INTRAVITREAL CONCENTRATION AND CLEARANCE OF TRIAMCINOLONE ACETONIDE IN NONVITRECTOMIZED HUMAN EYES

Preclinical modeling of intravitreal suspensions

There are a number of obstacles that complicate the development of intravitreal delivered small molecules therapies. One serious complication is the potential need for complex polymer depot formulations early in the drug discovery process. The development of such formulations often requires substantial investment of time and material which may not be readily available in preclinical development. Herein I present a diffusion limited pseudo-steady state model to provide prediction of drug release from an intravitreally administered suspension formulation. By using such a model, a preclinical formulator may be able to more confidently determine if development of a complex formulation is required or if a simple suspension may work to support a study design. In this report, the model is used to predict the intravitreal preformance of two different molecules (triamcinolone acetonide and GNE-947) at multiple dose levels in rabbit eyes as well as provide a prediction for the performance of a marketed formulation of Trimacinolone Acetonide in humans.

Lipid-Based Nanocarriers as Topical Drug Delivery Systems for Intraocular Diseases

Effective drug delivery to intraocular tissues remains a great challenge due to complex anatomical and physiological barriers that selectively limit the entry of drugs into the eye. To overcome these challenges, frequent topical application and regular intravitreal injections are currently used to achieve the desired drug concentrations into the eye. However, the repetitive installation or recurrent injections may result in several side effects. Recent advancements in the field of nanoparticle-based drug delivery have demonstrated promising results for topical ophthalmic nanotherapies in the treatment of intraocular diseases. Studies have revealed that nanocarriers enhance the intraocular half-life and bioavailability of several therapies including proteins, peptides and genetic material. Amongst the array of nanoparticles available nowadays, lipid-based nanosystems have shown an increased efficiency and feasibility in topical formulations, making them an important target for constant and thorough research in both preclinical and clinical practice. In this review, we will cover the promising lipid-based nanocarriers used in topical ophthalmic formulations for intraocular drug delivery.

Comparison of the intraocular pressure following an intravitreal triamcinolone acetonide injection for diabetic macula oedema in vitrectomised and non-vitrectomised eyes

Purpose

To compare the intraocular pressure (IOP) after an intravitreal triamcinolone acetonide (IVTA) between vitrectomised and non-vitrectomised eyes in patients with diabetes and diabetic macular oedema (DME).

Design

Retrospective comparative study

Methods

Medical records of 157 patients (157 eyes) with type 2 diabetes who received IVTA for DME were reviewed, and the best-corrected visual acuity, IOP and optical central retinal thickness (CRT) were compared preoperatively, at 1, 4, 12 and 24 weeks after IVTA between the vitrectomised and non-vitrectomised groups.

Results

IOP significantly increased at 1 (p<0.0001), 4 (p<0.0001), 8 (p<0.0001), 12 (p=0.0019), 16 (p=0.0006) and 20 weeks (p=0.0191) in the non-vitrectomised group, whereas a significant increase was only observed at 1 (p=0.0003) and 4 weeks (p=0.0006) in the vitrectomised group. ΔIOP, IOP changes from baseline, in the non-vitrectomised group was significantly higher than that in the vitrectomised group at 4 (p=0.0014), 8 (p=0.0081), 12 (p=0.0032) and 16 weeks (p=0.0038). No significant difference was observed in logMAR and CRT at any time point after IVTA between the two groups.

Conclusions

After an initial IVTA, increased IOP and ΔIOP from the baseline IOP were significantly more frequently observed in the non-vitrectomised than that in the vitrectomised group. IVTA is a safer and more effective treatment option for DME in vitrectomised than that in non-vitrectomised eyes.

Rebound Phenomenon after Intravitreal Injection of Triamcinolone Acetonide for Macular Edema

INTRODUCTION

The aim of this article was to report on a rebound phenomenon after intravitreal triamcinolone acetonide (IVTA) injection for macular edema secondary to diabetic retinopathy (DR) and central or branch retinal vein occlusion (CRVO/BRVO).

METHODS

The data were analyzed retrospectively. Complete ophthalmic examinations, including spectral domain optical coherence tomography, were performed before and 2 months after IVTA injection. The incidence of a rebound phenomenon was defined as an increase in central retinal thickness of >10% from baseline at 2 months after IVTA injection.

RESULTS

This retrospective study included 211 consecutive patients (268 eyes). One hundred ninety (71.2%), 39 (14.6%), and 39 (14.6%) eyes had macular edema (ME) due to DR, CRVO, and BRVO. In total, 9.7% of the eyes showed a rebound phenomenon (DR: 9.5%, CRVO: 5.2%, BRVO: 15.4%). The mean number of prior injections of vascular endothelial growth factor inhibitor or corticosteroid agent was statistically significantly higher in the rebound group (6.8 vs. 5.3) than in the nonrebound group (p = 0.01).

CONCLUSION

Our study shows that 9.7% of the eyes with ME secondary to DR and RVO developed a rebound phenomenon following IVTA injection, limiting its therapeutic effect. We found an increased number of prior intravitreal pharmacotherapy to be a risk factor for a rebound phenomenon.

