have not been defined yet. METHODS: An open, comparative multicenter study was conducted in 343 children with clinical symptoms of GABHS pharyngitis and a positive culture to evaluate the efficacy and safety of azithromycin (10 mg/kg) once daily for 3 days compared with penicillin V three times daily for 10 days. RESULTS: Among the evaluable patients bacteriologic eradication documented at follow-up visits was inferior with azithromycin when compared with penicillin V therapy: at Days 9 to 20 (mean, 12 days), negative cultures in 65% (99 of 152 patients) vs. 82% (128 of 126 patients) (P < 0.001); and at Days 17 to 57 (mean, 25 days), in 55% vs. 80% (P < 0.001). Overall clinical success (cure or improvement) was achieved in 93% (149 of 160 patients) of azithromycin-treated and in 89% (143 of 160 patients) of penicillin-treated patients (P > 0.50). There was no correlation between bacteriologic response and clinical outcome, as assessed shortly after completion of therapy or during 6-month follow-up. Both treatments were well-tolerated. CONCLUSIONS: In the present study on GABHS pharyngitis in children, a once daily (10-mg/kg), 3-day oral regimen of azithromycin was as clinically effective and as safe as traditional penicillin but appeared inferior in eliminating GABHS from the throat.

Acute Disease↗
PubMedDate not supplied

A clinical isolate of Neisseria gonorrhoeae with in vitro resistance to erythromycin and decreased susceptibility to azithromycin.

BACKGROUND AND OBJECTIVES: Erythromycin is a recommended treatment for penicillin-allergic pregnant women with gonorrhea, and azithromycin has been suggested as therapy for coexisting gonococcal and chlamydial infections. Although gonococcal resistance to erythromycin is not uncommon, decreased resistance to azithromycin is rare. A clinical isolate of Neisseria gonorrhoeae with in vitro resistance to erythromycin and decreased susceptibility to azithromycin is reported. STUDY DESIGN: This is a case report. RESULTS: Antimicrobial susceptibility testing of a clinical isolate of N. gonorrhoeae revealed a minimal inhibitory concentration (MIC) of 2 micrograms/ml to azithromycin and 32 micrograms/ml to erythromycin. Five hundred other urethral isolates were tested, resulting in an MIC for erythromycin ranging from 0.015 to 2 micrograms/ml. The range for azithromycin was 0.015 to 0.5 micrograms/ml. There was a strong correlation between erythromycin and azithromycin MICs (r = 0.73; P < 0.0001). CONCLUSIONS: Continued national monitoring is needed to detect the appearance and early dissemination of new types of gonococcal resistance.

Adult↗
PubMed2002

Azithromycin versus doxycycline for genital chlamydial infections: a meta-analysis of randomized clinical trials.

BACKGROUND: Azithromycin and doxycycline are recommended for treatment of genital Chlamydia trachomatis infection. A systematic review comparing these antibiotics could affect treatment guidelines. GOAL: The goal was to perform a meta-analysis to evaluate the efficacy and tolerance of azithromycin versus doxycycline for genital chlamydial infection. STUDY DESIGN: Studies were identified by searching computerized English-language databases for the period 1975 to August 2001, supplemented by a manual bibliographic search. Criteria for inclusion were (1) randomized trial design; (2) regimens of oral doxycycline (100 mg twice daily for 7 days) and oral azithromycin (1 g once); (3) males >15 years of age and nonpregnant females >15 years of age; (4) and evaluation of microbial cure at follow-up. Data were extracted on diagnostic assay, follow-up time, study design, sponsorship, patients' characteristics, adverse events, attrition rates, and outcomes. RESULTS: Twelve trials met the inclusion criteria; 1543 patients were evaluated for microbial cure and 2171 for adverse events. Cure rates were 97% for azithromycin and 98% for doxycycline. Adverse events occurred in 25% and 23% of patients treated with azithromycin and doxycycline, respectively. After pooling of the data, differences in efficacy and risk were computed. The efficacy difference for microbial cure (0.01; 95% CI, -0.01-0.02) and the risk difference for adverse events (0.01; 95% CI, -0.02-0.04) between the two drugs were not statistically significant. CONCLUSION: Azithromycin and doxycycline are equally efficacious in achieving microbial cure and have similar tolerability. Further head-to-head trials comparing these antibiotics are unnecessary.

