Penetration of imipenem into human aqueous and vitreous humor

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.

Revisiting systemic treatment of bacterial endophthalmitis: a review of intravitreal penetration of systemic antibiotics

BACKGROUND

Adjunctive systemic antibiotic therapy for treatment of bacterial endophthalmitis is controversial but common practice due to the severity of the disease. In the absence of guidance documents, several antibiotic regimens are being used without applying evidence-based prescribing, leading to inappropriate treatment of this serious eye condition.

OBJECTIVES

To summarize available data on intravitreal penetration of systemically administered antibiotics and to discuss their usefulness from a microbiological and pharmacological point of view.

SOURCES

We performed a systematic PubMed search of studies investigating antibiotic concentrations in the vitreous after systemic administration in humans, and selected animal models.

CONTENT

The best-documented agents achieving therapeutic levels in the vitreous are meropenem, linezolid and moxifloxacin. Vancomycin, cefazoline, ceftriaxone, ceftazidime, imipenem and trimethoprim-sulfamethoxazole reach levels justifying their use in specific situations. Available data do not support the use of ciprofloxacin, levofloxacin, aminoglycosides, aminopenicillins, piperacillin, cefepime and clarithromycin. With very limited but available promising data, the use of daptomycin and rifampicin deserves further investigation.

IMPLICATIONS

The choice of the adjunctive systemic antibiotic agent-in situations where it is considered relevant for treatment-must to date be made on an individual basis, considering microbiological aspects as well as operative status and inflammation of the eye. This review gives a systematic overview of antibiotic options and provides guidance to the clinician striving for optimal systemic antibiotic treatment of bacterial endophthalmitis.

Human Vitreous Penetration of Imipenem

The purpose of this study was to determine imipenem concentrations in vitreous humor of non-infected human eyes. Ten patients undergoing vitrectomy were infused with a single dose of either 0.5g (5 patients) or 1g (5 patients) of imipenem. Vitreous humor was withdrawn 2 or 4 hours after the end of the infusion. Results differed in relation to the dose. After 0.5g, vitreous levels were stable (approximately 0.20 mg/l), but after 1g they were significantly higher (approximately 2 mg/l). These levels were above the minimum inhibitory concentration of imipenem for 90% (MIC 90) of the main species responsible for endophthalmitis.

Clinical presentations, risk factors and outcomes of ceftazidime-resistant Gram-negative endophthalmitis

BACKGROUND

To describe the clinical features and outcomes of patients diagnosed with ceftazidime-resistant Gram-negative endophthalmitis and the role of intravitreal imipenem in these cases.

DESIGN

Retrospective consecutive interventional case series at a tertiary eye care centre in South India.

PARTICIPANTS

Consecutive cases of ceftazidime-resistant Gram-negative endophthalmitis from April 2010 to December 2014. Fifty-six cases diagnosed during this time period were included.

METHODS

All cases were managed with vitreous biopsy/vitrectomy, microscopy and undiluted vitreous culture, antimicrobial susceptibility of bacterial isolates and received intravitreal antibiotics.

MAIN OUTCOME MEASURES

Anatomic and visual outcome of these cases, antimicrobial susceptibility pattern of intravitreal imipenem and outcome of cases injected with it.

RESULTS

Commonest presentation was acute endophthalmitis following cataract surgery (27 eyes, 48.21%). Pseudomonas aeruginosa was isolated in 33 eyes (58.93%; 95% CI 46.05-71.81%). Nineteen eyes (34%; 95% CI 21.59-46.41%) developed phthisis; 14 eyes (25%; 95% CI 13.66-36.34%) had vision <20/200; 17 eyes (30.35%; 95% CI 18.31-42.39%) eyes had an ambulatory vision >20/200 (logMAR 1); 6 eyes (10.71%; 95% CI 2.61-18.81%) had a reading vision >20/40 (logMAR 0.3). Trend was towards better anatomic (72.73% vs. 40%) (P = 0.05) and visual improvement in the imipenem group (logMAR 3.94 + 0.21 to 2.43 + 1.4; P = 0.002), as compared with non-imipenem group (logMAR 2.99 + 1.3 to 2.55 + 1.4; P = 0.13).