Corticosteroids for Diabetic Macular Edema

Diabetic macular edema (DME) is a chronic condition with a multifactorial pathogenesis. Vascular endothelial growth factor (VEGF) and several inflammatory mediators are upregulated in eyes with DME. VEGF inhibitors and corticosteroids have all been used successfully in the management of DME. Currently available corticosteroids include triamcinolone acetonide (TA), the dexamethasone (DEX) intravitreal implant, and the fluocinolone acetonide (FA) intravitreal implant. The response to treatment can vary substantially with each treatment modality. Some cases of DME are VEGF driven, and in others, inflammation plays a key role. Chronicity appears to favor corticosteroid treatment. There are no clear guidelines to guide switching from an anti-VEGF to a corticosteroid. Combination therapy of an anti-VEGF drug and a corticosteroid does not appear to provide additional benefit over monotherapy with either drug. The main advantage of corticosteroids over VEGF inhibitors is their longer duration of action. Vitrectomy does not affect the pharmacokinetics of the corticosteroid implants. Common adverse events of corticosteroids include cataract formation, cataract progression, and ocular hypertension. TA may cause a sterile endophthalmitis and pseudoendophthalmitis. Migration of the intravitreal DEX and FA implants into the anterior chamber can be problematic. Because of their less favorable safety profile, corticosteroids are generally used as a second-line treatment for DME. Advantages of using an intravitreal corticosteroid implant include the reduction of treatment burden and predictable pharmacokinetics even in vitrectomized eyes. Pseudophakic eyes, previously vitrectomized eyes and eyes with long-standing DME, particularly of patients who have difficulty in maintaining a monthly appointment, may benefit from primary treatment with a corticosteroid intravitreal implant.

Treatment of Diabetic Macular Edema

PURPOSE OF REVIEW

Diabetes mellitus is a global epidemic which is growing in prevalence, and diabetic macular edema (DME) is a leading cause of visual impairment among patients affected by this disease. Our objective is to review current and upcoming therapeutic approaches to DME.

RECENT FINDINGS

Once considered the gold standard in treatment of DME, focal/grid laser is now reserved mostly for non-center-involving DME, while anti-vascular endothelial growth factor (anti-VEGF) therapy has become the first-line treatment. However, suboptimal responders to anti-VEGF and the burden of frequent injections have stimulated the development of novel approaches. Corticosteroids can be effective in treating DME, but adverse effects such as intraocular pressure elevation and cataract formation must be considered. Emerging therapeutics and drug delivery systems in the pipeline offer exciting potential solutions to this vision-threatening disease. Multiple types of therapeutics targeting various pathways implicated in the pathogenesis of DME may help lessen the global burden of vision loss from diabetes.

Retinal Angiomatous Proliferation Reactivation 6 Months after High-Dose Intravitreal Acetonide Triamcinolone and Photodynamic Therapy

Purpose

To describe the incidence of retinal angiomatous proliferation (RAP) reactivation after combined treatment with a high-dose intravitreal triamcinolone acetonide (IVTA) and photodynamic therapy (PDT) at 1-year follow-up.

Methods

All patients had undergone a full ophthalmic examination. High-dose IVTA (20 mg) was injected via pars plana. Four to 7 days later, PDT was delivered.

Results

Fourteen eyes of 13 patients were included. Eight lesions (57%) reopened and needed retreatment with combined therapy at 6 months follow-up. At 1-year follow up, the lesion was obliterated in nine cases (64.2%) and best-corrected visual acuity improved from 0.87 logMar (range, 0.7–1) to 0.79 logMar (range, 0.5–1).

Conclusions

Combined therapy using high-dose IVTA and PDT is beneficial in stabilizing RAP. However, a high incidence of RAP reactivation has been observed at 6 months, even with a high-dose IVTA injection.

Effect of intravitreal triamcinolone acetonide injection at the end of vitrectomy for vitreous haemorrhage related to proliferative diabetic retinopathy

Background/Aims

To investigate whether intravitreal injection of triamcinolone acetonide (IVTA) combined with vitrectomy prevents postoperative inflammation in patients with vitreous haemorrhage (VH) due to proliferative diabetic retinopathy (PDR).

Methods

This prospective, multicentre, randomised study conducted at seven sites in Japan enrolled patients diagnosed as having VH following PDR. Patients underwent vitrectomy with (IVTA+VIT group) or without (VIT group) IVTA at the end of the surgery. Anterior flare intensity (AFI), central retinal thickness (CRT), best-corrected visual acuity (BCVA) and intraocular pressure (IOP) were measured before and at 3 days, 1 week, 1, 3 and 6 months after surgery and compared.

Results

Number of patients who completed 6 months of follow-up was 40 and 41 in VIT group and IVTA+VIT group, respectively. AFI was significantly higher in the VIT group than in the IVTA+VIT group at 3 days (P=0.033), 1 week (P=0.019) and 1 month (P=0.037). There were no significant differences in CRT, BCVA and IOP between the groups through the observational periods. In the cases with macular oedema >350 µm of CRT at 3 days, CRT was significantly lower in the IVTA+VIT group than in the VIT group at 1 month (P=0.041).

Conclusions

IVTA combined with vitrectomy and cataract surgery contributed to inhibit the postoperative inflammation in patients with VH due to PDR. The effect of IVTA in the reduction of diabetic macular oedema may be limited to the early stage after surgery.

Trial registration number

UMIN000020376, Post-results.

Principles of pharmacology in the eye

The eye is a highly specialized organ that is subject to a huge range of pathology. Both local and systemic disease may affect different anatomical regions of the eye. The least invasive routes for ocular drug administration are topical (e.g. eye drops) and systemic (e.g. tablets) formulations. Barriers that subserve as protection against pathogen entry also restrict drug permeation. Topically administered drugs often display limited bioavailability due to many physical and biochemical barriers including the pre-corneal tear film, the structure and biophysiological properties of the cornea, the limited volume that can be accommodated by the cul-de-sac, the lacrimal drainage system and reflex tearing. The tissue layers of the cornea and conjunctiva are further key factors that act to restrict drug delivery. Using carriers that enhance viscosity or bind to the ocular surface increases bioavailability. Matching the pH and polarity of drug molecules to the tissue layers allows greater penetration. Drug delivery to the posterior segment is a greater challenge and, currently, the standard route is via intravitreal injection, notwithstanding the risks of endophthalmitis and retinal detachment with frequent injections. Intraocular implants that allow sustained drug release are at different stages of development. Novel exciting therapeutic approaches include methods for promoting transscleral delivery, sustained release devices, nanotechnology and gene therapy.

