Published in:
01-01-2000 | Adis Drug Evaluation
Moxifloxacin
A Review of its Clinical Potential in the Management of Community-Acquired Respiratory Tract Infections
Published in: Drugs | Issue 1/2000
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Abstract|
Moxifloxacin is an extended-spectrum fluoroquinolone which has improved coverage against Gram-positive cocci and atypical pathogens compared with older fluoroquinolone agents, while retaining good activity against Gram-negative bacteria. The antibacterial spectrum of moxifloxacin includes all major upper and lower respiratory tract pathogens; it is one of the most active fluoroquinolones against pneumococci, including penicillin- and macrolide-resistant strains. In in vitro studies, emergence of bacterial resistance was less common with moxifloxacin than with some other fluoroquinolones, but this requires confirmation in large-scale clinical studies.
As with other fluoroquinolones, moxifloxacin achieves good penetration into respiratory tissues and fluids. It shows a low potential for drug interactions and dosage adjustment is not required for patients of advanced age or those with renal or mild hepatic impairment.
The efficacy of oral moxifloxacin has been demonstrated in large, well-designed clinical trials in patients with community-acquired pneumonia, acute exacerbations of chronic bronchitis or acute sinusitis. Moxifloxacin 400mg once daily achieved bacteriological and clinical success rates of approximately 90% or higher. It was as effective as, or more effective than, comparators including clarithromycin, cefuroxime axetil and high dose amoxicillin in these trials.
The most commonly reported adverse events in patients receiving moxifloxacin are gastrointestinal disturbances. Moxifloxacin is also associated with QTc prolongation in some patients; there are, as yet, no data concerning the possible clinical sequelae of this effect in high-risk patients. Moxifloxacin has a low propensity for causing phototoxic reactions relative to other fluoroquinolones, and animal data suggest that it has a low potential for causing excitatory CNS and hepatotoxic effects.
Conclusions: As an extended-spectrum fluoroquinolone, moxifloxacin offers the benefits of excellent activity against pneumococci, once daily administration and a low propensity for drug interactions. Although studies are needed regarding its tolerability in at-risk patients with QT interval prolongation, available data suggest that moxifloxacin is likely to become a first-line therapy option for the treatment of community-acquired lower respiratory tract infections, particularly in areas where drug-resistant S. pneumoniae or H. influenzae are common.
Antibacterial Activity|
Moxifloxacin is an extended-spectrum fluoroquinolone which has an antibacterial spectrum that covers all of the major respiratory tract pathogens. It is one of the most active fluoroquinolones against Streptococcus pneumoniae (mean weighted MIC90<0.3 mg/L), including penicillin- and macrolide-resistant strains. It is also active against S. pyogenes or group A streptococci (mean weighted MIC90 0.24 mg/L) and methicillin-susceptible Staphylococcus aureus (mean weighted MIC90 0.10 mg/L), but has more variable activity against methicillin-resistant S. aureus (MIC90 2 to 8 mg/L) and borderline activity against ciprofloxacin-resistant strains of S. aureus (MIC90 1 to 2 mg/L).
Moxifloxacin has good activity against Enterobacteriaceae and other Gramnegative species, including Haemophilus influenzae, Moraxella catarrhalis (β-lactamase-positive or -negative strains of both species) and H. parainfluenzae (MIC90 0.03 to 0.125 mg/L). It is generally 2-fold less active than ciprofloxacin against Enterobacteriaceae and has poor activity (MIC90 4 to >32 mg/L) against Pseudomonas aeruginosa.
Moxifloxacin also demonstrates good activity against the atypical respiratory tract pathogens Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella spp. (MIC90 ≤1 mg/L).
Minimum bactericidal concentrations of moxifloxacin were equal to, or within 1 dilution of, MIC values. Postantibiotic effects of >1 hour have been demonstrated against a range of respiratory pathogens.
Moxifloxacin was active in experimental lung infections in animals, eradicating or markedly reducing the number of M. pneumoniae, S. pneumoniae, C. pneumoniae or L. pneumophila in the lung and protecting against death or dissemination of Legionella infection.
Moxifloxacin has similar inhibitory activity against both of the bacterial enzymatic targets of fluoroquinolones, topoisomerase IV and DNA gyrase. The inhibitory activity of moxifloxacin appears to be little affected by characterised single genetic mutations or by the presence of the NorA efflux mechanism, and emergence of bacterial resistance among Gram-positive pathogens in vitro studies was less common with moxifloxacin than with other fluoroquinolones tested.
Pharmacokinetic Properties|
Moxifloxacin is almost completely (≈90%) absorbed after oral administration. Thus, maximum plasma concentration (Cmax) and area under the concentrationtime curve (AUC) values are only slightly lower than after administration of the same dose by the intravenous route (as a 60-minute infusion). Oral absorption is not affected by food intake (including dairy products).
The pharmacokinetics of moxifloxacin are linear within the 50 to 800mg dose range. An oral dose of 400mg generally achieves a mean Cmax of approximately 2.5 to 5 mg/L within 1 to 2 hours (tmax) and an AUC of approximately 27 to 45 mg/L · h.
