Sodium fluoride is used as a medical treatment for otosclerosis. Its mechanism involves inhibition of which process in the otosclerotic focus?

• A Inhibits proteoglycan synthesis in enchondral bone, reducing abnormal remodeling
• B Inhibits measles virus replication, targeting the viral etiology
• C Competes with fluoride incorporated into enamel-like foci, stabilizing bone crystal
• D Inhibits lysosomal enzymes (acid phosphatase) in osteoclasts, reducing active bone resorption in the otosclerotic focus ✓

Explanation

Sodium fluoride slows progression of otosclerosis by converting hydroxyapatite to fluorapatite (more resistant to osteoclast resorption) and, more specifically, by inhibiting lysosomal acid phosphatase activity within osteoclasts of the active otosclerotic foci — reducing the vascular, resorptive phase (spongiosis) and thereby decreasing cochlear toxicity from released enzymes and inflammatory mediators. It does not improve existing hearing but slows progression of cochlear otosclerosis (sensorineural component). Bisphosphonates are alternative agents. The measles virus link to otosclerosis is pathogenic (viral antigen in foci) but fluoride's action is osteoclast-mediated, not antiviral.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.