Dorzolamide hydrochloride (L671152 Hcl; MK507 Hcl) is an anti-glaucoma agent, which is a carbonic anhydrase inhibitor. Target: carbonic anhydrase (CA) Dorzolamide hydrochloride is a carbonic anhydrase inhibitor. It is an anti-glaucoma agent, and acts by decreasing the production of aqueous humour [1]. Glaucoma was induced in the right eye of adult Wistar rats by episcleral venous occlusion. One experimental group was administered dorzolamide hydrochloride 2%-timolol 0.5% combination eye drops, while the other experimental group was administered dorzolamide hydrochloride2% eye drops. Control groups had surgery without drug administration. Drug application was initiated either 2 weeks before surgery (Group A), from the day of surgery (Group B), 2 weeks after surgery (Group C), or 4 weeks after surgery (Group D). RGCs were labeled by intratectal Fluorogold injections and counted from flat-mount preparations, and IOP was measured using Tonopen. Both dorzolamide-timolol combination and dorzolamide hydrochloride, when applied topically, significantly reduced IOP and improved RGC densities in experimental eyes when compared to control eyes. Earlier initiation, as well as longer duration of drug application, resulted in higher RGC densities [2]. Clinical indications: Glaucoma; Ocular hypertension FDA Approved Date: 1995 Toxicity: Dizziness, headache, shortness of breath, slow heartbeat, severe asthma, cardiac arrest