Implications for antimicrobial prescribing of strategies based on bacterial eradication

Generic versus non-generic formulation of extended-release clarithromycin in patients with community-acquired respiratory tract infections: a prospective, randomized, comparative, investigator-blind, multicentre study

BACKGROUND AND OBJECTIVE

There is a general concern about the use of multisource (generic) antibacterials in the clinical setting with registration based solely on bioequivalence data. In order to address this concern, two modified-release formulations of clarithromycin (i.e. the originator Klacid XL and the generic Klarithran MR) were compared in patients with acute community-acquired respiratory tract infections.

METHODS

Patients presenting with tonsillopharyngitis, sinusitis or pneumonia were randomized to receive either of the test drugs provided they clinically qualified for empirical clarithromycin treatment. The study endpoints were clinical and bacteriological cure rates, tolerability and safety. The study was designed to test for non-inferiority with regard to cure rates.

RESULTS

The main outcome of this study was that both agents had similar clinical (non-inferior) and bacteriological cure rates and demonstrated no difference in tolerability in patients. The study also demonstrated the clinical efficacy of clarithromycin when used as empirical treatment in patients with respiratory tract infections in community practice (i.e. 95% clinical cure rate).

CONCLUSION

The clarithromycin extended-release multisource product (Klarithran MR) does not differ significantly from the originator (Klacid XL) and the clinical cure rate of the generic formulation is non-inferior to that of the originator. The two formulations are tolerated similarly.

Spanish primary healthcare physicians' knowledge of resistance of respiratory germs and antimicrobial treatment in acute bronchitis

OBJECTIVES

To determine what Spanish primary healthcare physicians consider the rates of pneumococcal resistance to be, the type of antimicrobial treatment they would prescribe on suspicion of high resistance and ascertain in which cases of acute bronchitis these physicians would initiate antibiotic treatment.

METHODS

A cross-sectional, observational study was performed with a questionnaire distributed to 1368 physicians on their opinion on the degree of resistance of pneumococci to penicillins and macrolides in Spain. They were also asked which treatment they would recommend in penicillin-resistant pneumococcal infection and to indicate their degree of agreement regarding the use of antibiotics in different clinical situations of acute bronchitis.

RESULTS

843 physicians completed and returned the questionnaire, a response rate of 59.1%. Of the 750 physicians who answered the question concerning pneumococcal resistance, 312 stated resistance to be >30% (41.6%) while only 90 felt it to be <15% (12%). 153 physicians reported resistance to macrolides to be >30% (23%). In cases with suspicion of penicillin-resistant pneumococci, the clinicians stated they would prescribe quinolones (321, 40.3%) and macrolides (251, 31.5%). Of the 784 physicians who answered the questions on bronchitis, 662 preferred antibiotic therapy in acute bronchitis with purulent sputum (84.6%), 610 on uncertain diagnosis (77.8%), 569 in patients with fever over 38 degrees C (72.6%) and 210 on patient request (26.8%).

CONCLUSION

Primary healthcare physicians in Spain are more concerned about pneumococcal resistance to penicillins than to macrolides although 35% of the strains isolated are resistant to the latter while only 10% are resistant to aminopenicillins. Furthermore, many physicians believe macrolides to be effective against pneumococcal infections. Despite their lack of efficacy in the treatment of acute bronchitis, many physicians prescribe antibiotics, mainly in cases with purulent expectoration, thus justifying the high consumption of antimicrobial agents in this disease.

How antibiotics can make us sick: the less obvious adverse effects of antimicrobial chemotherapy

Antimicrobial agents are associated with side-effects, which are usually tolerated because the benefits of treatment outweigh the toxic effects. Clinicians know about these side-effects but are less likely to understand additional adverse events, such as the overgrowth of resistant microorganisms. Overgrowth can itself precipitate a secondary infection, which can be more difficult to treat. Resistant organisms then spread to other patients and the environment, and contribute to increasing antimicrobial resistance worldwide. Organisms exposed to antibiotics undergo molecular changes that might enhance virulence. Enhanced pathogenicity would affect patients, particularly if the organism is also multiply resistant. Clinicians have a responsibility to select the correct antibiotic as soon as they have diagnosed infection, but an absence of microbiological understanding and ignorance of the potential environmental effects have contributed to inappropriate prescribing. The less obvious results of antimicrobial consumption probably go unrecognised in routine clinical care.

Overview of newer antimicrobial formulations for overcoming pneumococcal resistance

The pharmacokinetic (PK) and pharmacodynamic (PD) profile of an antimicrobial agent provides important information that can be used to maximize bacteriologic and clinical efficacy, minimize selective pressure for the development of antimicrobial resistance, and determine an optimal dosing regimen. Judicious selection of an antimicrobial based on local susceptibility data and PK and PD parameters is imperative in this era of increasing resistance among Streptococcus pneumoniae, a leading cause of community-acquired respiratory tract infections. The beta-lactam antimicrobials display time-dependent bacterial killing with minimal to no persistent effects. Ketolides and fluoroquinolones display concentration-dependent bacterial killing, and tetracyclines and macrolides display time-dependent killing. All have prolonged persistent effects (e.g., postantibiotic effect) that retard or prevent bacterial regrowth when free drug levels fall below the minimum inhibitory concentration (MIC). New high-dose and/or extended-release formulations of traditional antimicrobials have been added to the current armamentarium for treatment of community-acquired respiratory tract infections. These formulations include amoxicillin-clavulanate potassium powder for oral suspension 90/6.4 mg/kg per day divided every 12 hours (Augmentin ES-600; GlaxoSmithKline, Research Triangle Park, NC), amoxicillin-clavulanate potassium extended-release tablets 2 x 1,000 mg/62.5 mg every 12 hours (Augmentin XR; GlaxoSmithKline), clarithromycin extended-release tablets 2 x 500 mg once daily (Biaxin XL; Abbott Laboratories, North Chicago, IL), and cefaclor extended-release tablets 375 mg or 500 mg every 12 hours (Ceclor CD; Eli Lilly Pharmaceuticals, Indianapolis, IN). Of these agents, only amoxicillin-clavulanate potassium powder for oral suspension and amoxicillin-clavulanate potassium extended-release tablets were designed to treat infections caused by penicillin-resistant pneumococci (penicillin MIC < or =2 microg/mL). Extended-release clarithromycin does not provide higher daily doses than its immediate-release counterpart; rather, it allows for once-daily dosing of this agent because of its slower absorption following oral administration. Extended-release cefaclor is considered clinically equivalent to 250 mg of immediate-release cefaclor pulvules administered 3 times daily; it cannot be used interchangeably with 500 mg 3-times-daily dosages of other cefaclor formulations. Thus, despite providing a similar or higher total daily dose than its immediate-release counterpart, extended-release cefaclor is indicated only for the treatment of patients with mild to moderate infections caused by susceptible strains of certain organisms.