Gel-forming solutions

Topical P-blockers are typically administered twice daily. A gel-forming solution of timolol (Timoptic-XE) can be administered once daily. Tachyphylaxis may occur in 20% to 50% of patients on monotherapy with a P-blocker, resulting in the need for a different agent or combination therapy. Patients on concurrent systemic P-blockers may experience less IOP reduction than patients only on topical P-blockers.10,38... 

Other quaternary ammonium germicides, ben-zethonium chloride and benzalkonium bromide, have been used in several ophthalmic solutions. While these have the advantage of not being a chemical mixture, they do not possess the bactericidal effectiveness of benzalkonium chloride and are subject to the same incompatibility limitations. In addition, the maximum concentration for benzethonium chloride is 0.01%. Several new products that form gels in the eye, like Timolol Gel Forming Solution and Timoptic-XE, employ another quaternary preservative, BDAB, in the formulation. 

Gel-Forming Solutions. One disadvantage of solutions is their relatively short residence time in the eye. This has been overcome to some degree by the development of solutions that are liquid in the container and thus can be instilled as eyedrops but gel on contact with the tear fluid and provide increased contact time with the possibility of improved drug absorption and increased duration of therapeutic effect. 

Shedden, A., Laurence, I, and Tipping, R. (2001), Efficacy and tolerability of timolol maleate ophthalmic gel-forming solution versus timolol ophthalmic solution in adults with open-angle glaucoma or ocular hypertension A six-month, double-masked, multicenter study, Clin. Then, 23(3), 440 150. 

Schenker, H. I., and Silver, L. H. (2000), Long-term intraocular pressure-lowering efficacy and safety of timolol maleate gel-forming solution 0.5% compared with timoptic XE 0.5% in a 12-month study, Am. J. Ophthalmol., 130(2), 145-150. 

Shedden, A. H., Laurence, J., Barrish, A., and Olah, T. V. (2001), Plasma timolol concentrations of timolol maleate Timolol gel-forming solution (TIMOPTIC-XE) once daily versus timolol maleate ophthalmic solution twice daily, Doc. Ophthalmol., 103(1), 73-79. 

Topically administered ophthalmic preparations can affect visual acuity. Examples are lubricating gels and ointments for dry eye, antimicrobial ointments for ocular infections, and gel-forming solutions for glaucoma. Although acuity is only slightly reduced and is only temporary, this effect can be annoying to patients and may lead to noncompliance. 

Capillary tubes are filled to a height 60-80 mm by the capillarity of the acrylamide-gel-forming solution. The surface of the gel solution is carefully overlayed with water-saturated n-butanol by means of a 25 xL Hamilton microlitre syringe. Polymerization is achieved at room temperature in less than 60 min. A 10 mm high stacking gel can be added. The gel surface is then rinsed with the running buffer. 

Prepare the stacking-gel-forming solution (7= 3.75 per cent, C = 6.66 per cent) as follows mix one part of 7.5 per cent acrylamide solution with one part of catalyst-buffer solution. 

Pour off the n-butanol layer and rinse the tops of the gels with the stacking-gel-forming solution. 

Pour 10 mm of the stacking-gel-forming solution onto the tops of the separating gels and overlayer with n-butanol as above. 

Plager DA, Whitson JT, Netland PA, Vijaya L, Sathyan P, Sood D, Krishnadas SR, Robin AL, Gross RD, Scheib SA, Scott H, Dickerson JE. BETOPTIC S Pediatric Study Group. Betaxolol hydrochloride ophthalmic suspension 0.25% and timolol gel-forming solution 0.25% and 0.5% in pediatric glaucoma a randomized clinical trial J AAPOS 2009 13(4) 384-90. 

Comparative studies In 105 children who were treated with either betaxolol hydrochloride ophthalmic suspension 0.25% or timolol maleate ophthalmic gel-forming solution 0.25% and 0.5% after randomization, adverse events were mostly non-seri-ous and mild to moderate in intensity [26 ]. No patient stopped treatment because of adverse events, which were hyperemia of the eye, discomfort, irritation of the eye, discharge from the eye, lid margin crusting, pruritus of the eye, a sticky sensation, bradycardia, and hypotension. 

A bulb-combined glass electrode (Phoenix, USA) as weU as a flat surface combination electrode (Phoenix, USA) respectively connected to a pH meter (Consort P901, EGG), were used for pH measurement of gel-forming solutions or films after their equilibration at the corresponding relative humidity of interest, respectively (Burin Buera, 2002). Calibrations were carried out with standard buffers of pH 4.00 and 7.02. 

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