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# Hyaluronic Acid ## Overview Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan found in connective, epithelial, and neural tissues. Therapeutically, it is used as a visco-supplement in joints, an ocular lubricant, and a topical humectant. It acts by restoring elasticity and viscosity to synovial fluid, providing mechanical cushioning and anti-inflammatory properties. ## Primary Indications * **Osteoarthritis:** Management of pain in osteoarthritis (OA) of the knee, hip, or shoulder in patients who have failed conservative non-pharmacologic therapy and simple analgesics. * **Ophthalmology:** Dry eye syndrome. * **Dermatology:** Wound healing and skin hydration. ## Adult Dosing * **Intra-articular (Knee OA):** * *Sodium Hyaluronate (e.g., Hyalgan):* 20 mg (2 mL) weekly for 5 weeks. * *Hylan G-F 20 (e.g., Synvisc):* 16 mg (2 mL) weekly for 3 weeks. * *Hylan G-F 20 (e.g., Synvisc-One):* 48 mg (6 mL) once as a single dose. * **Ophthalmic:** 0.1% to 0.3% solution; 1–2 drops in the affected eye(s) as needed. * *Note:* Specific dosing regimens (frequency and product concentration) vary significantly by brand and local institutional protocol. ## Pediatric Dosing Safety and efficacy in pediatric populations are not well-established. Use is generally off-label and limited to specialized rheumatologic care. Dosage should be determined by a pediatric rheumatologist. ## Dose Adjustments * **Renal/Hepatic Impairment:** No specific adjustments required, as HA is localized and subjected to minimal systemic absorption. * **Geriatric:** No specific adjustments required; caution in patients with history of local infection or severe joint effusion. ## Contraindications * Known hypersensitivity to hyaluronan preparations. * Active joint infection (septic arthritis). * Active skin disease or infection in the area of the injection site. * Known hypersensitivity to avian proteins (for products derived from avian sources). ## Adverse Effects * **Common:** Injection site pain, swelling, erythema, pruritus, transient joint effusion, and arthralgia. * **Serious:** Pseudoseptic reaction (acute inflammatory response requiring rule-out of bacterial infection), anaphylactoid reactions. * **Ocular:** Blurred vision, stinging, or redness (rare). ## Key Drug Interactions * **Disinfectants:** Do not use quaternary ammonium salts (e.g., benzalkonium chloride) for skin preparation prior to intra-articular injection, as hyaluronan can precipitate in their presence. ## Monitoring * **Joint Injection:** Monitor for severe pain or increased joint swelling post-injection to rule out septic arthritis. * **Ocular:** Monitor for persistent irritation or changes in visual acuity. ## Clinical Pearls * **Efficacy:** HA is generally considered a second- or third-line treatment for OA; clinical response may take several weeks. * **Injection Technique:** Strict aseptic technique is mandatory during intra-articular administration to prevent iatrogenic septic arthritis. * **Aspiration:** Always aspirate joint effusion prior to injection if present. * **Patient Counseling:** Instruct patients to avoid strenuous weight-bearing activities for 48 hours following knee injection. *** *Disclaimer: This information is for educational purposes only. Drug dosing, contraindications, and availability can change. Always verify current prescribing information through official FDA labels or institutional clinical decision support systems before administration.*