Evaluation of the drug-drug interaction between triazole antifungals and cystic fibrosis transmembrane conductance regulator modulators in a real-life cohort

Limited data on the clinical management of drug-drug interactions between triazoles and Cystic Fibrosis transmembrane conductance regulator (CFTR) modulators are available. We retrospectively evaluated azole target attainment and dose adaptations in patients from two Dutch CF centres concomitantly receiving triazoles and CFTR modulators. In total, 21 patients with 59 triazole trough concentrations were evaluated. Subtherapeutic concentrations were frequently observed, especially for itraconazole and voriconazole. Of the investigated antifungal agents, posaconazole appears the most preferable option. Our results emphasize the importance of adequate management of this interaction and underpin the added value of therapeutic drug monitoring of triazoles in this population.

Elexacaftor/tezacaftor/ivacaftor in liver or kidney transplanted people with cystic fibrosis using tacrolimus, a drug-drug interaction study

BACKGROUND

The use of elexacaftor/tezacaftor/ivacaftor (ETI) in people with cystic fibrosis (pwCF) after solid organ transplantation is controversial because of potential drug-drug interactions (DDI) with tacrolimus. We aimed to improve insight into the safety and clinical benefits of co-administration of ETI and tacrolimus in liver or kidney transplanted adult pwCF.

METHODS

In 5 pwCF, tacrolimus concentrations were monitored during 2 weeks before and 4 weeks after starting ETI treatment. Trough levels, area under the curve (AUC) and clinical effect of ETI were investigated. During the study (6 weeks in total) adverse events were monitored.

RESULTS

The DDI between tacrolimus and ETI resulted in an increased exposure of tacrolimus in all subjects, the dose adjusted AUC0-24h was 1.79 (median) times higher at the end of the study. Five dose adjustments were performed in 4 subjects in order to attain tacrolimus target range. No adverse events were reported and all subjects showed clinical improvement during ETI treatment.

CONCLUSION

The clinical value of ETI treatment in kidney and liver transplanted pwCF is clear. The use of ETI may increase tacrolimus levels moderately. Therefore, we recommend close monitoring of tacrolimus trough levels in patients who start ETI.

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.

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.

[Intoxications with synthetic cannabinoids]

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]

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.

Real-life safety of PD-1 and PD-L1 inhibitors in older patients with cancer: An observational study

OBJECTIVE

To compare the real-world safety profile of programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1) inhibitors between younger and older patients.

METHODS

All patients receiving pembrolizumab, nivolumab, atezolizumab or durvalumab between September 2016 and September 2019 at Haga Teaching Hospital, The Hague, The Netherlands were included in this retrospective study. Immune-related adverse drug reactions (irADRs) were manually retrieved from the electronic patient files. The cumulative incidence of irADRs were compared between younger (<65 years) and older (≥65 years) patients using a Pearsons Chi-square test.

RESULTS

We identified 217 patients who were treated with at least one dose of PD-(L)1 inhibitor. 58% were 65 years or older at the start of immunotherapy. 183 patients (84.3%) received monotherapy PD-(L)1 inhibitors and 34 (15.7%) received chemo-immunotherapy. A total of 278 irADRs were registered. Cutaneous irADRs (53.9%), thyroid gland disorders (20.3%), and non-infectious diarrhoea/colitis (17.5%) were the most frequently reported irADRs. The majority of the irADRs were mild to moderate and no fatal irADRs were observed. 61 (21.9%) of the irADRs needed systemic treatment, of which 19 (6.8%) required treatment with corticosteroids. 18 irADRs (6.5%) were severe and resulted in hospitalisation. The cumulative incidence of cutaneous irADRs was different between the age groups: 45.7% of the patients <65 years and in 60.0% of the patients ≥65 years (p = 0.036). No statistical difference was found in the cumulative incidence of other irADRs between the two age groups.

CONCLUSION

Advanced age is not associated with immune-related adverse drug reactions of PD-1 and PD-L1 inhibitors.

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.

Population pharmacokinetics of ceftriaxone administered as continuous or intermittent infusion in critically ill patients

OBJECTIVES

To describe the population pharmacokinetics and protein-binding characteristics of unbound ceftriaxone administered as continuous or intermittent infusion. Additionally, to determine the optimal dosing regimen in critically ill patients.

METHODS

A pharmacokinetic study was performed in the ICU of a tertiary teaching hospital. Patients were treated with ceftriaxone as continuous or intermittent infusion. A population pharmacokinetic model was developed with non-linear mixed-effects analysis. Subsequently, the PTA of a 100% T>MIC was assessed for influential patient characteristics using Monte Carlo simulation.

RESULTS

Fifty-five patients were included. The pharmacokinetics of ceftriaxone was best described by a one-compartment model with non-linear saturable protein binding including the following covariates: body weight, estimated CLCR, serum albumin concentration and mode of administration. For pathogens with an MIC of 1 mg/L, the simulation demonstrated that intermittent infusion of 2 g/24 h only resulted in a ≥90% PTA in patients with a reduced CLCR (0-60 mL/min). Intermittent infusion of 2 g/12 h led to sufficient exposure if CLCR was 0-90 mL/min and continuous infusion of 2 g/24 h led to a ≥90% PTA in all simulations (CLCR 0-180 mL/min).

