Comparative study of topical application of timolol and verapamil in patients with glaucoma within 6 months

Ocular delivery of felodipine for the management of intraocular pressure and inflammation: Effect of film plasticizer and in vitro in vivo evaluation

Glaucoma may cause irreversible eyesight loss and damage to the optic nerve. Trabecular meshwork obstruction may raise intraocular pressure (IOP) in open-angle and/or closed-angle type inflammatory glaucoma. Ocular delivery of felodipine (FEL) has been undertaken for the management of intraocular pressure and inflammation. FEL film was formulated using different plasticizers, and IOP has been assessed using a normotensive rabbit eye model. Ocular acute inflammation induced by carrageenan has also been monitored. Drug release has been enhanced significantly (93.9 % in 7 h) in the presence of DMSO (FDM) as a plasticizer in the film compared to others (59.8 to 86.2 % in 7 h). The same film also exhibited the highest ocular permeation of 75.5 % rather than others (50.5 to 61.0 %) in 7 h. Decreased IOP was maintained up to 8 h after ocular application of FDM compared to the solution of FEL only up to 5 h. Ocular inflammation has almost been disappeared within 2 h of using the film (FDM), whereas inflammation has been continued even after 3 h of the induced rabbit without film. DMSO plasticized felodipine film could be used for the better management of IOP and associated inflammation.

Sustained Delivery of Timolol Maleate for Over 90 Days by Subconjunctival Injection

PURPOSE

Medical treatment of glaucoma relies on intraocular pressure (IOP)-lowering medications, typically administered daily by the patient. While these medications are effective when applied correctly, patient adherence is a major obstacle in glaucoma treatment. We have developed a sustained-release formulation of timolol maleate that can be injected subconjunctivally to avoid patient noncompliance.

METHODS

A biodegradable microsphere formulation for timolol maleate was injected subconjunctivally in normal rabbits. We measured timolol levels in tears, aqueous humor, vitreous humor, and serum of study rabbits. Furthermore, IOP profiles were recorded longitudinally. Tissue compatibility and side effects were evaluated using histochemistry.

RESULTS

The microsphere formulation led to measureable amounts of timolol in the aqueous humor and the tear film for up to 90 days. Timolol was not detectable in the serum at any time. A significant reduction of IOP was observed in treated eyes. Clinically, the subconjunctival administration of the microspheres was well tolerated with no signs of inflammation or infection. The absence of local inflammation was confirmed by histology.

CONCLUSIONS

A single subconjunctival administration of timolol microspheres achieved delivery and IOP reduction in rabbits for up to 90 days without local or systemic inflammation or toxicity. This approach has the potential to improve the management of glaucoma in patient populations, who are challenged to adhere to a regimen of daily eye drops.

Prolonged mydriasis after inadvertent topical administration of the calcium channel antagonist amlodipine: implications for glaucoma drug development

CONTEXT

Calcium channel inhibitors are being investigated as potential therapeutic adjuncts to reduce painful ciliary muscle spasm and control intraocular pressure in glaucoma. Relatively little is known about the effect of topical administration of calcium channel blockers in humans.

OBJECTIVE

(1) To describe prolonged fixed pupil dilation resulting from exposure to topical amlodipine (2) to review the evidence that links calcium channel blockers with mydriasis and (3) to discuss the implications for glaucoma pharmacotherapy.

DESIGN

Single interventional case report, literature review (including human and animal studies) and analysis of reported adverse drug reactions (ADRs) records in the USA and UK.

CASE

A 35-year-old female doctor presented to eye casualty with blurred vision and bilateral, fixed, dilated pupils. A history of exposure to liquid amlodipine while preparing a paediatric chemotherapy regimen for a neuroblastoma patient was elicited. The patient was reassured and observed.

RESULTS

Pupil function returned to normal within 48 h. A multi-national review of adverse drug reactions reports was conducted, as well as an extensive literature search for case reports and experimental studies. To the authors' knowledge this is the first report of amlodipine causing mydriasis and we discuss the potential molecular mechanism.

CONCLUSIONS

This case is the first to suggest that calcium channel blockers can cause prolonged mydriasis. These agents have been investigated as potential adjuncts in glaucoma therapy. As accidental topical exposure to amlodipine can cause prolonged pupil dilation, it could precipitate angle closure in predisposed patients.

