Single-dose pharmacokinetic study of ciprofloxacin and fleroxacin in healthy adult Nigerian volunteers

Interethnic differences in pharmacokinetics of antibacterials

BACKGROUND

Optimal antibacterial dosing is imperative for maximising clinical outcome. Many factors can contribute to changes in the pharmacokinetics of antibacterials to the extent where dose adjustment may be needed. In acute illness, substantial changes in important pharmacokinetic parameters such as volume of distribution and clearance can occur for certain antibacterials. The possibility of interethnic pharmacokinetic differences can further complicate attempts to design an appropriate dosing regimen. Factors of ethnicity, such as genetics, body size and fat distribution, contribute to differences in absorption, distribution, metabolism and elimination of drugs. Despite extensive previous work on the altered pharmacokinetics of antibacterials in some patient groups such as the critically ill, knowledge of interethnic pharmacokinetic differences for antibacterials is limited.

OBJECTIVES

This systematic review aims to describe any pharmacokinetic differences in antibacterials between different ethnic groups, and discuss their probable mechanisms as well as any clinical implications.

METHODS

We performed a structured literature review to identify and describe available data of the interethnic differences in the pharmacokinetics of antibacterials.

RESULTS

We found 50 articles that met our inclusion criteria and only six of these compared antibacterial pharmacokinetics between different ethnicities within the same study. Overall, there was limited evidence available. We found that interethnic pharmacokinetic differences are negligible for carbapenems, most β-lactams, aminoglycosides, glycopeptides, most fluoroquinolones, linezolid and daptomycin, whereas significant difference is likely for ciprofloxacin, macrolides, clindamycin, tinidazole and some cephalosporins. In general, subjects of Asian ethnicity achieve drug exposures up to two to threefold greater than Caucasian counterparts for these antibacterials. This difference is caused by a comparatively lower volume of distribution and/or drug clearance.

CONCLUSION

Interethnic pharmacokinetic differences of antibacterials are likely; however, the clinical relevance of these differences is unknown and warrants further research.

Fleroxacin vs Ciprofloxacin in the Management of Typhoid Fever: A Randomised, Open, Comparative Study in Nigerian Patients

OBJECTIVE

The antibacterial efficacy of fleroxacin was compared with that of ciprofloxacin in 72 adult Nigerian patients with typhoid fever.

PATIENTS AND METHODS

On inclusion into the study, patients were randomised to treatment with either fleroxacin 400mg once daily for 7 days or ciprofloxacin 500mg twice daily for 14 days. Clinical evaluations were performed on days 0, 1, 2, 3, 5 and 7 or 14, and 2 weeks after treatment. Bacteriology was performed on days 0, 3, 7 or 14, and 21 or 28. Laboratory tolerability parameters were monitored for all patients as well as incidence of adverse events.

RESULTS

Bacteriological response on day 3 was 93.5 and 64.0% for fleroxacin and ciprofloxacin, respectively. At term and follow-up there was bacteriological cure in 97.0% of patients with fleroxacin and 100% with ciprofloxacin. The clinical cure was 100% for both groups at term. The incidence of adverse events was 5.4% with fleroxacin and 2.8% with ciprofloxacin.

CONCLUSION

The results demonstrated that while the clinical response rate with both drugs was comparable, fleroxacin exhibited a faster bacteriological clearance rate. We therefore concluded that 7 days' therapy with fleroxacin 400mg once daily was as effective as 14 days' therapy with ciprofloxacin 500mg given twice daily in the management of typhoid fever in Nigerian patients. It was also observed that the quinolones possessed greater potential and benefits as first-line therapy for the management of typhoid fever in this environment. The tolerability profile was good for both treatment regimens.

Evaluation of quinolone derivatives for antitrypanosomal activity

About 160 fluoroquinolones and derivatives were tested for antitrypanosomal activity in a drug sensitivity assay followed by fluorometric evaluation. The most active quinolone compounds had IC50 values in the range from 100 to 900 ng/ml, while several derivatives were not active at a concentration of 100 microg/ml. In a structure activity relationship study, modification of the quinolones at position R1, R2, R3 and R8 did not influence trypanocidal activity. An exchange of the fluor at position 6 may contribute to an increase in activity but does not entirely control it. Pyrrolidine substituents at position R7 generally were more active than other substituents at this position. Tetracyclic quinolone derivatives were amongst the most active compounds with IC50 values in the range of 0.3-8.8 microg/ml. The in vitro cytotoxicity on HT-29 cells was determined for active compounds with IC50 values below 1 microg/ml. In addition, six drugs with an IC50 below 1 microg/ml and a selectivity index of more than 10 were chosen for in vivo experiments. Dose escalation experiments with a maximum dose of 100 mg/kg/bid were performed in a mouse model without central nervous system involvement. For unknown reasons the in vitro effect of the drugs could not be confirmed in vivo, but the class of compound remains of interest for their mode of action, the low toxicity, pharmacological properties and the availability of a large number of synthesized compounds.