CONCLUSIONS

In the critically ill, the clearance of unbound ceftriaxone is closely related to CLCR. Furthermore, ceftriaxone protein binding is saturable, variable and dependent on serum albumin concentration. Intermittent dosing of 2 g/24 h ceftriaxone leads to subtherapeutic exposure in patients with a normal or increased CLCR. Treating these patients with continuous infusion of 2 g/24 h is more effective than an intermittent dosing regimen of 2 g/12 h.

Pharmacokinetics of fosfomycin in patients with prophylactic treatment for recurrent Escherichia coli urinary tract infection

Objectives

To evaluate the pharmacokinetics and clinical effectiveness of IV and oral fosfomycin treatment in patients with recurrent urinary tract infection (rUTI) with Escherichia coli.

Patients and methods

Patients with rUTI treated with 3 g of oral fosfomycin every 72 h for at least 14 days were included in a prospective open-label single-centre study. Serum samples were taken after oral and IV administration of fosfomycin. Urine was collected for 24 h on 3 consecutive days. Fosfomycin concentrations in serum and urine were analysed using validated LC–MS/MS. Pharmacokinetics were evaluated using a population model. EudraCT number 2018-000616-25.

Results

Twelve patients were included, of whom nine were also administered IV fosfomycin. Data were best described by a two-compartment model with linear elimination and a transit-absorption compartment. Median values for absolute bioavailability and serum half-life were 18% and 2.13 h, respectively. Geometric mean urine concentrations on Days 1, 2 and 3 were above an MIC of 8 mg/L after both oral and IV administration. Quality of life reported on a scale of 1–10 increased from 5.1 to 7.4 (P = 0.001). The average score of UTI symptoms decreased after fosfomycin dosing (by 3.1 points, 95% CI = −0.7 to 7.0, P = 0.10).

Conclusions

Oral fosfomycin at 3 g every 72 h provides plasma and urine concentrations of fosfomycin above the MIC for E. coli. This pharmacokinetic model can be used to develop optimal dosing regimens of fosfomycin in patients with UTI.

Pharmacokinetic interactions between ivacaftor and cytochrome P450 3A4 inhibitors in people with cystic fibrosis and healthy controls

BACKGROUND

Ivacaftor is currently the only CFTR potentiator approved and is increasingly used since the development of CFTR correctors. Ivacaftor is metabolized by CYP3A4 and therefore dose reduction is required when treating patients on ivacaftor with CYP3A4 inhibiting drugs. As this advice is based on studies in healthy volunteers and not in cystic fibrosis (CF) patients, we need to investigate this in both groups to be able to extrapolate these data to CF.

METHODS

A cohort of CF patients and healthy subjects were exposed to a single dose of ivacaftor in combination with a strong (ritonavir), moderate (clarithromycin) and mild (azithromycin) CYP3A4 inhibitor. Ivacaftor concentrations were measured in all blood samples in order to calculate the pharmacokinetic parameters for ivacaftor.

RESULTS

We found that exposure to ivacaftor was higher in healthy volunteers than in subjects with CF. However this difference was not statistically significant. No differences were observed in the interaction potential of CYP3A4 inhibitors between both study groups. The strong CYP3A4 inhibitor ritonavir, increased exposure to ivacaftor 7 times.

CONCLUSION

Our data support current recommendations for dose adjustment of ivacaftor in case of co-treatment with CYP3A4 inhibitors in people with CF. However, exposure to ivacaftor was higher in healthy subjects than in CF patients. Further study is needed to investigate the cause and implication of this difference.

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.

Sulpiride intoxication: Case report of a rare intoxication

Intoxications with sulpiride, an antipsychotic, are rare, and only limited literature is available. We describe a successful treatment of a sulpiride intoxication. A 67-year-old female, with a history of intentional suicide attempt, was admitted to the emergency department (ED) because of a suspected out-of-hospital cardiac arrest. At presentation, she was haemodynamically unstable, with a Glasgow Coma Scale of 3 and slight prolongation of QTc time. History taken from her husband raised suspicion of a suicide attempt with medication. Consultation of the on-call pharmacist and performance of a toxicology screening accelerated the diagnosis of a sulpiride intoxication. The patient was intubated because of respiratory insufficiency, admitted to the Intensive Care Unit (ICU) and treated with activated charcoal, laxatives and sodium bicarbonate. The following day, she was extubated with stable haemodynamics and a normalized ECG. Treatment of sulpiride intoxications is mainly symptomatic and consists of supportive care. An important note is the avoidance of antiarrhythmic drugs, except for lidocaine, epinephrine and dopamine, as they might worsen arrhythmia and hypotension.

Vancomycin pharmacokinetic model development in patients on intermittent online hemodiafiltration

BACKGROUND

Vancomycin is frequently used in hemodialysis (HD) and in hemodiafiltration (HDF) patients and is usually administered in the last 30 or 60 minutes of a dialysis session. Vancomycin pharmacokinetics are not well described in HDF patients. The aim of this study is to develop a population pharmacokinetic (PPK) model and dosing regimen for vancomycin in HDF patients and to evaluate its applicability in low-flux (LF-HD) patients.

METHODS

Two-compartment PPK models were developed using data from HDF patients (n = 17), and was parameterized as follows: non-renal clearance (CLm), renal clearance as a fraction of creatinine clearance (fr), central volume of distribution (V1), intercompartmental clearance (CL12), peripheral volume of distribution (V2) and extracorporeal extraction ratio (Eec). We evaluated the final model in a cohort of LF-HD patients (n = 21). Dosing schemes were developed for a vancomycin 24-h AUC of 400 mg*h/L.

