Norfloxacin dosage

Norfloxacin - Absorption is rapid. Food or dairy products may decrease absorption. Steady-state norfloxacin levels will be attained within 2 days of dosing. Norfloxacin is eliminated through metabolism, biliary excretion, and renal excretion. Renal excretion occurs by glomerular filtration and tubular secretion. In healthy elderly volunteers, norfloxacin is eliminated more slowly because of decreased renal function. In patients with Ccr rates 30 mL/min/1.73 m or less, the renal elimination decreases so that the effective serum half-life is 6.5 hours dosage alteration is necessary. 

Hepatic function impairment There are no data in patients with severe cirrhosis. Dosage adjustment is recommended in patients with mild-to-moderate cirrhosis. Eideriy Norfloxacin is eliminated more slowly because of decreased renal function. The apparent half-life of ofloxacin is 6 to 8 hours, compared to approximately 5 hours in younger adults. Lomefloxacin plasma clearance was reduced by 25% and the AUC was increased by approximately 33% in the elderly. 

Crystaiiuria Needle-shaped crystals were found in the urine of some volunteers who received either placebo or norfloxacin. Do not exceed the daily recommended dosage. The patient should drink sufficient fluids to ensure proper hydration and adequate urinary output. 

Fluoroquinolones are potent inhibitors of hepatic cytochrome P450 isozymes (150). They inhibit theophylline metabolism, and accumulation of theophylline has led to seizures (151). Theophylline clearance is reduced by about 10% by norfloxacin, 30% by ciprofloxacin, and 70% by enoxacin (152-162). In a comparison of grepa-floxacin (400 and 600 mg/day) and ciprofloxacin, increased theophylline concentrations associated with clinical symptoms were found with both doses of grepa-floxacin but not in patients taking ciprofloxacin (17). The dosage of theophylline should be reduced when a quino-lone is given. 

Early reports of acute interstitial nephritis [273] and of acute tubular necrosis [274] associated with the use of pirotnidic acid (a non-fluorinated quinolone available in Europe) have been published. At large dosage, crystals of norfloxacin can be occasionally seen in freshly voided urine, this, however, does not... 

Norfloxacin and ciprofloxacin decrease the systemic clearance of theophylline to an extent that could be of clinical significance (Prince et al.r 1989). The effect of the interaction can be avoided by adjusting the dosage rate of theophylline in accordance with the decreased clearance so that steady-state plasma theophylline concentrations remain within the therapeutic range (6-16 pig/mL). 

Information seems to be limited to these reports. They indicate that in children and adults the dosage of ciclosporin will probably need to be reduced in the presence of norfloxacin. Information with levofloxacin is currently limited, but a modest increase in ciclosporin levels may occur, and increased monitoring seems advisable. 

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