What are Immunomodulator medications
Immunomodulators are medications that weaken the body"s immune system. The immune system is composed of immune cells and the proteins that these cells produce. These cells and proteins serve to defend the body against harmful bacteria, viruses, fungi, and other foreign invaders. Activation of the immune system causes inflammation within the tissues where the activation occurs. (Inflammation is, in fact, an important mechanism to defend the body used by the immune system.) Normally, the immune system is activated only when the body is exposed to harmful invaders. In patients with Crohn"s disease and ulcerative colitis, however, the immune system is abnormally and chronically activated in the absence of any known invader. Immunomodulators decrease tissue inflammation by reducing the population of immune cells and/or by interfering with their production of proteins that promote immune activation and inflammation. Generally, the benefits of controlling moderate to severe ulcerative colitis outweigh the risks of infection due to weakened immunity. Examples of immunomodulators include azathioprine (Imuran), 6-mercaptopurine (6-MP, Purinethol), cyclosporine (Sandimmune), and methotrexate (Rheumatrex, Trexall).
Azathioprine (Imuran) and 6-MP (Purinethol)
Azathioprine and 6-mercaptopurine (6-MP) are medications that weaken the body"s immunity by reducing the population of a class of immune cells called lymphocytes. Azathioprine and 6-MP are related chemically. Specifically, azathioprine is converted into 6-MP inside the body. In high doses, these two drugs have been useful in preventing rejection of transplanted organs and in treating leukemia. In low doses, they have been used for many years to treat patients with moderate to severe Crohn"s disease and ulcerative colitis.
Azathioprine and 6-MP are increasingly recognized by doctors as valuable drugs in treating Crohn"s disease and ulcerative colitis. Some 70% of patients with moderate to severe disease will benefit from these drugs. Because of the slow onset of action and the potential for side effects, however, 6-MP and azathioprine are used mainly in the following situations:
Ulcerative colitis and Crohn"s disease patients with severe disease not responding to corticosteroids.
Patients who are experiencing undesirable corticosteroid-related side effects.
Patients who are dependent on corticosteroids and are unable to discontinue them without developing relapses.
When azathioprine and 6-MP are added to corticosteroids in the treatment of ulcerative colitis patients who do not respond to corticosteroids alone, there may be an improved response or smaller doses and shorter courses of corticosteroids may be able to be used. Some patients can discontinue corticosteroids altogether without experiencing relapses. The ability to reduce corticosteroid requirements has earned 6-MP and azathioprine their reputation as "steroid-sparing" medications.
In ulcerative colitis patients with severe disease who suffer frequent relapses, 5-ASA may not be sufficient, and more potent azathioprine and 6-MP will be necessary to maintain remissions. In the doses used for treating ulcerative colitis and Crohn"s disease, the long-term side effects of azathioprine and 6-MP are less serious than long-term oral corticosteroids or repeated courses of oral corticosteroids.
What Are the Side Effects of 6-MP and Azathioprine?
Side effects of 6-MP and azathioprine include increased vulnerability to infections, inflammation of the liver (hepatitis) and pancreas, (pancreatitis), and bone marrow toxicity (interfering with the formation of cells that circulate in the blood).
The goal of treatment with 6-MP and azathioprine is to weaken the body"s immune system in order to decrease the intensity of inflammation in the intestines; however, weakening the immune system increases the vulnerability to infections. For example, in a group of patients with severe Crohn"s disease unresponsive to standard doses of azathioprine, raising the dose of azathioprine helped to control the disease, but two patients developed cytomegalovirus (CMV) infection. (CMV usually infects individuals with weakened immune systems such as patients with AIDS or cancer, especially if they are receiving chemotherapy, which further weakens the immune system.
Azathioprine and 6-MP-induced inflammation of the liver (hepatitis) and pancreas (pancreatitis) are rare. Pancreatitis typically causes severe abdominal pain and sometimes vomiting. Pancreatitis due to 6-MP or azathioprine occurs in 3%-5% of patients, usually during the first several weeks of treatment. Patients who develop pancreatitis should not receive either of these two medications again.
Azathioprine and 6-MP also suppress the bone marrow. The bone marrow is where red blood cells, white blood cells, and platelets are made. Actually, a slight reduction in the white blood cell count during treatment is desirable since it indicates that the dose of 6-MP or azathioprine is high enough to have an effect; however, excessively low red or white blood cell counts indicates bone marrow toxicity. Therefore, patients on 6-MP and azathioprine should have periodic blood counts (usually every two weeks initially and then every 3 months during maintenance) to monitor the effect of the drugs on their bone marrow.
