Ciprofloxacin Calcium carbonate

Interference with T4 absorption Cholestyramine, chromium picolinate, colestipol, ciprofloxacin, proton pump inhibitors, sucralfate, sodium polystyrene sulfonate, raloxifene, sevelamer hydrochloride, aluminum hydroxide, ferrous sulfate, calcium carbonate, bran, soy, coffee. 

Chelation of ciprofloxacin (V) by aluminium hydroxide and calcium carbonate reduces bioavailability, as seen in Fig. 10.11. Other quinolones (VI-IX), undoubtedly suffer the same fate. 

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-... 

Erost RW, Lasseter KC, Noe AJ, Shamblen EC, Lettieri JT. Effects of aluminum hydroxide and calcium carbonate antacids on the bioavailability of ciprofloxacin. Andmi-... 

Sahai J, Healey DP, StotkaJ, Polk RE. The influence of chronic administration of calcium carbonate on the bioavailability of oral ciprofloxacin. BrJClin Pharmacol 99Z) 35, 302-4. 

Didanosine is extremely acid labile at pH values below 3, so one ofthe formulations contains buffering agents (dihydroxyaluminium sodium carbonate and magnesium hydroxide) to keep the pH as high as possible to minimise the acid-induced hydrolysis. Ciprofloxacin forms insoluble non-absorbable chelates with these metallic ions in the buffer so that its bioavailability is markedly reduced. See also Quinolones + Antacids or Calcium compounds , p.328. 

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