RESULTS

Model parameters (± SD) were: CLm = 0.473 (0.271) L/h, fr = 0.1 (fixed value), V1 = 0.278 (0.092) L/kgLBMc, CL12 = 9.96 L/h (fixed value), V2 = 0.686 (0.335) L/kgLBMc and Eec = 0.212 (0.069). The model reliably predicted serum levels of vancomycin in both HDF and LF-HD patients during and between dialysis sessions. The median of the prediction error (MDPE) as a measure of bias is -0.7% (95% CI: -3.4%-1.7%) and the median of the absolute values of the prediction errors (MDAPE) as a measure of precision is 7.9% (95% CI: 6.0%-9.8%). In both HDF and LF-HD, the optimal vancomycin loading dose for a typical patient weighing 70 kg is 1700 mg when administered during the last 60 minutes of the hemodialysis session. Maintenance dose is 700 mg if administered during the last 30 or 60 minutes of the hemodialysis session.

CONCLUSION

The developed PPK model for HDF is also capable of predicting serum levels of vancomycin in patients on LF-HD. A dosing regimen was developed for the use of vancomycin in HDF and LF-HD.

Fosfomycin as a potential therapy for the treatment of systemic infections: a population pharmacokinetic model to simulate multiple dosing regimens

Fosfomycin has emerged as a potential therapy for multidrug-resistant bacterial infections. In most European countries, the oral formulation is only approved as a 3 g single dose for treatment of uncomplicated cystitis. However, for the treatment of complicated systemic infections, this dose regimen is unlikely to reach efficacious serum and tissue concentrations. This study aims to investigate different fosfomycin-dosing regimens to evaluate its rationale for treatment of systemic infections. Serum concentration-time profiles of fosfomycin were simulated using a population pharmacokinetic model based on published pharmacokinetic parameter values, their uncertainty, inter-individual variability and covariates. The model was validated on published data and used to simulate a wide range of dosing regimens for oral and intravenous administration of fosfomycin. Finally, based on the minimum inhibitory concentration for E. coli, surrogate pharmacodynamic indices were calculated for each dosing regimen. This is the first population pharmacokinetic model to describe the oral pharmacokinetics of fosfomycin using data from different literature sources. The model and surrogate pharmacodynamic indices provide quantitative evidence that a dosing regimen of 6-12 g per day divided in 3 doses is required to obtain efficacious exposure and may serve as a first step in the treatment of systemic multi-drug-resistant bacterial infections.

A fast and sensitive LC-MS/MS method for the quantification of fosfomycin in human urine and plasma using one sample preparation method and HILIC chromatography

Fosfomycin is an old antibiotic that is increasingly prescribed because of emergence of the antibiotic resistance and the growing incidence of multi-drug resistant infections. Surprisingly, little is known about its pharmacokinetics (PK) and the pharmacodynamics (PD). Quantification of fosfomycin in both urine and plasma provides insight into the PK/PD characteristics of fosfomycin, which is crucial for the optimization of the therapy and the prevention of the emergence of resistance. An analytical method is therefore needed for the quantification of fosfomycin in both urine and plasma. A fast and sensitive tandem mass spectrometry method in combination with HILIC chromatography for the quantification of fosfomycin with a universal sample preparation method for urine and plasma was developed and validated according to FDA guidelines. The universal sample preparation method only requires 100μL of a sample, the addition of the internal standard fosfomycin-13C₃ benzylamine and an ultrafiltration step. The method is applicable for the concentration range of 0.75-375mg/L (R² of 0.9998 in both matrices) encompassing the clinically relevant concentration range based on the susceptibility of possible (uro)pathogens in the clinical setting. The validation results for urine and plasma for all QC levels, were <2.1% and <3.2% for accuracy, <1.5% and <1.7% for within day precision and <5.0% and <3.8% for between day precision, respectively. No matrix effects were encountered and the total recovery in urine and plasma was high (102.5% and 99.4%). Prepared samples were stable at 4°C and 15°C for at least 72h and stored samples at -80°C were stable for at least 6 months. Selectivity and sensitivity were confirmed and no carry-over was observed. The method was successfully applied in two pharmacokinetic studies in healthy volunteers and patients respectively.

Colistin methanesulfonate infusion solutions are stable over time and suitable for home administration

The stability of colistin methanesulfonate (CMS) was determined in quadruplicate in elastomeric home infusion pumps containing 1, 2 or 3 MU CMS and in infusion bags with 2 MU CMS all in 100 mL normal saline. Infusions were stored at room temperature (20°C-24°C) with or without exposure to natural light or refrigerated (4°C-8°C) and protected from light up to 2 weeks. In the initial solution of 2 MU CMS in 100 mL saline sampled immediately after reconstitution and dilution, 1.5% of CMS was hydrolysed to colistin. When stored at room temperature and exposed to natural light, colistin concentration in elastomeric infusion pumps increased to 2.6% in 8 days and to 2.1% when stored at 4°C. CMS stability increases at lower temperatures and higher concentrations. Based on the current data, chemical stability of CMS infusion solution is sufficient for a shelf life of 7 days refrigerated plus 1 day at room temperature.