CONCLUSIONS

Outcome of ceftazidime-resistant Gram-negative endophthalmitis is poor. P. aeruginosa is the commonest isolated organism. All cases were sensitive to imipenem. There was a trend towards better anatomic outcome in imipenem-treated eyes.

A case of postoperative endophthalmitis by extended-spectrum beta-lactamase-producing Escherichia coli

A 75-year-old female was transferred to our clinic three days after uneventful phacoemulsification with intraocular lens (IOL) implantation in the right eye that had been carried out at a local clinic. Under the diagnosis of postoperative endophthalmitis, the patient underwent pars plans vitrectomy, IOL explantation, silicone oil tamponade, and intravitreal antibiotic injection. Even after the procedure, the patient's condition was further aggravated, and extended-spectrum beta-lactamase-producing Escherichia coli were identified on bacterial identification test. Although meropenem was applied locally and systemically, the patient had no-light perception visual acuity.

Modeling Approach To Characterize Intraocular Doripenem Pharmacokinetics after Intravenous Administration to Rabbits, with Tentative Extrapolation to Humans

The aim of this study was to determine the penetration of doripenem administered intravenously into the rabbit aqueous and vitreous humors. Nineteen New Zealand White rabbits received a 20-mg dose of doripenem intravenously over 60 min. Specimens of aqueous humor, vitreous humor, and blood were obtained 30 min ( n = 5), 1 h ( n = 5), 2 h ( n = 5), and 3 h ( n = 4) after the beginning of the infusion and analyzed by high-performance liquid chromatography (HPLC). A pharmacokinetic (PK) model was developed to fit the experimental data. Doripenem concentrations in aqueous humor were lower than those in plasma ultrafiltrates at all sampling times, with an average aqueous humor-to-plasma ultrafiltrate area under the concentration-time curve ratio estimated as 8.3%. A pharmacokinetic model with peripheral elimination described the data adequately and was tentatively used to predict concentration-versus-time profiles and pharmacokinetic-pharmacodynamic (PK-PD) target attainment in patients under various dosing regimens. In conclusion, systematically administered doripenem does not seem to be a promising approach for the treatment of intraocular infections, especially since it could not be detected in the vitreous humor. However, this study has provided an opportunity to develop a new PK modeling approach to characterize the intraocular distribution of doripenem administered intravenously to rabbits, with tentative extrapolation to humans.

Intravitreal injection of therapeutic agents

BACKGROUND

Intravitreal injection (IVI) with administration of various pharmacological agents is a mainstay of treatment in ophthalmology for endopthalmitis, viral retinitis, age-related macular degeneration, cystoid macular edema, diabetic retinopathy, uveitis, vascular occlusions, and retinal detachment. The indications and therapeutic agents are reviewed in this study.

METHODS

A search of the English, German, and Spanish language MEDLINE database was conducted. A total of 654 references spanning the period through early 2008 were individually evaluated.

RESULTS

The advantage of the IVI technique is the ability to maximize intraocular levels of medications and to avoid the toxicities associated with systemic treatment. Intravitreal injection has been used to deliver several types of pharmacological agents into the vitreous cavity: antiinfective and antiinflammatory medications, immunomodulators, anticancer agents, gas, antivascular endothelial growth factor, and several others. The goal of this review is to provide a detailed description of the properties of numerous therapeutic agents that can be delivered through IVI, potential complications of the technique, and recommendations to avoid side effects.

CONCLUSION

The IVI technique is a valuable tool that can be tailored to the disease process of interest based on the pharmacological agent selected. This review provides the reader with a comprehensive summary of the IVI technique and its multitude of uses.

