What is Hydroxyurea?
Hydroxyurea (pronounced hy-DROK-see-yoo-REE-uh) was originally approved by the U.S. Food and Drug Administration (FDA), the agency responsible for reviewing and approving drugs, in 1967.
Research into using hydroxyurea to treat sickle cell disease would eventually lead FDA to approve its use in 1998. But the approval was for adults with sickle cell disease and not for children.
On December 21, 2017, FDA approved hydroxyurea to reduce the frequency of painful crises and the need for blood transfusions in pediatric patients 2 years of age and older with sickle cell anemia with recurrent moderate to severe painful crises: this is Siklos®.
What is Siklos®?
Siklos® is the only FDA-approved prescription medicine that is used to reduce the frequency of painful crises and reduce the need for blood transfusions in children, 2 years of age and older, with sickle cell anemia with recurrent moderate to severe painful crises.
It is not known if Siklos® is safe and effective in children less than 2 years of age.
This is the first FDA approval of hydroxyurea for use in pediatric patients with sickle cell disease.
Siklos® can lessen the frequency of pain for your child with sickle cell disease
Children with sickle cell disease experience “painful crises” when their sickle-shaped red blood cells block their blood vessels, preventing blood and oxygen from reaching their tissues and causing pain. Painful crises may result in hospitalization and require pain medication. A sickle cell crisis can also damage your child’s tissues and cause organ failure, such as liver or kidney failure.
Siklos® was studied in children from 2-18 years of age with sickle cell disease. After 12 months of hydroxyurea treatment, the percentage of children who had at least one painful crisis, one episode of pneumonia, one hospitalization due to sickle cell disease or one blood transfusion, decreased.
- Siklos® has been studied and proven safe and effective for patients 2 years of age and older.
- Siklos® is the only hydroxyurea-based treatment of its kind specifically indicated and approved for patients 2 years of age and older.
- With Siklos®, your child’s healthcare provider can tailor your child’s dose to his/her weight.
- Siklos® tablets can be dissolved in water if your child has trouble swallowing them whole.
Ask your child’s healthcare provider about Siklos® today.
How Siklos® Helps
Science does not fully understand how hydroxyurea works, but studies suggest that it increases the amount of fetal hemoglobin (HbF), as well as the amount of water, in red blood cells. In this way, Siklos® helps keep your child’s red blood cells round and flexible so they can travel more easily through the blood vessels. This may help reduce painful crises and some of the complications of the disease.
Babies are born with HbF to help protect them from health problems during their first few months of life. HbF helps prevent red blood cells from changing into a sickle shape.
In most people, the amount of HbF decreases after the first few months of life. Some people have more HbF than others. People with sickle cell disease who have higher levels of HbF may experience fewer complications of the disease.
For Siklos® to help your child, it must be taken every day, at the same time each day, with a glass of water, exactly as instructed by his/her healthcare provider.
It may take up to a year or more before your child feels the full benefits of Siklos® because his/her dose must be adjusted gradually until the right dose is reached. Therefore, your child will require continuous follow-up appointments with his/her healthcare provider throughout treatment.
Safety Information about Siklos®
The safety of Siklos® was established in pediatric patients aged 2-18 years with sickle cell anemia with recurrent moderate to severe painful crises. Use of Siklos® in these age groups is supported by evidence from a reliable scientific study (known as the ESCORT-HU). 405 pediatric patients ages 2 to under 18 were enrolled. Among the 405 pediatric patients treated with Siklos® in this study, 274 were children (2-11) and 108 were adolescents (12-16).
It is not known if Siklos® is safe and effective in children less than 2 years of age.
There are serious risks associated with taking Siklos®. The most common risks are infections as a result of low blood cell counts, including low red blood cells, white blood cells, and platelets. Some people have developed cancer, such as leukemia and skin cancer, after taking Siklos® for a long time. Your healthcare provider will check you for cancer. You should protect your skin from the sun using sunblock, hats, and sun-protective clothing. These are not all the risks. For this reason, your child will need regular blood tests to check blood counts. If white blood cell count is low, his/her healthcare provider may lower the dose of Siklos® or stop treatment until levels return to normal.
