Drug-drug interaction: decreased posaconazole trough concentrations during concomitant flucloxacillin treatment.

BACKGROUND AND OBJECTIVES: Posaconazole is used as prophylaxis of invasive fungal disease in immune-compromised haematological patients with prolonged neutropenia after intensive chemotherapy. During routine therapeutic drug monitoring of posaconazole, we repeatedly observed low posaconazole serum concentrations in patients that were concomitantly treated with flucloxacillin. A possible interaction between flucloxacillin and posaconazole was explored in this case series. PATIENTS AND METHODS: Posaconazole trough serum concentrations during and before/after flucloxacillin treatment were collected from 10 patients. RESULTS: With a median concentration of 0.5 mg/L (IQR 0.3-0.6), the posaconazole trough serum concentration decreased by 47% during flucloxacillin treatment compared with the concentration before/after flucloxacillin treatment (0.9 mg/L, IQR 0.6-1.3). As a result, the posaconazole target trough concentration of ≥0.7 mg/L was only achieved in five out of nine patients during flucloxacillin treatment. CONCLUSIONS: Careful monitoring of posaconazole serum trough concentrations is recommended when concomitant use of flucloxacillin cannot be avoided.

Hypokalaemia in patients treated with intravenous flucloxacillin: Incidence and risk factors.

INTRODUCTION: Hypokalaemia is a potentially life-threatening adverse event of flucloxacillin with unknown incidence. The risk of flucloxacillin-induced hypokalaemia has recently been suggested to be increased among females compared to males. The aim of this study is to describe the incidence and to determine the influence of sex and other risk factors on flucloxacillin-induced hypokalaemia. METHODS: A retrospective single-centre cohort study was performed. Patients treated with intravenous flucloxacillin for >24 hours between January 2017 and October 2020, a baseline potassium level of ≥3.5 mmol/L and potassium measurement during treatment were included. The primary endpoint was incidence of hypokalaemia defined as the percentage of patients with a potassium measurement <3.5 mmol/L during flucloxacillin treatment. Logistic regression modelling was used to establish risk factors for hypokalaemia. RESULTS: A total of 835 patients were included, 58.2% male and median age 71.0 years (interquartile range 61.0-81.0). The incidence of hypokalaemia was 23.7% (28.4% in females vs 20.4% in males). A dose-dependent relation between sex and the incidence of hypokalaemia was found. The risk of hypokalaemia was 4.41 (95% confidence interval 1.47-13.24) times higher in females compared to males when receiving a flucloxacillin dose of >8 g/24 h. No sex differences were found for lower daily doses. Other risk factors for hypokalaemia were older age, concomitant antibiotic use, lower bodyweight, lower baseline plasma potassium concentration and longer treatment duration. CONCLUSION: Hypokalaemia is a frequent complication in patients treated with intravenous flucloxacillin. Females receiving >8 g intravenous flucloxacillin per day are more prone to develop hypokalaemia compared to males.

Drug-induced Liver Injury in a Patient With Coronavirus Disease 2019: Potential Interaction of Remdesivir With P-Glycoprotein Inhibitors.

We report a case of a man with COVID-19 who developed acute hepatotoxicity related to remdesivir with probable interaction of P-glycoprotein (P-gp) inhibitors. Until further details on this interaction become available, we recommend physicians to be cautious with the prescription of P-gp inhibitors in patients receiving remdesivir therapy.

Population Pharmacokinetics of Trimethoprim/Sulfamethoxazole: Dosage Optimization for Patients with Renal Insufficiency or Receiving Continuous Renal Replacement Therapy.

The goal of the study was to describe the population pharmacokinetics of trimethoprim, sulfamethoxazole, and N-acetyl sulfamethoxazole in hospitalized patients. Furthermore, this study used the model to optimize dosing regimens of cotrimoxazole for Pneumocystis jirovecii pneumonia and in patients with renal insufficiency or with continuous renal replacement therapy (CRRT). This was a retrospective multicenter observational cohort study based on therapeutic drug monitoring (TDM) data from hospitalized patients treated with cotrimoxazole. We developed two population pharmacokinetic (POPPK) models: a model of trimethoprim and an integrated model with both sulfamethoxazole and N-acetyl sulfamethoxazole concentrations. Monte Carlo simulations were performed to determine the optimal dosing regimen. A total of 348 measurements from 168 patients were available. The estimated glomerular filtration rate (eGFR) and CRRT were included as covariates on the clearance of all three compounds. Cotrimoxazole TID 1,920 mg and b.i.d. 2,400 mg led to sufficient exposure for infections with P. jirovecii in patients without renal insufficiency. To reach equivalent exposure, a dose reduction of 33.3% is needed in patients with an eGFR of 10 mL/minute/1.73 m2 and of 16.7% for an eGFR of 30 mL/minute/1.73 m2. N-acetyl sulfamethoxazole accumulates in patients with a reduced eGFR. CRRT increased the clearance of sulfamethoxazole, but not trimethoprim or N-acetyl sulfamethoxazole, compared with the median clearance in the population. Doubling the sulfamethoxazole dose is needed for patients on CRRT to reach equivalent exposure.

[Intoxications with synthetic cannabinoids]. / Intoxicaties met synthetische cannabinoïden.

