Isoniazid Aluminium 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. 

Aluminium hydroxide delays gastric emptying," causing retention of the isoniazid in the stomach. Since isoniazid is largely absorbed from the intestine, this explains the slight decrease in plasma isoniazid concentrations. Aluminium hydroxide also appears to inhibit the absorption 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. 

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. ... 

---