A Bioequivalence Study With Pharmacokinetic Endpoints for Azithromycin Eye Drops

Azithromycin eye drops with a bioadhesive ocular drug-delivery system can offer a simplified dosing regimen. In this study, we compared the pharmacokinetic properties and assessed the bioequivalence of a newly developed generic azithromycin eye drop with a branded formulation. This open-label, single-dose, randomized, crossover, sparse-sampling ocular bioequivalence study was conducted on 48 healthy Chinese volunteers. Tear samples were collected for up to 36 hours, and each participant was randomly allocated to one of the prespecified sampling times. Tear drug concentrations were determined using a validated liquid chromatography-tandem mass spectrometry method. The pharmacokinetic parameters were calculated via noncompartmental analysis. A nonparametric bootstrap method was used to obtain 90% confidence intervals (CIs) for the ratios of the test and reference drugs. Tolerability was evaluated for adverse events (AEs). After bootstrapping (1000 iterations), the 90%CIs for the log-transformed ratios of Cmax , AUC0-t , and AUC0-∞ were within the acceptable bioequivalence range (80%-125%). No moderate-to-severe AEs were reported for either formulation. Bioequivalence was demonstrated between the two formulations. The sparse-sampling design with the bootstrapping technique is promising for bioequivalence studies of topical ophthalmic drugs.

Population Pharmacokinetic Modeling of Azithromycin Eyedrops in Tears Following Single-Dose Topical Administration in Healthy Volunteers

BACKGROUND AND OBJECTIVES

The disposition of azithromycin in the human eye following topical administration has not been fully explored. Population pharmacokinetic (PopPK) modeling can allow useful conclusions to be drawn based on limited tear sampling data. The aim of this study was therefore to develop and evaluate a PopPK model of azithromycin eyedrops in tears, investigate typical model parameters, and identify potential covariates following single-dose ocular instillation.

METHODS

A total of 84 tear samples were obtained from 42 healthy volunteers at seven time points over 24 h following topical administration of azithromycin eyedrops (2.5 mL/25 mg). Azithromycin concentrations in the tears were determined using a validated LC-MS/MS assay. PopPK analysis was performed using nonlinear mixed-effects modeling. Intraocular pressure, tear secretion measurement, age, and gender were evaluated as possible covariates. Bootstrap and visual predictive checks were used simultaneously to evaluate the PopPK model. The dosage regimen was further estimated based on Monte Carlo simulation and the area under the curve/minimal inhibitory concentration.

RESULTS

A linear two-compartment first-order elimination model was found to best describe the pharmacokinetic profile of azithromycin in tears. None of the covariates had a significant influence on the typical model parameters. The final PopPK model was demonstrated to be suitable and effective according to bootstrap and visual predictive checks. Twice-daily instillation of azithromycin eyedrops would appear to provide the required antibacterial activity.

CONCLUSION

A proposed linear two-compartment PopPK model of azithromycin eyedrops was found to be effective at describing the disposition of azithromycin in tears after ocular instillation.

Microbial flora and resistance in ophthalmology: a review

Antibiotic resistance in systemic infection is well-researched and well-publicized. Much less information is available on the resistance of normal ocular microbiome and that of ophthalmic infections. An understanding of the distribution of ocular microorganisms may help us in tailoring our empiric treatment, as well as in choosing effective pre-, peri- and postoperative management, to achieve the best results for patients. This study aims to summarize and review the available literature on the subject of normal ocular flora and its resistance, as well as the broader topic of antibiotic resistance in ophthalmology.

A randomized, double-masked, parallel-group, comparative study to evaluate the clinical efficacy and safety of 1% azithromycin-0.1% dexamethasone combination compared to 1% azithromycin alone, 0.1% dexamethasone alone, and vehicle in the treatment of subjects with blepharitis

Purpose

To evaluate the clinical efficacy and safety of a 1% azithromycin–0.1% dexamethasone combination in DuraSite (“combination”) compared to 0.1% dexamethasone in DuraSite, 1% azithromycin in DuraSite, and vehicle in the treatment of subjects with blepharitis.