Anti-Bacterial Agents↗
PubMed2003

The cost-effectiveness of single-dose azithromycin for treatment of incubating syphilis.

BACKGROUND: Treatment of incubating syphilis with intramuscular benzathine penicillin in exposed sex partners is not always practical in the field, and exposed partners may not adhere to referrals for treatment at clinical facilities. The availability of a single-dose oral therapy could increase the number of partners treated and reduce future infections. GOAL: The goal of the study was to evaluate the cost-effectiveness of directly observed oral administration of azithromycin as an alternative to referral for treatment with benzathine penicillin. STUDY DESIGN: Using published probability and cost estimates, we constructed a decision-analysis model to compare the direct costs and effectiveness of field treatment with azithromycin (1-g single dose) versus referral for standard benzathine penicillin therapy. RESULTS: At public-sector pricing ($11.50 U.S. dollars), directly observed field treatment with azithromycin is cost-saving from both the program and healthcare system perspectives at efficacy levels as low as 75%. Azithromycin therapy is cost-saving at the wholesale price of $17.32 U.S. dollars (sachet formulation) when efficacy is at least 90%. The more expensive tablet formulation (average wholesale price of $27.89 U.S. dollars) is not cost-saving from a program perspective, but it remains cost-saving from a healthcare system perspective if efficacy rates are at least 90%. Azithromycin therapy (1-g single dose) will result in fewer cases of early syphilis among exposed partners, provided that the drug's efficacy is at least 87%. CONCLUSIONS: Azithromycin is a cost-effective alternative treatment for incubating syphilis in settings where standard intramuscular therapy is not practical.

Administration, Oral↗
PubMed2005

Large dosage amoxicillin/clavulanate, compared with azithromycin, for the treatment of bacterial acute otitis media in children.

BACKGROUND: A large dosage pediatric formulation of amoxicillin/clavulanate with an improved pharmacokinetic/pharmacodynamic profile was developed to eradicate many penicillin-resistant strains of Streptococcus pneumoniae and Haemophilus influenzae (including beta-lactamase-producing strains). METHODS: This randomized, investigator-blinded, multicenter trial examined treatment of bacterial acute otitis media (AOM) in children 6-30 months of age with amoxicillin/clavulanate (90/6.4 mg/kg/d in 2 divided doses for 10 days) versus azithromycin (10 mg/kg for 1 day followed by 5 mg/kg/d for 4 days). Tympanocentesis was performed at entry for bacteriologic assessment, at the on-therapy visit (day 4-6) to determine bacterial eradication and at any time before the end-of-therapy visit (day 12-14) if the child was categorized as experiencing clinical failure. Clinical assessments were performed at the on-therapy, end-of-therapy and follow-up (day 21-25) visits. RESULTS: We enrolled 730 children; AOM pathogens were isolated at baseline for 249 of the amoxicillin/clavulanate group and 245 of the azithromycin group. For children with AOM pathogens at baseline, clinical success rates at the end-of-therapy visit were 90.5% for amoxicillin/clavulanate versus 80.9% for azithromycin (P < 0.01), and those at the on-therapy and follow-up visits were 94.9% versus 88.0% and 80.3% versus 71.1%, respectively (all P < 0.05). At the on-therapy visit, pretherapy pathogens were eradicated for 94.2% of children receiving amoxicillin/clavulanate versus 70.3% of those receiving azithromycin (P < 0.001). Amoxicillin/clavulanate eradicated 96.0% of S. pneumoniae (92.0% of fully penicillin-resistant S. pneumoniae) and 89.7% of H. influenzae (85.7% [6 of 7 cases] of beta-lactamase-positive H. influenzae). Corresponding rates for azithromycin were 80.4% (54.5%) for S. pneumoniae and 49.1% (100% [1 of 1 case]) for H. influenzae (all P < 0.01 for between-drug comparisons). CONCLUSION: Amoxicillin/clavulanate was clinically and bacteriologically more effective than azithromycin among children with bacterial AOM, including cases caused by penicillin-resistant S. pneumoniae and beta-lactamase-positive H. influenzae.

