Caution is recommended when prescribing iron supplements. Raltegravir binds to divalent cations such as iron and forms a complex at the level of the gastro-intestinal tract which results in less raltegravir being absorbed. The European product label for raltegravir states that taking iron salts at least two hours from the administration of raltegravir may allow to limit this effect. Note, drug-drug interaction studies with antacids containing divalent cations have shown a more pronounced reduction in raltegravir Cmin when raltegravir was administered once daily compared to a twice daily regimen. A similar effect for iron supplements cannot be excluded.