Your child should avoid unnecessary or prolonged sun exposure to sunlight and wear protective clothing and sunscreen.
You and your child’s healthcare provider will decide if Siklos® is right for your child.
Siklos® is a prescription medicine that is used to reduce the frequency of painful crises and reduce the need for blood transfusions in children, 2 years of age and older, with sickle cell anemia with recurrent moderate to severe painful crises.
What is the most important information I should know about Siklos®?
Siklos® can cause serious side effects, including:
Low blood cell counts are common with Siklos®, including low red blood cells, white blood cells, and platelets, and can be severe and life-threatening. If your white blood cell count becomes very low, you are at increased risk for infection. Your healthcare provider will check your blood cell counts before and during treatment with Siklos®. Your healthcare provider may change your dose or tell you to stop taking Siklos® if you have low blood cell counts.
Tell your healthcare provider right away if you get any of the following symptoms:
- fever or chills
- shortness of breath
- body aches
- unusual headache
- feeling very tired
- bleeding or unexplained bruising
Cancer. Some people have developed cancer, such as leukemia and skin cancer, after taking Siklos® for a long time. Your healthcare provider will check you for cancer. You should protect your skin from the sun using sunblock, hats, and sun-protective clothing.
Siklos® can harm your unborn baby.
For females taking Siklos® who can become pregnant:
- You should talk with your healthcare provider about the risks of Siklos® to your unborn baby.
- You should use effective birth control during treatment with Siklos® and for at least 6 months after treatment with Siklos®.
- Your healthcare provider will perform a pregnancy test before you start treatment with Siklos®.
- Tell your healthcare provider right away if you become pregnant or think you may be pregnant.
For males taking Siklos®: Siklos® can affect your sperm. If you have a female sexual partner who can become pregnant, you should use effective birth control during treatment with Siklos® and for at least 6 months after treatment.
Siklos® may cause fertility problems in males. Talk to your healthcare provider if this is a concern for you.
Do not take Siklos® if you are allergic to hydroxyurea or any of the ingredients in Siklos®. See the end of this Medication Guide for a list of the ingredients in Siklos®.
Before taking Siklos®, tell your healthcare provider about all medical conditions, including if you:
- have kidney problems or are receiving hemodialysis
- have liver problems
- have human immunodeficiency virus (HIV) or take HIV medicines.
Taking Siklos® with certain HIV medicines can cause serious reactions and may lead to death.
- have increased levels of uric acid in your blood (hyperuricemia)
- have a history of receiving interferon therapy or are currently receiving interferon therapy
- have leg wounds or ulcers
- plan to receive any vaccinations. You should not receive “live vaccines” during treatment with Siklos®.
- are pregnant or plan to become pregnant
- are breastfeeding or plan to breastfeed. It is not known if Siklos® can pass into your breast milk. Do not breastfeed during treatment with Siklos®.
Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
What are the possible side effects of Siklos®?
Siklos® may cause serious side effects, including:
See “What is the most important information I should know about Siklos®?”
Skin ulcers, including leg ulcers have happened in people who take Siklos®. This has happened most often in people who receive interferon therapy or have a history of interferon therapy. Your healthcare provider will decrease your dose or stop treatment with Siklos® if you develop any skin ulcers.
Enlarged red blood cells (macrocytosis). Macrocytosis is common in people who take Siklos® and can make it difficult to detect a decrease of folic acid. Your healthcare provider may prescribe a folic acid supplement for you.
The most common side effects of Siklos® include:
- skin problems including:
- skin reactions
- dry skin
- changes in skin and nail color
- stomach and intestine (gastrointestinal) problems including:
- decrease in vitamin D
- weight gain
These are not all the possible side effects of Siklos®. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.