6-MP can reduce the sperm count in men. When the partners of male patients on 6-MP conceive, there is a higher incidence of miscarriages and vaginal bleeding. There also are respiratory difficulties in the newborn. Therefore, it is recommended that whenever feasible, male patients should stop 6-MP and azathioprine for three months before conception.
Patients on long-term, high dose azathioprine to prevent rejection of the kidney after kidney transplantation have an increased risk of developing lymphoma, a malignant disease of lymphatic cells. There is no evidence at present that long term use of azathioprine and 6-MP in the low doses used in IBD increases the risk for lymphoma, leukemia or other malignancies.
Other Issues in the Use of 6-MP
One problem with 6-MP and azathioprine is their slow onset of action. Typically, full benefit of these drugs is not realized for three months or longer. During this time, corticosteroids frequently have to be maintained at high levels to control inflammation.
The reason for this slow onset of action is partly due to the way doctors prescribe 6-MP. Typically, 6-MP is started at a dose of 50 mg daily. The blood count is then checked two weeks later. If the white blood cell count (specifically the lymphocyte count) is not reduced, the dose is increased. This cautious, stepwise approach helps prevent severe bone marrow and liver toxicity, but also delays benefit from the drug.
Studies have shown that giving higher doses of 6-MP early can speed up the benefit of 6-MP without increased toxicity in most patients, but some patients do develop severe bone marrow toxicity. Therefore, the dose of 6-MP has to be individualized. Scientists now believe that an individual"s vulnerability to 6-MP toxicity is genetically inherited. Blood tests can be performed to identify those individuals with increased vulnerability to 6-MP toxicity. In these individuals, lower initial doses can be used. Blood tests can also be performed to measure the levels of certain by-products of 6-MP. The levels of these by-products in the blood help doctors more quickly determine whether the dose of 6-MP is right for the patient.
How Long Can Patients Continue on 6-MP?
Patients have been maintained on 6-MP or azathioprine for years without any important long-term side effects. Their doctors, however, should closely monitor their patients on long-term 6-MP. There is data suggesting that patients on long-term maintenance with 6-MP or azathioprine fare better than those who stop these medications. Those who stop 6-MP or azathioprine are more likely to experience relapses, more likely to need corticosteroids or undergo surgery.
Methotrexate
Methotrexate (Rheumatrex, Trexall) is an immunomodulator and anti-inflammatory medication. Methotrexate has been used for many years in the treatment of severe rheumatoid arthritis and psoriasis. It has been helpful in treating patients with moderate to severe Crohn"s disease who are either not responding to 6-MP and azathioprine or are intolerant of these two medications. Methotrexate also may be effective in patients with moderate to severe ulcerative colitis who are not responding to corticosteroids or 6-MP and azathioprine. It can be given orally or by weekly injections under the skin or into the muscles. It is more reliably absorbed with the injections.
One major complication of methotrexate is the development of liver cirrhosis when the medication is given over a prolonged period of time (years). The risk of liver damage is higher in patients who also abuse alcohol or have morbid (severe) obesity. Generally, periodic liver biopsies are recommended for a patient who has received a cumulative (total) methotrexate dose of 1.5 grams and higher.
Other side effects of methotrexate include low white blood cell counts and inflammation of the lungs.
Methotrexate should not be used in pregnancy.
Cyclosporine
Cyclosporine (Sandimmune) is a potent immunosuppressant used in preventing organ rejection after transplantation, for example, of the liver. It also has been used to treat patients with severe ulcerative colitis and Crohn"s disease. Because of the approval of infliximab (Remicade) for treating severe Crohn"s disease, cyclosporine probably will be used primarily in severe ulcerative colitis. Cyclosporine is useful in fulminant ulcerative colitis and in severely ill patients who are not responding to systemic corticosteroids. Administered intravenously, cyclosporine can be very effective in rapidly controlling severe colitis and avoiding or delaying surgery.
Cyclosporine also is available as an oral medication, but the relapse rate with oral cyclosporine is high. Therefore, cyclosporine seems most useful when administered intravenously in acute situations.
Side effects of cyclosporine include high blood pressure, impairment of kidney function, and tingling sensations in the extremities. More serous side effects include anaphylactic shock and seizures.