[Fatal intoxication with nicotine for e-cigarette]

BACKGROUND

Since the introduction of the electronic e-cigarette a few years ago, its use has greatly increased. The liquid formulations used in these e-cigarettes contain nicotine in high concentrations; ingestion of these liquids can be fatal.

CASE DESCRIPTION

A 42-year-old male was admitted to the Intensive Care ward due to cardiac arrest. The patient had ingested highly concentrated liquid nicotine, originating from a vial with liquid for e-cigarettes. When the ambulance personnel found the patient he did not have a pulse; following CPR and administration of adrenaline his pulse returned. Upon admission, the plasma nicotine level was high at 3.0 mg/l (reference values for a smoker are 0.01-0.05 mg/l) and the patient's neurological function was poor. The patient was treated symptomatically, but eventually died of a postanoxic encephalopathy.

CONCLUSION

Nicotine e-liquids are highly concentrated. Intentional ingestion can lead to toxic levels of nicotine which are associated with cardiac arrhythmias or arrest. Because even a few millilitres can be lethal, nicotine intoxication due to e-liquid ingestion should be considered potentially life-threatening.

[Fosfomycin, an old antibiotic with new possibilities]

- Fosfomycin is a broad-spectrum antibiotic agent used orally for uncomplicated cystitis. The intravenous form of administration has recently been authorised in the Netherlands.- Thanks to its broad spectrum and extensive tissue penetration, fosfomycin offers possibilities for the treatment of infections in different organs.- Infections with multidrug-resistant bacteria pose a significant threat to public health. Many of these multidrug-resistant bacteria are sensitive to fosfomycin, which means fosfomycin may be an option for the treatment of infections with multidrug-resistant bacteria. - There is a lack of knowledge about the pharmacological properties of fosfomycin to establish a good dosing schedule. Knowledge is also lacking about the safety of fosfomycin and the extent of its tolerability in the treatment of different infections. - More research is needed before fosfomycin can be used in the battle against multidrug-resistant bacteria.

Cardiac monitoring of high-dose verapamil in cluster headache: An international Delphi study

Background

In many patients, high-dose verapamil (HDV) is the only effective prophylactic treatment for cluster headache. Although cardiac adverse events and EKG abnormalities are relatively common, evidence-based guidelines for screening and monitoring patients on HDV are lacking.

Goal and methods

Using the Delphi approach, we interviewed 22 international clinical experts in cardiac rhythm disorders to formulate EKG guidelines for the pretreatment screening and monitoring of cluster headache patients using HDV.

Results

The panel agreed only on performing pretreatment EKG to screen for pre-existing cardiac arrhythmia. Pretreatment EKG was deemed not necessary by most panel members for patients who did not have cardiac adverse events during a previous period of cluster headache attacks treated with HDV. Half the panel advised Holter EKG for patients on verapamil ≥ 480 mg/day. The highest recommended daily doses varied between 240 and 960 mg. Contraindications for use of verapamil largely followed FDA guidelines.

Discussion

Experts in cardiac rhythm disorders agreed on pretreatment EKG monitoring, but no consensus was reached on EKG monitoring during HDV treatment and around dose adjustments.

Colistin: Revival of an Old Polymyxin Antibiotic

Colistin (polymyxin E) is a positively charged deca-peptide antibiotic that disrupts the integrity of the outer membrane of the cell wall of gram-negative bacteria by binding to the lipid A moiety of lipopolysaccharides, resulting in cell death. The endotoxic activity of lipopolysaccharides is simultaneously inhibited. Colistin is increasingly being prescribed as rescue treatment for infections with multidrug-resistant bacilli. Nephrotoxicity and, to a lesser degree, neurotoxicity occur often during systemic colistin therapy, and have severely limited its application in the past. However, these side effects are largely reversible and can be managed through close monitoring. The prodrug colistimethate sodium (CMS) is less toxic and is, therefore, the preferred formulation for parenteral administration. Importantly, resistance to colistin seems to emerge often unless it is combined with another antibiotic, but further studies into this phenomenon are necessary. Pharmacokinetic and pharmacodynamic properties have received little attention, partly because of the physicochemical peculiarities of polymyxin antibiotics, especially their propensity to stick to other molecules and surfaces. The ratio between the area under the curve of free colistin and the pathogen's Minimal Inhibitory Concentration (MIC) best predicts microbiological and clinical responses, but more studies are needed in this area. Likewise, further standardization is needed in production and labeling of colistin formulations, and in the way the susceptibility of bacteria to colistin is determined.

[Auto-intoxication with an illegal slimming product]

BACKGROUND

Dexaprine is an illegal slimming product with known serious adverse cardiac effects. Despite warnings from the Netherlands Food and Consumer Product Safety Authority, Dexaprine is still readily available online.

CASE DESCRIPTION

A 29-year-old woman was brought into the emergency room after a suicide attempt with 29 Dexaprine tablets. The symptoms on admission were agitation, nausea and vomiting, hypotension, atrioventricular nodal reentrant tachycardia and hypothermia. Extensive drug screening revealed that Dexaprine contains caffeine, amphetamine and theophylline, explaining the symptoms. The patient was admitted to the intensive care unit for supportive therapy overnight before being discharged.

