From a pharmacokinetic standpoint, Professor Lode began by looking at levofloxacin`s many advantageous features, including a long elimination time.Ciprofloxacin has a relatively short elimination, necessitating twice-daily administration schedules, and while sparfloxacin has a long elimination half-life, it is at a much lower plasma concentration level than that of levofloxacin.
Other differences can also be seen in pharmacokinetic data. C ranged from a low of 1.2 micrograms per milliliter per 70 kilograms for ciprofloxacin, to a high of 2.48 for levofloxacin, a statistically significant benefit for levofloxacin.In regard to AUC, ciprofloxacin again had the lowest value, while values for the other agents were similar, ranging from 15 to 19.7.
Gastrointestinal absorption of fluoroquinolones differ with 50 to 70% of low lipophilic agents absorbed. In contrast, those with medium lipophilic properties, such as levofloxacin, possess extremely good bioavailability rates of 100%. Once absorbed, there are two main metabolic pathways: through glucuronisation in the liver, or oxidation utilising the cytochrome P450 system followed by kidney elimination. Since sparfloxacin, grepafloxacin and moxifloxacin undergo considerable hepatic metabolisation, dosage adjustment is necessary in hepatically impaired patients.
All fluoroquinolones interact with aluminium- or magnesium-containing antacids, but there are differences in their degree of interaction with calcium-containing antacids. Reduction in bioavailability following co-administration with calcium-containing antacids is much more pronounced with ciprofloxacin than levofloxacin. Interaction with sucralfate is again more marked with ciprofloxacin. Bioavailability is reduced by about 50% when co-administered with iron compounds, with ciprofloxacin and moxifloxacin affected more than levofloxacin. Unlike the other fluoroquinolones, absorption of levofloxacin was not reduced when administered with food.
Another clinically important interaction is recognised between theophylline and enoxacin, pefloxacin and ciprofloxacin, but not for levofloxacin. This is particularly important when treating patients with respiratory tract infections who are likely to be on concomitant theophylline.
It is impressive that there is no clinical significant interaction between levofloxacin and food, or cyclosporine, digoxin, probenecid, theophylline, and warfarin, which are all frequently prescribed drugs.
Alterations in myocardial transfer channels are involved in cardiovascular adverse events associated with fluoroquinolones. The HERG channel, a potassium transferring channel, is affected to differing degrees by individual fluoroquinolones. At low doses, the percentage inhibition is highest for sparfloxacin, but as the dosage increases, the percentage inhibition rapidly increases for sparfloxacin as well as moxifloxacin and gatifloxacin.
Phototoxicity is another commonly described adverse event with fluoroquinolones. A study investigating the highest dose possible without phototoxicity revealed that ciprofloxacin and ofloxacin could be prescribed at more than 300 milligrams per kilogram, compared to 100 milligrams for enoxacin. For sparfloxacin, a small dose of 18 milligrams resulted in phototoxicity.This and other pharmacokinetic data show that levofloxacin maintains an exceptional safety profile compared to other fluoroquinolones.