Infliximab (Remicade)
Infliximab (Remicade) is an antibody that attaches to a protein called tumor necrosis factor-alpha (TNF-alpha). TNF-alpha is one of the proteins produced by immune cells during activation of the immune system. TNF-alpha, in turn, stimulates other cells of the immune system to produce and release other proteins that promote inflammation. In Crohn"s disease and in ulcerative colitis, there is continued production of TNF-alpha as part of the immune activation. Infliximab, by attaching to TNF-alpha, blocks its activity and in so doing decreases the inflammation.
Infliximab, an antibody to TNF-alpha, is produced by the immune system of mice after the mice are injected with human TNF-alpha. The mouse antibody then is modified to make it look more like a human antibody, and this modified antibody is infliximab. Such modifications are necessary to decrease the likelihood of allergic reactions when the antibody is administered to humans. Infliximab is given by intravenous infusion over two hours. Patients are monitored throughout the infusion for adverse reactions.
Infliximab has been used effectively for many years for the treatment of moderate to severe Crohn"s disease that was not responding to corticosteroids or immuno-modulators. In Crohn"s disease patients, 65% experienced improvement in their disease after one infusion of infliximab. Some patients noticed improvement in symptoms within days of the infusion. Most patients experienced improvement within two weeks. In patients who respond to infliximab, the improvements in symptoms can be dramatic. Moreover, there can be impressively rapid healing of the ulcers and the inflammation in the intestines after just one infusion.
For many years doctors were uncertain whether infliximab could be used to treat ulcerative colitis. Only recently, have doctors begun to use infliximab as treatment for ulcerative colitis. In one randomized placebo controlled study involving more than 700 patients with moderate to severe ulcerative colitis, infliximab (5mg or 10 mg per kilogram body weight) given intravenously was more effective than placebo in inducing and maintaining remission.
Side effects of infliximab
Infliximab, generally, is well tolerated. There have been rare reports of side effects during infusions, including chest pain, shortness of breath, and nausea. These effects usually resolve spontaneously within minutes if the infusion is stopped. Other commonly reported side effects include headache and upper respiratory tract infection.
Infliximab, like immuno-modulators, increases the risk for infection. One case of salmonella colitis and several cases of pneumonia have been reported with the use of infliximab. There also have been cases of tuberculosis (TB) reported after the use of infliximab.
Because infliximab is partly a mouse protein, it may induce an immune reaction when given to humans, especially with repeated infusions. In addition to the side effects that occur while the infusion is being given, patients also may develop a "delayed allergic reaction" that occurs 7-10 days after receiving the infliximab. This type of reaction may cause flu-like symptoms with fever, joint pain and swelling, and a worsening of Crohn"s disease symptoms. It can be serious, and if it occurs, a physician should be contacted. Paradoxically, those patients who have more frequent infusions of Remicade are less likely to develop this type of delayed reaction compared to those patients who receive infusions separated by long intervals (6-12 months). Although Remicade is only FDA approved for a single infusion at this time, patients should be aware that they are likely to require repeated infusions once Remicade therapy has been initiated.
There are some reports of worsening heart disease in patients who have received Remicade. The precise mechanism and role of infliximab in the development of this side effect is unclear. As a precaution, individuals with heart disease should inform their physician of this condition before receiving infliximab.
There have been rare reports of nerve damage such as optic neuritis (inflammation of the nerve of the eye) and motor neuropathy.
Precautions with infliximab
Infliximab can aggravate and cause the spread of an existing infection. Therefore, it should not be given to patients with pneumonia, urinary tract infection or abscess (localized collection of pus).
It now is recommended that patients be tested for TB prior to receiving infliximab. Patients who previously had TB should inform their physician of this before they receive infliximab.
Infliximab can cause the spread of cancer cells, therefore, it should not be given to patients with cancer.
Infliximab"s effects on the fetus are not known.
Because infliximab is partly a mouse protein, some patients can develop antibodies against infliximab with repeated infusions. The development of these antibodies can decrease the effectiveness of the drug. The chances of developing these antibodies can be decreased by concomitant use of 6-MP and corticosteroids.
While infliximab represents an exciting new class of medications in the fight against Crohn"s disease and ulcerative colitis, caution is warranted because of potentially serious side effects. Doctors are using infliximab in moderate to severe ulcerative colitis not responding to other medications.
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