Sodium fluoride is used in medical treatment of otosclerosis. Its mechanism is:

• A Inhibits osteoclast activity by blocking carbonic anhydrase in foci of active otosclerosis
• B Converts hydroxyapatite to fluorapatite, inhibiting enzymatic activation of otospongiotic foci and slowing remodelling ✓
• C Competitively inhibits collagenase, preventing matrix metalloproteinase activity in enchondral bone
• D Acts as calcium chelator, reducing calcium deposition in the stapes footplate

Explanation

Sodium fluoride, used as medical management of otosclerosis (0.5–1 mg/kg/day, usually 20–40 mg daily), acts by incorporating into bone apatite crystals, converting hydroxyapatite to the harder, more stable fluorapatite. This stabilises the spongiotic foci by reducing enzyme activity (particularly alkaline phosphatase and proteases) responsible for bone resorption, and reduces active bone remodelling. It may slow the progression of sensorineural hearing loss in cochlear otosclerosis. Bisphosphonates may also be used. Surgical stapedectomy remains definitive for conductive component.

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

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Written and medically reviewed by the StethoPrep medical team.