Acute Disease↗
PubMed2007

Efficacy of azithromycin administration in prevention of respiratory tract infection after bronchoscopic biopsy: a randomized, controlled trial.

BACKGROUND AND OBJECTIVE: Respiratory tract infection is a serious complication associated with bronchoscopic biopsy. This study attempted to examine its incidence and determine an efficacious therapy for preventing such infections. METHODS: Nine hundred and thirty patients who underwent bronchoscopic biopsy in Osaka City University Hospital outpatient clinic were enrolled in the study. All patients were randomly assigned to receive a 3-day course of azithromycin (500 mg/day), cefcapene pivoxil hydrochloride (300 mg/day) or no antibiotics. The primary outcome was the incidence of respiratory tract infection after bronchoscopic biopsy among the three groups. RESULTS: In the no-treatment group, nine of the 310 patients (2.9%) had respiratory tract infection after bronchoscopic biopsy. All patients with infection had abnormal bronchoscopic findings. Of the patients with respiratory tract infection, 60% were in the no-treatment group, 26.7% in the cefcapene group and 13.3% in the azithromycin group. Although not statistically significant, the incidence in the azithromycin group (0.7%) was lower than in the no-treatment group (P = 0.06). Among the patients with abnormal bronchoscopic findings, the incidence in the azithromycin group was significantly lower than that in the no-treatment group (3.0% vs. 14.8%; P = 0.02). Moreover, maximum C-reactive protein values also appeared to be lower in the azithromycin group than in the no-treatment group and the cefcapene group. CONCLUSIONS: A 3-day course of azithromycin administration is well tolerated and effective in preventing infection post bronchoscopy.

Adult↗
PubMed2000

Single dose oral azithromycin versus seven day doxycycline in the treatment of non-gonococcal mucopurulent endocervicitis.

The aim of this study was to compare single dose oral azithromycin versus seven-day doxycycline in the treatment of non-gonococcal mucopurulent cervicitis (MPC). One hundred and thirty-one women with non-gonococcal MPC were enrolled in a prospective-randomised study to compare the efficacy and safety of a single oral dose of 1 g azithromycin and a seven-day course of 100 mg doxycycline twice daily. Clinical examination and culture samples for Chlamydia trachomatis and other microorganisms were performed before and approximately 14 days after starting the treatment. Of the 131 women recruited (67 in the azithromycin group and 64 in the doxycycline group), Ureaplasma urealyticum was isolated from 21 (16%); Chlamydia trachomatis from 15 (11.5%); and Mycoplasma hominis from 3 (2.3%) of the patients at the initial examination. The eradication rate of baseline culture-positive cases at the follow-up visit in the azithromycin group was 71.4%, and 77.3% in the doxycycline group. There was no statistically significant difference in efficacy between the single dose azithromycin and seven-day course of doxycycline in the treatment of culture-positive cases. Azithromycin 1 g appears to be an effective and safe alternative to doxycycline for the treatment of non-gonococcal MPC.

Administration, Oral↗
PubMed1996

Azithromycin in the treatment of periodontal disease. Effect on microbial flora.

Azithromycin is an azalide antibiotic with excellent in vitro activity against a wide variety of oral bacteria. It has a long half-life, good tissue penetration and is preferentially taken up by phagocytes. We investigated the microbiological efficacy of azithromycin as an adjunct to the non-surgical treatment of adult chronic periodontitis; its clinical efficacy is dealt with in a separate paper. 46 patients were treated in a double-blind placebo controlled trial. Microbiological assessment of the same periodontal pocket (initially > 6 mm) was made at weeks 0, 2, 3, 6, 10 and 22. Either azithromycin 500 mg 1 x daily for 3 days or placebo was given at week 2. Particular attention was paid to the numbers of black pigmented anaerobes and spirochaetes present since these are the most commonly implicated pathogens in periodontal disease. Pigmented anaerobes were significantly reduced at weeks 3 and 6 in patients who received azithromycin compared to placebo and remained lower, although not significantly so, throughout the study. Counts of spirochaetes were significantly reduced throughout the study in patients who received azithromycin compared to placebo. Our microbiological study suggests that azithromycin may be useful as an adjunct in the treatment of periodontal disease.

