Hyaluronidase
What is Hyaluronidase?
Hyaluronidase is an enzyme which breaks down the bonds between hyaluronic acid molecules. Many hyaluronic acid molecules link together in the connective tissue and scar tissue to form a structure, so by breaking these bonds it is easier for certain medication such as epidural steroid injections to reach targets which were previously blocked by scar tissue.
Hyaluronidase is naturally present in the body. It has a physiological role in the body as connective tissues are in the constant process of formation and breakdown.
Hyaluronidase is licensed for many uses in medicine like ophthalmic procedures, local anaesthetic blocks, to enhance the distribution of certain medication through the body, in certain cancer treatments and in cosmetic surgery.
The action of Hyaluronidase is temporary and unless it is injected in a blood vessel, its effects are restricted to the area of the injection.
Why do we give Hyaluronidase?
At the Royal Orthopaedic Hospital, a variety of back surgical procedures are offered. The majority of patients experience long term benefits after the procedures, both in terms of function and the improvement of symptoms. Some patients do however experience temporary or no resolution of symptoms after the procedures.
Epidural administration (giving medication via an injection into the epidural space in the spine) of local anaesthetics or steroids often provides some relief to these patients. The presence of scar tissue in the epidural space can prevent local anaesthetics and steroids from reaching their target areas in the epidural space.
Hyaluronidase is being suggested as part of your treatment because it can help to increase the absorption of local anaesthetics and steroids at their targets in the epidural space; it does this by temporarily breaking down a substance called hyaluronic acid which is found in scar tissue in the epidural space. Hyaluronidase can help to increase the success of epidural steroid medication however it is not essential.
What are the risks?
Hyaluronidase can rarely cause side effects such as local swelling and allergic reactions which affect less than 1 in 100 patients when used in normal doses.
In the past allergic responses were linked to impurities found in Hyaluronidase sourced from animals. However, these impurities have been eliminated through the use of recombinant DNA technology, and as such allergic reactions are now rare.
If you do experience any symptoms of an allergic reaction such as breathing difficulty, rapid pulse, swelling or profuse sweating then contact your doctor or nurse immediately.
Hyaluronidase in chronic pain
Due to there being a small research evidence base for the use of Hyaluronidase in chronic pain epidurals, its use in this case is classified as “unlicensed.”
Unlicensed use is when a medication is used in a condition for which it has not been officially approved. This may be due to the medication not having enough evidence for its use in a particular condition or the medication being given in a different dosage form to what it is licensed, for example as a liquid instead of a tablet. The unlicensed use of Hyaluronidase is routinely used in many chronic pain departments in the NHS.
In the small number of studies performed on epidural Hyaluronidase, the addition of Hyaluronidase to local anaesthetics and steroids offered improvement in symptoms for longer periods before the symptoms eventually started to come back.
The addition of Hyaluronidase to the local anaesthetics and steroids mixture for epidurals is not mandatory but recommended in some cases.
More information
If you have further questions on the unlicensed use of Hyaluronidase, please speak to your Pain Consultant who will be happy to further assist you in making your decision.