Isoniazid Magnesium hydroxide

The absorption of isoniazid from the gut is modestly reduced by aluminium hydroxide, less so by magaldrate, and not by affected by aluminium/magnesium hydroxide tablets or didanosine chew-able tablets. 

Didanosine chewable tablets contain antacids (aluminium/magnesium hydroxide) in the formulation, but it has been shown that they do not affect the bioavailability of isoniazid. ... 

Information on this interaction is limited, and it is not established. The clinical importance of the modest reductions in isoniazid levels with aluminium hydroxide in one study is uncertain, but likely to be small. However, aluminium/magnesium hydroxide did not interact, and neither did didanosine chewable tablets. 

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