CONCLUSIONS

In contrast to the advertised composition, Dexaprine contains several pharmacologically active substances including caffeine, amphetamine and theophylline. In intoxications caused by products of unknown composition, additional toxicological screening is invaluable to determine the extent and severity of intoxication. In this case, the patient's symptoms were due to theophylline intoxication. Ultimately, the theophylline levels did not indicate additional treatment such as haemodialysis.

[Metformin, renal function and lactate: the MetClear Study]

OBJECTIVE

To map the relation between metformin prescription and renal function in an outpatient setting. To investigate whether there is an association between renal function, metformin concentration and lactate concentration.

DESIGN

Pilot for a prospective observational cohort study.

METHOD

We included outpatients with diabetes mellitus type 2 who were treated with metformin. At inclusion, we determined the HbA1c, lactate, metformin and creatinine concentrations and the estimated glomerular filtration rate (eGFR). Information on the prescribed dosage of metformin was acquired from patient files. Our primary outcome measure was the number of patients in whom the dose was not adjusted to the renal function. Our secondary outcome measure was the difference in median lactate concentration between patients with a normal (≤ 2.5 mg/l) and an increased (> 2.5 mg/l) metformin concentration.

RESULTS

Eighty-eight patients were included, 12 (14%) of whom had an eGFR ≤ 30, 31 (36%) an eGFR of 30-50 and 44 (50%) an eGFR > 51 ml/min/1.73 m2. In 27 (31%) of all patients, the daily dose of metformin exceeded the dose recommended in the practice guidelines. The 28 patients with an increased metformin concentration had a significantly higher median lactate concentration: 2.3 mmol/l compared to 1.5 mmol/l for the 60 patients with a normal metformin concentration (p < 0.0001).

CONCLUSION

Our study shows that in outpatient practice, the metformin dose is not sufficiently adjusted to a reduced renal function in 31% of the patients. The accumulation of metformin appears to be associated with an increased lactate concentration and a reduced renal function. Extra attention to the dose of metformin in reduced renal clearance is therefore recommended.

[Practical guideline for the use of colistin]

Colistin (polymyxin E) binds to the cell wall of gram-negative bacteria, leading to osmotic destruction of the cell. Since its introduction in 1959, colistin has been little used parenterally due to a high incidence of reversible nephrotoxicity and, to a lesser extent, neurotoxicity. Colistin use remained limited to combating Pseudomonas aeruginosa in cystic fibrosis patients. In addition, oral colistin is part of the recently introduced regime of selective digestive tract decontamination in ICU patients. Intravenous administration of colistin is now increasingly prescribed for the control of multi-resistant microorganisms. Colistin monotherapy, however, rapidly selects resistant subpopulations. Therefore, only combination therapy is advised. The prodrug colistimethate sodium is less toxic and is hydrolyzed in vivo to active colistin; colistin is renally cleared. Clinical practice remains hampered by lack of uniformity and standardization of names, dosage units, dosing recommendations and methods of concentration and susceptibility testing.

[Post-injection syndrome after depot injection of olanzapine]

BACKGROUND

Olanzapine pamoate injection is an anti-psychotic depot to be administered intramuscularly once every 2-4 weeks. A post-injection syndrome may occur shortly after administration, resulting in an acute intoxication with olanzapine.

CASE DESCRIPTION

A 42-year-old patient with a schizophrenic disorder lost consciousness 30 min after administration of olanzapine pamoate. He was admitted to a nearby hospital with tachycardia, hypotension, pin-point pupils and respiratory distress leading to reduced oxygen saturation. He was ventilated during one night and recovered within 2 days.

CONCLUSION

A post-injection syndrome may develop after administration of olanzapine pamoate when the entire dose olanzapine is released at once from the muscle. Therefore, the patient should be observed for at least 3 hours after every injection. The risk of a post-injection syndrome and the necessary observation period should to be taken into account when deciding to start treatment with olanzapine pamoate depot.

Azithromycin maintenance therapy in patients with cystic fibrosis: a dose advice based on a review of pharmacokinetics, efficacy, and side effects

Azithromycin maintenance therapy results in improvement of respiratory function in patients with cystic fibrosis (CF). In azithromycin maintenance therapy, several dosing schemes are applied. In this review, we combine current knowledge about azithromycin pharmacokinetics with the dosing schedules used in clinical trials in order to come to a dosing advise which could be generally applicable. We used data from a recently updated Cochrane meta analysis (2011), the reports of clinical trials and pharmacokinetic studies. Based on these data, it was concluded that a dose level of 22-30 mg/kg/week is the lowest dose level with proven efficacy. Due to the extended half-life in patients with CF, the weekly dose of azithromycin can be divided in one to seven dosing moments, depending on patient preference and gastro-intestinal tolerance. No important side effects or interactions with other CF-related drugs have been documented so far.

Safety and pharmacokinetics of intravenous levetiracetam infusion as add-on in status epilepticus

PURPOSE

To evaluate the feasibility and safety of intravenous (iv) levetiracetam (LEV) added to the standard therapeutic regimen in adults with status epilepticus (SE), and as secondary objective to assess a population pharmacokinetic (PK) model for ivLEV in patients with SE.

