Pharmacokinetic and pharmacodynamic aspects of oral moxifloxacin 400 mg/day in elderly patients with acute exacerbation of chronic bronchitis

Therapeutic Drug Monitoring of Antibiotics in the Elderly: A Narrative Review

PURPOSE

Antibiotic dosing adaptation in elderly patients is frequently complicated by age-related changes affecting the processes of drug absorption, distribution, metabolism, and/or elimination. These events eventually result in treatment failure and/or development of drug-related toxicity. Therapeutic drug monitoring (TDM) can prevent suboptimal antibiotic exposure in adult patients regardless of age. However, little data are available concerning the specific role of TDM in the elderly.

METHODS

This review is based on a PubMed search of the literature published in the English language. The search involved TDM studies of antibiotics in the elderly performed between 1990 and 2021. Additional studies were identified from the reference lists of the retrieved articles. Studies dealing with population pharmacokinetic modeling were not considered.

RESULTS

Only a few studies, mainly retrospective and with observational design, have specifically dealt with appropriate antibiotic dosing in the elderly based on TDM. Nevertheless, some clinical situations in which the selection of optimal antibiotic dosing in the elderly was successfully guided by TDM were identified.

CONCLUSIONS

Elderly patients are at an increased risk of bacterial infections and inadequate drug dosing compared to younger patients. Therefore, the availability of TDM services can improve the appropriateness of antibiotic prescriptions in this population.

Moxifloxacin in Chronic Obstructive Pulmonary Disease: Pharmacokinetics and Penetration into Bronchial Secretions in Ward and Intensive Care Unit Patients

This study aimed to evaluate the pharmacokinetic profile of moxifloxacin (MXF) in serum and sputum/bronchial secretions of 22 patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) hospitalized in the ward and intensive care unit (ICU). The data showed that ICU patients had lower concentrations in secretions (P = 0.01). However, no other statistically significant differences were observed in pharmacokinetic parameters and penetration in secretions between ward and ICU patients. MXF showed a favorable pharmacokinetic profile, and the pharmacodynamic targets for common pathogens for AECOPD were achieved.

Moxifloxacin in lower respiratory tract infections: in silico simulation of different bacterial resistance and drug exposure scenarios

Moxifloxacin has potent bactericidal activity against Streptococcus pneumoniae; a major causative organism of lower respiratory tract infections. This study aims to use the pharmacokinetic/pharmacodynamic indices to predict the therapeutic outcome under different scenarios of moxifloxacin exposure and pneumococcal resistance. STELLA(®) software was used to simulate the pharmacokinetics and pharmacodynamics of moxifloxacin in patients with severe pneumonia and acute exacerbations of chronic bronchitis (AECB). The current dose of moxifloxacin was found to be insufficient for eradication of ciprofloxacin resistant bacteria in ventilated patients with severe bronchopneumonia. This can be attributed to the lower tissue penetration observed in this population. Increasing the dose to 600 mg was able to achieve higher levels of free drug AUC/MIC in both bronchial and plasma compartments. In AECB, moxifloxacin achieved the same AUC/MIC values observed in pneumonia at the different MIC values. This may allow the extrapolation of findings of moxifloxacin studies in pneumonia to the management of patients with AECB.

Pharmacokinetics of moxifloxacin and high-dose levofloxacin in severe lower respiratory tract infections

This study evaluated the pharmacokinetics of intravenous moxifloxacin 400 mg once and levofloxacin 500 mg twice daily in patients with lower respiratory tract infections (LRTIs) and assessed their pharmacodynamic adequacy against common respiratory pathogens. Eighteen patients with LRTIs hospitalised in general wards were included. Serial blood samples were obtained at steady state and concentrations were determined using HPLC. Pharmacokinetic variables were estimated by a two-compartment model. The characteristic pharmacodynamic parameter for fluoroquinolones (AUC(0-24)/MIC) was calculated. Peak and trough concentrations were, respectively, 4.81 ± 1.03 and 0.59 ± 1.13 mg/L for moxifloxacin and 6.42 ± 1.08 and 0.79 ± 0.39 mg/L for levofloxacin. Pharmacokinetic data for moxifloxacin and levofloxacin, respectively, were: CL, 10.27 ± 1.24 and 22.66 ± 6.62 L/h; t1/2, 13.43 ± 5.12 and 6.75 ± 1.34 h; Vss, 163.03 ± 53.88 and 170.73 ± 39.59 L; and AUC(0-24), 39.38 ±5.28 and 47.06 ± 14.09 mg·h/L. The pharmacodynamic target was attained in all patients by both antibiotics against the majority of respiratory pathogens. Moxifloxacin proved to be pharmacodynamically efficacious against Gram-positive bacteria with MICs ≤ 0.79 mg/L and Gram-negative bacteria with MICs ≤ 0.32 mg/L. These MIC thresholds for levofloxacin were 1.1 mg/L and 0.38 mg/L, respectively. Moxifloxacin and high-dose levofloxacin show a favourable pharmacokinetic profile in plasma of patients with severe LRTIs, without significant interpatient variability. They ensure optimal pharmacodynamic exposure against the majority of microbes involved in these infections. However, the predicted efficacy against Gram-negative bacteria with MICs ≥ 0.5 mg/L appears to be low.