Adult↗
PubMed2006

Synergistic activities of azithromycin and amphotericin B against Naegleria fowleri in vitro and in a mouse model of primary amebic meningoencephalitis.

Naegleria fowleri is responsible for producing a rapidly fatal central nervous system infection known as primary amebic meningoencephalitis (PAM). To date, amphotericin B, an antifungal agent, is the only agent with established clinical efficacy in the treatment of PAM. However, amphotericin B is not always successful in treating PAM and is associated with severe adverse effects. We previously found azithromycin to be more effective than amphotericin B in a mouse model of PAM. We therefore investigated the combination of amphotericin B and azithromycin in vitro and in a mouse model of PAM. For the in vitro studies, 50% inhibitory concentrations were calculated for each drug alone and for the drugs in fixed combination ratios of 1:1, 3:1, and 1:3. We found amphotericin B and azithromycin to be synergistic at all three of the fixed combination ratios. In our mouse model of PAM, a combination of amphotericin B (2.5 mg/kg of body weight) and azithromycin (25 mg/kg) protected 100% of the mice, whereas amphotericin B alone (2.5 mg/kg) protected only 27% of mice and azithromycin alone (25 mg/kg) protected 40% of mice. This study indicates that amphotericin B and azithromycin are synergistic against the Lee strain of N. fowleri, suggesting that the combined use of these agents may be beneficial in treating PAM.

Amphotericin B↗
PubMed2006

Comparative pharmacokinetics of azithromycin in serum and white blood cells of healthy subjects receiving a single-dose extended-release regimen versus a 3-day immediate-release regimen.

The pharmacokinetic profiles of azithromycin given as a single-dose regimen (2.0-g extended-release microspheres) were characterized in serum and white blood cells (WBC) and compared with those of a 3-day regimen (a 500-mg immediate-release tablet once daily; total dose, 1.5 g) in an open-label, randomized, parallel-group study of 24 healthy adult subjects. Serial blood samples were collected up to 5 days after the start of dosing for both regimens. Safety assessments were conducted throughout the study. A single 2.0-g dose of azithromycin microspheres achieved significantly higher exposures in serum and WBC during the first 24 h after the start of dosing than a 3-day regimen: an approximately threefold higher area under the curve from time zero to 24 h postdose (AUC(0-24)) and an approximately twofold higher mean peak concentration on day 1. The single-dose regimen provided total azithromycin exposures in serum and WBC similar to those of the 3-day regimen, as evidenced by the similar AUC(0-120) and trough azithromycin concentrations in serum and WBC (mononuclear leukocytes [MNL] and polymorphonuclear leukocytes [PMNL]). For both regimens, the average total azithromycin exposures in MNL and PMNL were approximately 300- and 600-fold higher than those in serum. Azithromycin concentrations in MNL and PMNL remained above 10 microg/ml for at least 5 days after the start of dosing for both regimens. This "front-loading" of the dose on day 1 is safely achieved by the extended-release microsphere formulation, which maximizes the drug exposure at the time when the bacterial burden is likely to be highest.

Adolescent↗
PubMed2006

In vitro antimalarial activity of azithromycin, artesunate, and quinine in combination and correlation with clinical outcome.