Update on corticosteroids for diabetic macular edema

Diabetic macular edema (DME) remains an important cause of visual loss. Although anti-vascular endothelial growth factor (VEGF) agents are generally used as first-line treatments for patients with center-involving DME, there is an important role for corticosteroids as well. Corticosteroids may be especially useful in pseudophakic patients poorly responsive to anti-VEGF therapies, in patients wishing to reduce the number of required injections, and in pregnant patients. Intravitreal triamcinolone acetonide has been used for many years but is not approved for this indication. An extended-release bioerodable dexamethasone delivery system and an extended-release nonbioerodable fluocinolone acetonide insert have both achieved regulatory approval for the treatment of DME. All intravitreal corticosteroids are associated with risks of cataract progression, elevation of intraocular pressure, and endophthalmitis. There is no current consensus regarding the use of corticosteroids, but they are valuable for selected patients with center-involving DME.

Pharmacologic Treatment of Noninfectious Uveitis

Uveitis encompasses a spectrum of diseases whose common feature is intraocular inflammation, which may be infectious or noninfectious in etiology (Nussenblatt and Whitcup 2010). Infectious causes of uveitis are typically treated with appropriate antimicrobial therapy and will not be discussed in this chapter. Noninfectious uveitides are thought have an autoimmune component to their etiology and are thus treated with anti-inflammatory agents.

Nonbiological pharmacotherapies for the treatment of diabetic macular edema

INTRODUCTION

During the past decade, there have been significant advances in the pharmacotherapies for the treatment of diabetic macular edema (DME). Among the presently available treatment options, anti-vascular endothelial growth factors (anti-VEGF) agents are the most favored agents due to their efficacy and safety. The index review focuses on nonbiological therapies that have entered in phase 3 clinical trials for DME.

AREAS COVERED

An extensive review of the literature was performed to identify various nonbiological immunotherapies i.e., drugs other than '-mAbs' (monoclonal antibodies including anti-VEGF agents), '-mibs' (proteasome inhibitors), '-NAbs' (nanoparticle albumin-bound), and '-nibs' (small molecule inhibitor/tyrosine kinase inhibitors), among others. Extended-release low-dose corticosteroid devices have been recently approved for the treatment of DME. Other compounds such as non-steroidal anti-inflammatory drugs, antibody mimetic proteins, nonbiological growth factor inhibitors, and inhibitors of protein kinase C have been described.

EXPERT OPINION

A number of therapies are under development for the pharmacological management of DME. Due to the rising healthcare costs associated with anti-VEGF agents, a number of alternate treatment options have been explored recently. Some of these agents have reached phase 3 in clinical trials and appear to have a promising role in the management of DME. As further research is conducted, the role of each individual agent will become more defined, alone or in combination therapy.

Efficacy of Intravitreal Triamcinolone Acetonide for Diabetic Macular Edema After Vitrectomy

PURPOSE

To compare the efficacy of intravitreal injection of triamcinolone acetonide (IVTA) for diabetic macular edema (DME) in vitrectomized eyes with DME without vitrectomy eyes.

METHODS

This retrospective comparative study evaluated the efficacy of IVTA treatment of DME in 26 consecutive eyes (23 patients). Changes in mean best-corrected visual acuity (VA) and mean central retinal thickness (CRT) were retrospectively evaluated before IVTA and during the 6-month period after IVTA.

RESULTS

Subjects were divided into 2 groups: 13 consecutive eyes (11 patients) with proliferative diabetic retinopathy or DME that underwent vitrectomy (vitrectomized group), and 13 consecutive eyes (12 patients) with DME who received IVTA, but did not undergo vitrectomy (nonvitrectomized group). In the vitrectomized group, there was a significantly decreased CRT for up to 4 months as compared to the thicknesses before IVTA. In the nonvitrectomized group, there was a significantly decreased CRT for up to 5 months after IVTA. In both groups, there was significant improvement in the VA for up to 4 months after IVTA.

CONCLUSION

IVTA may represent a valid treatment option for DME, even in vitrectomized eyes.

The effectiveness and reliability of posterior sub-Tenon triamcinolone acetonide injection in branch retinal vein occlusion-related macular edema

OBJECTIVE

To investigate the effectiveness and reliability of posterior sub-Tenon triamcinolone acetonide (PSTA) application in branch retinal vein occlusion (BRVO)-related macular edema.

METHODS

Patients with confirmed BRVO-related macular edema were enrolled in the study. Patients were injected with a single, therapeutic dose of 40 mg PSTA. Detailed ophthalmic examination was performed at baseline and at 1, 3 and 6 months after the treatment. Best corrected visual acuity (BCVA), intraocular pressure (IOP), cataractogenic change (CC) and macular optical coherence tomography (OCT) analysis results were evaluated. The results were compared statistically.

RESULTS

Forty-one eyes of 41 patients with a mean age of 63.49 ± 10.99 (55-86) years, 15 (36.6%) females, were included in the study. BCVA in LogMAR values at 1 and 3 months were significantly better than at baseline, while no significant difference from baseline was observed in sixth month values (p < 0.001, p < 0.001 and p = 0.846, respectively). Central macular thickness values obtained using OCT were significantly lower at the first, third and sixth months compared to baseline (p < 0.001 for all). IOP elevation was determined in only two eyes (4.8%) at the end of the study period, and no CC was detected in any case.

