Levofloxacin weight-adjusted dosing and pharmacokinetic disposition in a morbidly obese patient

Drug dosing in obese critically ill patients, a literature review

INTRODUCTION

The prevalence of obesity represents a significant global public health challenge, and the available evidence concerning the appropriate dosing of pharmaceutical in patients with obesity is limited. It is uncommon for clinical trials in critically ill patients to include obese individuals, which results in a lack of specific dosing information in product data sheets. The objective of this literature review is to provide clinicians with efficacious and secure guidelines for this cohort of patients.

METHODS

A multidisciplinary team comprising pharmacists specialized in hospital pharmacy and physicians with expertise in intensive care medicine was established. The therapeutic groups and, in particular, the most commonly used active ingredients within the Intensive Care Unit were identified and subjected to detailed analysis. The following terms were included in the search: "obese", "overweight", "critical illness", "drug dosification", and "therapeutic dose monitoring". All the information was then evaluated by the working group, which reached a consensus on the dosing recommendations for each drug in obese critically ill patients.

RESULTS

A total of 83 drugs belonging to the following therapeutic groups were identified: antivirals, antibacterials, antifungals, immunosuppressants, antiepileptics, vasopressors, anticoagulants, neuromuscular blocking agents and sedatives. A table was produced containing the consensus dosing recommendations for each of the aforementioned drugs following a review of the available evidence.

CONCLUSIONS

Drug dosing in obese patients, both in critical and noncritical settings, remains an area with significant uncertainty. This review provides comprehensive and up-to-date information on the dosing of the main therapeutic groups in obese critically ill patients, offering a valuable resource physicians in critical care units and clinical pharmacists in their practice in this setting.

Therapeutic Drug Monitoring of Levoffoxacin in an Obese Adolescent: A Case Report

OBJECTIVES

To describe the pharmacokinetics of levofloxacin in an obese adolescent patient in the pediatric intensive care unit.

METHODS

A single-patient medical record review was conducted.

RESULTS

A 168-kg, 15-year-old female with past medical history of Prader-Willi syndrome and asthma initially presented with respiratory distress secondary to asthma exacerbation. She failed non-invasive ventilation and was subsequently intubated for respiratory failure and progressed to high-frequency oscillatory ventilation. On hospital day 1 (HD 1) an infectious workup was begun because of a fever, worsening clinical status, and initiation of vasopressors and an empiric antimicrobial regimen of cefepime and clindamycin. The urine culture subsequently grew Escherichia coli and the respiratory culture grew Pseudomonas aeruginosa. She continued to be febrile, which was thought to be due to an intra-abdominal abscess. On HD 14, the antimicrobial regimen was changed to levofloxacin because of continued fevers and no significant clinical improvement. Levofloxacin was initiated at 1000 mg IV every 24 hours. Levofloxacin serum levels were obtained at 0.5, 3.5, and 11.5 hours after infusion, which were 8.61, 5.76, and 2.7 mg/L, respectively. These concentrations translated into a peak level of 8.79 mg/L, a half-life of 6.4 hours, and an AUC of 80 mg·hr/L, which are discordant from the expected peak of 16 mg/L, a half-life of 8 hours, and an AUC of 120 mg·hr/L. Based on these values, the levofloxacin regimen was adjusted to 1000 mg IV every 12 hours, and repeat levels 0.5, 3.5, and 11.5 hours after infusion were 9.91, 6.56, and 3.27 mg/L, respectively, corresponding to a peak of 10.5 mg/L, a half-life of 5.18 hours, and an AUC of 200 mg·hr/L. After the adjustment in levofloxacin regimen, she became afebrile, WBC resolution and improvement in her overall clinical status, and she received a total duration for levofloxacin of 21 days.

CONCLUSION

A levofloxacin regimen of 1000 mg IV every 12 hours was successful in providing for an appropriate AUC exposure and was associated with a successful clinical outcome in this morbidly obese adolescent.

