Thrombocytopenia: Selenox can cause thrombocytopenia, leading to potentially fatal hemorrhage. Thrombocytopenia was reported as an adverse reaction in 74% of patients, and severe (Grade 3–4) thrombocytopenia occurred in 6% of patients treated with Selenox. The median time to onset of the first event was 22 days. Bleeding occurred in 23% of patients with thrombocytopenia, clinically significant bleeding occurred in 5% of patients with thrombocytopenia and fatal hemorrhage occurred in <1% of patients. Monitor platelet counts at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Institute platelet transfusion and/or other treatments as clinically indicated. Monitor patient for signs and symptoms of bleeding and evaluate promptly. Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
Neutropenia: Selenox can cause neutropenia, potentially increasing the risk of infection. Neutropenia was reported as an adverse reaction in 34% of patients, and severe (Grade 3–4) neutropenia occurred in 2% of patients treated with Selenox. The median time to onset of the first event was 25 days. Febrile neutropenia was reported in 3% of patients. Obtain neutrophil counts at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Monitor patient for signs and symptoms of concomitant infection and evaluate promptly. Consider supportive measures including antimicrobials for signs of infection and use of growth factors (e.g., G-CSF). Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
Gastrointestinal Toxicity: Gastrointestinal toxicities occurred in patients treated with Selenox.
Nausea/Vomiting: Nausea was reported as an adverse reaction in 72% of patients, and Grade 3 nausea occurred in 9% of patients treated with Selenox. The median time to onset of the first nausea event was 3 days. Vomiting was reported in 41% of patients, and Grade 3 vomiting occurred in 4% of patients treated with Selenox. The median time to onset of the first vomiting event was 5 days. Provide prophylactic 5-HT₃ antagonists and/or other anti-nausea agents prior to and during treatment with Selenox. Manage nausea/vomiting by dose interruption, reduction, and/or discontinuation. Administer intravenous fluids and replace electrolytes to prevent dehydration in patients at risk. Use additional anti-nausea medications as clinically indicated.
Diarrhea: Diarrhea was reported as an adverse reaction in 44% of patients, and Grade 3 diarrhea occurred in 6% of patients treated with Selenox. The median time to onset of diarrhea was 15 days. Manage diarrhea by dose modification and/or standard anti-diarrheal agents; administer intravenous fluids to prevent dehydration in patients at risk.
Anorexia/Weight Loss: Anorexia was reported as an adverse reaction in 53% of patients, and Grade 3 anorexia occurred in 5% of patients treated with Selenox. The median time to onset of anorexia was 8 days. Weight loss was reported as an adverse reaction in 47% of patients, and Grade 3 weight loss occurred in 1% of patients treated with Selenox. The median time to onset of weight loss was 15 days. Monitor patient weight at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Manage anorexia and weight loss with dose modification, appetite stimulants, and nutritional support.
Hyponatremia: Selenox can cause hyponatremia. Hyponatremia was reported in 59% of patients treated with Selenox. Grade 3 or 4 hyponatremia occurred in 22% of patients. The median time to onset of the first event was 8 days. Monitor sodium levels at baseline, during treatment, and as clinically indicated. Monitor more frequently during the first two months of treatment. Correct sodium levels for concurrent hyperglycemia (serum glucose >100 mg/dL) and high serum parathyroid levels. Treat hyponatremia per clinical guidelines (intravenous saline and/or salt tablets), including dietary review. Interrupt and/or reduce dose, or permanently discontinue based on severity of adverse reaction.
Infection: In patients receiving Selenox, 52% of patients experienced any grade of infection. Upper respiratory tract infection of any grade occurred in 21%, pneumonia in 13%, and sepsis in 6% of patients. Grade ≥3 infections were reported in 25% of patients, and deaths resulting from an infection occurred in 4% of patients. The most commonly reported Grade ≥3 infections were pneumonia in 9% of patients, followed by sepsis in 6%. The median time to onset was 54 days for pneumonia and 42 days for sepsis. Infections were not associated with neutropenia and were caused by non-opportunistic organisms.
Neurological Toxicity: Neurological toxicities occurred in patients treated with Selenox. Neurological adverse reactions including dizziness, syncope, depressed level of consciousness, and mental status changes (including delirium and confusional state) occurred in 30% of patients, and severe events (Grade 3–4) occurred in 9% of patients treated with Selenox. The median time to the first event was 15 days. Optimize hydration status, hemoglobin level, and concomitant medications to avoid exacerbating dizziness or mental status changes.
Embryo-Fetal Toxicity: Based on data from animal studies and its mechanism of action, Selenox can cause fetal harm when administered to a pregnant woman. Selenox administration to pregnant animals during organogenesis resulted in structural abnormalities and alterations to growth at exposures below those occurring clinically at the recommended dose. Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential and males with a female partner of reproductive potential to use effective contraception during treatment with Selenox and for 1 week after the last dose.