Visual Recovery FollowingMycobacterium chelonaeEndophthalmitis

Following uncomplicated cataract surgery, a patient receiving etanercept for psoriatic arthritis developed Mycobacterium chelonae endophthalmitis. Vitrectomy, capsulectomy, and intraocular lens removal was followed by intravitreal amikacin, topical gatifloxacin, intravenous imipenem, and oral clarithromycin for six months. The patient achieved a final corrected visual acuity of 20/20. Etanercept has been implicated in the development of numerous, severe granulomatous infections, though not previously with M. chelonae. This represents the first reported case of visual recovery following M. chelonae endophthalmitis.

[Intravitreal injection of antibiotics in endophthalmitis]

Early diagnosis and appropriate treatment with intravitreous antibiotics are the most important factors for the successful management of endophthalmitis. The intraocular concentration of antibiotics after intravitreous injection is far greater than that achieved by any other modality. The organisms in postoperative endophthalmitis are usually Gram-positive cocci and less commonly Gram-negative bacteria. Drug combinations are necessary to cover the full range of bacteria causing endophthalmitis. Vancomycin (1 mg/0.1 ml) is considered the drug of choice for Gram-positive organisms. Controversy remains concerning the best choice against Gram-negative bacteria. Aminoglycosides (amikacin, 0.4 mg/0.1 ml) have traditionally been recommended for Gram-negative coverage. However, because of their possible role in macular toxicity, recent trends have shifted to using ceftazidime (2.25 mg/0.1 ml) in combination with vancomycin.

Streptococcus pneumoniae endophthalmitis: a study of 36 cases with special reference to antibiotic resistance and treatment options

Patients (n = 36) diagnosed with pneumococcal endophthalmitis from six Spanish hospitals between 1986 and 2004 were studied retrospectively. The diagnosis was based on clinical findings, ophthalmological examination, and isolation of Streptococcus pneumoniae from vitreous and/or aqueous humours of 19 patients (definite diagnosis), and from other ocular specimens of 17 patients (probable diagnosis). The mean (+/- SD) age was 69.3 (+/- 16.5) years (range 1.5-89 years), and 20 (55.5%) patients were male. The origin of endophthalmitis was considered exogenous for 34 (94.5%) patients. The most common predisposing factors were previous ocular surgery (n = 25, 69.4%), ocular trauma (n = 5, 13.9%), and close-to-eye radiotherapy (n = 3, 8.3%). Eleven (30.5%) patients underwent evisceration as the first therapeutic measure (primary evisceration), and evisceration was performed after antibiotic treatment failure (secondary evisceration) for six (16.7%) patients. Primary evisceration was performed more commonly (63.6%) during 1998-2004, while secondary evisceration was only performed during 1986-1997. Eighteen (50%) patients received intra-vitreous antibiotics (mainly vancomycin), and 31 (86.1%) patients were given systemic antibiotic therapy. The most frequent pneumococcal serogroups isolated were 6, 19, 9, 15 and 23. Pulsed-field gel electrophoresis analysis of 23 isolates revealed that four belonged to the international clones Spain(23F)-1, Spain(6B)-2, Spain(9V)-3 and Sweden(15A)-25. Non-susceptibility rates (i.e., intermediately-resistant and resistant) were: co-trimoxazole, 44.8%; penicillin, 33.3%; tetracycline, 31.0%; erythromycin, 21.9%; chloramphenicol, 17.9%; rifampicin, 7.4%; cefotaxime, 5.9%; and levofloxacin, 0%. Although uncommon, pneumococcal endophthalmitis is a medical emergency because of the often aggressive clinical course, poor visual outcome and need for evisceration in a large proportion of patients.

Intravenous treatment of experimental Staphylococcus aureus endophthalmitis: imipenem versus the combination of ceftazidime and amikacin

BACKGROUND

To compare the efficacy of intravenous (IV) imipenem (IPM) and a combination of IV ceftazidime (CAZ) and amikacin (AN) in the treatment of Staphylococcus aureus endophthalmitis in a rabbit model.

METHODS

Right eyes of 60 albino rabbits were injected with 1000 colony-forming units of S. aureus intravitreally. After 24 h, treatment with either IV IPM (37.5 mg/kg) every 8 h ( n=18) or IV CAZ (50 mg/kg) and AN (10 mg/kg) every 8 hours ( n=18) was begun and continued until the animals were killed at the indicated timepoints; 24 control animals received no treatment. The concentration of bacteria in the vitreous from six animals per group was determined microbiologically on days 2, 3, and 5 after infection, and histologic examination was performed on all eyes.