Azithromycin when used in combination with faster-acting antimalarials has proven efficacious in treating Plasmodium falciparum malaria in phase 2 clinical trials. The aim of this study was to establish optimal combination ratios for azithromycin in combination with either dihydroartemisinin or quinine, to determine the clinical correlates of in vitro drug sensitivity for these compounds, and to assess the cross-sensitivity patterns. Seventy-three fresh P. falciparum isolates originating from patients from the western border regions of Thailand were successfully tested for their drug susceptibility in a histidine-rich protein 2 (HRP2) assay. With overall mean fractional inhibitory concentrations of 0.84 (95% confidence interval [CI]=0.77 to 1.08) and 0.78 (95% CI=0.72 to 0.98), the interactions between azithromycin and dihydroartemisinin, as well as quinine, were classified as additive, with a tendency toward synergism. The strongest tendency toward synergy was seen with a combination ratio of 1:547 for the combination with dihydroartemisinin and 1:44 with quinine. The geometric mean 50% inhibitory concentration (IC50) of azithromycin was 2,570.3 (95% CI=2,175.58 to 3,036.58) ng/ml. The IC50s for mefloquine, quinine, and chloroquine were 11.42, 64.4, and 54.4 ng/ml, respectively, suggesting a relatively high level of background resistance in this patient population. Distinct correlations (R=0.53; P=0.001) between quinine in vitro results and parasite clearance may indicate a compromised sensitivity to this drug. The correlation with dihydroartemisinin data was weaker (R=0.34; P=0.038), and no such correlation was observed for azithromycin. Our in vitro data confirm that azithromycin in combination with artemisinin derivatives or quinine exerts additive to synergistic interactions, shows no cross-sensitivity with traditional antimalarials, and has substantial antimalarial activity on its own.

Animals↗
PubMed1987

Spectrum and mode of action of azithromycin (CP-62,993), a new 15-membered-ring macrolide with improved potency against gram-negative organisms.

The macrolide antibiotic azithromycin (CP-62,993; 9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin A; also designated XZ-450 [Pliva Pharmaceuticals, Zagreb, Yugoslavia]) showed a significant improvement in potency against gram-negative organisms compared with erythromycin while retaining the classic erythromycin spectrum. It was up to four times more potent than erythromycin against Haemophilus influenzae and Neisseria gonorrhoeae and twofold more potent against Branhamella catarrhalis, Campylobacter species, and Legionella species. It had activity similar to that of erythromycin against Chlamydia spp. Azithromycin was significantly more potent versus many genera of the family Enterobacteriaceae; its MIC for 90% of strains of Escherichia, Salmonella, Shigella, and Yersinia was less than or equal to 4 micrograms/ml, compared with 16 to 128 micrograms/ml for erythromycin. Azithromycin inhibited the majority of gram-positive organisms at less than or equal to 1 micrograms/ml. It displayed cross-resistance to erythromycin-resistant Staphylococcus and Streptococcus isolates. It had moderate activity against Bacteroides fragilis and was comparable to erythromycin against other anaerobic species. Azithromycin also demonstrated improved bactericidal activity in comparison with erythromycin. The mechanism of action of azithromycin was similar to that of erythromycin since azithromycin competed effectively for [14C]erythromycin ribosomebinding sites.

Anti-Bacterial Agents↗
PubMed1991

Prophylactic and therapeutic activities of azithromycin in a mouse model of pneumococcal pneumonia.

Azithromycin is a new acid-stable 15-membered-ring macrolide that exhibits an extended half-life and excellent tissue distribution, including distribution in the lung. We compared its in vivo activity with that of erythromycin using two models of Streptococcus pneumoniae pneumonia, namely, a model of acute infection in Swiss mice and a model of subacute infection in C57BL/6j mice. Female mice were infected by oral delivery into the trachea of 10(5) CFU of a virulent serotype 3 strain of S. pneumoniae (P 4241). Prophylactic and therapeutic treatments were given orally (p.o.) or subcutaneously (s.c.) by various regimens. In the model of subacute infection, a single dose of azithromycin, 25 mg/kg, given p.o. 7 h before infection protected 92% of the mice, while erythromycin was completely ineffective. In the model of acute infection, a single dose of azithromycin, 50 mg/kg, given s.c. 24 h prior to challenge protected 80% of the mice, whereas only 35% of the mice survived with erythromycin, 50 mg/kg, 1 h before challenge. Therapy, which was studied exclusively in the model of subacute infection, was initiated 48 h postinfection. Two doses of 12.5 mg/kg given p.o. 12 h apart resulted in 80% survival of mice treated with azithromycin versus 7% survival of mice treated with erythromycin. Pulmonary clearance of bacteria was consistent with the survival rates. Two doses (25 mg/kg) of azithromycin given s.c. at 48 and 65 h after infection led to complete clearance of bacteria from the lungs and blood, whereas erythromycin-treated mice remained bacteremic. The pharmacokinetics of azithromycin account for its superior efficacy against S. pneumoniae pneumonia relative to the efficacy of erythromycin.

