Intraocular penetration of semisynthetic penicillins: methicillin, cloxacillin, ampicillin, and carbenicillin studies in experimental animals with a review of the literature

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.

The evolution of antibiotic therapy for bacterial conjunctivitis and keratitis: 1970-2000

The editors of this Festschrift asked us to review the use of antibiotics for the treatment of bacterial conjunctivitis and keratitis over the past 25 years, a period coinciding with the life of the Castroviejo Corneal Society. We believe it is more appropriate to begin our review in the late 1960s. about the time that experimental and clinical studies and algorithms for the clinical care derived from these studies helped shape a more rigorous approach to therapy. Those years saw the introduction of antibiotics that were adapted for ophthalmic use, many of which are still being used today. We will give more weight to our review of keratitis than conjunctivitis.

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.

Enterococcal endophthalmitis following cataract extraction, treated with ampicillin intravitreally

A case of Enterococcal endophthalmitis developed following an extracapsular cataract extraction. The infection was successfully treated with intravenous and intravitreal ampicillin, but a secondary glaucoma led to a later enucleation. We report a case of postoperative endophthalmitis with an unusual etiology, which did not respond to common treatment.

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.

Antimicrobial drug delivery to the eye

A major obstacle in the treatment of ocular infections is the difficulty in obtaining adequate antimicrobial drug concentration at the site of infection. This article reviews the pharmacokinetic principles of ophthalmic drug delivery as it pertains to antimicrobial therapy. The administration of antimicrobials by topical application, subconjunctival injection, intravitreal injection, vitreous replacement fluid, and systemic administration are addressed. Representative data on the intraocular penetration of antimicrobials as well as recommended doses of drugs for ocular infections are presented.

Prophylactic antibiotics for ophthalmic surgery

Preoperative or immediately postoperative antibiotics have been used by ophthalmic surgeons routinely as prophylaxis for postoperative endophthalmitis. The rationale for such prophylaxis, as the evidence which supports its efficacy are well founded. The optimal choice of antibiotics, however, from the standpoints of efficacy, delivery (route, dosage, and frequency of administration), adverse reactions, and cost is far less well established. This review considers these issues in the context of a critical evaluation of the pertinent literature.

Ampicillin penetration into the rabbit eye

Distribution of intravenously injected ampicillin of 50 mg/kg was studied in the rabbit eye using radioactive tracer method. Antibiotic concentration regarded as therapeutic in the treatment of gram-negative organisms was obtained in all vascularized ocular structures. Intermediate values were measured from the cornea and aqueous humour. In the vitreous body and lens, ampicillin was unable to approach a concentration that would be effective against the common gram-negative organisms. The low ampicillin concentration in the vitreous body and lens was unchanged by systemically administered probenecid, which in other parts of the eye caused significantly higher ampicillin levels.

Cloxacillin distribution in the rabbit eye after intravenous injection

Distribution of isotopically labelled and intravenously injected cloxacillin was studied in rabbit eye. The antibiotic concentration determined by liquid scintillation counting proved to be a reliable measure of the total antibiotic concentration when controlled by microbiological assay. In the rabbit eye after an intravenous injection of 50 mg/kg of cloxacillin sodium, longlasting antibiotic concentration regarded as therapeutic against penicillinase producing staphylococci was obtained in all vascularized ocular structures and in the cornea. The antibiotic present in the iris and ciliary body, and in the retina and choroid preparations, proved to be partly intravascular, whereas it penetrated better into the extravascular tissue compartment of the sclera and limbal area. Cloxacillin failed to achieve a therapeutic antibiotic concentration in the vitreous body and in the lens. Administration of probenecid had an enhancing effect on ocular cloxacillin concentration allowing improved drug diffusion into the eye by means of an elevated plasma concentration. No specific ocular effect of probenecid was noticed. Therapeutic concentration of cloxacillin in the aqueous humour, otherwise barely achieved, was more satisfactorily obtained with a previous injection of probenecid.

Penetration of ocular compartments by tetracyclines. I. An experimental study with tetracycline

Total antibiotic concentration of tetracycline hydrochloride was determined in the ocular structures of rabbits by radioactive tracer method. Concentration of tetracycline of 0.1 to 5 microgram/g, adequate to inhibit the growth of bacteria of high or medium susceptibility, was measured from all ocular structures with the exception of the lens. Tetracycline concentration in the aqueous humor was inferior to that in the vascularized ocular tissues and to that in the cornea. Vitreous body tetracycline level, about 0.3 microgram/g, was about half of the concentration in the aqueous humor. The disruption of the blood-aqueous barrier following paracentesis led to an immediate increase of tetracycline concentration in the anterior structures of the eye.

Herpes simplex keratitis

This article reviews the current concepts for the diagnosis and treatment of Herpes simplex keratitis and its complications, discussing characteristics of the virus, the prevalence of the disease, chemical and clinical differentiation between Types I and II Herpesvirus hominis, and the many clinical presentations of Type I disease. The antiviral agents commonly in use are reviewed, covering the historical development of the drugs, indications for their use and the associated toxic and untoward reactions. An outline for the medical treatment of the different forms of Herpes simplex keratitis is given, as well as the indications for surgical intervention in the treatment of the disease. The surgical complications and results following keratoplasty are discussed.