Should a patient with a decreasing platelet count from 731 to 632 while on Hydra (hydroxyurea) 500 mg continue the medication?

Management of Thrombocytosis in a Patient on Hydroxyurea

The patient should continue hydroxyurea 500 mg as the platelet count is showing an appropriate response, decreasing from 731 to 632, but has not yet reached the target range of <600 × 10⁹/L.

Assessment of Current Response

The patient is demonstrating a positive response to hydroxyurea therapy with a reduction in platelet count from 731 to 632 × 10⁹/L. This represents an appropriate therapeutic direction, though the platelet count remains above the ideal target range.

Target Platelet Levels

• For patients with essential thrombocythemia or other myeloproliferative disorders, maintaining platelet counts below 600 × 10⁹/L is recommended to reduce thrombotic risk 1
• Current platelet count of 632 × 10⁹/L shows improvement but has not yet reached this target threshold

Monitoring Recommendations

Regular monitoring is essential during hydroxyurea therapy:

• Frequency: Check complete blood counts weekly during dose adjustment phase, then monthly once stable dose is established 2
• Parameters to monitor:
  • Platelet count
  • White blood cell count
  • Hemoglobin/hematocrit
  • Signs of potential adverse effects

Dose Adjustment Considerations

When to continue current dose:

• When platelet count is decreasing but still above target range
• When no significant adverse effects are present
• When the rate of decrease is appropriate (as in this case)

When to increase dose:

• If platelet count remains significantly elevated after 4-8 weeks of therapy
• If no response is observed after adequate treatment duration
• If thrombotic events occur despite therapy

When to reduce dose or discontinue:

• If absolute neutrophil count decreases to <750/mm³ 3
• If platelet count decreases to <50,000/mm³ 3
• If hemolytic anemia develops 4, 5
• If cutaneous vasculitic toxicities occur 4

Safety Considerations

Hydroxyurea can cause several adverse effects that require monitoring:

• Myelosuppression: Most common manifestation is leukopenia, followed by thrombocytopenia and anemia 4
• Hemolytic anemia: Rare but serious side effect requiring drug discontinuation if confirmed 4, 5
• Cutaneous vasculitic toxicities: Including vasculitic ulcerations and gangrene 4
• Macrocytosis: Self-limiting and often seen early in treatment 4

Practical Recommendations

1. Continue hydroxyurea 500 mg as the platelet count is showing appropriate reduction
2. Schedule follow-up CBC in 2-4 weeks to ensure continued response
3. Target platelet count <600 × 10⁹/L for optimal thrombosis prevention
4. Monitor for adverse effects at each visit, particularly signs of myelosuppression
5. Consider dose increase only if platelet count stabilizes above target after 8 weeks of therapy
6. Advise patient to report any unusual bleeding, bruising, fever, or skin changes

Special Considerations

• If the patient develops symptoms of hemolysis (jaundice, dark urine, fatigue), laboratory evaluation should be performed immediately 4
• Prophylactic administration of folic acid is recommended during hydroxyurea therapy to prevent macrocytosis 4
• Long-term hydroxyurea use requires monitoring for potential secondary malignancies 4

The current response pattern (platelet reduction from 731 to 632 × 10⁹/L) indicates appropriate therapeutic effect, and continuing the current dose with close monitoring is the most appropriate management strategy.