Standard approaches are not appropriate when assessing pharmacokinetics of iron supplements due to the ubiquity of endogenous iron, its compartmentalized sites of action, and the complexity of the iron metabolism. The primary site of action of iron is the erythrocyte, and, in contrast to conventional drugs, no drug-receptor interaction takes place. Notably, the process of erythropoiesis, i.e., formation of new erythrocytes, takes 3–4 weeks. Accordingly, serum iron concentration and area under the curve (AUC) are clinically irrelevant for assessing iron utilization. Iron can be administered intravenously in the form of polynuclear iron(III)-hydroxide complexes with carbohydrate ligands or orally as iron(II) (ferrous) salts or iron(III) (ferric) complexes. Several approaches have been employed to study the pharmacodynamics of iron after oral administration. Quantification of iron uptake from radiolabeled preparations by the whole body or the erythrocytes is optimal, but alternatively total iron transfer can be calculated based on known elimination rates and the intrinsic reactivity of individual preparations. Degradation kinetics, and thus the safety, of parenteral iron preparations are directly related to the molecular weight and the stability of the complex. High oral iron doses or rapid release of iron from intravenous iron preparations can saturate the iron transport system, resulting in oxidative stress with adverse clinical and subclinical consequences. Appropriate pharmacokinetics and pharmacodynamics analyses will greatly assist our understanding of the likely contribution of novel preparations to the management of anemia.

An ideal preparation for intravenous iron replacement therapy should balance effectiveness and safety. Compounds that release iron rapidly tend to cause toxicity, while large molecules can induce antibody formation and cause anaphylactic reactions. There is therefore a need for an intravenous iron preparation that delivers appropriate amounts of iron in a readily available form but with minimal side effects and thus with an excellent safety profile. In this paper, a review is given on the chemistry, pharmacology, and toxicology of ferric carboxymaltose (FCM, Ferinject), a stable and robust complex formulated as a colloidal solution with a physiological pH. The complex is gradually taken up mainly from the hepatic reticulo-endothelial system (RES), followed by effective delivery of iron to the endogeneous transport system for the haem synthesis in new erythrocytes, as shown in studies on the pharmacodynamics and pharmacokinetics with radio-labelled FCM. Studies with radio-labelled FCM also demonstrated a barrier function of the placenta and a low transfer of iron into the milk of lactating rats. Safety pharmacology studies indicated a favourable profile with regard to cardiovascular, central nervous, respiratory, and renal toxicity. A high maximum non-lethal dose was demonstrated in the single-dose toxicity studies. Furthermore, based on the No-Observed-Adverse-Effect-Levels (NOAELs) found in repeated-dose toxicity studies and on the cumulative doses administered, FCM has good safety margins. Reproductive and developmental toxicity studies did not reveal any direct or indirect harmful effects. No genotoxic potential was found in in vitro or in vivo studies. Moreover, antigenicity studies showed no cross-reactivity of FMC with anti-dextran antibodies and also suggested that FCM does not possess sensitizing potential. Lastly, no evidence of irritation was found in local tolerance studies with FCM. This excellent toxicity profile and the high effectiveness of FCM allow the administration of high doses as a single infusion or bolus injection, which will enhance the cost-effectiveness and convenience of iron replacement therapy. In conclusion, FCM has many of the characteristics of an ideal intravenous iron preparation.

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The following review of iron(III)-hydroxide polymaltose complex (IPC, Maltofer) shows that iron is significantly bioavailable after oral administration, especially in iron-deficient subjects. Numerous clinical trials in men, women, children and infants have shown that IPC is effective in treating iron deficiency anaemia (IDA). Due to its kinetic properties, IPC is best given with meals, and probably in an iron dose slightly higher than that of the classical iron salts. In terms of acceptance and patient compliance, IPC presents a clear advantage over ferrous salts. Many studies have shown a lower rate of treatment interruption with IPC than with ferrous salts. This is usually associated with a lower incidence of adverse events related to the upper gastro intestinal tract.

Iron-deficiency anaemia (IDA) represents a major burden to public health worldwide. The therapeutic aim for patients with IDA is to return iron stores and haemoglobin (Hb) levels to within the normal range using supplemental iron therapy and erythropoiesis-stimulating agents. Oral and previous intravenous (i.v.) iron formulations have a number of disadvantages, including immunogenic reactions, oxidative stress, low dosages, long administration times and the requirement for a test dose. Ferric carboxymaltose (FCM, Ferinject) is a novel, next-generation i.v. iron formulation with the potential to overcome these limitations. In this single-centre, randomized, double-blind, placebo-controlled study, the pharmacokinetics (PK), pharmacodynamics (PD), safety and tolerability of single, escalating doses of FCM were investigated. Four ascending doses were investigated in a total of 24 patients with mild IDA (defined as serum ferritin < 20 microg/l and transferrin saturation [TfS] < 16%): 100 mg iron as FCM given as an i.v. bolus injection, and 500, 800 and 1000 mg iron as FCM given as an i.v. infusion over 15 min. At each dose level six patients received FCM and two received placebo. The decision to escalate to the next dose was based on evaluation of safety and tolerability data from the previous dose. The maximum duration of the study was 5 weeks from screening to final assessment. Assessments were made of PK iron-status parameters up to 168 h post-dose. Safety assessments included incidence of adverse events (AEs), clinical laboratory parameters and vital signs. PK and PD parameters were analysed using descriptive statistics. All analyses were performed on the safety population, which included all patients who received > or = 1 dose of study medication. Seventy-seven patients were screened and, of these, 32 male and female patients with pre-study Hb between 9.2 and 11.9 g/dl and serum ferritin < 20 microg/l were included in the study. Two patients had TfS > 16% (19.2% and 17.2%); both patients were considered by the investigator to be eligible for inclusion. Compared with placebo, a rapid, dose-dependent increase in total serum iron was observed across all dose groups. Mean (standard deviation) maximum total serum iron levels ranged between 36.9 (4.4) and 317.9 (42.3) microg/ml in the 100 and 1000 mg groups. Concentration-time curves of total serum iron continuously declined for up to 24 and 72 h post-dose in the 100 and 500-1000 mg groups, respectively. Non-compartmental analysis of PK parameters was truncated at 24 h (100 mg) and 72 h (500-1000 mg doses). A dose-dependent, but not dose-linear, increase in serum ferritin was seen in all treatment groups compared with placebo, with peak levels of a 23-210-fold increase above baseline occurring 48-120 h postdose. Iron-binding capacity was transiently almost fully utilized after doses of 500, 800 and 1000 mg (TfS > 95%). No meaningful changes in serum transferrin or serum transferrin receptor concentrations were observed during this study. The elimination pattern for FCM...