What is Aprotinin?
Aprotinin is a protein that is obtained and purified from cow's lungs. It has been used in medicine for many years as a drug in heart surgery, and is available in Australia under the brand name TRASYLOL. Recent research papers from Europe have studied the role of Aprotinin in treating chronic tendon injuries. (view Translated article from J Clinic Pharm (French) and Aprotinin, corticosteroids and normosaline in the management of patellar tendinopathy in athletes: a prospective randomized study (Capasso et al, Sports Exercise & Injury 1997, 3: 111-115, scanned .pdf - large file) and Preliminary results with peritendinous protease inhibitor injections in the management of Achilles tendinitis (Capasso et al., J Sports Traumatol Rel Res 1993, 15: 37-43, scanned .pdf - large file) )
How are tendon injuries treated?
Tendon injuries (or tendonitis, tendinosis or tendinopathy) have been traditionally treated in three stages according to severity: (1) initially, graded strengthening exercises under the supervision of a physiotherapist; (2) cortisone injections to the outside of the tendon; (3) surgery to remove damaged portions of the tendon and repair any ruptures. The problem with this management plan has been the lack of success of cortisone injections and surgery, in many cases (although they have been successful in others).
How do cortisone injections work?
Cortisone is a powerful anti-inflammatory drug, related to the anti-inflammatory tablets that are often used in sports medicine (like Voltaren, Naprosyn etc.) Inflammation is the means by which tendon injuries become painful and swollen. Cortisone injections are generally very good at making tendon injuries less painful and swollen in the first 1-2 weeks after injection. The two major problems they have is that the effects often quickly wear off and there is a small risk of tendon rupture after the injection. The risk of rupture is particularly relevant for big tendons like the achilles tendon that have no other tendons nearby to help with their job if they snap. Cortisone injections still have a role in the treatment of tendon injuries, but there is a need for alternatives in patients where they fail, or who are unwilling to take the risk of tendon rupture.
How does aprotinin work?
Aprotinin inhibits (stops) some of the enzymes in the body that break down protein, including tendon substance. Therefore, in theory, it might be able to reverse some of the tendon damage in a chronic tendon disor der. A recent European study of patella tendonitis has been published (see below) that showed aprotinin injections had a better success rate than patients who were injected with cortisone or a placebo (in the same study). Aprotinin may also work as an irritant substance (this type of injection is called 'prolotherapy') stimulating the body to produce more healing.
Are there any side effects?
The major side effect (approximately 1 in 500 people on the first injection but 1 in 30 if multiple injections are given within six weeks) is allergic reaction to the drug. Minor allergies give redness around the injection site and itching. It is possible to have an anaphylactic (major allergic reaction) to the drug. It would be expected that the risk of tendon rupture after aprotinin injection would be less than after cortisone injection, but for all patients with a tendon injury there is a small risk of tendon rupture with continued activity. Systemic allergic reaction (rash) to Aprotinin injection
How many injections will I need?
The patients in published studies have one to four injections, spaced a few weeks apart. Multiple injections must trade-off risk of allergy versus chance for further improvement, so single injections are safer. It would be best to avoid sport or train lightly for 5 days after an injection as a general precaution, although there is less concern about training soon after an Aprotinin injection than a cortisone injection. Aprotinin is mixed with local anaesthetic, which will numb the area for about 2 hours.