Animals↗
PubMed1992

Potentiation of antibacterial activity of azithromycin and other macrolides by normal human serum.

The interaction of azithromycin with normal human serum was examined in relation to serum protein binding, MIC, and kinetics of killing of bacteria. While the binding of azithromycin to serum proteins is low (8.5% at a concentration of 0.01 mM in 95% serum), the presence of 40% serum during the MIC test decreased MICs by 26-fold for serum-resistant Escherichia coli and 15-fold for Staphylococcus aureus. Erythromycin had a similar but lesser effect, while roxithromycin was less active against S. aureus in the presence of serum. The rate of killing of E. coli and S. aureus by azithromycin was increased in the presence of serum. The enhancement of antibiotic activity by serum was pH independent, and heat inactivation and preabsorption with homologous bacteria failed to inhibit enhancement by serum. The macromolecular incorporation of [3H]thymidine by E. coli continuously exposed to 2 micrograms of azithromycin per ml (0.25x the MIC) and 40% serum was decreased by 80% at pH 7.8 and by 48% at pH 7.2, while azithromycin alone failed to inhibit incorporation. Inhibition of nucleic acid biosynthesis at pH 7.2 in the presence of serum was also detected with sub-MICs of erythromycin, norfloxacin, and gentamicin but not roxithromycin. A diffusible serum factor was shown to interact with azithromycin to inhibit the growth of E. coli in an agar diffusion assay to detect antibiotic-serum synergy.

Anti-Bacterial Agents↗
PubMed1992

Azithromycin-induced block of elementary body formation in Chlamydia trachomatis.

The mechanism of action of azithromycin on the murine strain of Chlamydia trachomatis grown in tissue culture epithelial cells is addressed. Azithromycin at a concentration of 100 ng/ml inhibits chlamydial growth in tissue culture, a value that agrees well with prior in vitro data from human strains of C. trachomatis grown in tissue culture. By morphological criteria, the block to chlamydial growth appears to occur early in its life cycle. Azithromycin is not directly toxic to chlamydial elementary bodies but does inhibit chlamydial protein synthesis in chlamydia-infected cells. This inhibition appears quite general in nature and is rapid. It is further shown that azithromycin does not directly inhibit mRNA synthesis. Azithromycin blocks chlamydial protein synthesis in host cell-free chlamydial reticulate bodies in a manner similar to its inhibition in infected cells, albeit at slightly higher concentrations. The inhibition of chlamydial protein synthesis following a brief exposure to azithromycin is more long lasting than that following a brief exposure to erythromycin.

Animals↗
PubMed1992

In vitro evaluation of activities of azithromycin, erythromycin, and tetracycline against Chlamydia trachomatis and Chlamydia pneumoniae.

