May decrease absorption of other minrals eg, Ca, Zn, manganese, chromium & Mg. May interfere w/ absorption of other medicines. Decreased absorption of tetracyclines; digoxin, indomethacin, Fe salts; antifungals (eg, ketoconazole, itraconazole); azithromycin, nitrofurantoin, rifampicin, phenytoin, chloroquine, phenothiazine antipsychotics (eg, chlorpromazine) & bisphosphonates (eg, alendronate, etidronate, risedronate). May decrease excretion of weakly basic drugs (eg, quinidine, chlorpromazine, propranolol, diazepam) & increase excretion of acidic drugs (eg, phenytoin, pentobarb, warfarin). Changes in urine pH, increased urinary excretion & decreased of blood conc of salicylates eg, aspirin. Formation of insoluble metal ion chelates w/ fluoroquinolones (eg, ciprofloxacin, norfloxacin & ofloxacin) & penicillamine (for RA). Na alginate: May decrease absorption of Ca, Zn, Mn, chromium, & Mg if used concomitantly. Na bicarbonate: Increased rate of naproxen absorption.