RESULTS

The number of eyes with positive cultures on day 5 was lower in the group that received IV IPM (2/6) compared with the IV CAZ/AN group (4/6) and the control group (6/6). For the culture-positive eyes, the bacterial concentrations were significantly lower for the IV IPM group compared with the IV CAZ/AN group on days 2 and 5 ( P<0.05 and P<0.0065, respectively), but not on day 3 ( P <0.8. Bacterial counts in both treatment groups were significantly lower than in the control group ( P<0.005). Eyes in all groups, however, showed severe intraocular inflammation.

CONCLUSIONS

IV IPM is more effective than is IV CAZ/AN in reducing the number of bacteria in an animal model of S.aureus endophthalmitis.

Penetration and decay of meropenem into the human aqueous humor and vitreous

The aim of this study was to determine the penetration of intravenously administered meropenem into the human aqueous humor and vitreous. Thirty patients about to undergo cataract surgery and fourteen patients about to undergo vitrectomy received a 2 g dose of meropenem before surgery. Specimens of aqueous humor or vitreous and blood were obtained intraoperatively and analyzed by high performance liquid chromatography (HPLC). The study was designed as a non-randomized prospective trial. Thirty min to 12 hr after administration, mean aqueous humor levels of 13.4 and 1.1 mg/l and vitreous levels between 8.94 and 1.08 mg/l were found, respectively. The peak concentrations are distinctly above the in vitro measured minimum inhibitory concentration of meropenem for 90% (MIC90) of almost all relevant gram-positive and gram-negative organisms, including Pseudomonas aeruginosa and Enterobacteriaceae. With regard to its broad spectrum, high antibacterial activity, and good penetration into ocular fluids, meropenem seems to be an alternative to currently used systemic drugs. Its usefulness in perioperative prophylaxis, as initial therapy after perforating or penetrating injuries, or in the therapy of bacterial endophthalmitis has yet to be proved.

Carbapenems and monobactams: imipenem, meropenem, and aztreonam

Imipenem and meropenem, members of the carbapenem class of beta-lactam antibiotics, are among the most broadly active antibiotics available for systemic use in humans. They are active against streptococci, methicillin-sensitive staphylococci, Neisseria, Haemophilus, anaerobes, and the common aerobic gram-negative nosocomial pathogens including Pseudomonas. Resistance to imipenem and meropenem may emerge during treatment of P. aeruginosa infections, as has occurred with other beta-lactam agents; Stenotrophomonas maltophilia is typically resistant to both imipenem and meropenem. Like the penicillins, the carbapenems have inhibitory activity against enterococci. In general, the in vitro activity of imipenem against aerobic gram-positive cocci is somewhat greater than that of meropenem, whereas the in vitro activity of meropenem against aerobic gram-negative bacilli is somewhat greater than that of imipenem. Daily dosages may range from 0.5 to 1 g every 6 to 8 hours in patients with normal renal function; the daily dose of meropenem, however, can be safely increased to 6 g. Infusion-related nausea and vomiting, as well as seizures, which have been the main toxic effects of imipenem, occur no more frequently during treatment with meropenem than during treatment with other beta-lactam antibiotics. The carbapenems should be considered for treatment of mixed bacterial infections and aerobic gram-negative bacteria that are not susceptible to other beta-lactam agents. Indiscriminate use of these drugs will promote resistance to them. Aztreonam, the first marketed monobactam, has activity against most aerobic gram-negative bacilli including P. aeruginosa. The drug is not nephrotoxic, is weakly immunogenic, and has not been associated with disorders of coagulation. Aztreonam may be administered intramuscularly or intravenously; the primary route of elimination is urinary excretion. In patients with normal renal function, the recommended dosing interval is every 8 hours. Patients with renal impairment require dosage adjustment. Aztreonam is used primarily as an alternative to aminoglycosides and for the treatment of aerobic gram-negative infections. It is often used in combination therapy for mixed aerobic and anaerobic infections. Approved indications for its use include infections of the urinary tract or lower respiratory tract, intra-abdominal and gynecologic infections, septicemia, and cutaneous infections caused by susceptible organisms. Concurrent initial therapy with other antimicrobial agents is recommended before the causative organism has been determined in patients who are seriously ill or at risk for gram-positive or anaerobic infection.