Obesity is not strongly associated with increased risk for febrile neutropenia during levofloxacin prophylaxis in patients with hematological malignancies receiving intermediate-risk myelosuppressive chemotherapy

Levofloxacin given at a standard dose of 500 mg daily is recommended for antibacterial prophylaxis in patients receiving myelosuppressive chemotherapy. Obese patients have been shown to exhibit enhanced clearance of levofloxacin and may be at risk for prophylactic failure. This single center, retrospective cohort study from June 2014 to May 2017 evaluated adult patients with estimated creatinine clearance ≥50 mL/min receiving their first cycle of a National Comprehensive Cancer Network defined intermediate-risk regimen. Primary endpoint was incidence of febrile neutropenia. Secondary endpoints included 30-day mortality and the correlation between estimated levofloxacin area under the concentration-time curve and rates of febrile neutropenia. Febrile neutropenia occurred in 26 patients: 12 (35.3%) obese and 14 (21.9%) non-obese (P = 0.16). Six (23.1%) of these patients required intensive care, but there were no deaths within 30 days of a febrile neutropenia event. Estimated creatinine clearance was similar between obese and non-obese patients (median 97.5 vs. 91.8 mL/min, P = 0.39), as was estimated levofloxacin area under the concentration-time curve (median 85.6 vs. 90.8 mg×h/L, P = 0.39). There were no significant associations between body weight-related variables - total body weight (median 83.4 vs. 80.6 kg, P = 0.51), body mass index (mean 29.6 vs. 26.8 kg/m², P = 0.35), or body surface area (1.98 vs. 1.99 m², P = 0.68) - and febrile neutropenia in this cohort of patients with similar renal function. Obesity should not be a justification for more aggressive levofloxacin dosing schemes when used for febrile neutropenia prophylaxis.

Influence of Morbid Obesity on the Clinical Pharmacokinetics of Various Anti-Infective Drugs: Reappraisal Using Recent Case Studies-Issues, Dosing Implications, and Considerations

Owing to availability of scanty pharmacokinetic data, dosing decisions in morbid obesity is increasingly challenging in the field of anti-infective drugs. However, in recent years data are emerging that describe the pharmacokinetics of anti-infective drugs in morbidly obese subjects. The objectives of the present work were: (1) to collate the recent reports pertaining to the pharmacokinetics in morbidly obese subjects for several anti-infective drugs and provide an overview of the pharmacokinetic data along with the applicable pharmacodynamics and/or clinical outcome; (2) to perform regression analysis on limited dataset for a few drugs to verify the existence of relationships between Cmax/Ctrough versus steady-state volume of distribution (Vss)/clearance to enable data prediction in morbid obesity subjects; (3) to provide a general discussion on issues and dosing implications. The key findings of this review were: (a) drugs such as vancomycin, ethambutol, and fluconazole, where the VSS is substantially greater in morbidly obese patients, need a dosing strategy with the appropriate body mass descriptors; (b) other drugs such as moxifloxacin, linezolid, doripenem, meropenem, voriconazole, oseltamivir, tigecycline, levofloxacin may not ordinarily need dosing adjustments;

Development of a pharmacist-driven protocol for automatic medication dosage adjustments in obese patients

PURPOSE

A hospital protocol utilizing automatic dosage adjustments and pharmacist consultations to optimize the use of certain medications in obese patients is described.

SUMMARY

After conducting a literature search focused on medication dosing in obese patients, pharmacists at a large community hospital developed a list of commonly ordered medications appropriate for inclusion in a pharmacy-driven institutional protocol for automatic medication dosage adjustment in adult patients with obesity. Evidence-based recommendations on initial dosing of eight antimicrobials and two anticoagulant agents according to weight and renal function were formulated. Under the protocol, pharmacists receive electronic alerts regarding protocol-eligible patients during initial order verification and automatically adjust medication dosages as appropriate. For patients prescribed anticoagulants at specified dosage levels, clinical pharmacists consult with prescribers to help ensure safe and effective initial and ongoing therapy. Multidisciplinary educational initiatives were conducted prior to protocol implementation. During two designated three-week postimplementation data collection periods, pharmacists received a total of 372 protocol-eligible medication orders. Pharmacists adjusted a total of 149 dosages and verified an additional 183 dosages consistent with the protocol as originally ordered. Clinical pharmacy consults were completed for 10-15% of patients, with laboratory monitoring ordered in 25-30% of those cases (all patients were found to have appropriate test values). There have been no documented adverse drug reactions in patients whose medication dosages were adjusted per protocol.

CONCLUSION

Pharmacists implemented weight- and renal function-based dosage adjustments for obese patients in 40% of evaluated protocol-eligible cases to achieve 89% compliance with the protocol. Heparin and cefazolin were the medications most likely to require obesity-related dosage adjustments.

