Clinical implementation of partial oral treatment in infective endocarditis: the Danish POETry study.

BACKGROUND AND AIMS: In the Partial Oral Treatment of Endocarditis (POET) trial, stabilized patients with left-sided infective endocarditis (IE) were randomized to oral step-down antibiotic therapy (PO) or conventional continued intravenous antibiotic treatment (IV), showing non-inferiority after 6 months. In this study, the first guideline-driven clinical implementation of the oral step-down POET regimen was examined. METHODS: Patients with IE, caused by Staphylococcus aureus, Enterococcus faecalis, Streptococcus spp. or coagulase-negative staphylococci diagnosed between May 2019 and December 2020 were possible candidates for initiation of oral step-down antibiotic therapy, at the discretion of the treating physician. The composite primary outcome in patients finalizing antibiotic treatment consisted of embolic events, unplanned cardiac surgery, relapse of bacteraemia and all-cause mortality within 6 months. RESULTS: A total of 562 patients [median age 74 years (IQR, interquartile range, 65-80), 70% males] with IE were possible candidates; PO was given to 240 (43%) patients and IV to 322 (57%) patients. More patients in the IV group had IE caused by S. aureus, or had an intra-cardiac abscess, or a pacemaker and more were surgically treated. The primary outcome occurred in 30 (13%) patients in the PO group and in 59 (18%) patients in the IV group (P = .051); in the PO group, 20 (8%) patients died vs. 46 (14%) patients in the IV group (P = .024). PO-treated patients had a shorter median length of stay [PO 24 days (IQR 17-36) vs. IV 43 days (IQR 32-51), P < .001]. CONCLUSIONS: After clinical implementation of the POET regimen almost half of the possible candidates with IE received oral step-down antibiotic therapy. Patients in the IV group had more serious risk factors for negative outcomes. At 6-month follow-up, there was a numerically but not statistically significant difference towards a lower incidence of the primary outcome, a lower incidence of all-cause mortality and a reduced length of stay in the PO group. Due to the observational design of the study, the lower mortality may to some extent reflect selection bias and unmeasured confounding. Clinical implementation of PO regimens seemed feasible and safe.

Rifampicin reduces plasma concentration of linezolid in patients with infective endocarditis.

BACKGROUND: Linezolid in combination with rifampicin has been used in treatment of infective endocarditis especially for patients infected with staphylococci. OBJECTIVES: Because rifampicin has been reported to reduce the plasma concentration of linezolid, the present study aimed to characterize the population pharmacokinetics of linezolid for the purpose of quantifying an effect of rifampicin cotreatment. In addition, the possibility of compensation by dosage adjustments was evaluated. PATIENTS AND METHODS: Pharmacokinetic measurements were performed in 62 patients treated with linezolid for left-sided infective endocarditis in the Partial Oral Endocarditis Treatment (POET) trial. Fifteen patients were cotreated with rifampicin. A total of 437 linezolid plasma concentrations were obtained. The pharmacokinetic data were adequately described by a one-compartment model with first-order absorption and first-order elimination. RESULTS: We demonstrated a substantial increase of linezolid clearance by 150% (95% CI: 78%-251%), when combined with rifampicin. The final model was evaluated by goodness-of-fit plots showing an acceptable fit, and a visual predictive check validated the model. Model-based dosing simulations showed that rifampicin cotreatment decreased the PTA of linezolid from 94.3% to 34.9% and from 52.7% to 3.5% for MICs of 2 mg/L and 4 mg/L, respectively. CONCLUSIONS: A substantial interaction between linezolid and rifampicin was detected in patients with infective endocarditis, and the interaction was stronger than previously reported. Model-based simulations showed that increasing the linezolid dose might compensate without increasing the risk of adverse effects to the same degree.

Attainment of Target Antibiotic Levels by Oral Treatment of Left-Sided Infective Endocarditis: A POET Substudy.

BACKGROUND: In the POET (Partial Oral Endocarditis Treatment) trial, oral step-down therapy was noninferior to full-length intravenous antibiotic administration. The aim of the present study was to perform pharmacokinetic/pharmacodynamic analyses for oral treatments of infective endocarditis to assess the probabilities of target attainment (PTAs). METHODS: Plasma concentrations of oral antibiotics were measured at day 1 and 5. Minimal inhibitory concentrations (MICs) were determined for the bacteria causing infective endocarditis (streptococci, staphylococci, or enterococci). Pharmacokinetic/pharmacodynamic targets were predefined according to literature using time above MIC or the ratio of area under the curve to MIC. Population pharmacokinetic modeling and pharmacokinetic/pharmacodynamic analyses were done for amoxicillin, dicloxacillin, linezolid, moxifloxacin, and rifampicin, and PTAs were calculated. RESULTS: A total of 236 patients participated in this POET substudy. For amoxicillin and linezolid, the PTAs were 88%-100%. For moxifloxacin and rifampicin, the PTAs were 71%-100%. Using a clinical breakpoint for staphylococci, the PTAs for dicloxacillin were 9%-17%.Seventy-four patients at day 1 and 65 patients at day 5 had available pharmacokinetic and MIC data for 2 oral antibiotics. Of those, 13 patients at day 1 and 14 patients at day 5 did only reach the target for 1 antibiotic. One patient did not reach target for any of the 2 antibiotics. CONCLUSIONS: For the individual orally administered antibiotic, the majority reached the target level. Patients with sub-target levels were compensated by the administration of 2 different antibiotics. The findings support the efficacy of oral step-down antibiotic treatment in patients with infective endocarditis.

Severity of anaemia and association with all-cause mortality in patients with medically managed left-sided endocarditis.

OBJECTIVE: To assess the prevalence and severity of anaemia in patients with left-sided infective endocarditis (IE) and association with mortality. METHODS: In the Partial Oral versus Intravenous Antibiotic Treatment of Endocarditis trial, 400 patients with IE were randomised to conventional or partial oral antibiotic treatment after stabilisation of infection, showing non-inferiority. Haemoglobin (Hgb) levels were measured at randomisation. Primary outcomes were all-cause mortality after 6 months and 3 years. Patients who underwent valve surgery were excluded due to competing reasons for anaemia. RESULTS: Out of 400 patients with IE, 248 (mean age 70.6 years (SD 11.1), 62 women (25.0%)) were medically managed; 37 (14.9%) patients had no anaemia, 139 (56.1%) had mild anaemia (Hgb <8.1 mmol/L in men and Hgb <7.5 mmol/L in women and Hgb ≥6.2 mmol/L) and 72 (29.0%) had moderate to severe anaemia (Hgb <6.2 mmol/L). Mortality rates in patients with no anaemia, mild anaemia and moderate to severe anaemia were 2.7%, 3.6% and 15.3% at 6-month follow-up and 13.5%, 20.1% and 34.7% at 3-year follow-up, respectively. Moderate to severe anaemia was associated with higher mortality after 6 months (HR 4.81, 95% CI 1.78 to 13.0, p=0.002) and after 3 years (HR 2.14, 95% CI 1.27 to 3.60, p=0.004) and remained significant after multivariable adjustment. CONCLUSION: Moderate to severe anaemia was present in 29% of patients with medically treated IE after stabilisation of infection and was independently associated with higher mortality within the following 3 years. Further investigations are warranted to determine whether intensified treatment of anaemia in patients with IE might improve outcome.