Pharmacokinetics of intravenously administered tigecycline in eye compartments: an experimental study

ALTERNATIVE INTRAVITREAL ANTIBIOTICS: A Systematic Review for Consideration in Recalcitrant or Resistant Endophthalmitis

PURPOSE

To organize, categorize, and create a quick reference guide for the use of intravitreal antibiotic alternatives to the standard combination of vancomycin and ceftazidime for the treatment of endophthalmitis.

METHODS

A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. The authors searched for all available information regarding intravitreal antibiotics in the last 21 years. Manuscripts were selected according to relevance, level of information, and the available data regarding intravitreal dose, potential adverse effects, bacterial coverage, and relevant pharmacokinetic information.

RESULTS

The authors included 164 of 1810 manuscripts. The antibiotics were classified according to their class into fluoroquinolones, cephalosporins, glycopeptide and lipopeptide, penicillins and beta-lactams, tetracyclines, and miscellaneous. The authors also included information regarding intravitreal adjuvants for the treatment of endophthalmitis and one ocular antiseptic.

CONCLUSION

The treatment of infectious endophthalmitis is a therapeutic challenge. The current review summarizes the properties of possible intravitreal antibiotic alternatives that should be considered in cases of suboptimal response to initial treatment.

Antimicrobial guide to posterior segment infections

PURPOSE

This review article is meant to serve as a reference guide and to assist the treating physician in making an appropriate selection and duration of an antimicrobial agent.

METHODS

Literature review.

RESULTS

Infections of the posterior segment require prompt medical or surgical therapy to reduce the risk of permanent vision loss. While numerous options exist to treat these infections, doses and alternative therapies, especially with contraindications for first-line therapy, are often elusive. Antimicrobial agents to treat posterior segment infections can be administered via various routes, including topical, intravitreal, intravenous, and oral.

CONCLUSIONS

Although there are many excellent review articles on the management of endophthalmitis, we take the opportunity in this review to comprehensively summarize the appropriate antimicrobial regimen of both common and rare infectious etiologies of the posterior segment, using evidence from clinical trials and large case series.

Endogenous Endophthalmitis Caused by Carbapenem-Resistant Hypervirulent Klebsiella Pneumoniae: A Case Report and Literature Review

Purpose: To report a rare case of endogenous endophthalmitis caused by carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). Methods: A retrospective chart review was conducted. The isolates were characterized by hypermucoviscosity, resistance genes, virulence genes, and multilocus sequence typing. Results: A 47-year-old diabetic woman acquired carbapenem-resistant K. pneumoniae (CRKP) nosocomial pneumonia. Metastatic endophthalmitis occurred in the right eye a week after the occurrence of CRKP bloodstream infection (BSI). Visual acuity decreased to light perception within 3 days. Although vitrectomy relieved ocular pain, endophthalmitis deteriorated due to uncontrollable BSI, and developed to corneal perforation. The strains isolated from bronchoalveolar lavage fluid, blood, and intraocular pus originated from the same clone. The pathogen was hypermucoviscous, belonged to sequence type 11, harbored resistance genes bla_KPC-2, bla_TEM, bla_SHV, rmtB, and virulence genes rmpA2, iucABCD, iroBCD. Conclusions: Endogenous endophthalmitis caused by CR-hvKP has emerged, which is a treatment challenge for both ophthalmologists and physicians.

Analysis of pharmaceuticals and small molecules in aqueous humor

Aqueous humor (AH) is a transparent fluid found in the anterior chamber of the eye. The circulating AH nourishes the cornea and lens and removes the metabolic waste moving through the ocular chambers and drains from the eye to the venous blood. Analysis of drugs in AH is necessary to evaluate their pharmacokinetics parameters, which may be crucial to avoid potential adverse effects. Analysis of endogenous components of AH may help to understand its physiology as well as changes evoked by pathological situation. This review describes analytical methods used for determination of pharmaceuticals and small endogenous molecules in AH, focusing on sample preparation procedures and analytical techniques. Studies on human and animal samples are included. After inspection and filtering of records found in PubMed about 100 research papers were selected to review. In these articles AH samples of human and rabbit origin were studied most often. Sample evaporation and reconstitution in smaller solvent volume was the most popular method for analyte pre-concentration. Acetonitrile, methanol or mixture of both solvents were used most often for protein precipitation.

A comprehensive insight on ocular pharmacokinetics

The eye is a distinctive organ with protective anatomy and physiology. Several pharmacokinetics compartment models of ocular drug delivery have been developed for describing the absorption, distribution, and elimination of ocular drugs in the eye. Determining pharmacokinetics parameters in ocular tissues is a major challenge because of the complex anatomy and dynamic physiological barrier of the eye. In this review, pharmacokinetics of these compartments exploring different drugs, delivery systems, and routes of administration is discussed including factors affecting intraocular bioavailability. Factors such as precorneal fluid drainage, drug binding to tear proteins, systemic drug absorption, corneal factors, melanin binding, and drug metabolism render ocular delivery challenging and are elaborated in this manuscript. Several compartment models are discussed; these are developed in ocular drug delivery to study the pharmacokinetics parameters. There are several transporters present in both anterior and posterior segments of the eye which play a significant role in ocular pharmacokinetics and are summarized briefly. Moreover, several ocular pharmacokinetics animal models and relevant studies are reviewed and discussed in addition to the pharmacokinetics of various ocular formulations.