CONCLUSION

PSTA application is an effective and safe option in BRVO-related macular edema.

Unilateral choroidal granulomas complicated by choroidal neovascular membrane treated successfully with intravitreal triamcinolone in a patient with sarcoidosis

This case describes the use of intravitreal triamcinolone in the treatment of unilateral choroidal granulomas secondary to systemic sarcoidosis complicated by choroidal neovascular membrane. A single injection of 2 mg intravitreal triamcinolone was administered as treatment for rapidly progressing choroidal granulomas and associated choroidal neovascular membrane with subretinal fluid. Visual acuity had dropped from 6/5 to 6/48 with the progressing lesions. The patient was a 52-year-old woman with type 2 diabetes mellitus who was reluctant to consider oral steroids in view of their side effect profile. Ten days after injection, visual acuity improved to 6/24 and to 6/6 at 3 months follow-up with resolution of the subretinal fluid. There was no rise in intraocular pressure. There has been no recurrence at 5 months follow-up.

Intravitreal Corticosteroids in the Management of Diabetic Macular Edema

Diabetic macular edema (DME) remains an important worldwide cause of visual loss. Corticosteroids have a role in the treatment of some patients with advanced or recurrent DME. The best studied steroids for this indication are triamcinolone acetonide, dexamethasone, and fluocinolone acetonide. All steroids are associated with risks of cataract and intraocular pressure elevation. In addition, intravitreal injection of any medication is associated with risks of infectious endophthalmitis, which has led to the investigation of various extended-release steroid implants. At this time, no steroid is approved by the United States Food and Drug Administration (FDA) for the treatment of DME.

Congenital cataract surgery with intracameral triamcinolone: pre- and postoperative central corneal thickness and intraocular pressure

PURPOSE

To evaluate the change in intraocular pressure (IOP) and central corneal thickness (CCT) of children who underwent congenital cataract surgery with injection of triamcinolone acetonide into the anterior chamber at the end of the procedure.

METHODS

Fifty-three eyes of 34 children <2 years of age who underwent congenital cataract surgery with injection of 1.2 mg/0.03 mL of preservative-free triamcinolone acetonide into the anterior chamber at the end of the procedure were included in this study. IOP and CCT were measured preoperatively and at a mean of 2 and 12 months' follow-up.

RESULTS

The mean IOP was 8.7 ± 0.4 mm Hg preoperatively, 8.4 ± 0.6 mm Hg at the 2-month follow-up, and 8.1 ± 0.3 mm Hg at the 12-month follow-up. The mean CCT was 562 ± 11 μm preoperatively, 563 ± 10 μm at the 2-month follow-up, and 570 ± 10 μm at the 12-month follow-up. There was no significant change in either pre- or postoperative IOP (P = 0.700) or CCT (P = 0.419) over the study period.

CONCLUSIONS

Injection of 1.2 mg triamcinolone acetonide at the end of congenital cataract surgery in children <2 years of age did not significantly affect IOP or CCT in the first year after surgery.

Recent advances in ophthalmic drug delivery

Topical ocular drug bioavailability is notoriously poor, in the order of 5% or less. This is a consequence of effective multiple barriers to drug entry, comprising nasolacrimal drainage, epithelial drug transport barriers and clearance from the vasculature in the conjunctiva. While sustained drug delivery to the back of the eye is now feasible with intravitreal implants such as Vitrasert (-6 months), Retisert (-3 years) and Iluvien (-3 years), currently there are no marketed delivery systems for long-term drug delivery to the anterior segment of the eye. The purpose of this article is to summarize the resurgence in interest to prolong and improve drug entry from topical administration. These approaches include mucoadhesives, viscous polymer vehicles, transporter-targeted prodrug design, receptor-targeted functionalized nanoparticles, iontophoresis, punctal plug and contact lens delivery systems. A few of these delivery systems might be useful in treating diseases affecting the back of the eye. Their effectiveness will be compared against intravitreal implants (upper bound of effectiveness) and trans-scleral systems (lower bound of effectiveness). Refining the animal model by incorporating the latest advances in microdialysis and imaging technology is key to expanding the knowledge central to the design, testing and evaluation of the next generation of innovative ocular drug delivery systems.

Pharmacokinetic study of vitreous and serum concentrations of triamcinolone acetonide after posterior sub-tenon's injection

PURPOSE

To compare a theoretical pharmacokinetic model of triamcinolone acetonide after posterior sub-Tenon's injection with experimental serum and undiluted vitreous triamcinolone acetonide concentrations obtained during pars plana vitrectomy.

DESIGN

Clinical-practice, prospective, interventional case series study.

METHODS

This study compared computer-modeled triamcinolone acetonide diffusion after posterior sub-Tenon's injection with triamcinolone acetonide levels in experimental undiluted vitreous and serum samples from 57 patients undergoing vitrectomy assessed via mass spectrometry and high-pressure liquid chromatography. At least 5 pairs of samples were collected at each of 7 time points (1 day, 3 days, and 1, 2, 3, 4, and 8 weeks) after triamcinolone acetonide injection, with 6 controls without injection. Cortisol levels were measured in 31 sets of samples.

RESULTS

The theoretical model predicted that triamcinolone acetonide levels in systemic blood, vitreous, and choroidal extracellular matrix would plateau after 3 days at 15 ng/mL, 227 ng/mL and 2230 ng/mL, respectively. Experimental vitreous levels of triamcinolone peaked at 111 ng/mL at day 1, then reached a plateau in the range 15 to 25 ng/mL, while serum triamcinolone levels peaked at day 3 near 35 ng/mL and plateaued near 2 to 8 ng/mL. Serum triamcinolone and cortisol levels were inversely correlated (Spearman -0.42, P = .02).

