Treatment of Iron Deficiency Anemia with Ferrex (Ferrous Sulfate)
Start with ferrous sulfate 65 mg elemental iron (one 200 mg tablet) once daily on an empty stomach as first-line treatment for iron deficiency anemia. 1, 2
Initial Dosing Strategy
Ferrous sulfate is the preferred first-line oral iron formulation due to equivalent efficacy to other ferrous salts (including ferrous fumarate and ferrous gluconate) at significantly lower cost ($0.30-$4.50 per 30 tablets versus $3.90 for ferrous fumarate). 1, 2
Begin with one 200 mg ferrous sulfate tablet daily (providing 65 mg elemental iron) rather than the outdated three-times-daily dosing, as lower doses are equally effective with better tolerability. 1, 2, 3
Administer on an empty stomach for optimal absorption, though taking with food is acceptable if gastrointestinal side effects occur. 2
Add vitamin C 250-500 mg with each iron dose to enhance absorption. 1, 2
Managing Side Effects
If gastrointestinal side effects develop (nausea, abdominal pain, constipation):
Switch to alternate-day dosing (one tablet every other day) rather than changing formulations, as this maintains similar iron absorption with improved tolerability. 1, 2
If alternate-day dosing fails, consider switching to ferrous fumarate or ferrous gluconate, though evidence shows side effects are primarily dose-dependent rather than formulation-specific. 1, 2
Avoid tea and coffee within one hour of iron administration as these are powerful inhibitors of iron absorption. 1
Monitoring Response
Check hemoglobin at 2-4 weeks: expect at least a 1 g/dL (10 g/L) increase if treatment is effective. 1, 2
If hemoglobin fails to rise appropriately, verify adherence and consider switching to intravenous iron rather than trying different oral formulations. 1, 2
Continue treatment for 3 months after hemoglobin normalization to replenish iron stores (ferritin should increase within one month in adherent patients). 1, 2
When to Use Intravenous Iron Instead
Switch to IV iron if:
Oral iron is not tolerated despite alternate-day dosing. 1
Hemoglobin does not increase by 1 g/dL within 2 weeks or ferritin fails to rise within one month in adherent patients. 1
Conditions causing impaired absorption exist: post-bariatric surgery, active inflammatory bowel disease, celiac disease with poor gluten-free diet adherence. 1
Iron loss exceeds oral absorption capacity (ongoing bleeding). 1
Preferred IV formulations that replace iron deficits in 1-2 infusions include ferric carboxymaltose (750-1000 mg), ferric derisomaltose (1000 mg), or low-molecular-weight iron dextran (1000 mg), though ferric carboxymaltose carries risk of prolonged hypophosphatemia with repeated dosing. 1
Critical Pitfalls to Avoid
Do not use modified-release ferrous sulfate preparations as they have reduced bioavailability. 2
Do not assume ferrous fumarate or other ferrous salts are inherently better tolerated—gastrointestinal side effects are dose-related, not formulation-specific. 2, 4
Do not defer iron replacement while awaiting investigations unless colonoscopy is imminent, as this delays symptom improvement and store repletion. 1
Do not continue oral iron indefinitely without monitoring response—failure to respond indicates absorption issues, ongoing blood loss, or incorrect diagnosis rather than need for higher doses. 1, 2