Antimicrobial agents are widely used, and drug interactions are challenging due to increased risk of adverse effects or reduced efficacy. Among the interactions, the most important are those affecting metabolism, although those involving drug transporters are becoming increasingly known. To make clinical decisions, it is key to know the intensity of the interaction, as well as its duration and time-dependent recovery after discontinuation of the causative agents. It is not only important to be aware of all patient treatments, but also of supplements and natural medications that may also interact. Although they can have serious consequences, most interactions can be adequately managed with a good understanding of them. Especially in patients with polipharmacy it is compulsory to check them with an electronic clinical decision support database. This article aims to conduct a narrative review focusing on the major clinically significant pharmacokinetic drug-drug interactions that can be seen in patients receiving treatment for bacterial infections.

Background: Post-transplant cyclophosphamide (PTCy) is a standard graft-versus-host disease (GVHD) prophylaxis in allogeneic hematopoietic cell transplantation (allo-HCT). While effective, concerns remain about cyclophosphamide-related cardiotoxicity, especially in patients with pre-existing cardiac morbidity, a population often underrepresented in clinical trials. Objectives: To assess the incidence and outcomes of early (ECE, ≤100 days) and late (LCE, >100 days) cardiac events in acute myeloid leukemia (AML) patients with and without baseline cardiac morbidity undergoing allo-HCT with PTCy. Study Design: Retrospective multicenter study by the Grupo Español de Trasplante Hematopoyético y Terapia Celular (GETH-TC) including 461 AML patients (62 with cardiac morbidity) transplanted between 2012 and 2022. Cardiac morbidity was defined by documented cardiac disease or left ventricular ejection fraction < 45%. Cumulative incidence, overall survival (OS), and non-relapse mortality (NRM) were analyzed using competing risks models and adjusted with propensity score matching (PSM) and inverse probability weighting (IPW). Results: Cardiac events occurred in 13.2% of patients: 11% vs. 7% ECE (p = 0.93) and 8% vs. 5.3% LCE (p = 0.85) in those with vs. without cardiac morbidity. Most ECEs were arrhythmias or heart failure. Adjusted analyses confirmed no significant differences in CE incidence, OS, or NRM between groups. Two-year OS was 69% vs. 70% (p = 0.50); NRM was 18% vs. 17% (p = 0.20). ECE was associated with higher mortality in both groups. Conclusions: PTCy is feasible in AML patients with pre-existing cardiac morbidity when combined with comprehensive cardiovascular evaluation and cardio-oncology follow-up, supporting its safe use in broader patient populations with appropriate cardiologic support.

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare but severe drug hypersensitivity reaction with potentially life-threatening consequences. It is characterised by fever, extensive maculopapular exanthema, lymph node enlargement, abnormal blood cell counts, and organ-related complications. Diagnosis can be challenging due to incomplete or non-specific symptoms, and it can sometimes manifest as a purely systemic disease. Discontinuation of the causative drug is essential. Treatment may involve corticosteroids and supportive care. Genetic screening for specific markers, such as human leucocyte antigen (HLA)-A*68, A11:01, and A29:02, can help identify individuals at risk for severe reactions to benznidazole, a drug used to treat Chagas disease. This case report describes the rarity and severity of DRESS syndrome, underscoring the potential benefit of genetic screening to prevent adverse reactions in patients with Chagas disease.

Oral tyrosine kinase inhibitors and poly (adenosine diphosphate-ribose) polymerase inhibitors are widely used across solid tumors and hematologic malignancies and are typically administered at fixed doses. However, substantial interindividual pharmacokinetic variability results in heterogeneous systemic exposure, potentially leading to underexposure with reduced antitumor efficacy or overexposure with preventable toxicity. Therapeutic drug monitoring and model-informed precision dosing have emerged as complementary strategies to individualize dosing and optimize the exposure–response balance in routine oncology practice. This narrative problem-oriented review evaluates the clinical applicability of therapeutic drug monitoring and model-informed precision dosing for selected oral targeted agents, including epidermal growth factor receptor, anaplastic lymphoma kinase, BCR-ABL, vascular endothelial growth factor receptor, mitogen-activated protein kinase kinase, and multi-kinase inhibitors, as well as poly(adenosine diphosphate-ribose) polymerase inhibitors. For each agent, we assessed the presence of clinically meaningful exposure–response or exposure–toxicity relationships, the availability of validated assays, and the existence of actionable concentration thresholds. We also integrated an updated therapeutic drug monitoring usefulness score to contextualize the strength of recommendation. High-level evidence, including prospective interventional studies, supports exposure-guided dosing for imatinib and sunitinib, demonstrating improved molecular or clinical outcomes when predefined trough concentration targets are achieved. For alectinib, cabozantinib, trametinib, and lenvatinib, consistent exposure–response or exposure–toxicity relationships and pragmatic concentration thresholds support selective implementation, although randomized validation remains limited. For agents such as osimertinib, brigatinib, olaparib, and niraparib, monitoring appears most clinically relevant in toxicity-driven scenarios rather than for efficacy optimization. In contrast, lorlatinib currently lacks a clearly defined therapeutic window, limiting routine applicability. Across drugs, steady-state trough concentration remains the default sampling strategy. Clinical scenarios warranting measurement include early or unexpected disease progression, recurrent or severe adverse events, suspected drug–drug interactions, altered absorption, organ dysfunction, or concerns regarding adherence. Model-informed precision dosing extends conventional monitoring by integrating patient-specific covariates with pharmacokinetic models to simulate individualized dosing regimens. In conclusion, therapeutic drug monitoring and model-informed precision dosing are ready for selective clinical adoption in a subset of oral targeted therapies. Future prospective trials integrating pharmacometric tools with patient-centered outcomes are required to refine exposure targets and expand evidence-based implementation.

