Clinical role of the quinolones today and in the future

Fluoroquinolones in pediatrics and their nephrotoxicity in adults: minireview

In recent years there is increasing pressure to use fluoroquinolones in pediatric patients but relatively few data have been published in the literature. Therefore this paper reviews the available information about the pharmacokinetics of fluoroquinolones in children and their use in pediatric urinary tract infections, taking into account their potential as nephrotoxic agents. From the available data it seems reasonable to suggest that there is no risk of quinolone-induced nephrotoxicity and that this class of antibiotics may therefore be considered as potential candidates in urinary tract infections in children. Nevertheless adequate pharmacokinetic investigations and further studies on long-term monitoring for potential toxicity need to be conducted in pediatric populations.

Ten-year survey of quinolone resistance in Escherichia coli causing urinary tract infections

In a ten-year survey (1983-1992) of quinolone resistance in Escherichia coli causing urinary tract infections in a general practice patient population, 9,934 strains were tested. Resistance increased remarkably from 1989 onwards. The rate of resistance to pipemidic acid was < or = 6% before 1989 and 18% in 1992; the rate of resistance to ciprofloxacin (MIC > or = 4 mg/l) was 0.8% in 1989 and 7.1% in 1992. Although the consumption of older quinolones decreased the total consumption of quinolones increased yearly.

Quinolones in the treatment of acute bacterial diarrhoeal diseases

Acute bacterial diarrhoea is still an important disease, especially in developing countries. Resistance to antibiotics among enteric pathogens is relatively common in many parts of the world. The quinolones are active in vitro against these organisms, and achieve high stool concentrations. Because of these features, quinolones have been used in the treatment of acute diarrhoeal diseases caused by various bacteria. They appear to be effective in the therapy of shigellosis and travellers' diarrhoea, as well as in the prevention of diarrhoeal disease in travellers. However, their role in the treatment of salmonella gastroenteritis has not been established yet.

Embryotoxicity studies of norfloxacin in cynomolgus monkeys. II. Role of progesterone

Norfloxacin, an orally active fluoroquinolone antimicrobial, has been reported to be embryolethal but not teratogenic when administered to pregnant cynomolgus macaques prior to gestational day (GD) 36 at doses > or = 200 mg/kg/day. Additional studies have been performed in an effort to examine the mechanism responsible for this effect, particularly regarding the role of progesterone (P). The first study (Study I) investigated the effect of norfloxacin administration during early pregnancy (200 mg/kg/day; daily GD 20-30) in the absence of a functional corpus luteum (CL). The CL was surgically removed from 16 gravid females on GD 19 in order to focus on placental-derived P; ten were dosed with norfloxacin and six received vehicle only. Embryolethality was observed for 7/10 (70%) of the treated animals during GD 25-31 versus 0/6 (0%) for controls. A reduction in serum P was noted prior to embryonic loss, although no significant effects on chorionic gonadotropin (CG), 17 beta-estradiol (E2), or P or E urinary metabolites were observed. A second study (Study II) was performed in order to evaluate the capacity of norfloxacin (200 mg/kg) to reduce CL-derived P in both normally cycling and CG-stimulated nonpregnant females (ten treated, ten controls; daily for 8 days). No effects on P production or on luteal phase or menstrual cycle lengths were observed. The third study (Study III) was designed to examine the effect of norfloxacin on the metabolism and excretion of P in nonpregnant females. Silastic P implants were placed subcutaneously in order to maintain constant P levels during a 10 day treatment regimen (200 mg/kg/day; ten controls, nine treated). Five of the controls and four of the norfloxacin-treated females also received 14C-P intravenously within 1 hr of the last dose of norfloxacin in order to study excretory patterns. No significant differences between control and treated groups were observed. The results of these studies combined suggest that the developmental toxic effects observed in prior studies and Study I are specific to pregnancy and directly related to placental-derived P production.