Mycobacterium chelonei keratitis: a case report and review of previously reported cases

A 56-year-old woman who wore hard contact lenses developed a keratitis due to Mycobacterium chelonei. The organism was only sensitive to imipenem and partially to ciprofloxacin and erythromycin. After an initial response to topical therapy with these antibiotics the infection relapsed and a penetrating keratoplasty was performed, with resulting cure. M. chelonei has not previously been reported as a cause of keratitis associated with hard contact lens wear; neither has its treatment with imipenem and/or ciprofloxacin. A detailed photographic record showing the natural history of the keratitis is presented. Previously reported cases of M. chelonei keratitis are reviewed.

Intravitreal penetration of oral pefloxacin in humans

We measured vitreous and serum levels of pefloxacin after oral administration. Twenty patients with retinal detachments undergoing vitrectomy were recruited into this study. Each patient received 400 mg pefloxacin orally 1 to 12 hours before vitrectomy. Vitreous fluid (0.1 mL) was aspirated at surgery. Vitreous levels of pefloxacin were determined by high-performance liquid chromatography. Six hours after oral administration, an average level of 1.37 microgram/mL of pefloxacin was measured in the vitreous samples. These levels were well above the minimum inhibitory concentration (MIC) for most organisms termed sensitive to pefloxacin. Oral administration of pefloxacin may play an important role in the prevention or management of endophthalmitis.

Infective endophthalmitis following vitreoretinal surgery

Eleven cases of endophthalmitis occurring after vitreoretinal surgery are described. At Moorfields Hospital, London, from 1986 to 1990 the incidence of endophthalmitis after explant surgery with or without drain was 0.19% and after vitrectomy was 0.15%. We conclude that the parity may be due to the intraocular instrumentation of most conventional retinal detachment repair procedures. The best indicator of poor prognosis was speed of onset of symptoms, those with rapid evolution having the worst outcome; 2 of these cases were enucleated. Those presenting at 2-3 days had the best outcome, consistent with infection due to a less virulent organism. Delays in diagnosis were in part due to the posterior location of signs of infection. Potential risk factors amenable to prophylactic strategy were identified in 10 of the 11 patients. Supplementary prophylaxis using ciprofloxacin or imipenem is proposed for cases with an identifiable risk factor. After systemic administration these antibiotics achieve vitreous levels that exceed the MIC90 of the commonest causative pathogens.

Endophthalmitis at the Bristol Eye Hospital: an 11-year review of 47 patients

We reviewed data from 47 patients who were treated for endophthalmitis at our hospital during the 11-year period 1980-90. The most common clinical features were hypopyon (75%), diminished vision (72%), ocular pain (68%), discharge (57%), corneal oedema (51%), conjunctival injection (49%), abnormal red reflex (34%), corneal ulcer (32%) and corneal perforation (6%). A total of 54 isolates were obtained from 41 (87%) of the 47 patients. Gram-positive bacteria were more common (72%), than Gram-negative organisms (22%). Two cases were due to fungi, and herpes simplex virus was isolated from one case. The two most common Gram-positive organisms were coagulase-negative staphylococci (25%), and Staphylococcus aureus (11%), while Pseudomonas aeruginosa predominated among the Gram-negative bacteria isolated (15%). Mixed bacterial species were obtained from 29% of the infected patients, including one from whom Vibrio fluvialis was isolated. Predisposing factors included ocular surgery (60%)--mostly for cataract extraction (47%), penetrating trauma (15%) and periocular (15%) or systemic (11%) infections. All patients received antibiotics (generally chloramphenicol and/or a beta-lactamase-stable penicillin plus an aminoglycoside) prior to culture, when treatment was adjusted according to specific aetiological agents. Seventy-nine per cent of patients received topical or systemic steroids. Vitrectomy (diagnostic and therapeutic) was performed on 21% of patients. Sixty-three per cent of culture-positive patients lost vision (no perception of light) in the affected eye, compared to 17% of culture-negative cases (P < 0.05 Fisher exact test). Similarly, a better visual outcome (acuity of 6/12 or better) was associated with coagulase-negative staphylococcal infection than with streptococcal or fungal infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Endophthalmitis following extracapsular cataract surgery: a review of 32 cases