Materials and methods

This was a Phase III, double-masked, vehicle-controlled, four-arm study in which 907 subjects with blepharitis were randomized to combination (n=305), 0.1% dexamethasone (n=298), 1% azithromycin (n=155), or vehicle (n=149). Ten study visits were scheduled: screening visit, days 1 and 4 (dosing phase) and 15, and months 1–6 (follow-up phase). On day 1, subjects applied one drop of the study drug to the eyelid of the inflamed eye(s) twice daily, and continued with twice-daily dosing for 14 days. After completing 14 days of dosing, subjects were followed for 6 months for efficacy and safety.

Results

A total of 57 subjects (6.3%) had complete clinical resolution at day 15: 25 (8.2%), 17 (5.7%), 8 (5.2%), and 7 (4.7%) subjects in the combination-, 0.1% dexamethasone-, 1% azithromycin-, and vehicle-treatment groups, respectively. The combination was superior to 1% azithromycin and vehicle alone, but not to 0.1% dexamethasone alone. Mean composite (total) clinical sign and symptom scores improved in all four treatment groups during the post-treatment evaluation phase for the intent-to-treat population, but outcomes were superior when a drop containing 0.1% dexamethasone was utilized. Clinical response was noted as early as day 4, and persisted as long as 6 months. Most adverse events were considered mild in severity and not related to the study drug.

Conclusion

A higher percentage of subjects in the combination group achieved complete clinical resolution of the signs and symptoms of blepharitis at day 15 than with 1% azithromycin and vehicle, but outcomes were similar to treatment with 0.1% dexamethasone alone. The combination was well tolerated.

Can tetracycline antibiotics duplicate the ability of azithromycin to stimulate human meibomian gland epithelial cell differentiation?

PURPOSE

Azithromycin and tetracyclines are commonly prescribed in the United States for the treatment of meibomian gland dysfunction (MGD). The efficacy of these antibiotics has been believed to be their antiinflammatory and antibacterial actions, which suppress MGD-associated posterior blepharitis and growth of lid bacteria. However, we recently discovered that azithromycin can act directly on human meibomian gland epithelial cells (HMGECs) to stimulate their function. In this study, we sought to determine whether tetracycline antibiotics can duplicate this azithromycin effect.

METHODS

Immortalized HMGEC were cultured in the presence of a vehicle, azithromycin, doxycycline, minocycline, or tetracycline for 5 days. Cells were evaluated for cholesterol and neutral lipid staining, and the lipid composition of cellular lysates was analyzed by high-performance thin-layer chromatography.

RESULTS

Our results demonstrate that azithromycin's ability to stimulate the differentiation of human meibomian gland cells is unique, and is not duplicated by doxycycline, minocycline, or tetracycline. Azithromycin, but not the other antibiotics, significantly increased the cellular accumulation of cholesterol, cholesterol esters, phospholipids, and lysosomes. These differentiative actions of azithromycin were paralleled by an increased expression of sterol regulatory element-binding protein 1.

CONCLUSIONS

Our findings show that the stimulatory effects of azithromycin on HMGEC function are unique and are not duplicated by the antibiotics doxycycline, minocycline, or tetracycline. Our results further suggest that this stimulatory influence of azithromycin may contribute to its beneficial effect in treating MGD and its associated evaporative dry eye disease.