The in vitro activities of azithromycin (CP-62,993; Pfizer), erythromycin, and tetracycline were evaluated by inhibiting Chlamydia trachomatis and Chlamydia pneumoniae, formerly TWAR, propagation in vitro in McCoy cells, HeLa cells, and HL cells. Eleven clinical isolates of C. trachomatis (serovars D, E, F, J, K, and L2) and four strains of C. pneumoniae were tested with an inoculum of 10(3) inclusion-forming units in a 96-well microtiter plate. The MIC ranges of these antimicrobial agents against C. trachomatis were as follows: azithromycin, 0.125 to 0.5 microgram/ml; erythromycin, 0.25 to 0.1 microgram/ml; and tetracycline, 0.0625 to 1.0 microgram/ml. The MBC ranges, calculated from passage into antibiotic-free medium, were as follows: azithromycin, 0.125 to 4.0 micrograms/ml; erythromycin, 0.5 to 8.0 micrograms/ml; and tetracycline, 0.0625 to 4.0 micrograms/ml. The MIC ranges for C. pneumoniae in both HeLa and HL cells were as follows: azithromycin, 0.125 to 1.0 micrograms/ml; erythromycin, 0.0625 to 1.0 microgram/ml; and tetracycline, 0.125 to 1.0 microgram/ml. The MBC ranges were as follows: azithromycin, 0.25 to 1.0 microgram/ml; erythromycin, 0.25 to 1.0 microgram/ml; and tetracycline, 0.125 to 4.0 micrograms/ml. From the results of this in vitro study, azithromycin appears to be an effective antibiotic comparable to tetracycline and erythromycin for use in the treatment of both C. trachomatis and C. pneumoniae infections.

Azithromycin↗
PubMed1992

Synergistic activity of azithromycin and pyrimethamine or sulfadiazine in acute experimental toxoplasmosis.

The efficacy of azithromycin administered alone or combined with pyrimethamine or sulfadiazine was examined in a murine model of acute toxoplasmosis. Outbred Swiss mice acutely infected with tachyzoites of the virulent RH strain were treated for 10 days from day +1 postinfection. The efficacy of each regimen was assessed in terms of survival rates and sequential titration of parasites in blood, brain, and lungs by using a tissue culture method. Administration of azithromycin at 300, 150, or 75 mg/kg of body weight per day resulted in prolonged survival relative to that of untreated controls; sequential examination of parasite burden showed early eradiaction of Toxoplasma gondii from the lungs, whereas dissemination to the brain was not prevented. A remarkable synergistic effect was observed when azithromycin (150 mg/kg/day) was administered in combination with pyrimethamine or sulfadiazine at noncurative dosages, i.e., 12.5 and 200 mg/kg/day, respectively. In mice treated with azithromycin plus sulfadiazine and azithromycin plus pyrimethamine, parasite burdens in blood and organs, relapses after cessation of therapy, and mortality were all markedly reduced relative to mice treated with any of the agents alone. These results show that azithromycin, which is remarkably active on pulmonary Toxoplasma infection, significantly potentiates the curative effect of sulfadiazine or pyrimethamine.

Animals↗
PubMed1992

In vitro and in vivo intraleukocytic accumulation of azithromycin (CP-62, 993) and its influence on ex vivo leukocyte chemiluminescence.

The accumulation of azithromycin in phagocytic cells was studied both in vitro by using a radiolabelled drug and a bioassay and in vivo for 12 volunteers receiving 1.5 g (total dose) orally within 3 days. In vitro, neutrophils and unfractionated blood leukocytes accumulated azithromycin up to 160-fold the extracellular concentration within 1 h at 37 degrees C but less than 3-fold at 4 degrees C. Dead cells accumulated up to 30-fold azithromycin, whereas NaF-treated cells accumulated up to 60-fold arithromycin. The mean efflux from preloaded cells was at most 31.0% +/- 10.6% (standard error of the mean) of the cell-associated concentration within 4 h of incubation at 37 degrees C in drug-free buffer. In vivo, the azithromycin concentration was 45.2 +/- 6.1 mg/liter of intracellular fluid at 2 h after the third dose and 36.6 +/- 8.3 mg/liter at 1 week thereafter. The corresponding concentrations in serum were 0.2 +/- 0.1 (2 h) and less than 0.05 (1 week). The luminol-enhanced chemiluminescence response induced by phorbol myristate acetate, opsonized zymosan, and two opsonized strains of Haemophilus influenzae (a type b capsulated strain and a noncapsulated strain) was also studied ex vivo by using the blood leukocytes from the 12 test volunteers and 4 control volunteers at 2 and 6 h after the third oral dose of azithromycin and at 2, 4, and 7 days thereafter. Azithromycin did not influence this response despite high levels of cellular accumulation.

Adult↗