High-Dose Nebulized Colistin Methanesulfonate and the Role in Hospital-Acquired Pneumonia Caused by Gram-Negative Bacteria with Difficult-to-Treat Resistance: A Review

Hospital-acquired pneumonia, including ventilator-associated pneumonia (VAP) due to difficult-to-treat-resistant (DTR) Gram-negative bacteria, contributes significantly to morbidity and mortality in ICUs. In the era of COVID-19, the incidences of secondary nosocomial pneumonia and the demand for invasive mechanical ventilation have increased dramatically with extremely high attributable mortality. Treatment options for DTR pathogens are limited. Therefore, an increased interest in high-dose nebulized colistin methanesulfonate (CMS), defined as a nebulized dose above 6 million IU (MIU), has come into sight. Herein, the authors present the available modern knowledge regarding high-dose nebulized CMS and current information on pharmacokinetics, clinical studies, and toxicity issues. A brief report on types of nebulizers is also analyzed. High-dose nebulized CMS was administrated as an adjunctive and substitutive strategy. High-dose nebulized CMS up to 15 MIU was attributed with a clinical outcome of 63%. High-dose nebulized CMS administration offers advantages in terms of efficacy against DTR Gram-negative bacteria, a favorable safety profile, and improved pharmacokinetics in the treatment of VAP. However, due to the heterogeneity of studies and small sample population, the apparent benefit in clinical outcomes must be proven in large-scale trials to lead to the optimal use of high-dose nebulized CMS.

Challenge for higher colistin dosage in critically ill patients receiving continuous venovenous haemodiafiltration

Traditionally, reduced daily doses of colistin methanesulphonate (CMS) in critically ill patients receiving continuous venovenous haemodiafiltration (CVVHDF) have resulted in suboptimal colistin concentrations. The necessity of a loading dose (LD) at treatment initiation has been proposed. A LD of 9 million IU (MU) [ca. 270 mg of colistin base activity (CBA)] was administrated with a maintenance dose of 4.5 MU (ca. 140 mg CBA) every 12 h (q12h) to eight critically ill patients receiving renal replacement therapy. Blood samples were collected immediately before and at different time intervals after the LD and the fourth dose, whilst pre-filter and post-filter blood samples were also collected. CMS and colistin concentrations were determined using an LC-MS/MS assay. Median maximum observed concentrations after the LD were 22.1 mg/L for CMS and 1.55 mg/L for colistin, whereas during maintenance dosing the corresponding values were 12.6 mg/L and 1.72 mg/L, respectively. CVVHDF clearance was determined as 2.98 L/h for colistin, equivalent to 62% of total apparent colistin clearance in CVVHDF patients. Both CMS and colistin were cleared by CVVHDF. Application of a LD of 9 MU CMS resulted in more rapid achievement of the target colistin concentration. Following implementation of a predicted pharmacokinetic model on plasma CMS/colistin concentrations, a LD of 12 MU CMS appears more appropriate, whilst a CMS maintenance dosage of at least 6.5-7.5 MU q12h is suggested in patients undergoing CVVHDF. However, further clinical studies are warranted to assess the safety of a LD of 12 MU CMS in patients receiving CVVHDF.

Concentration-related mydriasis in a patient with renal dysfunction treated with phenytoin

INTRODUCTION

There is very limited evidence concerning phenytoin-related mydriasis.

CASE REPORT

A 59-year-old male was hospitalized in the intensive care unit due to a head injury. During his hospitalization, phenytoin was administrated. Some days later he presented bilateral mydriasis.  At that time he had impaired creatinine clearance 7 ml/min, albumin levels 3.4 gr/dl, and phenytoin serum concentration 19.94 μg/dl. Evaluation with brain computed tomography and magnetic resonance imaging did not reveal any potential cause of mydriasis, while none of the co-administrated drugs have been reported to cause significant mydriasis. After initiation of continuous venovenous hemodiafiltration and discontinuation of phenytoin, mydriasis was reversed.

CONCLUSION

Clinicians should be aware that mydriasis due to a toxic concentration of phenytoin may be manifested. Hippokratia 2016, 20(2): 166-168.

Tuberculosis and malignancy

BACKGROUND

Tuberculosis (TB) and malignancy represent global threats claiming millions of lives and inflicting formidable suffering worldwide. Surprisingly, the pathophysiological and practical implications of their co-existence have received little attention.

METHODS

Therefore, we sought to review the available literature on the field and identify data regarding the association between TB and malignancy in order to highlight the neglected aspects of this association and probably derive clinically useful information. We searched PubMed up to June 2008 for case reports, case series, non-comparative and comparative studies that were written in English and reported data on the occurrence of both TB infection and a neoplastic disorder in the same patient(s). The development of mycobacterial infections in patients with immunocompromized conditions is well known and was considered outside the scope of this review.

EVIDENCE SYNTHESIS

The synthesis of the available evidence enabled us to establish three different types of association between malignancy and TB: (i) the development of cancer on the background of a previous tuberculous infection; (ii) the concurrent existence of TB and malignancy in the same patient(s) or clinical specimen(s); and (iii) the diagnostic challenges arising from the multi-faceted presentations of these two disorders.

CONCLUSION

We conclude that clinicians need to be aware of the protean manifestations of TB and cancer and maintain a high index of suspicion for simultaneous and/or misleading presentations. In addition, further research is required to determine if a tuberculous infection, being similar to other chronic infections and inflammatory conditions, may facilitate carcinogenesis.