One man's poison is another man's meat: using azithromycin-induced phospholipidosis to promote ocular surface health

Drug-induced phospholipidosis (PLD) is a common adverse effect which has led to the termination of clinical trials for many candidate pharmaceuticals. However, this lipid-inducing effect may be beneficial in the treatment of meibomian gland dysfunction (MGD). MGD is the major cause of dry eye disease (DED), which affects 40 million people in the USA and has no cure. Azithromycin (AZM) is a PLD-inducing antibiotic that is used off-label to treat MGD, and is presumably effective because it suppresses the MGD-associated conjunctival inflammation (i.e. posterior blepharitis) and growth of lid bacteria. We hypothesize that AZM can act directly to promote the function of human meibomian gland epithelial cells by inducing PLD in these cells, characterized by the accumulation of lipids and lysosomes. Immortalized human meibomian gland epithelial cells (HMGEC) were cultured with or without azithromycin for 5 days. Cells were evaluated for cholesterol (Filipin) and neutral lipid (LipidTox) staining, as well as the appearance of lysosomes (LysoTracker) and lamellar bodies (transmission electron microscopy, TEM). The lipid composition of cellular lysates was analyzed by high performance thin-layer chromatography. Our findings demonstrate that AZM stimulates the accumulation of free cholesterol, neutral lipids and lysosomes in HMGEC. This AZM-induced increase of neutral lipid content occurred predominantly within lysosomes. Many of these vesicles appeared to be lamellar bodies by TEM, which is the characteristic of PLD. Our findings also show that AZM promotes an accumulation of free and esterified cholesterol, as well as phospholipids in HMGECimmortalized. Our results support our hypothesis and confirm the beneficial effect of PLD induced by AZM on HMGEC. Our discovery reveals a new potential use of PLD-inducing drugs, and makes this adverse effect a beneficial effect.

Efficacy and safety of azithromycin 1.5% eye drops in paediatric population with purulent bacterial conjunctivitis

Objective

To determine the efficacy and safety of azithromycin 1.5% eye drops in a paediatric population with purulent bacterial conjunctivitis.

Patients and methods

This was a multicentre, international, randomised, investigator-masked study in 286 children with purulent discharge and bulbar conjunctival injection. Patients received either azithromycin 1.5% eye drops (twice daily for 3 days) or tobramycin 0.3% eye drops (every 2 h for 2 days, then four times daily for 5 days). Clinical signs were evaluated on day (D) 0, 3 and 7, and cultures on D0 and D7. The primary variable was the clinical cure (absence of bulbar conjunctival injection and discharge) on D3 in the worse eye for patients with positive cultures on D0.

Results

286 patients (mean age 3.2 years; range 1 day–17 years) were included; 203 had positive cultures on D0. Azithromycin was superior to tobramycin in clinical cure rate on D3 (47.1% vs 28.7%, p=0.013) and was non-inferior to tobramycin on D7 (89.2% vs 78.2%, respectively). Azithromycin treatment eradicated causative pathogens, including resistant species, with a similar resolution rate to tobramycin (89.8% vs 87.2%, respectively). These results were confirmed in a subgroup of patients younger than 24 months old.

Conclusions

Azithromycin 1.5% eye drops provided a more rapid clinical cure than tobramycin 0.3% eye drops in the treatment of purulent bacterial conjunctivitis in children, with a more convenient twice-a-day dosing regimen.

Antimicrobial Agents in Ophthalmology

Many types of antimicrobial agents have been introduced for the treatment of ocular infectious diseases. Some ocular infections have been eradicated such as smallpox, while others have been controlled by public health measures such as trachoma. The resilience of viruses and the tenacity of bacteria have led to the evolution of old diseases and the emergence of new infections. Continuous search for new antimicrobial agents for the treatment of infectious diseases is, therefore, highly desirable.

New infectious agents are discovering the human race, and the ecological changes are exposing mankind to new viruses and bacteria. In addition, air travel and disruption of geographic barriers are leading to new forms of infectious diseases.

In the twentieth century, there was a widespread false optimism that infectious diseases are eradicated by antimicrobial agents. It was soon discovered that many infections require new strategies for the treatment of ocular infections.

