Yes, Hydrea (hydroxyurea) can cause constipation as a recognized gastrointestinal side effect.
Constipation is explicitly listed as a known toxicity of hydroxyurea in authoritative guidelines and FDA labeling, though it occurs less frequently than other GI symptoms like nausea, vomiting, and diarrhea 1, 2.
Evidence from Guidelines and Drug Labeling
The most definitive evidence comes from the 2009 American Academy of Dermatology guidelines for psoriasis management, which clearly lists constipation among the GI symptoms associated with hydroxyurea toxicity. The guideline specifically states that GI symptoms include "stomatitis, anorexia, nausea, vomiting, diarrhea, and constipation" 1.
The FDA drug label for Hydrea confirms gastrointestinal disorders as adverse reactions identified during post-marketing surveillance, though it does not itemize constipation separately from other GI manifestations 2.
Multiple European LeukemiaNet guidelines (2011,2017) for myeloproliferative neoplasms consistently identify "GI symptoms" as unacceptable hydroxyurea-related nonhematologic toxicities that may warrant treatment discontinuation 3, 4, 3. While these guidelines use the umbrella term "GI symptoms," this encompasses the full spectrum of gastrointestinal effects including constipation.
Clinical Context and Frequency
Important caveats:
Constipation is not among the most common hydroxyurea side effects. The predominant GI toxicities are typically nausea, vomiting, anorexia, and diarrhea rather than constipation 1.
The frequency of constipation specifically is not well-quantified in the literature, as most studies report GI adverse events collectively.
When constipation occurs in patients taking hydroxyurea, consider whether it may be multifactorial—potentially related to concurrent medications (especially opioids if used for pain management), dehydration, or the underlying disease process rather than hydroxyurea alone.
Practical Management
If constipation develops in a patient on Hydrea:
- First assess for other contributing factors: opioid use, inadequate hydration, other constipating medications, metabolic abnormalities (hypercalcemia, hypokalemia)
- Consider standard constipation management: increased fluid intake, dietary fiber (if adequate hydration), stimulant laxatives (senna, bisacodyl), osmotic agents (polyethylene glycol, lactulose) 5
- Monitor whether constipation is severe or persistent enough to constitute an "unacceptable GI toxicity" that would warrant dose reduction or discontinuation per guideline criteria 3, 4
The recognition of constipation as a hydroxyurea side effect is well-established in authoritative sources, though it remains less prominent than other GI manifestations in clinical practice.