TOPOSAR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TOPOSAR (TOPOSAR).
Topoisomerase II inhibitor; stabilizes the topoisomerase II-DNA complex, preventing religation of DNA strands and inducing DNA double-strand breaks, leading to apoptosis.
| Metabolism | Hepatic; primarily via renal excretion (40-70% unchanged), with minor metabolism by CYP3A4 and glucuronidation. |
| Excretion | Primarily renal (approximately 40-60% as unchanged drug via glomerular filtration and tubular secretion). Biliary/fecal excretion accounts for about 20-30% (including metabolites). |
| Half-life | Terminal elimination half-life is approximately 3-5 hours in patients with normal renal function. In patients with creatinine clearance <20 mL/min, half-life may be prolonged up to 8-10 hours, necessitating dose reduction. |
| Protein binding | Approximately 96-97% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is 0.2-0.4 L/kg, indicating minimal tissue binding. Higher Vd (up to 0.6 L/kg) may occur in patients with ascites or pleural effusions. |
| Bioavailability | Bioavailability is approximately 50% for oral capsules; however, TOPOSAR is an intravenous formulation, so bioavailability is 100% by IV route. |
| Onset of Action | IV: Therapeutic effect (antitumor response) typically observed within 1-3 weeks after initiation of therapy. Oral: Not applicable for etoposide (TOPOSAR is IV formulation). |
| Duration of Action | Duration of action is variable, lasting days to weeks depending on the regimen and tumor type. Myelosuppression (neutrophil nadir) occurs at 7-14 days, with recovery by day 21. |
IV: 50-100 mg/m² daily for 5 consecutive days, repeated every 3-4 weeks; or 100 mg/m² IV on days 1, 2, and 3 every 3 weeks.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-50 mL/min: administer 75% of normal dose; CrCl <10 mL/min: administer 50% of normal dose. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: not recommended. |
| Pediatric use | IV: 100-150 mg/m² daily for 3-5 days every 3-4 weeks; for refractory leukemias, doses up to 250 mg/m² daily for 5 days. |
| Geriatric use | No specific dose adjustment; monitor renal function and adjust accordingly due to age-related decline in creatinine clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TOPOSAR (TOPOSAR).
| Breastfeeding | Etoposide is excreted into human breast milk. The milk-to-plasma (M/P) ratio is approximately 0.53. Due to potential serious adverse reactions in the nursing infant, including myelosuppression and secondary malignancy, breastfeeding is contraindicated during therapy and for at least 2 weeks after the last dose. |
| Teratogenic Risk | Toposar (etoposide) is a topoisomerase II inhibitor with documented teratogenic effects in animal studies. In humans, first-trimester exposure is associated with increased risk of congenital anomalies, including craniofacial defects, skeletal abnormalities, and low birth weight. Second and third trimester exposure may cause fetal growth restriction, myelosuppression, and increased risk of preterm labor. Use is contraindicated in pregnancy unless clearly indicated for maternal survival. |
■ FDA Black Box Warning
Risk of secondary leukemia (acute myeloid leukemia or myelodysplastic syndrome), especially with high cumulative doses and concurrent use of other DNA-damaging agents. Risk increases with longer duration of therapy.
| Serious Effects |
Severe hepatic impairment, severe myelosuppression (absolute neutrophil count <1,000 cells/mm³ or platelet count <50,000/mm³), active infections, hypersensitivity to etoposide or any formulation components.
| Precautions | Myelosuppression (dose-limiting), hypersensitivity reactions (including anaphylaxis), hypotension with rapid infusion, hepatotoxicity (elevated liver enzymes), tumor lysis syndrome, extravasation injury, fetal harm (Pregnancy Category D). |
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| Fetal Monitoring | Monitor complete blood count (CBC) with differential weekly during therapy. Assess renal and hepatic function prior to each cycle. Perform fetal ultrasound for growth and anatomy if exposure occurs during pregnancy. Monitor for signs of fetal distress with non-stress testing or biophysical profile in third trimester. Maternal monitoring includes blood pressure, uric acid levels, and tumor lysis syndrome surveillance. |
| Fertility Effects | Etoposide can cause gonadal suppression, leading to amenorrhea in women and azoospermia in men. Ovarian failure with permanent infertility is dose-dependent. Pre-treatment fertility preservation counseling is recommended. Long-term fertility impairment may occur, especially with alkylating agent combination regimens. |