Are there any side effects to treatment with clotting factors?
Because clotting factors are manufactured forms of natural body substances, there are very few side effects compared to drugs you may take for other medical conditions. Clotting factors used to be only made from human blood and then there was a risk of picking up an infection from the donors’ blood, such as hepatitis or HIV. In the 80s, donor screening as well as techniques for treated plasma-derived clotting factors such as dry heat, solvent-detergent treatment, and pasteurisation vastly reduced this risk. Starting in the late 90s, most patients in the UK now use clotting factors made in the lab, without the need for human
The most common problem is pain at the injection site when having the treatment.
There are a couple of ways of helping children to cope. One is putting anaesthetic cream on the injection site about half an hour before giving the treatment.36 This numbs the area so they are less likely to find the needle going in painful, but they can still find having the injection upsetting. Another is to put in a central venous access device often called a ‘port’. This is a device that sits just under the skin that you inject into.32 The needle still has to go through the skin, but it’s less painful. The port connects to a vein inside the body so the treatment can still get straight into your blood. There can be problems with venous access devices. They can become infected or blocked and then have to be taken out.32
Some people with haemophilia develop a strong dislike of injecting and prefer to only treat if they have a bleed rather than have preventative factor (prophylaxis – pronounced prof-ill-ax-iss). This means they will have fewer injections. But it also means they are more at risk of painful bleeds into joints and muscles.25 Over years, joints can become seriously damaged by the bleeds, causing pain and disability.25, 36
Having repeated injections over a lifetime can cause problems with veins. People with haemophilia are advised to vary their injection sites. Even so, though some veins become unusable most people with haemophilia become very good at finding usable veins.
The most serious side effect of treatment with clotting factors is the development of inhibitors.37 These are antibodies to the clotting factor and mean your immune system is reacting against it.38 About 3 in every 10 people with haemophilia A develop inhibitors at some point.37 It is much rarer in haemophilia B, with about 3 in every 100 people developing them.37 Developing inhibitors is serious because it means that controlling bleeding is much more difficult.38 People with inhibitors may have bleeding controlled with a treatment called activated prothrombin complex concentrate or another clotting factor called VIIa (7a).26,29
There is treatment to get rid of inhibitors. It involves having larger and more frequent infusions of clotting factor to get your immune system to learn to tolerate it again.39 This is called Immune Tolerance Induction. This is effective in about 2 out of every 3 people who develop inhibitors.29 There is now a newer treatment available called emicizumab (pronounced em-ih-siz-oo-mab),.29 This is an injection under the skin that you have once a week. It works by bypassing factor VIII (8) in blood clotting and so controls bleeding.29