Synthetic Cannabinoid Receptor Agonists (SCRAs) are a group of New Psychoactive Substances. They are used recreationally to mimic the effects of THC in cannabis. However, THC is a partial agonist of the CB1-receptor and SCRAs are full agonists. Because of this specificity and potency serious adverse events may occur among which psychological, cardiovascular, and gastro-intestinal symptoms. Because of the low incidence in the Netherlands clinical information on SCRA intoxications is limited, making diagnosis and treatment difficult. In this clinical lesson, two cases of SCRA intoxications are described followed by treatment recommendations.

[Intoxications with synthetic cannabinoids]. / Intoxicaties met synthetische cannabinoïden.

Synthetic Cannabinoid Receptor Agonists (SCRAs) are a group of New Psychoactive Substances. They are used recreationally to mimic the effects of THC in cannabis. However, THC is a partial agonist of the CB1-receptor and SCRAs are full agonists. Because of this specificity and potency serious adverse events may occur among which psychological, cardiovascular, and gastro-intestinal symptoms. Because of the low incidence in the Netherlands clinical information on SCRA intoxications is limited, making diagnosis and treatment difficult. In this clinical lesson, two cases of SCRA intoxications are described followed by treatment recommendations.

Optimization of ß-Lactam Dosing Regimens in Neonatal Infections: Continuous and Extended Administration versus Intermittent Administration.

BACKGROUND AND OBJECTIVE: In neonates, ß-Lactam antibiotics are almost exclusively administered by intermittent infusion. However, continuous or prolonged infusion may be more beneficial because of the time-dependent antibacterial activity. In this pharmacokinetic/pharmacodynamic simulation study, we aimed to compare treatment with continuous, extended and intermittent infusion of ß-lactam antibiotics for neonates with infectious diseases. METHODS: We selected population pharmacokinetic models of penicillin G, amoxicillin, flucloxacillin, cefotaxime, ceftazidime and meropenem, and performed a Monte Carlo simulation with 30,000 neonates. Four different dosing regimens were simulated: intermittent infusion in 30 min, prolonged infusion in 4 h, continuous infusion, and continuous infusion with a loading dose. The primary endpoint was 90% probability of target attainment (PTA) for 100% ƒT>MIC during the first 48 h of treatment. RESULTS: For all antibiotics except cefotaxime, continuous infusion with a loading dose resulted in a higher PTA compared with other dosing regimens. Sufficient exposure (PTA >90%) using continuous infusion with a loading dose was reached for amoxicillin (90.3%), penicillin G (PTA 98.4%), flucloxacillin (PTA 94.3%), cefotaxime (PTA 100%), and ceftazidime (PTA 100%). Independent of dosing regimen, higher meropenem (PTA for continuous infusion with a loading dose of 85.5%) doses might be needed to treat severe infections in neonates. Ceftazidime and cefotaxime dose might be unnecessarily high, as even with dose reductions, a PTA > 90% was retained. CONCLUSIONS: Continuous infusion after a loading dose leads to a higher PTA compared with continuous, intermittent or prolonged infusion, and therefore has the potential to improve treatment with ß-lactam antibiotics in neonates.

Rapid Response to Remdesivir in Hospitalised COVID-19 Patients: A Propensity Score Weighted Multicentre Cohort Study.

INTRODUCTION: Remdesivir is a registered treatment for hospitalised patients with COVID-19 that has moderate clinical effectiveness. Anecdotally, some patients' respiratory insufficiency seemed to recover particularly rapidly after initiation of remdesivir. In this study, we investigated if this rapid improvement was caused by remdesivir, and which patient characteristics might predict a rapid clinical improvement in response to remdesivir. METHODS: This was a multicentre observational cohort study of hospitalised patients with COVID-19 who required supplemental oxygen and were treated with dexamethasone. Rapid clinical improvement in response to treatment was defined by a reduction of at least 1 L of supplemental oxygen per minute or discharge from the hospital within 72 h after admission. Inverse probability of treatment-weighted logistic regression modelling was used to assess the association between remdesivir and rapid clinical improvement. Secondary endpoints included in-hospital mortality, ICU admission rate and hospitalisation duration. RESULTS: Of 871 patients included, 445 were treated with remdesivir. There was no influence of remdesivir on the occurrence of rapid clinical improvement (62% vs 61% OR 1.05, 95% CI 0.79-1.40; p = 0.76). The in-hospital mortality was lower (14.7% vs 19.8% OR 0.70, 95% CI 0.48-1.02; p = 0.06) for the remdesivir-treated patients. Rapid clinical improvement occurred more often in patients with low C-reactive protein (≤ 75 mg/L) and short duration of symptoms prior to hospitalisation (< 7 days) (OR 2.84, 95% CI 1.07-7.56). CONCLUSION: Remdesivir generally does not increase the incidence of rapid clinical improvement in hospitalised patients with COVID-19, but it might have an effect in patients with short duration of symptoms and limited signs of systemic inflammation.

Ceftriaxone for the Treatment of Chronic Bacterial Prostatitis: A Case Series and Literature Review.

Chronic bacterial prostatitis is increasingly difficult to treat due to rising antimicrobial resistance limiting oral treatment options. In this case series, 11 men with CBP (including patients with urological comorbidities) due to multi-resistant E. coli were treated with once-daily ceftriaxone intravenously for 6 weeks. Nine patients were clinically cured at 3 months follow up. No early withdrawal of medication due to side effects occurred. A literature review was conducted to describe the prostate pharmacokinetics of ceftriaxone and its use in prostatic infection. In conclusion, ceftriaxone can be considered an appropriate treatment of chronic bacterial prostatitis.