The intraocular pressure lowering efficacy of 0.5% timolol maleate versus 1% brinzolamide in cases of primary open angle glaucoma and ocular hypertension

Objectives: The aim of this study was to compare the intraocular pressure lowering efficacy of timolol maleate with brinzolamide in cases of primary open angle glaucoma and ocular hypertension. Methods and Materials: This prospective, open, randomized, parallel group, comparative study was conducted in patients coming to the Department Of Ophthalmology, Rajindra Hospital attached to Government Medical College, Patiala. 60 patients of POAG or ocular hypertension were selected. Patients were then randomized into two groups (group I, II) and received 0.5 % timolol maleate and 1% brinzolamide respectively. Effectiveness of the drugs was calculated in terms of mm Hg fall in mean intraocular pressure at the end of 3 months. The observations thus made in both groups were compared. Results: In group I the mean pre-treatment IOP, mean post-treatment IOP and mean reduction in IOP were 24.30 ± 0.99, 18.53 ± 1.22 and 5.77 (23.74%) for peak measurements, and 24.50 ± 1.08, 18.80 ± 1.22 and 5.70 (23.27%) for trough measurements. In group II the mean pre-treatment IOP, mean post-treatment IOP and mean reduction in IOP were 24.33 ± 0.96, 19.43 ± 1.14 and 4.90 (20.14%) for peak measurements, and 24.57 ± 0.97, 19.73 ± 1.11 and 4.84 (19.69%) for trough measurements. Conclusions: In conclusion, there was a statistically significant difference between the IOP lowering in the two groups with timolol maleate producing more reduction in IOP than brinzolamide. Key-words: Brinzolamide; Glaucoma; lOP; Ocular hypertension; POAG; Timolol. Access this article online Quick Response Code: Website: www.innovativepublication.com DOI: 10.5958/2395-1451.2015.00018.9 INTRODUCTION More than 67 million persons worldwide are affected by glaucoma, of which about 10% or 6.6 million are estimated to be blind. [1] According to National Survey on Blindness 20012002, prevalence of blindness in India is 1.1 %. The foremost cause of blindness in India being cataract, accounts for 62.6%, whereas glaucoma accounts for 5.8%. [2] Glaucomatous optic neuropathy is the common denominator to all forms of glaucoma and is derived from multiple risk factors of which raised IOP is the most important. [3] Primary open angle glaucoma is defined by 3 criteria which are an IOP consistently above 21 mmHg in at least on eye, an open, normal appearing anterior chamber angle with no apparent ocular or systemic abnormality that might account for elevated IOP, and typical glaucomatous visual field and/or optic nerve head damage. Ocular hypertension is defined as an intraocular pressure consistently above 21 mmHg in the absence of the other two criteria. [4] Since IOP is the only risk factor amenable to therapy, lowering of IOP is the treatment of choice to impede further neuronal damage. [5] Any medical or surgical treatment that controls the IOP will be an effective therapy for glaucoma. Medical treatment is the first therapeutic approach while surgery is reserved for cases that cannot be controlled by drugs. [6] Currently, there are five major classes of drugs used for the treatment of glaucoma which are cholinergic agonists, alpha adrenergicreceptor agonist, beta adrenergicreceptor antagonists, topical and systemic carbonic anhydrase inhibitors and hypotensive lipids i.e. prostaglandin analogues and prostamides. [7] Timolol maleate is a non-selective 1β and 2β adrenergic antagonist that does not have substantial membranestabilizing properties and intrinsic sympathomimetic activity. β -adrenergic antagonists reduce IOP by decreasing aqueous humor formation without changing the outflow pathway. Timolol enters the eye rapidly; following topical administration, IOP begins to fall in 30–60 minutes, becomes lowest in 2 hours, and then in 24–48 hours, returns to normal. [8] Brinzolamide is a carbonic anhydrase inhibitor indicated in patients with ocular hypertension or openangle glaucoma for the treatment of elevated intraocular pressure. Pharmacologically, it is a highly specific, reversible, non-competitive and potent inhibitor of carbonic anhydrase II (CA-II) [9] , because of which it is Shray Dogra et al. The Intraocular Pressure Lowering Efficacy Of 0.5% Timolol Maleate Versus 1%... Indian Journal of Clinical and Experimental Ophthalmology, October – December 2015;1(4):223-227 224 able to suppress formation of aqueous humour and thus decrease IOP. Following topical administration, brinzolamide is absorbed into the systemic circulation where due to its affinity for CA-II, brinzolamide distributes extensively into the RBCs and exhibits a long half-life of approximately 111 days. MATERIALS AND METHODS In this prospective, open, randomized, parallel group, comparative study, 60 patients of POAG or ocular hypertension attending the Outpatient Department of Ophthalmology, Govt. Medical College, Patiala were included. Due permission from the ethical committee of the institute was obtained. The patients fulfilling the inclusion criteria and having none of the exclusion criteria were enrolled in the study after obtaining written informed consent. Patients of a minimum age of 18 years, having unilateral/bilateral primary open angle glaucoma/ ocular hypertension with an IOP > 21 mm Hg and </= 30 mm Hg were included in the study. Exclusion criteria for patients were history of acute angle closure glaucoma, established diagnosis of secondary glaucoma, closed anterior chamber angle, ocular inflammation, ocular infection, pregnant and lactating females, patient unable to attend follow up, known sensitivity to drug, chronic use of ocular medication other than the glaucoma medications and patients having any contraindication to the use of beta blockers and carbonic anhydrase inhibitors. Patients who were already on any other anti-glaucoma treatment were taken up for study after a washout period of 7 days for miotics and carbonic anhydrase inhibitors, 14 days for alpha and beta adrenergic agonists and 21 days for beta blockers, prostaglandin analogues and combination drugs. Patients requiring treatment for bilateral POAG were treated for both eyes but the right eye was the study eye. Patients selected were randomised into two groups of 30 each. Group I and Group II instilled 1 drop of timolol 0.5% and brinzolamide 1% respectively, into study eye twice daily at 9.00 a.m. and 9.00 p.m. for 12 weeks. During the study patients visited the hospital on day 0, week 4, week 8 and week 12. IOP readings were taken from the study eye with the Goldmann applanation tonometer at each visit. IOP was measured on day 0 at 9.00 a.m. and 11.00 a.m before administration of the study drugs to get the baseline IOP and then on each follow-up visit at 9.00 a.m. and 11.00 a.m. to record the peak and trough of each medication. Observations thus made were recorded and subjected to statistical analysis at the end of the study. Table-1: Sex Distribution of Patients in Group I and Group II Gender Group I Group II Total Timolol Maleate 0.5% Brinzolamide 1% No. of Patients %age No. of Patients %age No. of Patients %age Female 14 46.67% 11 36.67% 25 41.67% Male 16 53.33% 19 63.33% 35 58.33% Total 30 100% 30 100% 60 100% Table-2: Mean IOP in Group I and Group II at Different Points of Time