Respiratory fluoroquinolones for the treatment of community-acquired pneumonia: a meta-analysis of randomized controlled trials

BACKGROUND

We investigated whether the use of respiratory fluoroquinolones was associated with better clinical outcomes compared with the use of macrolides and beta- lactams among adults with pneumonia.

METHODS

We searched PubMed, Current Contents, Scopus, EMBASE, ClinicalTrials.gov and Cochrane with no language restrictions. Two reviewers independently extracted data from published trials that compared fluoroquinolones (levofloxacin, moxifloxacin, gemifloxacin) with macrolides or beta-lactams or both. A meta-analysis was performed with the clinical outcomes of mortality, treatment success and adverse outcomes.

RESULTS

We included 23 trials in our meta-analysis. There was no difference in mortality among patients who received fluoroquinolones or the comparator antibiotics (OR 0.85, 95% CI 0.65-1.12). Pneumonia resolved in more patients who received fluoroquinolones compared with the comparator antibiotics for the included outcomes in the intention-to-treat population (OR 1.17, 95% CI 1.00-1.36), clinically evaluable population (OR 1.26, 95% CI 1.06-1.50) and the microbiologically assessed population (OR 1.67, 95% CI 1.28-2.20). Fluoroquinolones were more effective than a combination of beta-lactam and macrolide (OR 1.39, 95% CI 1.02-1.90). They were also more effective for patients with severe pneumonia (OR 1.84, 95% CI 1.02-3.29), those who required admission to hospital (OR = 1.30, 95% CI 1.04-1.61) and those who required intravenous therapy (OR = 1.44, 15% CI 1.13-1.85). Fluoroquinolones were more effective than beta-lactam and macrolide in open-label trials (OR = 1.35, 95% CI 1.08-1.69) but not in blinded randomized controlled trials (OR = 1.13, 95% CI 0.85-1.50).

INTERPRETATION

Fluoroquinolones were associated with higher success of treatment for severe forms of pneumonia; however, a benefit in mortality was not evident. A randomized controlled trial that includes patients with severe pneumonia with or without bacteremia is needed.

Early switch to oral treatment in patients with moderate to severe community-acquired pneumonia: a meta-analysis

BACKGROUND

Early switch to oral antibacterials is recommended for the treatment of hospitalized patients with community-acquired pneumonia (CAP). However, its efficacy and safety in patients with more severe forms of CAP have not been well established.

OBJECTIVE

To evaluate early switch to oral treatment in hospitalized patients with moderate to severe CAP.

METHODS

Two reviewers independently extracted data from relevant randomized controlled trials (RCTs) with the same total duration of antibacterial treatment in the compared groups (early switch from intravenous to oral and conventional intravenous treatment for the whole duration of therapy).

RESULTS

Six RCTs including 1219 patients fulfilled the criteria for inclusion in the meta-analysis. Treatment success was not different between early switch to oral treatment and intravenous only treatment groups in both intention to treat (odds ratio [OR] 0.76; 95% CI 0.36, 1.59) and clinically evaluable patients (OR 0.92; 95% CI 0.61, 1.39). Mortality and recurrence of CAP were not different (OR 0.81; 95% CI 0.49, 1.33 and OR 1.81; 95% CI 0.70, 4.72, respectively), while duration of hospitalization was shorter (weight mean difference -3.34; 95% CI -4.42, -2.25) and drug-related adverse events were fewer in the early switch group (OR 0.65; 95% CI 0.48, 0.89). Findings were similar in patients with severe CAP.

CONCLUSIONS

Early conversion to oral antibacterials seems to be as effective as continuous intravenous treatment in patients with moderate to severe CAP and results in substantial reduction in duration of hospitalization.

Short- versus long-course antibacterial therapy for community-acquired pneumonia : a meta-analysis

BACKGROUND

The evidence for traditionally recommended 7- to 14-day duration of antibacterial therapy for community-acquired pneumonia (CAP) is not well established.

OBJECTIVES

We endeavoured to assess the effectiveness and safety of shorter than traditionally recommended antibacterial therapy for CAP.

METHODS

We performed a meta-analysis of randomized controlled trials (RCTs) comparing short- (< or = 7 days) versus long- (> or = 2 days difference) course therapy for CAP with the same antibacterial regimens, in the same daily dosages.

RESULTS

Five RCTs involving adults (including outpatients and inpatients who did not require intensive care) and two RCTs involving children (aged 2-59 months, residing in developing countries) were included. All RCTs were double-blind and assessed patients with CAP of mild to moderate severity. No differences were found between short- (adults 3-7 days; children 3 days) and long- (adults 7-10 days; children 5 days) course regimens (adults - amoxicillin, cefuroxime, ceftriaxone, telithromycin and gemifloxacin; children - amoxicillin) regarding clinical success at end-of-therapy (six RCTs; 5107 patients [1095 adults, 4012 children]; fixed-effect model [FEM]; odds ratio [OR] = 0.89; 95% CI 0.74, 1.07), clinical success at late follow-up, microbiological success, relapses, mortality (seven RCTs; 5438 patients; FEM; OR = 0.57; 95% CI 0.23, 1.43), adverse events (five RCTs; 3214 patients; FEM; OR = 0. 90; 95% CI 0.72, 1.13) or withdrawals as a result of adverse events. No differences were found in subset analyses of adults or children, and of patients treated with no more than 5-day short-course regimens versus at least 7-day long-course regimens.

CONCLUSION

No difference was found in the effectiveness and safety of short- versus long-course antimicrobial treatment of adult and paediatric patients with CAP of mild to moderate severity.