Synvisc is an injectable substance approved for the treatment of knee osteoarthritis in patients who have failed previous non-surgical treatments. It is made from hyaluronan, a complex carbohydrate, which is the main component of joint fluid. According to the Lancet, as the body ages, the production of hyaluronan and joint fluid decreases, causing cartilage wear and tear and osteoarthritis, or OA. In the United States, there are two available preparations of hyaluronan: sodium hyaluronate, which is hyaluronan in form of a salt preparation, and hylan G-F 20, or Synvisc.
About Synvisc
According to the Genzyme Corporation, Synvisc is a mixture composed of hylan A, hylan B, and salt water. Initially, hyaluronan molecules are extracted from the chicken combs, and then cross-linked to produce water-soluble hylan A. Water-insoluble hylan B is made by cross-linking hylan A molecules. Each 2 ml Synvisc injection contains 80 percent hylan A and 20 percent hylan B. Administration of Synvisc injection into a knee joint, once a week for a total of three injections, is thought to increase viscosity and the amount of joint fluid and improve the pain associated with OA.
Indications
Synvisc injection is approved by the Federal Drug Administration for treatment of the knee OA in patients who have failed non-pharmacologic therapy including weight loss and exercise, and pharmacologic therapy with over the counter pain medications, such as Tylenol and ibuprofen. Treatment of hip OA with Synvisc is not approved by the FDA. However, Synvisc hip injections are performed on a select group of patients with hip OA, especially if surgical management is not feasible. According to American Family Physician, current studies suggest there may be a subpopulation of patients with OA, such as those over 60 years of age, who would respond well to Synvisc therapy.
Contraindications
Synvisc should not be administered to patients with known allergies to feathers, eggs, and hyaluronan and its derivatives. Also, treatment with Synvisc injection is precluded in patients with inflammation or infection of the knee and poor circulation of venous blood or lymphatic fluid, according to Genzyme Corporation.
Benefits
According to the UpToDate review of multiple, independent clinical trials, administration of Synvisc knee injections showed minimal to no improvement in pain as compared to the placebo, which is salt water injections. In addition, there was no improvement in overall physical function. When Synvisc was compared to naproxen, a non-steroidal anti-inflammatory drug commonly used for pain control, there was no difference in pain relief between the two. There are conflicting results when Synvisc is compared to glucocorticoid knee injections, and further studies are needed to elucidate if Synvisc is superior to glucocorticoids in treatment of OA. A single study showed significant decrease in hip pain after Synvisc injection with temporary worsening of pain in 10 percent of patients.
Risks
After Synvisc injection, some patients may experience temporary increase in pain, stiffness and swelling, or may develop a joint effusion, hives, respiratory difficulties and facial swelling. The safety and effectiveness of Synvisc has not been established in children or pregnant women. In order to minimize side effects, patients should avoid strenuous and weight-bearing activities for 48 hours after the injection.
References
- "The Lancet"; Pathogenesis and Management of Pain in Osteoarthritis
- UpToDate; Pharmacologic Therapy of Osteoarthritis; Kenneth Kalunian M.D. et al.; May 2010
- "American Family Physician"; Intra-articular Hyaluronic Acid Injections for Knee Osteoarthritis; Dennis Wen M.D.; August 2000
- Genzyme Corporation; Synvisc Hylan G-F 20; March 2010
- "Journal of Managed Care Pharmacy"; Total Knee Replacement Delayed With Hylan G-F 20 Use in Patients With Grade IV Osteoarthritis; March 2007