The new antimicrobial agents that have been introduced over the past century can be classified into four major categories including (1) antibiotics that inhibit cell wall synthesis and integrity, (2) antibiotics that inhibit and suppress cell membrane functions, (3) antibiotics that interfere the protein synthesis, and (4) antibiotics that modulate nucleic acid synthesis.

The selection of antimicrobial agents for the treatment of ocular infectious diseases is based on the most frequently encountered organisms, the pharmacokinetics of the antibiotics, the dosage required, the ocular penetration, and the cost of therapy. The stumbling blocks to safe and effective antimicrobial therapy in ocular infections include the resistance of the microorganisms, toxicity of the drug, and poor ocular penetration of antimicrobial agents.

A single-blinded randomized clinical trial comparing polymyxin B-trimethoprim and moxifloxacin for treatment of acute conjunctivitis in children

OBJECTIVE

To perform a randomized controlled trial comparing moxifloxacin hydrochloride with polymyxin B-trimethoprim for the treatment of acute conjunctivitis.

STUDY DESIGN

Patients ages 1-18 years old with acute conjunctivitis had cultures performed and were randomized to receive either moxifloxacin hydrochloride or polymyxin B-trimethoprim ophthalmic solution for 7 days. Response to treatment was determined by phone query on day 4-6 and by examination with post-treatment conjunctival culture on day 7-10.

RESULTS

One hundred and twenty-four patients were enrolled. Eighty patients (65%) had recognized pathogens (55 Haemophilus influenzae, 22 Streptococcus pneumoniae, 4 Moraxella catarrhalis) isolated from their conjunctiva. One hundred fourteen (56/62 moxifloxacin and 58/62 polymyxin B-trimethoprim) completed the 4-6 day evaluation, with 43/56 (77%) of the moxifloxacin group and 42/58 (72%) of the polymyxin B-trimethoprim group clinically cured according to parents (noninferiority test P = .04). Eighty-nine (39/56 moxifloxacin and 50/58 polymyxin B-trimethoprim) patients completed the 7-10 day evaluation. Clinical cure was observed in 37/39 (95%) of the moxifloxacin and 49/51 (96%) of the polymyxin B-trimethoprim treated groups (noninferiority test P ≤ .01). Clinical cure rates for culture positive and negative conjunctivitis were not different. There was no statistically significant difference in bacteriologic cure rates between the 2 groups.

CONCLUSIONS

Polymyxin B-trimethoprim continues to be an effective treatment for acute conjunctivitis with a clinical response rate that does not differ from moxifloxacin. Use of polymyxin B-trimethoprim for the treatment of conjunctivitis would result in significant cost savings compared with fluoroquinolones.

Topical azithromycin or ofloxacin for endophthalmitis prophylaxis after intravitreal injection

BACKGROUND

The number of patients who have undergone intravitreal injections has increased enormously in recent years, but a consensus is still lacking on prophylaxis for endophthalmitis. The aim of this prospective, observational study was to evaluate the prophylactic effect of azithromycin eye drops versus ofloxacin eye drops.

METHODS

The study was conducted in five hospitals in Spain and included all patients undergoing intravitreal injections of triamcinolone, bevacizumab, ranibizumab, or pegaptanib over one year. Patients received azithromycin 15 mg/g eye drops (twice daily on the day prior to injection and for another 2 days) or ofloxacin 3 mg/g eye drops (every 6 hours on the day prior to injection and for another 7 days).

RESULTS

In the azithromycin group, there were 4045 injections in 972 eyes of 701 patients. In the ofloxacin group, there were 4151 injections in 944 eyes of 682 patients. There were two cases of endophthalmitis (0.049%) in the azithromycin group and five (0.12%) in the ofloxacin group. The odds ratio of presenting with endophthalmitis in the ofloxacin group compared with the azithromycin group was 2.37 (95% confidence interval [CI] 1.32-3.72, P < 0.001). There were two cases of noninfectious uveitis after triamcinolone injection in the azithromycin group (0.049%) and two (0.048%) in the ofloxacin group; no significant differences were observed (odds ratio 0.902, 95% CI 0.622-1.407, P = 0.407). Conjunctival hyperemia was observed in 12 cases in the azithromycin group and none in the ofloxacin group.