Early cardiac events (ECE) are a recognized cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT), especially with the widespread use of post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis. Identifying patients at risk for ECE is crucial to optimize preventive strategies and improve outcomes. To validate the predictive performance of the CARE-BMT score for identifying patients at risk of ECE after allo-HCT and to determine whether incorporating PTCy exposure enhances its prognostic value. A retrospective cohort study including 593 adult patients who underwent allo-HCT between 2011 and 2023 at a single institution. ECE was defined as any new cardiac event within 100 days post-HCT. The CARE-BMT score-based on age, race, cardiac comorbidities, serum creatinine, triglyceride levels, and prior anthracycline exposure-was applied to stratify patients into intermediate- and high-risk groups. A modified-CARE-BMT score was developed by adding two points for standard-dose PTCy exposure. Survival analyses, cumulative incidence functions, and multivariate regression models were used to assess associations. ECE occurred in 47 patients (7.9%), with a median onset at 21 days post-HCT, and was associated with inferior one-year overall survival (48.6% vs. 75.0%, p<0.001). The CARE-BMT score stratified patients into intermediate- and high-risk groups with Day +100 ECE incidences of 5.8% and 11.2%, respectively (p=0.033). Standard-dose PTCy (50 mg/kg/day) was independently associated with increased ECE risk (p=0.014). The modified-CARE-BMT score stratified patients into low-, intermediate-, and high-risk groups with respective ECE incidences of 4.5%, 9.5%, and 12.7% (p=0.037). EASIX trajectories further supported the stratification capability of the modified model. The CARE-BMT score effectively predicts early cardiac events in allo-HCT recipients. Incorporating PTCy exposure into a modified risk model enhances its discriminatory power, allowing improved identification of high-risk patients who may benefit from tailored cardioprotective interventions and monitoring strategies.

Enoxaparin, a low molecular weight heparin, is widely used for venous thromboembolism treatment and prevention. While routine anti-factor Xa (anti-Xa) monitoring is not generally required, it may be valuable in high-risk populations such as patients with obesity or renal impairment. To evaluate the impact of clinical variables on therapeutic enoxaparin dosing and assess the effectiveness of anti-Xa monitoring in real-world clinical practice. A retrospective, single-centre, descriptive study was conducted in adults admitted to hospital and receiving therapeutic enoxaparin with correctly timed peak anti-Xa measurements (4 hours after dose) between December 2021 and January 2023. Demographic, clinical and dosing data were extracted from medical records. Predictors of peak anti-Xa concentration were identified using multiple linear regression. Dose-concentration correlations were examined overall and by obesity status. A total of 146 patients were included (mean age 67±12.3 years; 56.2% male; mean body mass index 29.6±7.5 kg/m²; 30.1% with obesity). Enoxaparin dose (p<0.001) and obesity (p=0.007) were independent predictors of peak anti-Xa concentration; renal impairment and critical illness were not. The correlation between dose and concentration was strong in patients without obesity (r=0.56) but weak in those with obesity (r=0.16). Only 46.6% achieved therapeutic concentrations; 40.4% were subtherapeutic and 12.9% supratherapeutic. Among patients with out-of-range values, dose adjustments were made in 67.9%, but follow-up anti-Xa measurement occurred in only 45.3%; 79.2% of these achieved target concentrations. Obesity significantly influences enoxaparin pharmacokinetics, reducing predictability of anti-Xa concentrations with actual body weight dosing. Targeted anti-Xa monitoring in high-risk groups, particularly patients with obesity, and structured dose-adjustment protocols may improve therapeutic achievement and safety.