Antibiotic therapy in elderly patients with acute exacerbation of chronic bronchitis

Chronic bronchitis (CB) is a critical component of chronic obstructive pulmonary disease (COPD). Emphysema, reversible airway disease and bronchiectasis also contribute to COPD. Elderly patients are at increased risk for COPD and its components - emphysema, CB and bronchiectasis. In addition, older patients are at increased risk for resistant organisms during episodes of acute exacerbation of CB (AECB). These organisms include the more common bacteria implicated in AECB, such as Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae, and less common nonenteric, Gram-negative organisms such as Pseudomonas aeruginosa. Risk-stratified antibiotic treatment guidelines for AECB appear to be useful, although they have not been prospectively validated for the general CB population, and especially not in the elderly CB population. Many of the AECB treatment guidelines that are stratified based on risk factors have recommended that the oral respiratory fluoroquinolone antibiotics (gemifloxacin, levofloxacin and moxifloxacin) play a second-line but pivotal role, particularly in patients who have failed initial antibiotic treatment for simple CB or as initial treatment for complicated CB.

Moxifloxacin in the treatment of skin and skin structure infections

Moxifloxacin is a recent addition to the fluoroquinolone class, differing from ciprofloxacin and other older agents in having much better in vitro activity against Gram-positive aerobes while retaining potent activity against Gram-negative aerobes. It is also active against the pathogens of human and animal bite wounds and those species of atypical mycobacteria associated with dermatologic infections. Its activity against anaerobes is quite variable. Moxifloxacin penetrates well into inflammatory blister fluid and muscle and subcutaneous adipose tissues. Moxifloxacin should thus be a reasonable option for the treatment of skin and skin structure infections (SSSIs). In 3 randomized controlled trials (RCTs), oral moxifloxacin was as effective as cephalexin in the treatment of uncomplicated SSSIs in adults while in 2 RCTs, intravenous/oral moxifloxacin was as effective as intravenous/oral β-lactam/β-lactamase inhibitor therapy in the treatment of complicated SSSIs in adults. Moxifloxacin does not inhibit cytochrome P450 enzymes and thus interact with warfarin or methylxanthines. However, multivalent cations can reduce its oral bioavailability substantially. Dosage adjustment is not required in the presence of renal or hepatic impairment. The clinical relevance of its electrophysiologic effects (QT_c prolongation) remains unresolved.

Acute exacerbations of chronic bronchitis in elderly patients: pathogenesis, diagnosis and management

Chronic bronchitis (CB) is a disorder that is characterised by chronic mucus production. This disorder is called chronic obstructive pulmonary disease (COPD) when airflow obstruction is present. The majority of patients with COPD, which often goes undiagnosed or inadequately treated in the elderly, have symptoms consistent with CB. The clinical course of CB is usually punctuated by periodic acute exacerbations linked to infections caused by viral and typical or atypical bacterial pathogens. Acute exacerbations of chronic bronchitis (AECB) often lead to a decline in lung function and poor quality of life in association with increased risk of mortality and a significant economic impact on the healthcare system and society because of the direct costs of hospitalisations. In elderly individuals with COPD, co-morbidities play a vital role as determinants of health status and prognosis. Failure to eradicate infecting pathogens contributes to persistence of infection and inflammation that requires repeated courses of therapy and hospitalisation. Stratifying patients with AECB according to symptoms, degree of pulmonary function impairment and risk factors for poor outcome can help clinicians choose empirical antimicrobial chemotherapy regimens that are most likely to result in treatment success. Failure to cover likely pathogens associated with episodes of AECB can lead to lengthy hospital admissions and significant declines in functional status for elderly patients. Fluoroquinolones may provide the best therapeutic option for elderly patients with COPD who have complicated underlying CB but who are sufficiently stable to be treated in the outpatient setting. Optimised treatment for stable outpatients with CB may diminish the frequency of AECB, and effective antimicrobial therapy for AECB episodes can significantly diminish healthcare costs and maintain quality of life in the elderly patient.