METHODS

In 12 adults presenting with SE, 2,500 mg ivLEV was added as soon as possible to standardized protocol, consisting of iv clonazepam and/or rectal diazepam, as needed followed by phenytoin or valproic acid. ivLEV was administered over approximately 5 min, in general after administration of clonazepam, regardless the need for further treatment. During 24-h follow-up, patients were observed for any clinically relevant side-effects. Blood samples for PK analysis were available in 10 patients. A population PK model was developed by iterative two-stage Bayesian analysis and compared to PK data of healthy volunteers.

RESULTS

Eleven patients with a median age of 60 years were included in the per protocol analysis. Five were diagnosed as generalized-convulsive SE, five as partial-convulsive SE, and one as a nonconvulsive SE. The median time from hospital admission to ivLEV was 36 min. No serious side effects could be related directly to the administration of ivLEV. During PK analysis, four patients showed a clear distribution phase, lacking in the others. The PK of the population was best described by a two-compartment population model. Mean (standard deviation, SD) population parameters included volume of distribution of central compartment: 0.45 (0.084) L/kg; total body clearance: 0.0476 (0.0147) L/h/kg; distribution rate constants, central to peripheral compartment (k(12)): 0.24 (0.12)/h, and peripheral to central (k(21)): 0.70 (0.22)/h. Mean maximal plasma concentration was 85 (19) mg/L.

DISCUSSION

The addition of ivLEV to the standard regimen for controlling SE seems feasible and safe. PK data of ivLEV in patients with SE correspond to earlier values derived from healthy volunteers, confirming a two-compartment population model.

Pharmacokinetics and sputum penetration of azithromycin during once weekly dosing in cystic fibrosis patients

In this study we examined pharmacokinetics, systemic exposure and sputum penetration of azithromycin (AZM) in CF patients on chronic daily AZM therapy after changing to a once weekly dosing scheme. Eight adult CF patients using AZM 500 mg/day were changed to a once weekly dose of 1000 mg during 3 months. Once per month sputum and blood samples were collected. AZM was quantified in blood plasma and polymorphonuclear neutrophils. The cumulative weekly dose was reduced with a factor of 3.5 (7x500 mg vs. 1x1000 mg weekly). This led to a reduction in area under the curve (AUC+/-S.D.) with a factor of 2.5+/-0.8 in plasma, 2.8+/-0.9 in blood, 2.2+/-1.1 in PMNNs and to a reduction in average sputum concentration with a factor of 3.0 (+/-1.5). At 1000 mg once weekly reduced but still substantial concentrations were achieved in PMNNs and in sputum. Although not significant, a tendency towards less than linear reduction was found. In order to calculate and propose an optimal dosing scheme we need to establish a relation between exposure levels and clinical efficacy.

Epilepsy in patients with brain tumours: epidemiology, mechanisms, and management

Epilepsy is common in patients with brain tumours and can substantially affect daily life, even if the tumour is under control. Several factors affect the mechanism of seizures in brain tumours, including tumour type, tumour location, and peritumoral and genetic changes. Prophylactic use of antiepileptic drugs is not recommended, and potential interactions between antiepileptic and chemotherapeutic agents persuades against the use of enzyme-inducing antiepileptic drugs. Multidrug-resistance proteins prevent the access of antiepileptic drugs into brain parenchyma, which partly explains why seizures are frequently refractory to treatment. Lamotrigine, valproic acid, and topiramate are first-line treatments of choice; if insufficient, add-on treatment with levetiracetam or gabapentin can be recommended. On the basis of clinical studies, we prefer to start treatment with valproic acid, adding levetiracetam if necessary. Risks of cognitive side-effects with antiepileptic drugs can add to previous damage by surgery or radiotherapy, and therefore appropriate choice and dose of antiepileptic drug is crucial.

Intrapleural extravasation of epirubicin, 5-fluouracil, and cyclophosphamide, treated with dexrazoxane

The extravasation of DNA-binding vesicant drugs, such as epirubicin, is a feared complication of chemotherapy and can lead to extensive damage at injury sites. We describe a 56-year-old woman with breast cancer who received adjuvant chemotherapy after a breast-preserving surgical procedure. Due to catheter tip misplacement, epirubicin, 5-fluouracil, and cyclophosphamide were administered intrapleurally. To minimize long-term sequelae, flushing of the cavities and systemic administration of steroids were performed. Besides this treatment, empirically, 3-day therapy with dexrazoxane was added to prevent tissue damage and the risk of cardiac damage. Because of the potential benefits of dexrazoxane and its relatively mild side effects, its use should be considered in cases of the intrapleural extravasation of anthracyclines. We do emphasis the need for stringent surgical and oncological nursing procedures when using central venous access catheters in oncology.

Pharmacokinetics of azithromycin in plasma, blood, polymorphonuclear neutrophils and sputum during long-term therapy in patients with cystic fibrosis