CONCLUSIONS

The theoretical model predicts efficient delivery of triamcinolone acetonide from the posterior sub-Tenon's space to the extracellular choroidal matrix. The experimental findings demonstrate low levels of serum triamcinolone that alter systemic cortisol levels and higher vitreous levels lasting at least 1 month. Both assessments support trans-scleral delivery of posterior sub-Tenon's triamcinolone.

Spontaneous resolution of intravitreal steroid-induced bilateral cytomegalovirus retinitis

A 73-year-old woman underwent vitrectomy and intravitreal triamcinolone acetonide (IVTA) of the right eye and cataract surgery with IVTA of the left eye, for bilateral diabetic macular edema. The patient presented with visual loss in both eyes three-months postoperatively. The fundoscopic examination revealed white-yellow, necrotic peripheral lesions in the superotemporal quadrant of both eyes. Although bilateral acute retinal necrosis was suspected, azotemia resulting from diabetic nephropathy limited the use of acyclovir. Antiviral treatment was not started. A sample of the aqueous humor for polymerase chain reaction (PCR) analysis was obtained. One week later, the PCR results indicated the presence of cytomegalovirus (CMV). Since the retinal lesions did not progress and did not threaten the macula, the patient was followed without treatment for CMV. The retinal lesions progressively regressed and completely resolved in both eyes by six months of follow-up. Patients with IVTA-induced CMV retinitis may not require systemic treatment with ganciclovir.

Pharmacokinetics of triamcinolone acetonide for the treatment of macular edema

INTRODUCTION

The use of intravitreal triamcinolone acetonide (TA) for the treatment of various types of macular edema has been widespread, particularly for the last decade. Currently, there is a scant amount of evidence-based literature evaluating the pharmacokinetic profile of TA despite clinical data showing the efficacy of intravitreal TA for multiple forms of macular edema.

AREAS COVERED

This paper is an extensive review of human and experimental studies published on the pharmacokinetics of TA for the treatment of macular edema. The literature search was conducted via OVID, TRIP Database and EMBASE, up to April 2011.

EXPERT OPINION

The pharmacokinetic profile of TA is unpredictable and the agent has a time-limited therapeutic action due to its relatively short half-life. This has led to the need for repeated injections. Future research should investigate the pharmacokinetic profiles of TA when administered intravitreally, as well as through alternate routes in more robust studies.

Critical appraisal of the clinical utility of the dexamethasone intravitreal implant (Ozurdex) for the treatment of macular edema related to branch retinal vein occlusion or central retinal vein occlusion

Macular edema is a common cause of visual loss in patients with retinal vein occlusions. Ozurdex^®, a dexamethasone intravitreal implant, has been shown in randomized controlled trials to reduce macular edema and improve visual acuity in patients with either branch retinal vein occlusions or central retinal vein occlusions. It was approved in the United States in 2009. Since then, new therapeutic agents and clinical data have emerged. The purpose of this review is to critically evaluate the clinical utility of Ozurdex^® in the current treatment strategy of macular edema related to retinal vein occlusion.

Development of ocular hypertension and persistent glaucoma after intravitreal injection of triamcinolone

Purpose

This study evaluates intraocular pressure (IOP) elevation secondary to intravitreal injection of triamcinolone acetonide (IVTA) and discusses its management.

Methods

The records of 175 patients who underwent IVTA treatment and regular eye examinations in the period 2003–2006 were reviewed. One hundred and twenty-two of these patients were included in the study, of which 147 eyes that received IVTA (4 mg/0.1 ml) were followed for at least 9 months. Mean IOPs observed after IVTA injection as well as IOP elevations defined as moderate (≥5 mm Hg), important (≥10 mm Hg) and severe (>25 mm Hg) during the follow-up period were evaluated and compared statistically.

Results

Overall, the mean IOPs following IVTA injection were statistically significantly higher than the preinjection IOP (15.8 ± 2.6), after the first hour (17.7 ± 2.9), the first week (18.7 ± 4.1), the first month (19.6 ± 6.2), the second month (19.1 ± 6.1), the third month (18.0 ± 4.1), the sixth month (17.3 ± 4.0), and the ninth month (17.0 ± 2.7), but not after the first day (16.3 ± 7.6). Important IOP elevations were observed mostly in the first (17.7%) and second months (10.2%). In 40 (27.7%) eyes, topical antiglaucomatous therapy was needed and 7 later required surgical intervention to lower the IOP. Of the remaining 33 eyes, topical treatment was continued in 14 (9.5%) because of IOPs ≥20 mm Hg.

Conclusion

The persistence of IOP elevation beyond the IVTA clearance period and the development of intractable secondary glaucoma requiring surgical intervention substantiate the need for careful consideration of IVTA indication and follow-up.

Intraocular and systemic pharmacokinetics of triamcinolone acetonide after a single 40-mg posterior subtenon application

PURPOSE

To characterize the pharmacokinetics of triamcinolone acetonide (TA) in aqueous, vitreous, and systemic circulation after a single subtenon injection.

DESIGN

Prospective interventional case series.

PARTICIPANTS

Thirty-six patients (36 eyes) who received a single posterior subtenon injection of TA (40 mg in 0.4 ml).

METHODS

Aqueous, vitreous, and blood samples were obtained at 1-hour, 1-day, 3-day, 5-day, 10-day, 14-day, 21-day, and 28-day time points after the posterior subtenon TA injection. At each time point, there were 3 to 6 eyes (patients). The concentrations of TA in the aqueous, vitreous, and plasma were analyzed using ultra-performance liquid chromatography coupled with tandem mass spectrometry.

