Azathioprine is one of a series of drugs called "immunosuppressives". This means that they alter the way in which the immune system is working in various forms of arthritis. It is not a painkiller.
WHAT DOES AZATHIOPRINE DO ?
Azathioprine alters the way in which diseases such as rheumatoid arthritis affect the joints by altering the function of the immune system. Azathioprine can decrease the numbers and activity of the cells lining the joint which are responsible for attracting white blood cells from the circulation into the effected joint. This means that there will be fewer white blood cells present inside the joint which produce the chemicals that cause pain, joint swelling and damage to the cartilage and bone inside the joints.
HOW DO I TAKE AZATHIOPRINE ?
Azathioprine is available in tablets of either 25 or 50 mg. These should be taken with a meal to reduce stomach upsets. It may be prescribed as a single dose or to be taken twice a day. Usually the starting dose will be between 50 to 100mg per day. The maintenance dose for most people is between 100-200mg per day depending on how well the disease is controlled.
WILL MY ARTHRITIS GET BETTER ?
Most patients starting azathioprine respond quite well, with many patients improving quite dramatically. Some patients may even go into a "remission", where the arthritis virtually disappears. A minority of people do not respond well to azathioprine and in this case, it is sometimes helpful to continue on a little longer with a higher daily dose.
HOW LONG WILL IT TAKE TO WORK
Usually it takes between 8 to 12 weeks before you will notice any improvement in your arthritis. This doesn't mean that azathioprine won't work so do not get discouraged !!. Often you will be given other medications when you start azathioprine so that you will improve more quickly. If it is effective, treatment may be continued for months or even years.
ARE THERE ANY SIDE EFFECTS ?
As with all medications, there is a potential for side effects to occur. The most common side effect is nausea which is less frequent if azathioprine is taken with food. Itchy rashes, a sore mouth or throat and mouth ulcers may occur. Sometimes the liver may be irritated by azathioprine which causes abnormal blood tests, but this very rarely causes any symptoms.
There are some potentially serious side effects with azathioprine, mainly concerning the blood count. Azathioprine can cause a drop in the numbers of white blood cells which are needed to fight infection. Because your doctor monitors your blood count very closely, it is unusual for this to be a serious problem. Also, azathioprine can decrease the numbers of cells called platelets in the blood, but again it is rare for this to actually cause problems. If however you develop mouth ulcers, easy bruising, nosebleeds or bleeding gums, your doctor needs to know about this straight away.
Because the immune system may be depressed, you should avoid contact with people with infectious diseases such as chicken pox and consult with your doctor before having any vaccinations.
As the skin may become more sensitive to the sun's harmful rays you should avoid excessive exposure. Wear a hat and sunscreen when outside in the sun.
HOW OFTEN DO I NEED TO HAVE MY BLOOD COUNTS TESTED ?
Azathioprine may effect the blood count and the liver, so blood tests will be necessary every 2 weeks for the first 8 weeks of treatment and monthly after this. This makes giving azathioprine as safe as possible.
DO ANY OTHER MEDICATIONS INTERFERE WITH AZATHIOPRINE
Generally there are no drugs that make a side effect more likely or which interact with azathioprine, particularly most anti-inflammatory tablets or painkillers. However, certain medications (allopurinol) which are used in the treatment of gout may elevate the level of azathioprine in the blood and these are best avoided or the dose modified.
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