Most Bioavailable Oral Iron Formulation
Oral iron formulations with ferrous (Fe2+) salts are the standard reference formulations for treatment of iron deficiency because they consistently increase body iron measures in clinical trials. [1]
In the most directly comparable randomized trial identified, ferrous sulfate produced a larger increase in ferritin than ferrous bisglycinate at different elemental iron doses. [1]
Medication Selection Algorithm
- Ferrous sulfate (high-dose elemental iron in trials) is selected when maximal hematologic response is prioritized. [1]
- Ferrous bisglycinate (lower-dose elemental iron in trials) is selected when dosing convenience or tolerability is prioritized, with expected response potentially lower at the tested elemental dose. [1]
Key Evidence Supporting This Recommendation
- In a randomized, double-blind noninferiority trial in nonpregnant Cambodian women (12 weeks), mean ferritin at 12 weeks was higher with 60 mg elemental iron as ferrous sulfate than with 18 mg elemental iron as ferrous bisglycinate. [1]
- Reported mean ferritin at 12 weeks was 99 (95% CI 95 to 103) mcg/L with ferrous sulfate, 84 (95% CI 80 to 88) mcg/L with ferrous bisglycinate, and 78 (95% CI 74 to 82) mcg/L with placebo. [1]
- The adjusted mean ferritin difference between the iron groups was 14.6 (95% CI 7.6 to 21.6) mcg/L in analyses comparing the two iron groups. [1]
Monotherapy Versus Combination Therapy
- Oral iron is administered as monotherapy for iron deficiency when an oral route is appropriate. [1]
- Combination therapy is not supported by this evidence as providing superior ferritin response to the compared oral iron preparations. [1]
Important Clarifications or Nuances
- “Most bioavailable” is not uniquely determined by formulation name alone because trial dosing of elemental iron differed between ferrous sulfate and ferrous bisglycinate in the available head-to-head study. [1]
- The head-to-head trial evidence supports superior ferritin response with ferrous sulfate at the studied regimen rather than establishing that ferrous bisglycinate is more bioavailable. [1]
Targets or Goals of Therapy
- The ferritin increase toward repletion is the principal target in iron-repletion trials comparing oral iron formulations. [1]