MAIN OUTCOME MEASURES

Triamcinolone acetonide concentration in the samples was measured, and pharmacokinetic parameters were calculated.

RESULTS

The TA concentration-time profile in aqueous consisted of a fast distribution phase during the first 24 hours and a slow elimination phase thereafter. In contrast, the TA concentration-time profile in vitreous consisted of an absorption phase during the first 24 hours followed by a slow elimination phase. The TA in plasma followed a mono-exponential elimination during the study course. The TA concentration peak time for aqueous and plasma was at 1 hour and 24 hours, for vitreous after subtenon injection. The terminal elimination half-life in aqueous, vitreous, and plasma was 11.8, 17.1, and 25 days, respectively. The integral of the area under the concentration time curve (AUC(0-∞)) was 862 ng/day/ml for aqueous, 1262 ng/day/ml for vitreous, and 17.4 ng/day/ml for plasma. The total TA exposure to vitreous was 46% more than total TA exposure to the aqueous. The TA concentration in vitreous was 70- to 98-fold higher than that in plasma.

CONCLUSIONS

Posterior subtenon TA application can provide a sustained high local ocular TA level while also resulting in a very low systemic TA level, which may be well below the normal glucocorticoid level in humans.

Pharmacotherapeutic efficacy of preservative-free intravitreal triamcinolone acetonide

Preservative-free formulations of triamcinolone acetonide have recently been introduced to the market over concerns of local toxicity of the vehicle and preservatives, including benzyl alcohol in the original formulation, which was not designed for intraocular use. The pharmacokinetics and pharmacodynamics of intravitreal triamcinolone (IVTA) are discussed. The therapeutic effects of IVTA include improvement of visual acuity and reduction of macular edema. However, ongoing treatment is usually required to maintain its effects. The efficacy of IVTA for both FDA-approved and 'off-labeled' indications is reviewed. Elevation of intraocular pressure and cataract formation are the two major side effects of IVTA; these are manageable but require close long-term follow-up. More studies are required to determine the optimal dosage and treatment frequency in different posterior segment disease.

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.

Targeting retinal and choroid neovascularization using the small molecule inhibitor carboxyamidotriazole

Neovascular ocular diseases as exemplified by proliferative diabetic retinopathy (PDR), exudative age-related macular degeneration (AMD), and retinopathy of prematurity (ROP) are severe diseases affecting all age groups in the US. We asked whether a small molecule, carboxyamidotriazole (CAI) known for its anti-angiogenic and anti-tumor effects and its ability to be administered orally in humans, could have anti-angiogenic effects in ocular in vitro and in vivo angiogenesis models. The anti-proliferative effects of CAI were examined by BrdU incorporation using human retinal and dermal endothelial cells and human pigment epithelial cells. The effect of CAI was determined using the Matrigel tube formation assay. The mouse model of choroidal neovascularization (CNV) initiated by laser rupture of Bruch's membrane was used to quantify in vivo effects of aqueous beta-hydroxypropyl cyclodextrin (bHPCD) formulations of CAI on neovascularization. The pharmacokinetics (PK) of CAI after intravitreal administration of bHPCD-CAI was studied in rabbit. The intravitreal toxicology of bHPCD-CAI was also examined in rat ocular tissue. We observed that CAI treatment of human endothelial cells decreased cell proliferation in a dose-dependent manner. In the in vivo tests bHPCD-CAI treatment reduced choroidal neovascular lesion volume, also in a dose-dependent manner. The intravitreal PK of bHPCD-CAI demonstrated that highly efficacious concentrations of CAI are reached in the vitreous compartment. No ocular toxicology was observed with intravitreous injection of CAI. These studies support the potential of developing intravitreal CAI in an bHPCD ocular formulation for treatment of proliferative retinopathies in humans.

Intracameral dexamethasone reduces inflammation on the first postoperative day after cataract surgery in eyes with and without glaucoma

Purpose:

To evaluate whether dexamethasone injected intracamerally at the conclusion of surgery can safely and effectively reduce postoperative inflammation and improve surgical outcomes in eyes with and without glaucoma.

Methods:

Retrospective chart review of 176 consecutive eyes from 146 patients receiving uncomplicated phacoemulsification (PE) (n = 118 total, 82 with glaucoma), glaucoma drainage device (GDD) (n = 35), combined PE/GDD (n = 11) and combined PE/endoscopic cyclophotocoagulation (n = 12). Ninety-one eyes from 76 patients were injected with 0.4 mg dexamethasone intracamerally at the conclusion of surgery. All eyes received standard postoperative prednisolone and ketorolac eyedrops. Outcomes were measured for four to eight weeks by subjective complaints, visual acuity (VA), slit-lamp biomicroscopy, intraocular pressure (IOP) and postoperative complications.

Results:

Dexamethasone significantly reduced the odds of having an increased anterior chamber (AC) cell score after PE (p = 0.0013). Mean AC cell score ± SD in nonglaucomatous eyes was 1.3 ± 0.8 in control and 0.8 ± 0.7 with dexamethasone; scores in glaucomatous eyes were 1.3 ± 0.7 in control and 0.9 ± 0.8 with dexamethasone. Treated nonglaucomatous eyes had significantly fewer subjective complaints after PE (22.2% vs 64.7% in control; p = 0.0083). Dexamethasone had no significant effects on VA, corneal changes, IOP one day and one month after surgery, or long-term complications.

Conclusions:

Intracameral dexamethasone given at the end of cataract surgery significantly reduces postoperative AC cells in eyes with and without glaucoma, and improves subjective reports of recovery in nonglaucomatous eyes. There were no statistically significant risks of IOP elevation or other complications in glaucomatous eyes.

