Lonsurf (Trifluridine/Tipiracil) Dosing: No Loading Dose Required
Lonsurf (trifluridine/tipiracil) does not require a loading dose at the start of treatment. The standard dosing regimen begins immediately at the therapeutic dose without any initial loading period 1.
Standard Dosing Regimen
Lonsurf is administered according to the following schedule:
- Dose: 35 mg/m² twice daily (maximum 80mg per single dose)
- Schedule: Days 1-5 and days 8-12 of each 28-day cycle
- Administration: Oral tablets taken within 1 hour after morning and evening meals
This dosing regimen is consistent across multiple guidelines and research studies 2, 1, 3.
Important Dosing Considerations
Dose Calculation
- The dose is calculated based on body surface area (BSA)
- Maximum single dose should not exceed 80mg regardless of calculated BSA
- Tablets come in two strengths (15mg and 20mg) and are combined to achieve the appropriate dose
Administration Pattern
The standard 28-day cycle consists of:
- Days 1-5: Active treatment (twice daily)
- Days 6-7: Rest
- Days 8-12: Active treatment (twice daily)
- Days 13-28: Rest period
Monitoring and Dose Adjustments
Unlike some cancer medications, Lonsurf does not utilize a higher initial dose (loading dose) to achieve rapid steady-state concentrations. Instead, the same therapeutic dose is maintained throughout treatment, with potential adjustments based on tolerability 3, 4.
Common reasons for dose modifications include:
- Neutropenia (most common)
- Thrombocytopenia
- Anemia
- Gastrointestinal toxicities
Combination Therapy Considerations
When Lonsurf is used in combination with bevacizumab, the Lonsurf dosing remains the same (no loading dose), while bevacizumab is typically administered at 5 mg/kg intravenously on day 1 of each 28-day cycle 1.
Clinical Relevance
The absence of a loading dose simplifies administration and may reduce initial toxicity. The current dosing regimen (35 mg/m² twice daily on days 1-5 and 8-12) has demonstrated efficacy in improving overall survival in metastatic colorectal cancer patients while maintaining a manageable safety profile 3, 5, 4.
Understanding the correct dosing schedule is essential for optimal treatment outcomes and minimizing unnecessary toxicity that could result from incorrect dosing assumptions.