Intraocular acyclovir levels after subconjunctival and topical administration

Evidence in the prevention of the recurrence of herpes simplex and herpes zoster keratitis after eye surgery

OBJECTIVE

Herpetic keratitis, either due to herpes simplex keratitis (HSK) or herpes zoster ophthalmicus (HZO), can recur after eye surgery.º Prophylaxis is postulated as necessary to avoid it. The objective of this study was to review the scientific evidence on the preventive methods used in the perioperative period in patients previously affected by HSK/HZO.

METHODS

An exhaustive search was carried out in the PubMed and Web of Science databases to identify relevant articles on prophylaxis and risk of recurrence of HSK/HZO in patients undergoing eye surgery up to 31 December 2019.

RESULTS

There is strong evidence that oral prophylaxis should be recommended after penetrating keratoplasty in patients who have previously had HSK/HZO. For other types of surgery, the evidence is less compelling. However, a latent period of inactivity should be considered between disease and oral prophylaxis.

CONCLUSIONS

Penetrating and lamellar keratoplasty, corneal crosslinking, cataract surgery, and photorefractive and phototherapeutic surgery cause an alteration of the subbasal nerve plexus of the cornea. Due to surgical trauma, as well as the modulation of the ocular immune response caused by steroids applied in the postoperative period, it is possible to induce the reactivation of HSK/HZO, which is common in some cases. Within this article, we discuss the available evidence for HSK/HZO prophylaxis in eye surgery. Further studies are necessary to define the real risk of HSK/HZO recurrence after ocular surgeries, particularly in cataract surgery, and to confirm the efficacy of perioperative prophylaxis with anti-HSK/HZO antivirals.

Ocular surgery after herpes simplex and herpes zoster keratitis

PURPOSE

The recurrence of herpetic stromal keratitis (HSK) and herpes zoster ophthalmicus (HZO) has been reported after a variety of ocular surgeries. The aim of this study was to review the evidence on the preventive methods employed in the perioperative period in patients having undergone HSK/HZO.

METHODS

The PubMed and Web of Science databases were the main resources used to conduct the medical literature search. An extensive search was performed to identify relevant articles concerning the prophylaxis against and risk of HSK/HZO recurrence in patients undergoing ocular surgery up to December 31, 2019.

RESULTS

The disturbance of the corneal nerve plexus occurs during several ocular surgeries including penetrating keratoplasty, lamellar keratoplasty, corneal cross-linking, cataract surgery, as well as photorefractive and phototherapeutic procedures. Such trauma, as well as modulation of the ocular immunological response caused by steroids applied postoperatively, might engender the HSK/HZO reactivation which is not uncommon. There is strong evidence that oral prophylaxis should be recommended just after surgery in patients undergoing penetrating keratoplasty and having suffered from HSK/HZO. For other types of surgeries, the evidence is less compelling; nevertheless, a period of disease quiescence and oral prophylaxis should still be considered.

CONCLUSIONS

Within the article, we discuss the available evidence for HSK/HZO prophylaxis in ocular surgery. Additional studies would be required to define the real risk of HSK/HZO recurrence following eye surgeries, and particularly cataract surgery, and to confirm the utility of perioperative HSK/HZO prophylaxis.

Clinical Evaluation of Intravitreal Injection of Ganciclovir in Refractory Corneal Endotheliitis

Purpose: To evaluate the efficacy and safety of intravitreal ganciclovir (GCV) injection in refractory endotheliitis.Methods: Retrospectively recruited 25 eyes with endotheliitis, proved by clinical manifestations, positive PCR for viral DNA and responded poor to topical and systemic antiviral medications. All patients received additional continued intravitreal GCV injections.Results: Cytomegalovirus (CMV), varicella zoster virus (VZV), and herpes simplex virus (HSV) DNA were detected in 64.0%, 28.0%, and 8.0% of the eyes, respectively. Within 2 weeks after the last injection, 16/25 eyes recovered corneal clarity; active keratic precipitates (KPs) were eliminated in 21/25 eyes; intraocular pressure (IOP) was controlled in 12/15 eyes with elevated IOP on study entry. Best-corrected visual acuity increased at the last follow-up (p = 0.016). Clinical recurrence occurred in three patients. No complications were detected.Conclusions: CMV endotheliitis was the main type of refractory endotheliitis. Despite its invasive nature, intravitreal GCV injection appears to be an effective method for refractory endotheliitis.