Antibiotic dosing in obesity: the search for optimum dosing strategies

Global obesity has nearly doubled and is now a common occurrence in high-income and developing countries. The World Health Organization estimates that more than 1.4 billion adults are obese. Although the prevalence of obesity is increasing over the last decades, pharmacokinetic evaluations are still conducted in individuals with a body weight of approximately 70 kg. Morbid obesity is associated with several pathophysiological changes that can profoundly affect drug distribution and clearance. There are currently no specific dosing recommendations for antibiotics in obese patients, making dosing suggestions primarily based on pharmacokinetic characteristics of the medications and dosing recommendations in other disease states. Understanding of the pharmacokinetic alterations and maximum doses of antibiotics safely used is paramount to appropriate treatment in the obese population.

Antibiotic therapy of pneumonia in the obese patient: dosing and delivery

Purpose of review

Obesity has been shown to be associated with antibiotic underdosing and treatment failure. This article reviews the recent literature on antibiotic dosing in obese patients with pneumonia.

Recent findings

Obesity is associated with several alterations in antibiotic pharmacokinetics and pharmacodynamics, including increases in the antibiotic volume of distribution and clearance. These alterations necessitate changes in the dosing of certain antibiotics. However, data on antibiotic dosing for pneumonia in obese patients are limited and come mainly from observational studies. Additionally, dosing recommendations are often extrapolated from healthy obese volunteers and from the studies of antibiotics given for other indications.

Summary

Recognizing obesity-related pharmacokinetic and pharmacodynamic alterations is important in treating obese patients with pneumonia. Studies that evaluate such alterations and assess the impact of antibiotic dosing and delivery on the clinical outcomes of this patient population are needed.

Personalized therapeutics for levofloxacin: a focus on pharmacokinetic concerns

Background

Personalized medicine should be encouraged because patients are complex, and this complexity results from biological, medical (eg, demographics, genetics, polypharmacy, and multimorbidities), socioeconomic, and cultural factors. Levofloxacin (LVX) is a broad-spectrum fluoroquinolone antibiotic. Awareness of personalized therapeutics for LVX seems to be poor in clinical practice, and is reflected in prescribing patterns. Pharmacokinetic–pharmacodynamic studies have raised concerns about suboptimal patient outcomes with the use of LVX for some Gram-negative infections. Meanwhile, new findings in LVX therapeutics have only been sporadically reported in recent years. Therefore, an updated review on personalized LVX treatment with a focus on pharmacokinetic concerns is necessary.

Methods

Relevant literature was identified by performing a PubMed search covering the period from January 1993 to December 2013. We included studies describing dosage adjustment and factors determining LVX pharmacokinetics, or pharmacokinetic–pharmacodynamic studies exploring how best to prevent the emergence of resistance to LVX. The full text of each included article was critically reviewed, and data interpretation was performed.

Results

In addition to limiting the use of fluoroquinolones, measures such as reducing the breakpoints for antimicrobial susceptibility testing, choice of high-dose short-course of once-daily LVX regimen, and tailoring LVX dose in special patient populations help to achieve the validated pharmacokinetic–pharmacodynamic target and combat the increasing LVX resistance. Obese individuals with normal renal function cleared LVX more efficiently than normal-weight individuals. Compared with the scenario in healthy subjects, standard 2-hour spacing of calcium formulations and oral LVX was insufficient to prevent a chelation interaction in cystic fibrosis patients. Inconsistent conclusions were derived from studies of the influence of sex on the pharmacokinetics of LVX, which might be associated with sample size and administration route. Children younger than 5 years cleared LVX nearly twice as fast as adults. Patients in intensive care receiving LVX therapy showed significant pharmacokinetic differences compared with healthy subjects. Creatinine clearance explained most of the population variance in the plasma clearance of LVX. Switching from intravenous to oral delivery of LVX had economic benefits. Addition of tamsulosin to the LVX regimen was beneficial for patients with bacterial prostatitis because tamsulosin could increase the maximal concentration of LVX in prostatic tissue. Coadministration of multivalent cation-containing drugs and LVX should be avoided. For patients receiving warfarin and LVX concomitantly, caution is needed regarding potential changes in the international normalized ratio; however, it is unnecessary to seek alternatives to LVX for the sake of avoiding drug interaction with warfarin. It is unnecessary to proactively reduce the dose of cyclosporin or tacrolimus when comedicated with LVX. Transporters such as organic anion-transporting polypeptide 1A2, P-glycoprotein, human organic cation transporter 1, and multidrug and toxin extrusion protein 1 are involved in the pharmacokinetics of LVX.

Conclusion

Personalized LVX therapeutics are necessary for the sake of better safety, clinical success, and avoidance of resistance. New findings regarding individual dosing of LVX in special patient populations and active transport mechanisms in vivo are opening up new horizons in clinical practice.