Ranitidine absorption extent

Excipients such as mannitol can affect small intestinal transit, which in turn can affect the absorption of certain drugs. Oral solutions are rarely likely to fall short of bioequivalence relative to solid oral formulations, although during the development of a ranitidine effervescent oral solution dosage form containing sodium acid pyrophosphate (SAPP), a marked decrease in absorption was observed in the extent of ranitidine absorption from the liquid formulation relative to the conventional oral tablet. The formulation contained 150 mg ranitidine with 1132 mg SAPP together with 1.5 MBq hndium chloride solutions. Small intestinal transit time was decreased to 56% in the presence of the excipient. The rapid small intestinal transit associated with an excipient of a solution dosage form resulted in a decreased extent of ranitidine absorption. " ... 

In 14 healthy subjects famotidine 40 mg raised the peak plasma levels of enteric-coated diclofenac 100 mg from 5.84 to 7.04 mg/L. Peak plasma diclofenac levels also occurred more rapidly (2 versus 2.75 hours). The extent of the absorption was unchanged. Diclofenac did not affect the pharmacokinetics of ranitidine nor its ability to suppress gastric pH. Another study also found that the pharmacokinetics of diclofenac were unaffected by ranitidine. ... 

Valproic acid may reduce the clearance of temozolomide. Car-bamazepine, H2-receptor antagonisits, dexamethasone, phenobar-bital, phenytoin, prochlorperazine and ondansetron did not affect the clearance. Food, but not ranitidine slightly reduced extent of absorption of temozolomide. 

The absorption of cimetidine, famotidine, nizatidine, and ranitidine may possibiy be reduced to some extent by antacids, but it seems doubtful if this significantly reduces their effects. Separating the dosages by 1 to 2 hours minimises any interaction. Roxa-tidine absorption appears not to be affected by antacids. Cimetidine appears not to interfere with the effectiveness of Gaviscon (sodium alginate compound). 

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