Pharmacokinetic behavior of intravitreal triamcinolone acetonide prepared by a hospital pharmacy

PURPOSE

We developed a new hospital pharmaceutical preparation of triamcinolone acetonide (TA) for intravitreal injections using sodium hyaluronate as the vehicle. The purpose of this study was to compare the pharmacokinetic behavior of this hospital pharmacy preparation of TA (HPP-TA) to that of a commercial preparation of TA (CP-TA) in rats.

METHODS

We injected the two preparations of TA into the vitreous humor of male Wistar rats. The rats were killed between days 1 and 21, and the concentration of TA in the vitreous was measured by high-performance liquid chromatography to determine the pharmacokinetic parameters. We also examined the microscopic appearance of the TA particles in these preparations.

RESULTS

The elimination half-life was 6.08 days for the CP-TA and 5.78 days for the HPP-TA. A two-compartment model was suitable to approximate the pharmacokinetic behavior of HPP-TA in the vitreous body, but this model was not suitable for CP-TA, because its pharmacokinetic behavior was not sufficiently stable. The particle size of CP-TA was largest, followed by TA powder and HPP-TA. Many particles were agglutinated in the CP-TA preparation, whereas the TA particles were fine and dispersed in the HPP-TA medium.

CONCLUSIONS

The TA particle size and the suspension medium are likely important factors in the preparation of a safe and stable suspension of TA. HPP-TA satisfied these requirements and should be suitable for clinical use.

Safety and efficacy of intraoperative intravitreal injection of triamcinolone acetonide injection after phacoemulsification in cases of uveitic cataract

PURPOSE

To evaluate the safety and efficacy of a single intraoperative intravitreal injection of triamcinolone acetonide after phacoemulsification in patients with chronic idiopathic anterior uveitis or intermediate uveitis.

SETTING

Dr. R.P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.

METHODS

This prospective randomized controlled study included 40 eyes (40 patients) with chronic idiopathic anterior uveitis or intermediate uveitis that had phacoemulsification with intraocular lens implantation. Twenty eyes received an intravitreal injection of triamcinolone acetonide (4 mg/0.1 mL) intraoperatively (triamcinolone acetonide group), and 20 received oral steroids (steroid group) postoperatively. Outcome measures were Early Treatment Diabetic Retinopathy Study best corrected visual acuity (BCVA), anterior chamber reaction, intraocular pressure (IOP) by applanation tonometry, and central macular thickness by optical coherence tomography.

RESULTS

The mean BCVA (decimal) improved from a baseline of 0.13 +/- 0.14 to 0.64 +/- 0.32 in the triamcinolone acetonide group and from 0.05 +/- 0.06 to 0.61 +/- 0.36 in the steroid group (P = .74). There were no statistically significant differences between the 2 groups in postoperative anterior chamber reaction, IOP, or central macular thickness. Four patients in the triamcinolone acetonide group and 5 in the steroid group had recurrence of uveitis; 5 patients in the triamcinolone acetonide group had ocular hypertension. One patient in the triamcinolone acetonide group and 3 in the steroid group had cystoid macular edema postoperatively.

CONCLUSION

A single intraoperative intravitreal injection of triamcinolone acetonide seemed to be a safe and efficacious route of steroid delivery during phacoemulsification in patients with chronic idiopathic anterior uveitis or intermediate uveitis and is recommended as a substitute for postoperative oral steroid administration.

Intravitreal Triamcinolone Improves Recovery of Visual Acuity in Nonarteritic Anterior Ischemic Optic Neuropathy

BACKGROUND

The visual outcome in untreated nonarteritic anterior ischemic optic neuropathy (NAION) is dismal. Because intravitreal triamcinolone (IVTA) has shown promise in improving edematous retinal disorders, a pilot trial of this therapy in NAION was considered reasonable.

METHODS

Four eyes of 4 patients with severe visual loss due to NAION were treated with 4 mg IVTA (study group). The control group consisted of 6 consecutive patients with NAION who received no treatment. Patients were evaluated by the visual acuity and visual field measurements of the Early Treatment Diabetic Retinopathy Study (ETDRS) and fluorescein angiography.

RESULTS

All patients completed at least 9 months of follow-up. In the study group, the mean improvement in visual acuity were 4, 5.8, and 6.2 ETDRS lines at the first and third weeks and final visit, respectively. Optic disc swelling and leakage had markedly decreased at the first postinjection week and had disappeared by the third week examination in all eyes. In the control group, the mean improvements in visual acuity were 0, 0.7, and 1.3 ETDRS lines at the first and third weeks and final visit, respectively. Control eyes showed resolution of the optic disc swelling between the fourth week and third month visits. No marked change in visual field defects was observed in either group.

CONCLUSIONS

IVTA provided relatively improved recovery of visual acuity and relatively rapid resolution of optic disc swelling in a small sample of patients with acute NAION. It did not provide visual field improvement. A larger trial is merited by the results of this small pilot study.

The use of intravitreal corticosteroids, evidence-based and otherwise

PURPOSE OF REVIEW

To provide a current update on the use of intravitreal corticosteroids as a treatment for a variety of retinal diseases.