Development of eye drops containing antihypertensive drugs: formulation of aqueous irbesartan/γCD eye drops

Aqueous nanoparticulated eye drop formulations based on γ-cyclodextrin (γCD) complexes were developed and tested in vitro. Three antihypertensive drugs, i.e. enalapril maleate, irbesartan and verapamil HCl, that have been shown to possess IOP-lowering activity were selected for this study. All three drugs displayed Bs-type phase-solubility diagrams in aqueous γCD solutions and had relatively low affinity for γCD. Irbesartan was selected for further formulation development. The drug was relatively stable at pH 4.5 but somewhat less stable at physiologic pH. However, presence of γCD in the aqueous media enhanced the chemical stability of irbesartan. Aqueous γCD-based eye drop formulations containing 1% and 2% (w/v) irbesartan were prepared and the effect of pH on the particles size distribution and drug release investigated. Only ∼2% of the drug was in solution in the pH 4.5 formulations but up to 45% in the pH 7 formulations. The pH 7 formulations, where larger fraction of the drug was in solution, displayed somewhat greater drug permeation flux but much lower drug permeation coefficients than the pH 4.5 formulations. Dynamic light scattering studies indicated the faster permeation was due to formation of smaller particles in presence tyloxapol.

Effect of Topical Calcium Channel Blockers on Intraocular Pressure in Steroid-induced Glaucoma

Purpose: To evaluate the effect of 0.125% verapamil and 0.5% diltiazem eye drops on intraocular pressure (IOP) in steroid-induced glaucoma in rabbit eyes.

Methods: A total of 18 rabbits with steroid-induced glaucoma were divided into three groups (A, B and C; n = 6 each). Right eyes in groups A, B and C received 0.5% diltiazem, 0.125% verapamil and 0.5% timolol eye drops twice daily for 12 days, respectively; whereas, left eyes received distilled water. IOP was measured with Tono-pen XL at baseline, day 4, day 8, and day 12 of treatment.

Results: Both 0.5% diltiazem and 0.125% verapamil eye drops significantly reduced IOP compared to control eyes (p < 0.05). Reduction of IOP by 0.5% diltiazem, 0.125% verapamil eye drops were comparable to 0.5% timolol. No surface toxicity or systemic side effects were noted during the study period.

Conclusion: Calcium channel blockers, verapamil, and diltia-zem significantly reduced IOP in rabbiteyes. This group of drugs may have a potential role in treatment of glaucoma

How to cite this article: Ganekal S, Dorairaj S, Jhanji V, Kudlu K. Effect of Topical Calcium Channel Blockers on Intraocular Pressure in Steroid-induced Glaucoma. J Current Glau Prac 2014;8(1):15-19.

Thioredoxin interacting protein is a novel mediator of retinal inflammation and neurotoxicity

BACKGROUND AND PURPOSE

Up-regulation of thioredoxin interacting protein (TXNIP), an endogenous inhibitor of thioredoxin (Trx), compromises cellular antioxidant and anti-apoptotic defences and stimulates pro-inflammatory cytokines expression, implying a role for TXNIP in apoptosis. Here we have examined the causal role of TXNIP expression in mediating retinal neurotoxicity and assessed the neuroprotective actions of verapamil, a calcium channel blocker and an inhibitor of TXNIP expression.

EXPERIMENTAL APPROACH

Retinal neurotoxicity was induced by intravitreal injection of NMDA in Sprague-Dawley rats, which received verapamil (10 mg·kg(-1), p.o.) or vehicle. Neurotoxicity was examined by terminal dUTP nick-end labelling assay and ganglion cell count. Expression of TXNIP, apoptosis signal-regulating kinase 1 (ASK-1), NF-κB, p38 MAPK, JNK, cleaved poly-ADP-ribose polymerase (PARP), caspase-3, nitrotyrosine and 4-hydroxy-nonenal were examined by Western and slot-blot analysis. Release of TNF-α and IL-1β was examined by elisa.

KEY RESULTS

NMDA injection enhanced TXNIP expression, decreased Trx activity, causing increased oxidative stress, glial activation and release of TNF-α and IL-1β. Enhanced TXNIP expression disrupted Trx/ASK-1 inhibitory complex leading to release of ASK-1 and activation of the pro-apoptotic p38 MAPK/JNK pathway, as indicated by cleaved PARP and caspase-3 expression. Treatment with verapamil blocked these effects.

CONCLUSION AND IMPLICATIONS

Elevated TXNIP expression contributed to retinal neurotoxicity by three different mechanisms, inducing release of inflammatory mediators such as TNF-α and IL-1β, altering antioxidant status and disrupting the Trx-ASK-1 inhibitory complex leading to activation of the p38 MAPK/JNK apoptotic pathway. Targeting TXNIP expression is a potential therapeutic target for retinal neurodegenerative disease.