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# Arsil (Arsenic Trioxide)
## Overview
Arsenic trioxide is a potent antineoplastic agent that induces differentiation and apoptosis in target cells. It is primarily used for hematologic malignancies.
## Primary Indications
* First-line treatment of adult patients with low-risk acute promyelocytic leukemia (APL) in combination with tretinoin.
* Relapsed or refractory APL.
## Adult Dosing
* **Induction:** 0.15 mg/kg IV once daily until bone marrow remission or up to 60 days.
* **Consolidation:** 0.15 mg/kg IV once daily for 25 doses over up to 5 weeks.
* **Administration:** Infuse IV over 1–2 hours (may extend to 4 hours if vasomotor reactions occur).
## Pediatric Dosing
* **Safety/Efficacy:** Established for children ≥5 years in APL.
* **Dosing:** Same as adult dosing (0.15 mg/kg/dose). Use caution due to potential for cumulative toxicity.
## Dose Adjustments
* **QTc Prolongation:** If QTc >500 msec, withhold dose and correct electrolyte imbalances (K+, Mg2+). Resume at 50% of the dose once QTc returns to ≤460 msec; if no recurrence after 1 week, resume full dose.
* **Renal/Hepatic:** No specific dose adjustments provided; use with extreme caution in patients with preexisting renal/hepatic impairment due to potential toxicity.
## Contraindications
* Hypersensitivity to arsenic trioxide.
## Adverse Effects
* **APL Differentiation Syndrome:** Dyspnea, fever, weight gain, pulmonary infiltrates, leukocytosis. Requires prompt dexamethasone.
* **Cardiac:** QTc prolongation (torsades de pointes risk), tachycardia.
* **Neurological:** Peripheral neuropathy, seizures, fatigue, headache.
* **Metabolic:** Hyperglycemia, hypokalemia, hypomagnesemia.
## Key Drug Interactions
* **QTc-Prolonging Agents:** Avoid concurrent use of antiemetics (e.g., ondansetron), antipsychotics, or certain antifungals (e.g., posaconazole, voriconazole) due to additive risk of cardiac arrhythmia.
* **Diuretics:** May exacerbate electrolyte depletion (K+, Mg2+), indirectly increasing QTc risk.
## Monitoring
* **ECG:** At baseline and at least twice weekly during induction/consolidation.
* **Electrolytes:** Maintain K+ >4.0 mEq/L and Mg2+ >1.8 mg/dL.
* **CBC:** Monitor for leukocytosis (differentiation syndrome).
* **Renal/Hepatic Function:** Monitor closely if symptoms arise.
## Clinical Pearls
* **Differentiation Syndrome:** Always have high clinical suspicion. If symptoms occur, initiate dexamethasone (10 mg IV BID) immediately, regardless of white cell count.
* **Hydration:** Ensure adequate hydration to support renal excretion.
* **Handling:** Arsenic trioxide is a human carcinogen and teratogen; handle according to hazardous drug protocols.
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**Educational Disclaimer:** This information is for educational purposes only. Always verify dosing, contraindications, and drug interactions against institutional protocols and the most current FDA-approved prescribing information (package insert) before prescribing or administering.
