Normally, carbonic anhydrase converts carbonic acid (H2CO3) into bicarbonate (HCO3), releasing a proton (H+) into solution. The H+ is then exchanged for  sodium (Na+) ions, which facilitates the production of aqueous humor. By blocking the function of carbonic anhydrase, the Na+/H+ exchange is unable to occur, which leads to a decrease in Na+ in the cell and prevents aqueous humor production. History
This drug, developed by Merck, was the first drug in human therapy (market introduction 1995) that resulted from structure-based drug design. It was developed to circumvent the systemic side effects of acetazolamide which has to be taken orally. References
Further reading
Kubinyi H (1999). "Chance favors the prepared mind--from serendipity to rational drug design". J Recept Signal Transduct Res. 19 (1–4): 15–39. doi:10.3109/10799899909036635. PMID 10071748. Plummer C, MacKay E, Gelatt K (2006). "Comparison of the effects of topical administration of a fixed combination of dorzolamide-timolol to monotherapy with timolol or dorzolamide on IOP, pupil size, and heart rate in glaucomatous dogs". Veterinary Ophthalmology. 9 (4): 245–9. doi:10.1111/j.1463-5224.2006.00469.x. PMID 16771760. Grover S, Apushkin M, Fishman G (2006). "Topical dorzolamide for the treatment of cystoid macular edema in patients with retinitis pigmentosa". Am J Ophthalmol. 141 (5): 850–8. doi:10.1016/j.ajo.2005.12.030. PMID 16546110. Almeida G, Faria e Souza S (2006). "Effect of topical dorzolamide on rabbit central corneal thickness". Braz J Med Biol Res. 39 (2): 277–81. doi:10.1590/S0100-879X2006000200015. PMID 16470316.
According to Kastens review published in the Mayo Clinic Proceedings, a serum concentration of more than 50 μg/mL is a warning sign, while Hammett-Stabler and John states that the common therapeutics peak level is 10-20 μg/mL and is expected to achieve after 0.5-1.5 hours of intravenous administration in their review of antimicrobial drugs. The common onset of signs and symptoms are 2 to 9 days after the initiation of the medication, which allows the serum concentration to build up to reach the toxic concentration above. Common signs and symptoms include loss of appetite, fussiness, vomiting, ashen gray color of the skin, hypotension (low blood pressure), cyanosis (blue discoloration of lips and skin), hypothermia, cardiovascular collapse, hypotonia (muscle stiffness), abdominal distension, irregular respiration, and increased blood lactate. Pathophysiology
Two pathophysiologic mechanisms are thought to play a role in the development of gray baby syndrome after exposure to chloramphenicol. This condition is due to a lack of glucuronidation reactions occurring in the baby (phase II hepatic metabolism), thus leading to an accumulation of toxic chloramphenicol metabolites:
Metabolism: The UDP-glucuronyl transferase enzyme system in infants, especially premature infants, is not fully developed and incapable of metabolizing the excessive drug load needed to excrete chloramphenicol. Elimination: Insufficient renal excretion of the unconjugated drug.Insufficient metabolism and excretion of chloramphenicol leads to increased blood concentrations of the drug, causing blockade of the electron transport of the liver, myocardium, and skeletal muscles. Since the electron transport is an essential part of cellular respiration, its blockade can result in cell damage.