Thirty two cases of endophthalmitis following extracapsular cataract surgery that had occurred within our department and had undergone intraocular diagnostic tap between May 1982 and May 1991 were reviewed. An infectious agent was identified in 20 cases (62.5%). The commonest organism was Staphylococcus epidermidis (11 cases) (55%). Proteus was the only gram negative organism identified (four cases) (20%). Both of these organisms were associated with a favourable visual outcome. In the culture positive subgroup 15 eyes (75%) achieved a final acuity of 6/60 or better with 10 eyes (50%) gaining 6/12 or better. Thirteen (65%) of the culture positive cases were managed without vitreal intervention. Of these 11 (85%) achieved 6/60 or better with eight (62%) gaining 6/12 or better. It appears that when an endophthalmitis follows uncomplicated extracapsular cataract surgery delivery of antibiotic by the 'conventional' routes (topical, subconjunctival and systemic) is consistent with a favourable visual result in many cases. A modified anterior chamber diagnostic tap technique is described.

Intravitreal penetration of oral ciprofloxacin in humans

Nineteen patients about to undergo elective vitreous surgery received 1 oral dose of 750 mg of ciprofloxacin before surgery. Specimens of serum and vitreous were collected 90 minutes to 18 hours after drug administration and were assayed for antibiotic content with a microbiologic disk agar technique. From 4 hours and 50 minutes to 16 hours and 50 minutes after a single oral dose, ciprofloxacin reached intravitreal levels above its minimal inhibitory concentration for 90% of Staphylococcus epidermidis, Bacillus species, and Enterobacteriaceae. However, intravitreal levels never exceeded the MIC90 for Staphylococcus aureus and Pseudomonas.

Imipenem

Imipenem is the first of a new class of beta-lactam antibiotics, the carbapenems, to be released for clinical use. It has the broadest antibacterial activity of all antibiotics available for systemic use in humans. It is active against streptococci, methicillin-sensitive staphylococci, Neisseria, Haemophilus, anaerobes, and the common aerobic gram-negative nosocomial pathogens including Pseudomonas. Resistance to imipenem may emerge during treatment of P. aeruginosa infections, as has occurred with other beta-lactam agents; P. maltophilia and P. cepacia are typically resistant to it. Like the penicillins, imipenem has inhibitory activity against enterococci. Daily doses may range from 500 mg to 1 g, every 6 to 8 hours, in patients with normal renal function. The principal toxic effects have been nausea and vomiting, which occur during intravenous infusion, and seizures, which develop in 1 to 3% of treated patients and are likely to occur in the setting of renal insufficiency and underlying disease of the central nervous system. Imipenem should be considered for treatment of mixed bacterial infections and treatment of resistant aerobic gram-negative bacteria that are not susceptible to other beta-lactam agents. In addition to provoking unnecessary toxicity, indiscriminate use of this agent will promote dissemination of resistance against it.

Postoperative endophthalmitis

Postoperative endophthalmitis is a rare complication of ophthalmic surgery. The use of prophylactic antibiotics and scrupulous surgical techniques will help to reduce its incidence, but sporadic cases may still occur. If postoperative endophthalmitis is a diagnostic possibility aggressive investigation and initial management improves the prognosis. More work needs to be done to evaluate the penetration of newer antibiotics into the eye and their therapeutic role. The use of corticosteroids also needs to be more carefully defined in the treatment of this potentially devastating disease.