BACKGROUND: The optimal dosing strategy of four-factor prothrombin complex concentrate (4F-PCC) for vitamin K antagonists (VKAs) reversal is unknown.
METHODS: We conducted systematic search on the PubMed, SCOPUS, and Embase databases from inception to December 2020 for clinical studies that compared the fixed-dose versus variable-dose of 4-PCC for VKAs reversal with at least one reported clinical outcome. The treatment effects were expressed as relative ratios (RR) with 95% confidence intervals (CIs) and pooled by a random-effects model.
RESULTS: Ten studies, including 988 patients, were included. Fixed-dose 4-PCC was associated with lower rate of mortality (RR= 0.65, 95% CI 0.47 to 0.9, p= 0.009), comparable rate of thromboembolic event (TEE) (RR= 1.10, 95%CI 0.44 to 2.80, p= 0.826), and lower goal INR reached (RR= 0.87, 95%CI 0.78 to 0.96, p= 0.007). Less 4-PCC cumulative dose, shorter duration of order-to-needle time, similar hospital length of stay, the comparable time required for INR reversal, higher post-4-PCC INR, and a higher need for additional dose were observed in fixed-dose.
CONCLUSIONS: The use of a fixed-dose of 4-PCC may be considered an effective and safe dosing strategy for VKAs reversal in various clinical situations. However, further well-designed, controlled studies should be conducted focusing on clinical outcomes to determine the optimal dose of 4-PCC for VKAs reversal.

Trastuzumab, a key treatment for HER2-positive breast cancer, is available in weight-based IV and fixed-dose (600 mg) SC formulations. While the Phase 3 HannaH trial indicated non-inferiority of the SC formulation, there is some concern that the target plasma concentration may not be reached in overweight/obese patients whereas low-body-weight patients may be at risk of toxicity. This scoping review evaluated whether overweight/obese patients are at risk of below-target exposure with fixed-dose SC trastuzumab, whether low-body-weight patients are at risk of increased toxicity, especially cardiotoxicity, and whether IV and SC trastuzumab are equivalent in terms of treatment-emergent adverse events (TEAEs) (e.g. infections). Thirty-seven publications that met the eligibility criteria were included. Body weight is not an important determinant of exposure to trastuzumab at steady state (i.e. pre-dose cycle 8); however, real-world evidence suggests that the target concentration (20 μg/mL) may not be reached with the first SC dose in overweight/obese patients. There is no evidence that low-body-weight patients are at increased risk of cardiotoxicity with SC trastuzumab, although this may be confounded by the higher rate of cardiovascular comorbidities in overweight patients. In Phase 3 trials, SC trastuzumab was associated with higher rates of ISRs, ADAs and SAEs, the latter often requiring hospitalization and occurring during adjuvant treatment when patients are not burdened by chemotherapy. The route of administration of trastuzumab (IV vs SC) in different treatment settings should be discussed with the patient, taking into account the risks and benefits associated with each route.