Testing equivalence of two doses of intravenous iron to treat iron
deficiency in pregnancy: A randomised controlled trial
Abstract
Objective To test equivalence of two doses of intravenous iron (ferric
carboxymaltose) in pregnancy. Design Parallel, two-arm equivalence
randomised controlled trial with an equivalence margin of 5%. Setting
Single centre in Australia. Population 278 pregnant women with iron
deficiency. Methods Participants received either 500 mg (n=152) or
1000mg (n=126) of intravenous ferric carboxymaltose in the second or
third trimester. Main outcome measures The proportion of participants
requiring additional intravenous iron (500mg) to achieve and maintain
ferritin >30ug/L (diagnostic threshold for iron deficiency)
at 4 weeks post-infusion, and at 6 weeks, and 3-, 6- and 12-months
postpartum. Secondary endpoints included repeat infusion rate, iron
status, birth, and safety outcomes. Results The two doses were not
equivalent within a 5% margin at any timepoint. At 4 weeks post
infusion, 26/73 (36%) participants required a repeat infusion in the
500 mg group compared with 5/67 (8%) in the 1000 mg group (difference
in proportions, 0.283 95% confidence interval (0.177, 0.389)). Overall,
participants in the 500 mg arm received twice the repeat infusion rate
(0.81 (SD= 0.824 vs 0.40 (SD= 0.69), rate ratio 2.05, 95% CI (1.45,
2.91)). Conclusions Administration of 1000mg ferric carboxymaltose in
pregnancy maintains iron stores and reduces the need for repeat
infusions. A 500 mg dose requires ongoing monitoring to ensure adequate
iron stores are reached and sustained.