CONCLUSION

The risk of endophthalmitis was significantly greater with ofloxacin than with azithromycin. These findings provide a valuable addition to the ever-increasing pool of information on endophthalmitis prophylaxis after intravitreal injection, although further large-scale studies are required to provide definitive conclusions.

Azithromycin 1.5% ophthalmic solution: in purulent bacterial or trachomatous conjunctivitis

The second-generation macrolide azithromycin is available as a 1.5% ophthalmic solution for use in the treatment of bacterial or trachomatous conjunctivitis. This article reviews the pharmacological properties of azithromycin 1.5% ophthalmic solution and its clinical efficacy and tolerability in patients with purulent bacterial conjunctivitis or trachomatous conjunctivitis caused by Chlamydia trachomatis. Azithromycin 1.5% ophthalmic solution had good in vitro activity against Haemophilus influenzae and C. trachomatis, and achieved good concentrations in tear samples from healthy volunteers. Azithromycin 1.5% ophthalmic solution for 3 days (1 drop twice daily) was noninferior to tobramycin 0.3% ophthalmic solution for 7 days (1 drop every 2 hours) in paediatric and adult patients with purulent bacterial conjunctivitis, with regard to clinical cure and bacteriological resolution on day 9, in a randomized, investigator-masked, multicentre study. In children with trachomatous inflammation, 3-day treatment with azithromycin 1.5% ophthalmic solution was noninferior to a single dose of azithromycin oral suspension, with regard to clinical cure rate in the worst eye at 60 days, in a randomized, double-masked, multicentre study. Azithromycin 1.5% ophthalmic solution was well tolerated in patients with bacterial or trachomatous conjunctivitis. Most events were of mild to moderate severity.

Review of Azithromycin Ophthalmic 1% Solution (AzaSite(®)) for the Treatment of Ocular Infections

AzaSite(®) (azithromomycin 1.0%) ophthalmic solution was approved in 2007 by the US Food and Drug Administration (FDA) as the first commercially available formulation of ophthalmic azithromycin for the treatment of bacterial conjunctivitis. AzaSite(®) utilizes a vehicle delivery system called DuraSite(®), which stabilizes and sustains the release of azithromycin to the ocular surface, leading to a longer drug residence time, less frequent dosing, and an increase in patient compliance. AzaSite(®) is a broad spectrum antibiotic, effective against Gram-positive, Gram-negative, and atypical bacteria. AzaSite(®) has been studied for the treatment of ocular conditions beyond its clinical indication. A number of clinical studies have evaluated its efficacy and safety in the management of ocular conditions such as bacterial conjunctivitis and blepharitis on both the pediatric and adult populations. This article aims to evaluate the peer-reviewed published literature on the use of azithromycin 1.0% ophthalmic for current and possible future ophthalmic uses.

[Efficacy assessment of azithromycin 1.5% eye drops versus tobramycin 0.3% on clinical signs of purulent bacterial conjunctivitis]

INTRODUCTION

Bacterial conjunctivitis is characterized by hyperemia and discharge of one or both eyes. These clinical signs appear quickly and are contagious. This study compares the clinical efficacy (signs and symptoms) and safety of azithromycin 1.5% eye drops with tobramycin 0.3%.

PATIENTS AND METHODS

This was a multicenter, randomized, investigator-masked study including 1,043 patients with purulent bacterial conjunctivitis. Patients received either azithromycin twice daily for 3 days or tobramycin, 1 drop every 2 hours for 2 days, then four times daily for 5 days. The primary variable was clinical cure at the test-of-cure (TOC) visit (D9) on the worst eye. The cure was defined as bulbar conjunctival injection and discharge scores of 0. Clinical signs were evaluated at D0, D3, and D9.