RECENT FINDINGS

Pharmacokinetic studies demonstrate that a single 4 mg injection of intravitreal triamcinolone acetonide is present in the vitreous for up to 3 months. Many recent studies demonstrate a significant reduction in macular edema often with a significant improvement in vision for up to several months followed by a waning of treatment effect and recurrence of macular edema. Retreatments have been shown to be efficacious. Intravitreal triamcinolone acetonide may help lead to a reduction in subfoveal hard exudates in diffuse diabetic macular edema. It has been shown to be a more potent treatment than sub-Tenon's and retrobulbar triamcinolone acetonide for persistent macular edema. It may also be a significant adjunctive treatment for choroidal neovascularization treated with photodynamic therapy. Intravitreal corticosteroid implants have also been shown to be beneficial in early trials for persistent macular edema.

SUMMARY

Intravitreal triamcinolone acetonide provides a potent short-term treatment for persistent macular edema and may be a useful adjunctive treatment for choroidal neovascularization. It remains to be determined whether intravitreal corticosteroids can provide long-term visual gain or stabilization. The side-effect profile of intravitreal corticosteroids is significant with corticosteroid-induced intraocular pressure rises. With longer-term studies, the rate of posterior subcapsular cataract formation is higher than previously reported, and there is a small but potential risk of endophthalmitis.

Measuring triamcinolone acetonide in aqueous humor by gas chromatography-electron-capture negative-ion mass spectrometry

Intravitreal triamcinolone acetonide (IVTA) injection has been used in the treatment of various posterior segment diseases. One of the side effects of IVTA is raised intraocular pressure, which may be secondary to triamcinolone acetonide (TAA)'s effects on the trabecular meshwork that affects aqueous outflow. In order to study the biological effects of TAA on the trabecular meshwork, we firstly need to reliably and accurately detect the concentration of TAA in tissue cells or fluids. In this study we have described a technique of using gas chromatography-electron-capture-negative-ion mass spectrometry (GC-NCI-MS) to develop a simple, sensitive, selective and validated method to detect TAA in aqueous humor (AH) of rabbits following IVTA and subconjunctival TAA injections. We derivatized TAA from extracted aqueous sample by acetic anhydride and BSTFA, respectively, and analyzed by GC-NCI-MS. The detection limit was 0.3ng/ml, linearity over 0.995 from 0 to 300ng/ml. The reproducibility ranged from 10.4 to 3.9 for concentrations from 3 to 300ng/ml, and recovery was over 95% for the concentrations 10, 60, and 200ng/ml. No interference was found from 159 aqueous samples. There was no TAA residue carried to the next injection from previously high concentration injection, 10,000ng/ml. We have provided an alternative, rapid, and robust method other than LC-MS-MS for TAA detection in AH.

Triamcinolone reduces neovascularization, capillary density and IGF-1 receptor phosphorylation in a model of oxygen-induced retinopathy

PURPOSE

To study the effects of intravitreous triamcinolone acetonide (TA) on neovascularization (NV), capillary density, and retinal endothelial cell (REC) viability in a model of oxygen-induced retinopathy (OIR).

METHODS

Newborn rats exposed to OIR underwent intravitreous injections (right eye) at day 14 to achieve intravitreous concentrations of: dexamethasone (DEX) (0.3 mg/mL), triamcinolone (TA; 0.4-4 mg/mL), or PBS. Animals were removed to room air and at day 18, retinal flatmounts were assayed for clock hours of NV, percent peripheral avascular retina, capillary density, apoptosis, and VEGF protein. At day 15, retinas were assayed for insulin-like growth factor (IGF)-1 receptor phosphorylation (IGF-1Rphos). Human RECs exposed to TA were assayed for trypan blue exclusion or activated caspase-3.

RESULTS

TA but not DEX or PBS reduced NV (ANOVA, P < 0.001), capillary density (ANOVA, P < 0.001), and systemic weight gain (ANOVA, P = 0.002). VEGF protein was not different between TA- and PBS-injected or noninjected groups. Apoptosis was not increased in vivo or in vitro between groups, but there was a dose-dependent toxic effect of TA on cultured RECs (P < 0.001). At day 15, retinas from the 4 mg/mL TA-injected OIR group had a trend toward reduced IGF-1Rphos compared with room air-raised PBS- or non-injected OIR groups.

CONCLUSIONS

TA caused dose-dependent reductions in NV, retinal vascularization, and systemic weight gain associated with a reduction in IGF-1Rphos. Long-term studies are needed to assess TA toxicity in vivo. TA doses should be carefully considered before administering the drug in diseases with ongoing retinal vascular development, such as retinopathy of prematurity.

Evaluation of the toxicity of subretinal triamcinolone acetonide in the rabbit

PURPOSE

Subretinal triamcinolone acetonide (TCA) might be a useful adjuvant in the treatment of subretinal neovascularization. The purpose of this study was to test the toxicity of subretinal TCA in the rabbit eye.

METHODS

Sixteen New Zealand rabbits were vitrectomized and injected with either decanted TCA solution or vehicle. The concentration of injected TCA was 2 mg, and the delivered volume was 10 microL. Rabbits were examined on days 1, 3, and 7 and then once a week up to 3 months after surgery. Optical coherence tomography was performed at months 1, 2, and 3. After the last examination, which included electroretinography, the rabbits were killed, and the eyes were enucleated for histopathologic analysis.

RESULTS

Subretinal TCA appeared as a white circumscribed deposit. As the drug disappeared, areas of hyperpigmentation were seen adjacent to the drug deposit. Electroretinography tracings were normal, indicating no widespread toxic effect. Histologic analysis revealed areas of absence and/or hyperpigmentation of the retinal pigment epithelium and damage to photoreceptors and the outer nuclear layer of the retina.

CONCLUSION

Subretinal injection of TCA crystals can be toxic to the outer retina and retinal pigment epithelium. Whether the potential beneficial effect of such a high-dose steroid in limiting subretinal inflammation, angiogenesis, and proliferation outweighs toxicity can only be determined from a clinical trial.