Plateau iris is a less common medical condition of the eye resulting from anterior displacement of the peripheral iris by the ciliary body causing angle closure glaucoma. First line treatment for all causes of narrow angle glaucoma is laser iridotomy. If narrow angle glaucoma persists after iridotomy then it is called plateau iris syndrome and subsequently managed either medically (miotics) or surgically (laser peripheral iridoplasty). Plateau iris is a less common form of narrow angle glaucoma and is sometimes discovered after an iridotomy causes a rapid increase in eye pressure. Since this condition is not common, most ophthalmologists are unfamiliar with, and have little experience with, the anatomy of and treatments for this condition. References
Further reading
Wand, M; Grant, WM; Simmons, RJ; Hutchinson, BT (January 1977). "Plateau iris syndrome". Transactions. Section on Ophthalmology. American Academy of Ophthalmology and Otolaryngology. 83 (1): 122–130. PMID 898466. NAID 10029605696. Pavlin, Charles J.; Ritch, Robert; Foster, F. Stuart (April 1992). "Ultrasound Biomicroscopy in Plateau Iris Syndrome". American Journal of Ophthalmology. 113 (4): 390–395. doi:10.1016/s0002-9394(14)76160-4. PMID 1558112. Ritch, Robert (April 1992). "Plateau Iris Is Caused by Abnormally Positioned Ciliary Processes". Journal of Glaucoma. 1 (1): 23–26. doi:10.1097/00061198-199204000-00006. S2CID 72047734. Diniz Filho, Alberto; Cronemberger, Sebastião; Mérula, Rafael Vidal; Calixto, Nassim (October 2008). "Plateau iris". Arquivos Brasileiros de Oftalmologia. 71 (5): 752–758. doi:10.1590/S0004-27492008000500029. PMID 19039479. Ritch, Robert; Tham, Clement C.Y; Lam, Dennis S.C (January 2004). "Long-term success of argon laser peripheral iridoplasty in the management of plateau iris syndrome". Ophthalmology. 111 (1): 104–108. doi:10.1016/j.ophtha.2003.05.001. PMID 14711720.
A similar antihistamine, brompheniramine, led to the discovery of the selective serotonin reuptake inhibitor (SSRI) zimelidine.A study found that dexchlorphenamine had Ki values for the human cloned H1 receptor of 2.67 to 4.81 nM while levchlorphenamine had Ki values of 211 to 361 nM for this receptor, indicating that dexchlorphenamine is the active enantiomer. Another study found that dexchlorphenamine had a Ki value of 20 to 30 μM for the muscarinic acetylcholine receptor using rat brain tissue while levchlorphenamine had a Ki value of 40 to 50 μM for this receptor, indicating that both enantiomers have very low affinity for it. Pharmacokinetics
The elimination half-life of chlorphenamine has variously ranged between 13.9 and 43.4 hours in adults following a single dose in clinical studies. Chemistry
Chlorphenamine is an alkylamine and is a part of a series of antihistamines including pheniramine (Naphcon) and its halogenated derivatives including fluorpheniramine, dexchlorphenamine (Polaramine), brompheniramine (Dimetapp), dexbrompheniramine (Drixoral), deschlorpheniramine, and iodopheniramine. The halogenated alkylamine antihistamines all exhibit optical isomerism, and chlorphenamine in the indicated products is racemic chlorphenamine maleate, whereas dexchlorphenamine is the dextrorotary stereoisomer. Synthesis
There are several patented methods for the synthesis of chlorphenamine. In one example, 4-chlorophenylacetonitrile is reacted with 2-chloropyridine in the presence of sodium amide to form 4-chlorophenyl(2-pyridyl)acetonitrile. Alkylating this with 2-dimethylaminoethylchloride in the presence of sodium amide gives γ-(4-chlorphenyl)-γ-cyano-N,N-dimethyl-2-pyridinepropanamine, the hydrolysis and decarboxylation of which lead to chlorphenamine. A second method boom starts from pyridine, which undergoes alkylation by 4-chlorophenylacetonitrile, giving 2-(4-chlorobenzyl)pyridine. Alkylating this with 2-dimethylaminoethylchloride in the presence of sodium amide gives chlorphenamine.