Pharmacokinetics of tigecycline in turkeys following different routes of administration

The aim of this research had been to determine the pharmacokinetics of tigecycline (TIG) in turkey after intravenous (i.v.), intramuscular (i.m.), subcutaneous (s.c.), and oral (p.o.) administration at a dose of 10 mg/kg. TIG concentrations in plasma were determined using high-performance liquid chromatography with tandem mass spectrometry. Mean concentrations of TIG in turkey plasma in the i.v. group were significantly higher than concentrations of this drug obtained after using the other administration routes. No significant differences were demonstrated in respect to the concentrations achieved after i.m. and s.c. administration. The bioavailability of TIG after i.m., s.c., and p.o. administration was 32.59 ± 5.99%, 34.91 ± 9.62%, and 0.97 ± 0.57%, respectively. Values of half-life in the elimination phase were 23.49 ± 6.51 hr, 25.42 ± 4.42 hr, and 26.62 ± 5.19 hr in i.v., i.m., and s.c. groups, respectively, values of mean residence time were 7.92 ± 1.41 hr, 19.62 ± 2.82 hr, and 17.55 ± 2.59 hr in i.v., i.m., and s.c. groups, respectively, whereas the volume of distribution was 14.85 ± 5.71 L/kg, 14.68 ± 2.56 L/kg, and 15.37 ± 3.00 L/kg in i.v., i.m., and s.c. groups, respectively. Because TIG is not absorbed from the gastrointestinal tract in turkeys to a clinically significant degree, this drug given p.o. could find application in commercial turkey farms only to treat gastrointestinal tract infections.

Ocular penetration of topically applied 1% tigecycline in a rabbit model

AIM

To evaluate ocular penetration of topically applied 1% tigecycline.

METHODS

Forty-two New Zealand White rabbits were divided into 3 groups. A 50 µL drop of 1% tigecycline was administered in group 1. In groups 2 and 3, the drop was administered every 15min for 60min (keratitis protocol). Aqueous humor samples in groups 1 and 2 were collected under general anesthesia at 15, 30, 45, 60, 120, and 180min after the last drop. All animals in group 3 were euthanatized. Cornea, vitreous and blood samples were collected 60 and 120min after the last drop. Tigecycline concentrations were measured using high performance liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

The peak aqueous humor tigecycline concentration [mean 0.73±0.14 mg/L (SD) and 2.41±0.14 mg/L, respectively] occurred 45min after topical drug application in groups 1 and 2. Group 3 mean values in the cornea, and vitreous, were 3.27±0.50 µg/g, and 0.17±0.10 mg/L at 60min and 3.17±0.77 µg/g and 0.20±0.07 mg/L at 120min, respectively. Tigecycline serum concentrations were negligible.

CONCLUSION

Tigecycline levels in the aqueous humor in groups 1 and 2, and in the cornea in group 3 exceeded the minimum inhibitory concentrations of most gram-positive organisms that cause bacterial keratitis and endophthalmitis.

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility: literature review and options for treatment

BACKGROUND

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or resistance is an important clinical issue worldwide.

PURPOSE

To review the published literature on endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance.

METHODS

The data were analysed from a PubMed search of endophthalmitis cases caused by Gram-positive organisms with reported reduced vancomycin susceptibility and/or vancomycin resistance from 1990 to 2015.

RESULTS

From 18 publications identified, a total of 27 endophthalmitis cases caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance were identified. The aetiologies of endophthalmitis were exogenous in 19/27 cases (11 post-cataract surgery, 2 post-penetrating keratoplasty, 1 post-glaucoma surgery, 4 post-open globe injury, 1 post-intravitreal injection of ranibizumab), and endogenous in 4/24 cases; no details were available about the four remaining patients. The causative organisms included Enterococcus species (7/27), coagulase-negative staphylococci (4/27), Staphylococcus aureus (4/27), Bacillus species (4/27), Streptococcus species (3/27), Leuconostoc species (3/27), Staphylococcus hominis (1/27), and unidentified Gram-positive cocci (1/27). Visual acuity of 20/400 or better at the final follow-up was recorded in 10/26 patients (38.5%; data were not available for one patient). Treatment options include fluoroquinolones, penicillin, cephalosporins, tetracyclines, and oxazolidinones.

CONCLUSIONS

In the current study, visual acuity outcomes were generally poor. Enterococcus and Staphylococcus species were the most common organisms reported and postoperative endophthalmitis after cataract surgery was the most common clinical setting.