Norfloxacin Antacids

Absorption Only 35-70% of oral norfloxacin is absorbed. However, 70-90% of the other fluoroquinolones are absorbed after oral administration. Bioavailability is greatest for ofloxacin and lomefloxacin. Intravenous preparations of ciprofloxacin and ofloxacin are available. Ingestion of the fluoroquinolones with sucralfate, antacids containing aluminum or magnesium, or dietary supplements containing iron or zinc can interfere with the absorption of these antibacterial agents. 

Bind to other drugs that are administered within 1 or 2 hours of the antacid, This process results in reduced availability of the co-administered drug for absorption, For example, the chelation of tetracyclines (e.g, tetracycline, doxycycline) will decrease their absorption by up to 90%, Avery similar process - precipitation - occurs with drugs such as quinine with aluminium and magnesium hydroxide preparations, which results in a decreased absorption of quinine, It has to be noted that the absorption of fluoroquinolones (e g. ciprofloxacin, norfloxacin, ofloxacin, enoxacin, perfloxacin i will be decreased by 60-75% if they are co-administered with divalent and trivalent cations. Patients are recommended not to take these divalent and trivalent cationic preparations until fluoroquinolone therapy is discontinued. 

Concurrent treatment with antacids reduces the oral absorption of many quinolones, such as ciprofloxacin and enoxacin (127), moxifloxacin (16), norfloxacin (128), ofloxacin (129), and sparfloxacin (130). 

Cordoba-Diaz M, Cordoba-Borrego M, Cordoba-Diaz D. Influence of pharmacotechnical design on the interaction and availability of norfloxacin in directly compressed tablets with certain antacids. Drug Dev Ind Pharm 2000 26(2) 159-66. 

Norfloxacin can interact with antacids containing aluminium or magnesium salts, by complexation, reducing its solubility and therefore its absorption this can result in therapeutic failure. In an in vitro study, dissolution rates were markedly reduced in the presence of all antacids studied however, this phenomenon was practically avoided when a disintegrant (sodium starch glycolate or crospovidone) was included in the tablet (13). 

Clinically important, potentially hazardous interactions with antacids, azathioprine, basiliximab, cholestyramine, corticosteroids, cyclophosphamide, cyclosporine, daclizumab, hemophilus B vaccine, mercaptopurine, metronidazole, norfloxacin, tacrolimus, vaccines... 

The nurse encourages patients who receive tlie fluoroquinolone to increase tlieir fluid intaka Norfloxacin and enoxacin are given on an empty stomach (, 1 hour before or 2 hours after meals). Ciprofloxacin and lome-floxacin can be given without r ard to meals. However, tlie manufacturer recommends that the drug be given 2 hours after a meal. Moxifloxacin is given once a day for tlie period pr ribed. If the patient is taking an antacid, moxifloxacin should be administered 4 hours before or 8 hours after the antacid. 

Information about the interactions with calcium carbonate is more limited than with the aluminium/magnesium antacids, but Table 10.3 , (p.329) shows that the bioavailabilities of ciprofloxacin and norfloxacin, and to a lesser extent gemifloxacin, can be reduced. These reductions are less than those seen with the aluminium/magnesium antacids, but using ciprofloxacin as a guide a very broad rule-of-thumb would be to separate the drug administration by about 2 hours to minimise this interaction. This is clearly not necessary with levofloxacin, lomefloxacin, moxifloxacin or ofloxacin, nor probably with some of the other qui-... 

Sodium bicarbonate does not interact significantly with norfloxacin but information about other quinolones appears to be lacking. However, bear in mind that in the case of ciprofloxacin an excessive rise in urinary pH (which can be caused by antacids like sodium bicarbonate) may possibly result in urinary crystalluria and kidney damage. "... 

Nix DE, Wilton JH, Ronald B, Distlerath L, Williams VC, Norman A. Inhibition of norfloxacin absorption by antacids. Antimicrob Agents Chemother (1990) 34,432-5. 

The proposed reason for these changes is that the calcium in milk and yoghurt or other dairy products combines with the ciprofloxacin and norfloxacin to produce insoluble chelates. Compare also Quinolones -i-Antacids or Calcium compounds , p.328. 

Campbell NRC, Kara M, Hasinoff BB, Haddara WM, McKay DW. Norfloxacin interaction with antacids and minerals. BrJ Clin Pharmacol (1992) 33, 115-16. 

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