Chronic therapy with the macrolide antibiotic azithromycin (AZM) is widely practiced in the treatment of patients with cystic fibrosis (CF) and chronic lung infection with Pseudomonas aeruginosa. Azithromycin dosage is variable, based on published studies, and not supported by pharmacokinetic data. This study describes the pharmacokinetics of the long-term administration of AZM (500 mg per day) in CF patients. AZM concentrations were quantified in the plasma, blood, isolated polymorphonuclear neutrophils (PMNNs), and sputum of 8 adult CF patients. The AZM distribution t1/2 was 0.1 hours in plasma. The (mean +/- standard deviation) elimination t(1/2) was 102 +/- 20 hours in plasma, 180 +/- 68 hours in blood, and 289 +/- 166 hours in PMNNs. The C(max) of AZM was 0.67 +/- 0.31 mg/L in plasma and 2.01 +/- 0.74 mg/L in blood, of which 1.44 +/- 0.69 mg/L was found in PMNNs. In sputum the concentration of AZM ranged from 12 to 53 mg/L and was still detectable at concentrations in the range 4 to 27 mg/L 10 days after the last dose. On average, the concentration in PMNNs was 2100 times the C(plasma) 24 hours after dosing AZM. These results confirm the accumulation of AZM in PMNNs. The authors conclude that sputum levels are elevated far above plasma and blood concentrations. The long t(1/2) in blood and PMNNs and the slow decrease in sputum levels indicate a less frequent dosing schedule (for instance once weekly) should be studied in future clinical trials of AZM in patients with cystic fibrosis.

[Partial resistance to acenocoumarol and phenprocoumon caused by enzyme polymorphism]

A 78-year-old man was treated with coumarin derivatives following myocardial infarction. The international normalised ratio was not increased by using standard loading doses and dose adjustments for acenocoumarol and phenprocoumon. The desired level of anticoagulation was achieved with a high dosage of phenprocoumon (18-21 mg daily). This dose was associated with a phenprocoumon serum concentration that was ten times higher than the normal therapeutic concentration. The serum concentration of vitamin K1 was low. After exclusion of alternative causes, we concluded that the exceptionally high dose of phenprocoumon needed was due to partial resistance to coumarin derivatives. Partial resistance is related to a polymorphism of the gene coding for the enzyme vitamin K epoxide reductase. The patient was successfully treated with chronic high-dose phenprocoumon. Resistance to coumarin derivatives caused by a congenital polymorphism in the vitamin K reductase gene is a rare phenomenon. Resistance is seldom absolute. The desired anticoagulation effect can be achieved with doses that are 10-20 times higher than standard doses. Phenprocoumon is advantageous in this situation because it requires fewer tablets than acenocoumarol. Determination of serum concentrations of acenocoumarol and phenprocoumon can be used to exclude other causes of treatment resistance.

Treating seizures in patients with brain tumors: drug interactions between antiepileptic and chemotherapeutic agents

Seizures are a common complication in patients with primary brain tumors or brain metastases that require treatment with antiepileptic drugs (AEDs). However, because many AEDs and chemotherapeutics share common metabolic pathways via the hepatic cytochrome P450 (CYP) isoenzymes, there is potential for drug interactions. Phenytoin, carbamazepine, and phenobarbital are potent enzyme-inducing AEDs (EIAEDs) that can cause a decrease in the serum concentration of chemotherapeutics, potentially compromising antitumor activity. Likewise, chemotherapeutics can alter the pharmacokinetics of EIAEDs, resulting in decreased seizure control. Other agents, such as valproic acid, are enzyme-inhibiting AEDs that can impede the metabolism of other drugs, potentially increasing the serum concentration of chemotherapeutics. Therefore, patients receiving valproic acid with concomitant chemotherapy should be monitored closely. A new generation of AEDs that are not metabolized by CYP isoenzymes is currently being developed. Of these, gabapentin and levetiracetam show the most promise in treating epileptic seizures in patients with brain tumors. Interactions between these newer AEDs and chemotherapeutic agents have not been reported. In summary, the potential interactions between AEDs and chemotherapy should be anticipated and appropriate proactive adjustments implemented. Future studies will define the role of newer AEDs in the treatment of patients with primary brain tumors.

[Levetiracetam: an anti-epileptic drug with interesting pharmacokinetic properties]

Levetiracetam is a new anticonvulsant for adjunctive treatment of partial epilepsy. It is well tolerated, with no significant risks, at a dose of 1000-3000 mg/day in adults. The efficacy (> 50% reduction in attacks) in refractory partial epilepsy is 22-40%, depending on the dose. Efficacy was also seen with levetiracetam monotherapy in more than half of the positive responders. Levetiracetam does not cause induction or inhibition of the P450 enzyme system or other enzyme systems, there is no active metabolite and it exhibits almost no protein binding. These factors mean that this drug undergoes no significant interactions with other medication and appears suitable for elderly patients and for conditions requiring complex pharmacotherapy. Compared with other recently registered anti-epilepsy drugs, levetiracetam appears promising in terms of efficacy, tolerability and pharmacokinetics. The simple dosing schedule is an additional benefit.

A prospective study evaluating the response of patients with unrelieved cancer pain to parenteral opioids

BACKGROUND

The initiation of continuous parenteral (subcutaneous or intravenous) opioids or a change of opioid (opioid rotation) are treatment options for patients who fail on oral or transdermal opioids. There are insufficient data on the efficacy of these strategies, and comparative data are unavailable.

METHODS

The authors prospectively evaluated the efficacy of the start of parenteral opioids in 100 patients with cancer pain who failed on conventional opioids. Pain intensity was rated at rest and during movement from 0 to 10 and was categorized as mild (0-4), moderate (5-6), or severe (7-10): Clinically important pain control was defined as a decrease >or= 2 points in pain intensity and pain intensity < 7. Pain control was evaluated on the second day and again when a clinical decision was made to continue or change parenteral opioid treatment after a median of 6 days. The presence of side effects (absent, mild, moderate, or severe) was evaluated.

