Fluoroquinolones

Comparative pharmacodynamics of three newer fluoroquinolones versus six strains of staphylococci in an in vitro model under aerobic and anaerobic conditions

Six strains of staphylococci were exposed to levofloxacin, moxifloxacin, or trovafloxacin in an in vitro pharmacodynamic model under both aerobic and anaerobic conditions. Each agent demonstrated a rapid 3-log(10) kill versus susceptible isolates regardless of condition. Against clinical isolates with reduced susceptibility, regrowth occurred by 24 h and was frequently associated with further increases in MICs.

A novel approach to determining physicochemical and absorption properties of 6-fluoroquinolone derivatives: experimental assessment

The ToSS MoDe approach is used to estimate the n-octanol/buffer partition coefficient, the apparent intestinal absorption rate constant and intestinal permeability from a 6-fluoroquinolone data set. Improved in silico methods for predicting a drug's ability to be transported across biological membranes and other biopharmaceutical properties is highly desirable to optimize new drug development. The physicochemical property (Log P) of 26 6-fluoroquinolone derivatives and the absorption properties (Log K(a) and Log P(eff)) of 21 derivatives were well described by the present approach. The models obtained confirm the important role of lipophilicity in the absorption process and its relation with the piperazinyl ring spectral moment and general local spectral moment. The normalized group contributions to each property, at the R4 and R5 positions of a 6-fluoroquinolone framework, were calculated. Principal factor analysis between these contributions and the Hammett and Hansch constant, molar refractivity and sterimol parameters was also carried out. Three principal factors explained 78% of the total variance and the correlation coefficients were higher than 0.98. The isocontribution zone analysis for the Log P and Log K(a) of Sarafloxacin and Sparfloxacin, used as external corroboration compounds, was carried out. The absorption rate constants (in situ rat gut technique) for these drugs were also evaluated, and the results were compared with the values predicted by theoretical models for evaluating predictive performance. The present approach proved to be a good method for studying the oral absorption of drug candidates in drug development studies.

A review of antibiotics in dermatology

BACKGROUND

Since the early 1930s when antibiotics were first introduced, they have revolutionized the way physicians treat infections. Skin conditions from acne to leprosy, which were once shunned by society, are now easily treated with oral antibiotics.

OBJECTIVE

Antibiotics are chemicals derived from bacteria and fungi that uniquely have antibacterial action. The most notable example is penicillin, which is derived from a mold. With hundreds of antibiotics available to the practicing physician, improper use of these drugs has become widespread and expensive and has spawned resistant strains. For the dermatologist, antibiotics are vital weapons in the drug armamentarium for treating various skin conditions.

CONCLUSION

This review explores the newest and most common oral, parenteral, and topical antibiotics used in dermatology, their indications, adverse effects, dosage, and spectrum of activity. Furthermore, systemic antibacterial prophylaxis and vaccines pertinent to dermatology are discussed. The penicillins, cephalosporins, tetracyclines, macrolides, fluoroquinolones, sulfonamides, aminoglycosides, lincosamides, folate inhibitors, and a new synthetic class of drugs, the oxazolidinones, are reviewed. These antibiotics are used to treat a variety of organisms.

Possible levofloxacin-induced acute hepatocellular injury in a patient with chronic obstructive lung disease

Levofloxacin is one of the most commonly prescribed antibiotics for both inpatient and outpatient care of respiratory tract infection. It is generally well tolerated, and it has an excellent safety profile. We report a case of severe acute liver toxicity that apparently complicated intravenous administration of levofloxacin, which resolved after discontinuation of the drug.

Mechanism of action of and resistance to quinolones

A topoisomerase was identified as the bacterial target site for quinolone action in the late 1970s. Since that time, further study identified two bacterial topoisomerases, DNA gyrase and topoisomerase IV, as sites of antibacterial activity DNA gyrase appears to be the primary quinolone target for gram-negative bacteria. Topoisomerase IV appears to be the preferential target in gram-positive organisms, but this varies with the drug. Three mechanisms of resistance against quinolones are mutations of topoisomerases, decreased membrane permeability, and active drug efflux. Although these mechanisms occur singly, several resistance factors are often required to produce clinically applicable increases in minimum inhibitory concentrations. Appropriate drug selection and dosage and prudent human and veterinary interventions are important factors in controlling the emergence of resistance.

Seizures associated with fluoroquinolones

OBJECTIVE

To report two cases of seizures following administration of levofoxacin and ciprofloxacin.

CASE SUMMARY

A 75-year-old white woman admitted to the hospital was prescribed levofloxacin for ischemic toes. After receiving three doses of oral levofloxacin, the patient experienced a seizure. One month later, the patient was rechallenged with ciprofloxacin and again experienced a seizure. The patient was hypomagnesemic and had elevated serum creatinine at the time of both seizures, and was hyponatremic during the second seizure. A 74-year-old white woman admitted to the hospital was prescribed levofloxacin for bacterial pneumonia. After five doses, the patient experienced a seizure. The woman had no electrolyte imbalances at the time of the seizure and no history of a seizure disorder.

DISCUSSION

Quinolone antibiotics vary in their ability to induce seizures, with trovafloxacin having the greatest potential and levofloxacin possibly having the least potential. Neither patient had a history of a previous seizure disorder. Electrolyte imbalances are common with previous reports of fluoroquinolone-induced seizures.

CONCLUSIONS

Although levofloxacin monotherapy has not been implicated in inducing seizures, it appears to be the causative agent in the second case. In the first case, the quinolones may have been a necessary, but not sufficient, cause in a patient with electrolyte abnormalities. Risk factors for fluoroquinolone-induced seizures may Include seizure history, electrolyte imbalances,dose unadjusted for renal insufficiency, and concomitant treatment with agents that lower the seizure threshold.

Quinolone Resistance: Older Concepts and Newer Developments

New quinolone compounds have been recommended for use in the treatment of respiratory tract infections, particularly pneumonia caused by multi drug-resistant Streptococcus pneumoniae. Of concern, however, is the recent emergence of pneumococcal isolates with reduced susceptibilities to both old and new quinolone compounds. This necessitates the employment of quinolone-use strategies aimed at restricting the emergence of resistance, to extend the effectiveness of this very important class of antibacterial agents. This article provides a comprehensive review of the recent discoveries in type II topoisomerase/quinolone structure-function relationships. It also addresses new insights into the mechanisms of quinolone resistance, the predicted trends in quinolone resistance, and possible strategies for quinolone use against S. pneumoniae.