Siklos Side Effects
Generic name: hydroxyurea
Medically reviewed by Drugs.com. Last updated on Jul 20, 2022.
Note: This document contains side effect information about hydroxyurea. Some dosage forms listed on this page may not apply to the brand name Siklos.
Applies to hydroxyurea: oral capsules.
- Highly toxic drug with a low therapeutic index.c
- Possible severe, sometimes life-threatening or fatal, adverse effects.177 178
Limit to Qualified Personnel
- Administer only under supervision of qualified clinicians experienced in use of cytotoxic therapy.177 178 (See Adequate Patient Evaluation and Monitoring under Cautions.)
- Hydroxyurea is genotoxic and is a presumed human carcinogen;177 178 also, mutagenic and clastogenic in vitro.177 178
- Secondary leukemias have been reported in patients receiving long-term therapy for myeloproliferative disorders (e.g., polycythemia vera, thrombocythemia).177 178
- Carefully consider risks of developing secondary malignancies against the benefits of therapy.a (See Carcinogenicity under Cautions.)
Side effects include:
Bone marrow suppression.
For Healthcare Professionals
Applies to hydroxyurea: compounding powder, oral capsule, oral tablet.
The more commonly reported adverse reactions among children have been infections and neutropenia. Among adults, hematologic, gastrointestinal symptoms, infections, headache, anorexia, and dry skin have been commonly reported.
Very common (10% or more): Neutropenia (13%)
Common (1% to 10%): Thrombocytopenia, anemia
Pancreatitis has occurred when hydroxyurea was administered concomitantly with antiretroviral drugs, including didanosine and stavudine.[Ref]
Common (1% to 10%): Fever, asthenia, pyrexia, fatigue, peripheral edema
Postmarketing reports: Chills, malaise[Ref]
Very common (10% or more): Dry skin (12%)
Common (1% to 10%): Skin ulcer, alopecia
Postmarketing reports: Skin ulceration, cutaneous lupus erythematosus, dermatomyositis-like skin changes, peripheral and facial erythema, nail hyperpigmentation, atrophy of skin and nails, scaling, violet papules, skin reactions (oral, ungula and cutaneous pigmentation), rash, melanonychia[Ref]
Leukemia secondary to long-term hydroxyurea (the active ingredient contained in Siklos) has also been reported in patients with sickle cell disease. Leukemia has also been reported in patients with sickle cell disease and no prior history of treatment with hydroxyurea. Skin cancer has also been reported in patients receiving long-term hydroxyurea.[Ref]
Frequency not reported: Leukemia, skin cancers[Ref]
Common (1% to 10%): Urinary tract infection
Very common (10% or more): Headache (20%)
Common (1% to 10%): Dizziness
Frequency not reported: Peripheral neuropathy
Postmarketing reports: Drowsiness, convulsions[Ref]
Uncommon (0.1% to 1%): Hepatotoxicity, hepatic enzyme increased, cholestasis, hepatitis
Common (1% to 10%): Cough, lung disorder, dyspnea, nasopharyngitis
Common (1% to 10%): Vitamin D deficiency, other metabolic and nutrition disorders, weight gain, increased weight
Very rare (less than 0.01%): Tumor lysis syndrome
Postmarketing reports: Hallucinations, disorientation[Ref]
Postmarketing reports: Elevations in serum uric acid, blood urea nitrogen (BUN), and creatinine levels[Ref]
Drug-induced fever requiring hospitalization has been reported in the postmarketing period. It has been reported concurrently with gastrointestinal, pulmonary, musculoskeletal, hepatobiliary, dermatological or cardiovascular manifestations. Onset typically occurred within 6 weeks of initiation and resolved upon discontinuation of hydroxyurea (the active ingredient contained in Siklos) Upon re-administration fever reoccurred typically within 24 hours.
Postmarketing reports: Drug-induced fever
Common (1% to 10%): Viral infections, bacterial infections, influenza
Postmarketing reports: Systemic lupus erythematosus
Common (1% to 10%): Arthralgia, back pain, extremity pain
More about Siklos (hydroxyurea)
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Related treatment guides
1. "Product Information. Droxia (hydroxyurea)." Bristol-Myers Squibb (2001):
2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
4. "Product Information. Hydroxyurea (hydroxyurea)." Par Pharmaceutical Inc (2022):
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.