In common with other fluoroquinolones, moxifloxacin exhibits a high volume of distribution (2 to 3.5 L/kg), relatively low binding to plasma proteins (39%) and penetrates well into respiratory tissues and fluids. Concentrations achieved in bronchial mucosa, epithelial lining fluid, sinus tissues and alveolar macrophages exceed concurrent plasma concentrations and are ≥1 mg/L (or mg/kg) 24 hours after a 400mg dose(s). Evidence from animal studies suggests that moxifloxacin penetrates the placental and blood-brain barriers and into breast milk.
Moxifloxacin is metabolised to a sulfo- (M1) and a glucuronide (M2) derivative. The cytochrome P450 system is not involved in the metabolism of the agent. Approximately 15 to 22% of a dose is found unchanged in the urine, with a similar amount in the faeces.
The terminal elimination half-life of moxifloxacin ranges from approximately 8 to 16 (median 12.4) hours. Plasma clearance ranges from 9 to 15 L/h and renal clearance from 1.3 to 3 L/h.
The pharmacokinetics of moxifloxacin do not appear to be affected by advanced age, gender, race, renal impairment or mild hepatic impairment.
Clinical Potential|
Oral moxifloxacin 400mg once daily was effective in the treatment of patients with community-acquired pneumonia, acute exacerbations of chronic bronchitis or acute sinusitis, achieving bacteriological and clinical success/resolution rates of approximately 90% or higher in clinical trials at treatment end. Clinical success/resolution was generally defined as complete resolution or considerable improvement in signs and symptoms of infection, such that no further antimicrobial treatment was required.
In patients with community-acquired pneumonia, moxifloxacin 400 mg/day was as effective as amoxicillin 1g 3 times daily and moxifloxacin 200 or 400 mg/ day was as effective as clarithromycin 500mg twice daily in 3 large, well-designed trials.
In acute exacerbations of chronic bronchitis, a 5-day course of moxifloxacin 400 mg/day was more bacteriologically effective than a 7-day course of clarithromycin (91 vs 68% of patients), but achieved similar clinical success rates to 7- or 10-day treatment with clarithromycin in 2 large trials.
In patients with acute sinusitis, a 7-day course of moxifloxacin 400 mg/day was more effective than a 10-day course of cefuroxime axetil 250mg twice daily (clinical success: 97 vs 91%; bacteriological success: 95 vs 84% of patients) in one trial. However, in a second trial, 10-day treatment courses of moxifloxacin 400 mg/day and cefuroxime axetil 500 mg/day produced almost identical clinical response rates (90 vs 89%).
Tolerability|
The most commonly reported adverse events in patients receiving moxifloxacin are gastrointestinal disturbances, mostly nausea (7.2% of 4926 patients in clinical trials) and diarrhoea (5.7%). Dizziness occurred in 2.8% of patients.
In comparative studies, moxifloxacin was associated with a similar overall incidence of drug-related adverse events to high dose amoxicillin and clarithromycin but a slightly higher rate of events than cefuroxime axetil in patients with respiratory tract infections.
Moxifloxacin 400 mg/day was associated with a mean prolongation of the QTc interval of 6 msec (n = 4008) versus 1 msec in recipients of comparator agents (clarithromycin, cefalexin, cefuroxime axetil, amoxicillin, doxycycline and metronidazole; n = 3689); 1 versus 4 patients experienced a cardiovascular event. At present, there are no data concerning the use of moxifloxacin in patients who have pre-existing QT prolongation or who are taking drugs which prolong the QTc interval.
Moxifloxacin appears to have a low propensity for causing phototoxic reactions relative to other fluoroquinolones, as demonstrated in preclinical and clinical studies; no phototoxic events occurred in almost 5000 patients treated with the drug. Animal data suggest that the drug has a low potential for causing CNS excitatory and hepatotoxic effects.
Drug Interactions|
As with other fluoroquinolones, the bioavailability of moxifloxacin is substantially reduced by coadministration with an antacid, sucralfate or an iron preparation. However, the extent of absorption of moxifloxacin is unaffected by concurrent administration of calcium-containing supplements, although the rate of absorption is slowed.
Moxifloxacin does not interact with theophylline, β-acetyldigoxin, probenecid, ranitidine, warfarin or oral contraceptives, in contrast to some other compounds of this class.
Dosage and Administration|
Moxifloxacin is indicated for the treatment of acute bacterial exacerbations of chronic bronchitis, community-acquired pneumonia and acute bacterial sinusitis. The recommended oral dosage for all indications is 400mg administered once daily. Moxifloxacin should be administered for 5 days for acute exacerbations of chronic bronchitis and 10 days for acute sinusitis or community-acquired pneumonia.
No dosage adjustment is required in the elderly, patients with mild hepatic impairment or in patients with any degree of renal impairment. Currently there are no recommendations concerning the use of moxifloxacin in patients with moderate to severe liver impairment or in patients undergoing renal dialysis.
Moxifloxacin has been shown to prolong the Qtc interval in some patients. Its use should be avoided in patients with known QT interval prolongation or in those receiving concomitant drugs known to prolong the Qtc interval.