Hydroxyurea

Sickle Cell Anemia

Hydroxyurea is used to reduce the frequency of painful crises and the need for blood transfusions in patients with sickle cell anemia. It is approved for use in both adults and children 2 years of age and older who experience recurrent moderate to severe painful episodes.

Cancer Treatment

This medication is used to treat certain types of cancer by slowing or stopping the growth of cancer cells. These include:

• Chronic myelogenous leukemia (CML): A type of cancer that begins in the blood-forming cells of the bone marrow.
• Head and neck cancers: Specifically squamous cell carcinomas of the head and neck (excluding the lip). For these conditions, hydroxyurea is typically used in combination with radiation therapy.

Other Blood Disorders

Hydroxyurea may also be prescribed to manage other myeloproliferative disorders, which are conditions that cause the bone marrow to produce too many blood cells. These include:

• Polycythemia vera: A condition where the body produces too many red blood cells.
• Essential thrombocythemia: A condition where the body produces too many platelets, which can increase the risk of blood clots.

Interfering with Cell Growth

Hydroxyurea belongs to a class of medications known as antimetabolites. It works by blocking an enzyme called ribonucleotide reductase, which cells need to produce DNA. By interfering with DNA synthesis, the medication can slow or stop the growth of certain types of cancer cells.

Effects on Sickle Cell Anemia

In people with sickle cell anemia, hydroxyurea helps the body produce more fetal hemoglobin. This type of hemoglobin is generally more effective at carrying oxygen and prevents red blood cells from deforming into a sickle or crescent shape. Benefits of this process include:

• Improved cell flexibility: Red blood cells stay rounder and more flexible, allowing them to move through small blood vessels more easily.
• Reduced blockages: Because the cells do not sickle as easily, they are less likely to clog blood vessels and cause pain or organ damage.

While the exact mechanism for how hydroxyurea increases fetal hemoglobin is not fully understood, its ability to change the composition of red blood cells is the primary way it manages sickle cell disease.

Common Side Effects

Many people taking hydroxyurea experience mild side effects. These may include:

• Nausea, vomiting, or diarrhea
• Loss of appetite or constipation
• Mouth or throat sores
• Skin changes, such as darkening, thinning, or redness
• Temporary hair loss
• Dizziness or headache
• Weight gain

Serious Side Effects

Some side effects can be severe and require immediate medical attention. Contact a healthcare provider right away if you experience:

• Signs of infection, such as fever, chills, or a persistent sore throat
• Unusual bruising or bleeding, such as nosebleeds or bleeding gums
• Extreme tiredness, pale skin, or shortness of breath
• Painful skin ulcers, particularly on the legs
• Numbness, tingling, or burning sensations in the hands or feet
• Confusion, hallucinations, or seizures
• Yellowing of the eyes or skin (jaundice)
• Severe stomach pain or dark urine

Long-term use of hydroxyurea may increase the risk of developing other conditions, such as skin cancer or leukemia. It is important to protect your skin from sun exposure and attend all scheduled blood tests to monitor your health.

Boxed Warnings

Bone Marrow Suppression: Hydroxyurea can cause a severe decrease in blood cell counts, including white blood cells, platelets, and red blood cells. This may increase the risk of serious infections or bleeding. Treatment is typically not started if blood counts are too low and may be interrupted if they drop significantly during therapy.

Secondary Malignancies: Long-term use of hydroxyurea has been linked to the development of secondary cancers, including leukemia and skin cancer. Patients are advised to protect their skin from sun exposure and monitor for any new skin changes.

Other Serious Precautions

Embryo-Fetal Toxicity

Hydroxyurea can cause fetal harm when administered to a pregnant person. Effective contraception is recommended for both females and males of reproductive potential during treatment and for a specific period after the final dose. Breastfeeding is generally not recommended while taking this medication.

Vascular Toxicity

Serious complications, including leg ulcers and blood vessel inflammation (vasculitis), have occurred in patients with certain blood disorders. These issues may require stopping the medication.

Vaccinations

The use of live vaccines should be avoided during treatment with hydroxyurea, as the medication suppresses the immune system and may increase the risk of infection from the vaccine.

Drug Interactions

Taking hydroxyurea with certain antiretroviral medications used for HIV, such as didanosine or stavudine, may increase the risk of severe side effects, including liver damage, pancreatitis, and nerve damage.

Safe Handling and Monitoring

Because hydroxyurea is a cytotoxic (cell-killing) drug, it must be handled with care. Caregivers should wear disposable gloves when handling the medication or its packaging and wash their hands thoroughly before and after contact. Regular blood tests are required to monitor blood cell counts and organ function throughout the duration of treatment.

Pregnancy

Hydroxyurea can cause fetal harm and birth defects if used during pregnancy. It is important to inform a healthcare provider if you are pregnant or planning to become pregnant. Individuals who can become pregnant should have a pregnancy test before starting treatment and must use effective birth control during treatment and for at least six months after the final dose.

Men with partners who can become pregnant should also use effective contraception during treatment and for at least six months to one year after the final dose, depending on the specific condition being treated. If a pregnancy occurs while taking this medication, you should contact a healthcare professional immediately to discuss the potential risks to the fetus.

Breastfeeding

Hydroxyurea is known to pass into human breast milk. Because of the potential for serious side effects in a nursing infant, breastfeeding is not recommended while using this medication. Patients should consult with their healthcare provider to decide whether to stop breastfeeding or stop the medication, based on the importance of the treatment to the mother.

Available Forms

Hydroxyurea is administered orally and is available in the following manufactured forms:

• Capsules: A common oral form used for various conditions.
• Tablets: Some tablet formulations are designed to be scored, which allows them to be split into smaller portions when necessary.

The specific form prescribed may depend on the brand name, the condition being treated, and the age of the patient.

FDA Approval and Indications

Hydroxyurea is approved by the U.S. Food and Drug Administration (FDA) for the treatment of several conditions in both adults and children:

• Sickle Cell Anemia: It is approved for adults and pediatric patients aged 2 years and older to reduce the frequency of painful crises and the need for blood transfusions.
• Cancer: It is approved for the treatment of chronic myeloid leukemia and certain squamous cell carcinomas of the head and neck (excluding the lip).

Boxed Warning

The FDA requires a boxed warning for hydroxyurea due to serious safety concerns:

• Severe Myelosuppression: The medication can cause a significant drop in blood cell counts, including white blood cells, red blood cells, and platelets. This can lead to life-threatening infections or bleeding.
• Secondary Malignancies: There is an increased risk of developing other cancers, such as leukemia or skin cancer, in patients receiving long-term hydroxyurea therapy.

Regulatory and Safety Requirements

Because of the risk of myelosuppression, the FDA requires frequent monitoring of blood counts during treatment. Healthcare providers must typically check blood levels every week or two, and the dosage may need to be adjusted or temporarily stopped if counts fall too low. Additionally, hydroxyurea is classified as a hazardous drug, meaning there are specific regulatory guidelines for its handling and disposal to prevent accidental exposure to caregivers or healthcare workers.

Alcohol and Side Effects

Consuming alcohol while taking hydroxyurea may increase the risk or severity of side effects related to the central nervous system. Because hydroxyurea can cause dizziness and drowsiness, alcohol may intensify these feelings.

Potential risks of combining alcohol with this medication include:

• Increased dizziness or lightheadedness
• Extreme drowsiness or fatigue
• Confusion or disorientation

These effects can impair your ability to drive, operate heavy machinery, or perform other tasks that require alertness. You should consult your healthcare provider to discuss whether it is safe for you to drink alcohol during your treatment.