INTRODUCTION
Desferrioxamine (Desferal) is the drug that chronically-transfused patients use to remove excess iron (Fe) from their bodies. Since iron is usually not ingested in large amounts, the body holds onto what it receives and has no way of ridding itself of any excess. Iron overload is therefore the leading cause of death among thalassemia patients in industrialized nations. Desferrioxamine was isolated from Streptomyces pilosus in the 1960s, and has since been put to widespread use for the chelation of iron. It is used subcutaneously (sub-Q) and intravenously to chelate iron in all children who have hemosiderosis secondary to chronic transfusions. An oral iron chelator (L-1) exists, but is less effective and has troublesome side effects (agranulocytosis and arthritis) and is not currently available. It is no longer recommended in countries where Desferal is available.
Goal
The goal of chelation therapy is to maintain the total body iron load in a near normal range. The gold standard for estimation of total body iron is a liver biopsy. Clinically, serum ferritin can be used only as a rough estimate of total body iron. Tissue iron (Fe) measured from a liver biopsy specimen is the reference method for body Fe quantitation. Serum ferritin is an acute phase reactant and may increase with any inflammation. Normal ferritin levels are less than 500 mg/ml, higher levels are determined by serial dilution.
Side Effects
Desferrioxamine is not without side effects. The most common is tinnitus and a transient hearing loss that can be reversible. It is not dose dependent. Decreased night vision is less common but does occur. Pulmonary hypersensitivity is rare. Allergic reactions including anaphylaxis are not uncommon. An expected acute reaction with a sub-Q injection is a localized erythematous rash. Hydrocortisone can be mixed with Desferal to decrease this reaction. A common occurrence is irritation at the site of administration. This can be decreased by diluting the Desferal. Over-chelation will cause growth disturbance and mineral deficiency.
Compliance
The most common problem encountered with the administration of desferrioxamine is compliance. This chelator does remove iron, but only if used. Adolescent patients and some parents frequently miss doses or do not give the drug at all. A rising or unchanging ferritin is frequently a sign of noncompliance, not inadequate dosage.
