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Ferriprox

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Ferriprox

CLINICAL PHARMACOLOGY

Mechanism of Action

Deferiprone is a chelating agent with an affinity for ferric ion (iron III). Deferiprone binds with ferric ions to form neutral 3:1 (deferiprone:iron) complexes that are stable over a wide range of pH values. Deferiprone has a lower binding affinity for other metals such as copper, aluminum and zinc than for iron.

Pharmacodynamics

No clinical studies were performed to assess the relationship between the dose of Ferriprox and the amount of iron eliminated from the body.

Pharmacokinetics

Deferiprone is rapidly absorbed from the upper part of the gastrointestinal tract, appearing in the blood within 5 to 10 minutes of oral administration. Peak serum concentrations occur approximately 1 hour after a single dose in fasted healthy subjects and patients, and up to 2 hours after a single dose in the fed state. Administration with food decreased the Cmax of deferiprone by 38% and the AUC by 10%. While a food effect cannot be ruled out, the magnitude of the exposure change does not warrant dose adjustment.

In healthy subjects, the mean maximum concentration (Cmax) of deferiprone in serum was 20 mcg/mL, and the mean total area under the concentration-time curve (AUC) was 53 mcg·h/mL following oral administration of a 1,500 mg dose of Ferriprox tablets in the fasting state. Dose proportionality over the labeled dosage range of 25 to 33 mg/kg three times per day (75 to 99 mg/kg per day) has not been studied. The elimination half life (t½) of deferiprone was 1.9 hours. The accumulation of deferiprone and its glucuronide metabolite at the highest approved dosage level of 33 mg/kg three times per day has not been studied. The volume of distribution of deferiprone is 1.6 L/kg in thalassemia patients, and approximately 1 L/kg in healthy subjects. The plasma protein binding of deferiprone in humans is less than 10%.

In humans, the majority of the deferiprone is metabolized, primarily by UGT1A6. The contribution of extrahepatic (e.g., renal) UGT1A6 is unknown. The major metabolite of deferiprone is the 3-O-glucuronide, which lacks iron binding capability. Peak serum concentration of the glucuronide occurs 2 to 4 hours after administration of deferiprone in fasting subjects.

More than 90% of deferiprone is eliminated from plasma within 5 to 6 hours of ingestion. Following oral administration, 75% to 90% is recovered in the urine in the first 24 hours, primarily as metabolite.

Special populations

The pharmacokinetics of deferiprone has not been studied in geriatric or pediatric populations, and the influence of race, gender, or obesity has not been established.

QT/QTc Prolongation

No clinical studies of the effects of Ferriprox on the cardiac QT interval have been performed in human subjects [see WARNINGS AND PRECAUTIONS].

Clinical Studies

In a prospective, planned, pooled analysis of patients from several studies, the efficacy of Ferriprox was assessed in transfusion-dependent iron overload patients in whom previous iron chelation therapy had failed or was considered inadequate due to poor tolerance. The main criterion for chelation failure was serum ferritin > 2,500 mcg/L before treatment with Ferriprox. Ferriprox therapy (35-99 mg/kg/day) was considered successful in individual patients who experienced a ≥ 20% decline in serum ferritin within one year of starting therapy.

Data from a total of 236 patients were analyzed. Of the 224 patients with thalassemia who received deferiprone monotherapy and were eligible for serum ferritin analysis, 105 (47%) were male and 119 (53%) were female. The mean age of these patients was 18.2 years.

For the patients in the analysis, the endpoint of at least a 20% reduction in serum ferritin was met in 50% (of 236 subjects), with a 95% confidence interval of 43% to 57%.

A small number of patients with thalassemia and iron overload were assessed by measuring the change in the number of milliseconds (ms) in the cardiac MRI T2* value before and after treatment with deferiprone for one year. There was an increase in cardiac MRI T2* from a mean at baseline of 11.8 ± 4.9 ms to a mean of 15.1 ± 7.0 ms after approximately one year of treatment. The clinical significance of this observation is not known.

Last reviewed on RxList: 5/4/2012
This monograph has been modified to include the generic and brand name in many instances.

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