The quinolones. An overview of their pharmacology

The fluoroquinolones represent a relatively new class of antibiotics with outstanding therapeutic potential, attributable to their broad spectrum of antimicrobial activity and favourable tissue distribution. They are highly active against most Gram-negative pathogens, as well as Staphylococcus aureus and coagulase-negative staphylococci. In addition, the fluoroquinolones have useful pharmacokinetic properties: they are orally active, and their lipophilicity and low degree of plasma protein binding allow for excellent tissue penetration and concentrations, as reflected in their particularly large apparent volumes of distribution. Infections due to aerobic Gram-negative pathogens are considered those most susceptible to the quinolones. Disease indications in which these agents appear to offer the greatest therapeutic advantage over currently available alternatives include the following: complicated urinary tract infections (particularly those caused by Pseudomonas aeruginosa or resistant Gram-negative microorganisms); suspected bacterial gastroenteritis; eradication of Salmonella typhi from the faeces in known carriers; P. aeruginosa-associated respiratory exacerbation in patients with cystic fibrosis; and chronic Gram-negative bacterial osteomyelitis. Direct comparisons of the various quinolones are too limited to date to provide clear therapeutic options. Nevertheless, this class of compounds is likely to play a major role in providing effective oral therapy for conditions that have previously required prolonged parenteral treatment.

Bowel microorganisms--a target for selective antimicrobial control

This article reviews the eight factors that determine the outcome of selective antimicrobial control (SAC) a technique aimed at the clearance of intestinal Gram-negative bacillary carriage by means of lethal faecal anti-microbial concentrations. They are as follows: (i) the carrier state; (ii) compliance; (iii) SAC aiming at prophylaxis vs treatment; (iv) minimum bactericidal concentration (MBC) of the antimicrobial; (v) dosage; (vi) pharmacokinetics; (vii) faecal inactivation; and (viii) microorganisms to be controlled. In the second part, non-absorbable SAC regimens are compared with absorbable trimethoprim/sulphamethoxazole (TMP/SMZ) and the fluoroquinolones in different clinical settings including neutropenia, intensive care, hepatic encephalopathy, liver transplantation and the salmonella carrier state. Ablation of gut carriage and superinfections are the main endpoints reviewed in this article. The newer fluoroquinolones are potent SAC agents to deal with enterobacteria. Pseudomonads are the major gap in their SAC spectrum. TMP/SMZ emerges as a SAC agent of limited value, whilst the newer non-absorbable combination of polymyxin/tobramycin seems to be the most potent SAC programme since it has activity against pseudomonads. In a third part, three current issues--the emergence of resistance, the selectivity and the tissue effect are discussed. Finally, a potent fluoroquinolone combined with oral polymyxin/tobramycin seems to be the most effective SAC programme currently available to control enterobacteria and pseudomonads in patients in whom bacterial translocation is a risk with minimal risk of resistance emerging.

Use of quinolones in pediatrics

Compared to nalidixic acid, the new quinolones possess an enlarged antimicrobial spectrum, greatly enhanced bactericidal activity, and substantial pharmacokinetic advantages. Because their activity against streptococci is limited the quinolones presently available will never be included in routine regimens for children. Moreover, adequate pharmacokinetic studies are still lacking in pediatrics, and potential drug toxicity warrants further long-term monitoring. Nevertheless, various studies strongly suggest that there is no quinolone-induced cartilage toxicity in humans, and the results of published clinical trials with fluoroquinolones in pediatric patients show promising efficacy and safety. From a review of the available data it is concluded that use of the quinolones in children should be limited to specific infections which are usually caused by Pseudomonas aeruginosa, Staphylococcus aureus or Staphylococcus epidermidis, and are complicated by underlying pathologic or special conditions such as cystic fibrosis or urologic abnormality. In each case, careful monitoring to determine efficacy, potential adverse effects including drug-drug interaction and toxicity, and any emergence of bacterial resistance is mandatory.