RESULTS

In the azithromycin group 87.8% of patients and in the tobramycin group 89.4% were clinically cured at D9. Clinical cure with azithromycin was not inferior to tobramycin at D9: discharge was absent in 96.3% of patients treated with azithromycin and 95.1% with tobramycin. Azithromycin was well tolerated.

CONCLUSIONS

Azithromycin 1.5% for 3 days (six drops) was as effective as tobramycin for 7 days (36 drops). Furthermore, patients on azithromycin presented earlier clinical cure on Day 3 than patients on tobramycin. Azyter, with its convenient dosing (bid for 3 days), is a step forward in the management of purulent bacterial conjunctivitis.

Ocular pharmacokinetics of besifloxacin following topical administration to rabbits, monkeys, and humans

PURPOSE

Studies were conducted to evaluate the ocular penetration and systemic exposure to besifloxacin, a fluoroquinolone antibiotic, following topical ocular administration to animals and humans.

METHODS

Besifloxacin ophthalmic suspension (0.6%) was administered as a topical ocular instillation to pigmented rabbits, cynomolgus monkeys, and human subjects. At predetermined intervals after dosing, samples of ocular tissues and plasma were collected and analyzed for besifloxacin levels using HPLC/MS/MS methods.

RESULTS

Besifloxacin demonstrated good ocular penetration in rabbits and monkeys, with rapid absorption and sustained concentrations observed in anterior ocular tissues through 24 h after a single administration. Maximum besifloxacin concentrations in conjunctiva, cornea, and aqueous humor of monkeys were 6.43 microg/g, 2.10 microg/g, and 0.796 microg/mL, respectively, after a single topical dose, and concentrations declined in these tissues with an apparent half-life of 5-14 h. Following a single topical ocular administration to humans, the maximum besifloxacin concentration in tears was 610 microg/g with concentrations decreasing to approximately 1.6 microg/g at 24 h. The resulting pharmacokinetic parameters for besifloxacin in human tears were evaluated relative to the MIC(90) values (microg/mL) for besifloxacin against Streptococcus pneumoniae (0.125), Staphylococcus aureus (0.25), Staphylococcus epidermidis (0.5), and Haemophilus influenzae (0.06). Following a single topical administration, the C(max)/MIC(90) ratios for besifloxacin in human tears were > or =1,220, and the AUC((0-24))/MIC(90) ratios were > or =2,500 for these relevant ocular pathogens. Following repeated 3-times daily (TID) topical ocular administration to human subjects with clinically diagnosed bacterial conjunctivitis, maximum besifloxacin concentrations in plasma were less than 0.5 ng/mL, on average.

CONCLUSIONS

Taken together, the results of the current investigation provide a PK/PD-based rationale that supports the use of besifloxacin for the safe and effective treatment of ocular infections.

Ocular signs, symptoms and tear function tests of papulopustular rosacea patients receiving azithromycin

BACKGROUND

Tetracycline derivatives provide moderate benefit in the treatment of ocular rosacea. Recently, azithromycin has been found to be an effective alternative in the treatment of cutaneous papulopustular rosacea.

OBJECTIVE

We planned a study to evaluate the effects of azithromycin on ocular symptoms, signs and tear function tests of papulopustular rosacea patients.

METHODS

An open-labelled study was performed in a population of 20 papulopustular rosacea patients.

RESULTS

Eighteen subjects completed the trial. Significant improvement was seen in ocular symptoms, eyelid findings and conjunctival hyperaemia scores (P = 0.002, P < 0.0001, and P = 0.005, respectively). Therapeutic benefit was not observed in ocular surface staining scores. Baseline values of Schirmer test results were within normal limits. No significant side-effects were observed. Limitations The study population is limited to dermatology patients who had been referred to the ophthalmology clinic.

CONCLUSION

Azithromycin may be a new promising therapeutic alternative in ocular rosacea.