Chemistry of loteprednol etabonate and related steroids. II. Reactions at ring C and NMR structural studies of the resulting compounds

Synthesis and Physicochemical Characterization of the Process-Related Impurities of Eplerenone, an Antihypertensive Drug

Two unknown impurities were observed during the process development for multigram-scale synthesis of eplerenone (Inspra^®). The new process-related impurities were identified and fully characterized as the corresponding (7β,11α,17α)-11-hydroxy- and (7α,11β,17α)-9,11-dichloroeplerenone derivatives 12a and 13. Seven other known but poorly described in the literature eplerenone impurities, including four impurities A, B, C and E listed in the European Pharmacopoeia 8.4 were also detected, identified and fully characterized. All these contaminants result from side reactions taking place on the steroid ring C of the starting 11α-hydroxy-7α-(methoxycarbonyl)-3-oxo-17α-pregn-4-ene-21,17-carbolactone (12) and the key intermediate (7α,17α)-9(11)-enester 7, including epimerization of the C-7 asymmetric center, oxidation, dehydration, chlorination and lactonization. The impurities were isolated and/or synthesized and fully characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrometry/electrospray ionization (HRMS/ESI). Their ¹H- and ¹³C-NMR signals were fully assigned. The molecular structures of the eight impurities, including the new (7β,11α,17α)-11-hydroxy- and (7α,11β,17α)-9,11-dichloroeplerenone related substances 12a and 13, were solved and refined using single-crystal X-ray diffraction (SCXRD). The full identification and characterization of these impurities should be useful for the quality control and the validation of the analytical methods in the manufacture of eplerenone.

Critical appraisal of loteprednol ointment, gel, and suspension in the treatment of postoperative inflammation and pain following ocular and corneal transplant surgery

Purpose

To review comprehensively the available peer-reviewed published articles in the literature on loteprednol suspension, gel, and ointment in the treatment of ocular inflammation and pain following ocular surgery.

Methods

We conducted a PubMed literature search review of all published articles on keywords associated with loteprednol etabonate and ocular surgery.

Results

A total of 59 peer-reviewed articles were found in the literature. The focus of the majority of the articles was on the safety and efficacy of loteprednol etabonate 0.5% in postoperative control of inflammation and pain following cataract surgery. There were only three articles with a remote association between loteprednol etabonate and keratoplasty.

Conclusion

Lotemax® ointment may also have potential as a first-line anti-inflammatory agent of choice in postoperative settings of strabismus and penetrating glaucoma, and following low-risk penetrating keratoplasty procedures.