Cyclophosphamide is a medication that suppresses the immune system. It is commonly used to treat patients with severe myasthenia gravis who do not respond to other treatments such as corticosteroids. It is available in oral and injectable forms.
How cyclophosphamide works
In myasthenia gravis, certain types of white blood cells, a key part of the immune system, make antibodies, proteins that normally fight off foreign invaders, such as bacteria, that instead turn against the body’s own tissues, known as autoantibodies. Muscle weakness is a result of these autoantibodies destroying acetylcholine receptors, a key protein for muscle movement.
Cyclophosphamide is an alkylating agent that is able to dampen the abnormal immune activity in myasthenia gravis by interfering with the DNA of these white blood cells that produce autoantibodies. By disrupting DNA, which is crucial for cell replication and growth, cyclophosphamide can reduce the levels of these damaging autoantibodies.
Cyclophosphamide in clinical trials for myasthenia gravis
Although no clinical trials have been conducted on using cyclophosphamide specifically for myasthenia gravis, it is an accepted treatment option for people with severe forms of the disease where other treatments have been found to be ineffective, also known as refractory myasthenia gravis.
One study found that 22 patients with generalized myasthenia gravis who were given cyclophosphamide through the bloodstream in six different sessions, or pulses, showed improvements in their symptoms. The disease was fully controlled (disease remission) after an average of three and a half months following initial cocyclophosphamide treatment. Disease remission was maintained for an average of one year and eight months. However, patients also experienced several side effects, causing four of them to stop the medication.
Another study looked into the benefits of giving a high dose of cyclophosphamide to induce myasthenia gravis disease remission. Doses of 200 mg/kg of cyclophosphamide were given to 12 patients, who were then monitored for between one and nine years. These patients had various lengths of remission ranging from five months to seven and a half years. Most of the patients (seven out of 12) had remission periods of more than a year.
Cyclophosphamide use also decreased the amount of steroid use by patients while improving muscle weakness, especially in muscles responsible for speaking, swallowing, and eye movements.
Cyclophosphamide is an extremely potent medication, and patients often experience several side effects. It commonly causes nausea, vomiting, hair loss (alopecia), skin discoloration and rash, and may also increase the risk of getting severe infections. Serious side effects include severe bladder irritation leading to painful and bloody urination known as hemorrhagic cystitis, and an increased risk of developing cancer later in life. Drinking plenty of water while taking this medication can help reduce the risk of hemorrhagic cystitis.
Infertility is also a major consequence of cyclophosphamide use. Women on this therapy should also take steps to avoid getting pregnant, as it can cause birth defects. Women should also avoid breastfeeding while taking this medication.
Cyclophosphamide was approved for use in the U.S. in 1959. It is widely used as a component in chemotherapy for treating cancers such as lymphomas, leukemias, neuroblastoma (a type of brain cancer), retinoblastoma (cancer of the retina), and breast cancer. Cyclophosphamide is also approved to treat a kidney disease that most commonly affects children, called minimal change nephrotic syndrome.
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