RESULTS

The mean pain intensity at rest decreased significantly from 6.3 to 4.4 at 48 hours and to 3.4 at the end of treatment. The mean pain intensity during movement decreased significantly from 8.4 to 5.7 at 48 hours and to 4.6 at the end of treatment. Clinically important pain control at rest was seen in 52% of patients at 48 hours, in 71% of patients at the end of treatment; and clinically important pain control during movement was seen in 43% of patients at 48 hours and in 61% of patients at the end of treatment. The proportion of patients with mild pain increased significantly both at rest and during movement. Side effects were present in 78% of patients, and they resolved completely in 32% of patients. The median intravenous morphine equivalent dose increased from 80 mg per day to 135 mg per day at 48 hours and to 201 mg per day at the end of treatment. Results were not different for opioid rotation or for change of route only, nor did the start of antitumour treatment influence the results. In 34% of patients, it was decided to rotate to a second-line parenteral opioid or to start either spinal analgesia or a sedation procedure after a median of 6 days. During follow-up, 18% of patients who were dismissed with parenteral opioids (and 6% of all patients) needed a further change of treatment.

CONCLUSIONS

Parenteral opioids improved the balance between analgesia and side effects in patients with cancer pain who failed on conventional opioids, with an important improvement seen in 71% of patients. On the basis of this study, it is concluded that parenteral opioids are a good alternative to spinal opioids. Furthermore, it is suggested that a change of route alone is as effective as opioid rotation.

[Treatment of pain in cancer with systemically administered opioids]

The World Health Organization guidelines for cancer pain relief have been proven efficacious in 90% of the patients with cancer pain. The patient's self-report of pain is the focus of treatment. When initiating treatment, controlled-release preparations of opioids are generally favoured, and are combined with immediate release morphine to prevent or treat 'breakthrough' pain and to enable the optimum opioid dosage to be calculated. (Breakthrough pain is a transient increase in pain in a patient who has stable, persistent pain treated with opioids.) In patients with an unfavourable balance between analgesia and side effects, the following strategies may be useful, together with appropriate treatment of the side effects: Sequential opioid trials (so-called opioid rotation) is an approach which is effective in 50-70% of the patients. Changing the route of opioid administration is successful in 70-95% of the patients. When selecting an invasive technique, continuous subcutaneous infusion is medically preferred. Spinal analgesia is an alternative. Knowledge of the relative potency of opioid drugs and of their biologic availability is needed to guide changes in drugs or routes of administration.

Pathophysiological aspects and clinical outcome of intra-anal application of isosorbide dinitrate in patients with chronic anal fissure

BACKGROUND

Relaxation of the internal anal sphincter can be achieved by local application of exogenous nitric oxide donors.

AIM

To evaluate the influence of topical application of isosorbide dinitrate (ISDN) on anal pressure, anodermal blood flow, and fissure healing.

PATIENTS

Thirty four consecutive patients (male/female: 18/16; mean age (SEM): 39 (10)) with a chronic anal fissure were studied.

METHODS

All patients were treated for at least six weeks or a maximum period of 12 weeks. Before treatment and at three and six weeks 22 patients underwent conventional anal manometry and laser Doppler flowmetry of the anoderm.

RESULTS

Within 10 days the fissure related pain was resolved in all patients. At six, nine, and 12 weeks the anal fissure was completely healed in 14, 22, and 30 patients respectively. At three and six weeks manometry was performed at least one hour after the last application of ISDN. These recordings showed a reduction of the maximum resting anal pressure (mean (SD), pretreatment 111 (26) mm Hg; three weeks 86 (19); six weeks 96 (27), p < 0.001). Simultaneous recordings of anodermal blood flow showed a significant increase of flow (pretreatment 0.53 (0.17); three weeks 0.80 (0.16); six weeks 0.76 (0.31), p < 0.005). The mean (SEM) duration of follow up after successful outcome was 11 (5) months. Within this period fissure relapsed in two of 30 patients (7%), eight and 10 weeks after treatment had been stopped.

CONCLUSIONS

Local application of ISDN reduces anal pressure and improves anodermal blood flow. This dual effect results in a fissure healing rate of 88% at 12 weeks. This new and simple treatment modality seems to be an attractive alternative for the current available surgical procedures.

[Intra-anal application of isosorbide dinitrate in chronic anal fissure]

OBJECTIVE

To evaluate the effect of intra-anal application of isosorbide dinitrate on the healing rate of chronic anal fissure.

DESIGN

Prospective, descriptive.

SETTING

Outpatient clinic of the department of Surgery, University Hospital Dijkzigt, Rotterdam.

METHOD

Sixteen patients with chronic (more than three months' duration) anal fissure were treated by intra-anal application of isosorbide dinitrate ointment every 3 hours, except during the night. The maximal duration of therapy was 12 weeks. Every three weeks the following aspects were investigated: clinical symptoms, side-effects and fissure healing.

RESULTS

All patients experienced mild and transient headache shortly after the beginning of the treatment. At three weeks the fissure-related pain was resolved in all patients. At 6, 9 and 12 weeks the fissure was completely healed in 9, 11 and 15 patients respectively.

CONCLUSION

The majority of chronic anal fissures can be treated effectively by local application of isosorbide dinitrate. This new and simple treatment modality appears to be an attractive alternative to the currently available surgical procedures.