Species Differences in the Metabolism and Disposition of Antiviral Nucleoside Analogues: 1. Acyclovir

The acyclic nucleoside analogue, acyclovir, is an antiviral drug with activity against the herpes group of DNA viruses. Clinically, it is used as a selective therapeutic agent for the treatment of herpes simplex and varicella-zoster virus infections. Studies on the disposition of acyclovir, during the course of its preclinical and clinical development, indicated significant species differences in the absorption, metabolism and elimination of the drug. Gastrointestinal absorption was adequate in dogs and in mice; but in rats and primates it was limited to less than 20% of the administered dose. Whereas in some species (mice, rats, and dogs), acyclovir was virtually unmetabolized, significant biotransformation was apparent in guinea pigs, rabbits, and some primates. Acyclovir tissue distribution was extensive and indicated few differences across species. This review summarizes diverse studies on acyclovir absorption, metabolism, and disposition in different species, including humans, and indicates the relevance and importance of such studies in drug development.

Quantification of uptake and clearance of acyclovir in skin layers

BACKGROUND

Quantification of drug uptake and clearance in the skin layers could provide better insight into the skin kinetics of dermatological formulations aimed for deeper skin tissues. This study assessed the skin kinetics of acyclovir in different skin layers following topical application on the abdominal region of Wistar rats.

METHODS

In vivo skin pharmacokinetics parameters were determined by two different protocols such as post drug load assessment and subsequent drug load assessment following topical application of 500 mg of cream formulation containing 5% (w/w) of acyclovir.

RESULTS

Topical application of acyclovir exhibited concentration gradient between the skin layers (stratum corneum > viable epidermis > dermis) which were inconsistent over the time-course of the study. The rate and extent of drug reaching target site (basal epidermis) was relatively low. The drug uptake and clearance profiles were found to be distinct in all the three skin layers suggesting no drug concentration correlation (P<0.05) between skin layers. Drug concentration in the viable epidermis continued to increase even after termination of therapy (Tmax=4 h) and then declined rapidly. The availability of acyclovir in the target was comparatively low (approximately 0.4% of the applied dose) although an order of magnitude higher percentage was determined in the stratum corneum.

CONCLUSIONS

The data observed in this study demonstrates low skin uptake and rapid clearance of acyclovir in the target site. Further, the methodology employed can be useful for studying other topical antiviral agents as well as for optimizing formulations for drugs (such as acyclovir) that may enhance their efficacy.

Antiviral selection in the management of acute retinal necrosis

There is no consensus on the optimal antiviral regimen in the management of acute retinal necrosis, a disease caused by herpetic viruses with devastating consequences for the eye. The current gold standard is based on retrospective case series. Because the incidence of disease is low, few well-designed, randomized trials have evaluated treatment dosage and duration. Newer oral antiviral agents are emerging as alternatives to high-dose intravenous acyclovir, avoiding the need for inpatient intravenous treatment. Drug resistance is uncommon but may also be difficult to identify. Antiviral drugs have few side effects, but special attention needs to be paid to patients who have underlying renal disease, are pregnant or are immunocompromised.

Applications of liposomes in ophthalmology

This review outlines the applications of liposomal formulations in ophthalmology. In ophthalmology, liposomes have been used to treat disorders of both the anterior and posterior segments. These include dry eyes, keratitis, corneal transplant rejection, uveitis, endophthalmitis, and proliferative vitreoretinopathy. Liposomes also have shown promise as vectors for genetic transfection and monoclonal antibody-directed vehicles. Furthermore, heat-activated liposomes have spurred research in focal laser and heat-induced release of liposomal drugs and dyes for selective drug delivery. These techniques have been useful in selective tumor and neovascular vessel occlusion, angiography, and retinal and choroidal blood-flow studies. Although verteporfin is the only liposomal drug currently approved for use in the eye, the benefits of liposomes will likely be applied widely in all treatment, diagnostic, and research aspects of ophthalmology in the future.

Ocular disease associated with Epstein-Barr virus infection

Epstein-Barr virus (EBV) is a ubiquitous DNA virus of the herpesvirus genus with a high prevalence rate for antibody (about 90%) in the adult population. It is the most common causative agent of infectious mononucleosis syndrome. During recent years an increasing number of ocular disease entities have been reported to be linked to EBV infection. These entities include oculoglandular syndrome, conjunctivitis, dry eye, keratitis, uveitis, choroiditis, retinitis, papillitis and ophthalmoplegia. While EBV-specific serologic tests can now document recent and past primary infection with EBV and also identify patients manifesting atypical immunologic reactions to EBV, the lack of an animal model, the absence of clear-cut response to therapy and the paucity of documentation by culture render the pathogenesis uncertain or the association questionable in many of these cases.