Effects of Adrenergic Agents on Alpha-Chymotrypsin-Induced Ocular Hypertension in Albino and Pigmented Rabbits: A Comparative Study

Abstract

Mplia-chyirotrypsiji-irKïuced ocular hypertension in albino rabbits is widely used as an experimental model to screen potential antiglaucoma drugs. The present study compares the intraocular pressure (IOP) response following the ocular application of single or repeated adrenergic agents in conscious albino and pigmented rabbits. A single instillation of clonidine was not as effective in lowering the IOP in pigmented hypertensive rabbit eyes as in albino hypertensive eyes. Similarly, betaxolol moderately lowered the IOP in albino rabbits but induced a slight response when pigmented rabbits were used as an experimental model.Twice-a-day applications of betaxolol in pigmented hypertensive eyes permitted an identical level of IOP decrease to be reached, as observed in a oneday study in albino rabbits, after at least 6 days of treatment. It has been suggested that the pigmented layers of the iris-ciliary body may act as sites for topically applied antiglaucoma drugs. Non-specific binding could explain in part the frequent discrepancy observed between the preclinical results obtained in albino hypertensive rabbit eyes and clinical results obtained in glaucomatous human eyes.

Brimonidine Tartrate–Eudragit Long-Acting Nanoparticles: Formulation, Optimization, In Vitro and In Vivo Evaluation

“…Eudragit-based nanoparticles controlled the release of drug (in vitro) and reduced IOP for up to 72 h [BENP-1:1(150)] showing a significant increase in both extent and duration of IOP reduction. As the study was carried out on rabbits after glaucoma induction, the results can be extrapolated to humans as this model is shown to be identical to human glaucoma (38,39). The obtained results shows that the developed nanoparticle formulations have potential in improving BRT delivery to the eye in treating glaucoma and can potentially increase patient compliance by reducing the frequency of administration.…”

“…This model has been found suitable for the studies involving comparison of drug effects on IOP reduction and can thus be extrapolated into human glaucoma (38,39). Both the test product (designed nanoparticle dispersions) and reference conventional eyedrop solution was administered only once to obtain relative comparison between single- n Release exponent indicator of drug release mechanism; t 20% , t 50% , and t 90% time taken (in h) for 20%, 50% and 90% drug release, respectively The Eudragit RS100-and Eudragit RL100-based nanoparticle formulations with improved in vitro characteristics (BENP-D30, BENP-IP4, BENP-PF20 and BENP-1:1(150)) were selected for in vivo studies.…”

Sustained release ocular inserts of brimonidine tartrate for better treatment in open-angle glaucoma

“…As the study was performed on glaucomatous Each data point represents the average of two batches in triplicate with standard deviation rabbits, where an elevation in IOP was brought about, the results can be extrapolated to humans, as this model is shown to be identical to human glaucoma [23,24]. The duration of IOP-lowering effect was shown to be prolonged for 24 h; thus, better patient compliance can be achieved by reducing the frequency of BRT administration.…”

“…This model has been found suitable for the studies involving comparison of effect of drugs on IOP reduction and can thus be extrapolated into human glaucoma [23,24]. Two animals that developed severe topical inflammation were excluded from the study.…”

Comparative Effects of Alpha-2 and DA-2 Agonists on Intraocular Pressure in Pigmented and Nonpigmented Rabbits

“…However, the Dutch Belted (pigmented) rabbits have also been used less frequently due, in part, to the fact that they are less responsive than their albino counterparts (4). Many adrenergic drugs have been screened using these animal models and have been demonstrated to lower IOP in both albino and pigmented rabbits (4). Although most ocular antihypertensive drugs are tested initially in the albino rabbits, these drugs are, however, intended for clinical use in pigmented human eyes.…”