Desferal
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This page was last modified on:
01/29/2001 10:15:00 http://sickle.bwh.harvard.edu/dfsc.html
Subcutaneous Desferal® for
Transfusional Iron Overload
Desferal® is used to treat iron overload
in patients who require chronic transfusion therapy. The drug can be given
intranveously or subcutaneously. Each route has strengths and drawbacks.
The subcutaneous route is the simpler of the two, but produces painful
skin irritation in many patients. The intravenous route avoids the skin
irritation, but has the risk of infection or thrombosis of the indwelling
central catheter. In general, the best approach is to begin with
subcutaneous administration. The intravenous route can be tried if this
fails.
Procedure
- The Desferal® can be given as an infusion
of 2 grams or 2.5 grams. The higher dose tends to produce intolerable
local skin irritation.
- The Desferal® is mixed to its final
volume in sterile water. When a syringe-based infusion pump is used,
the maximum volume is about 5 cc. With infusion pumps that use plastic
reservoirs, a larger volume can be employed. The more dilute the
Desferal® solution, the less skin
irritation occurs.
- . Infusion tubing with a 25 or 27 g needle is used. The Desferal®
solution is filled to the end of the tubing so that no air is present.
The needle is inserted beneath the skin on the abdomen and taped
securely into place with paper tape.
- The infusion pump should be set to deliver the Desferal®
over about 12 to 16 hours. Iron mobilization is most efficient with
longer durations of infusion. Patient compliance can be a problem
under these circumstances, however. A compromise between physician and
patient often is necessary.
- A physician should be present for at least 20 minutes, during the
initial infusion. Patients rarely have anaphylactic reactions to the
drug. Appropriate corrective measures, including the cessation of the
infusion, should be instituted should this occur. Another problem that
requires immediate cessation of infusion is the development of
urticaria at the site of infusion. Although local urticaria is not a
necessary harbinger of more serious problems, such as laryngeal edema,
the risk should not be taken.
- . Almost all adults develop some irritation at the site of infusion.
This is a chemical reaction to the Desferal®
and not an allergic reaction. The main problems are redness, slight
swelling and tenderness. The site of infusion should be rotated from
one side of the abdomen to the other on a daily basis. Also, infusion
into the upper thigh can be done (with infusion tubing of appropriate
length) to give some relief to the abdomen. The irritation can be
reduced by the inclusion of 10 to 20 milligrams of hydrocortisone in
the Desferal infusion mixture. Also, local application of
hydrocortisone ointment to the site after the infusion is complete
sometimes dampens the irritation
- When testing the efficacy of Desferal® therapy, 24 h urine
collection should be performed on the 3d day for iron determination.
This value should be compared with a preinfusion 24 h urine iron
determination. In order to gain benefit from the use of Desferal®,
a 24 h excretion of 30 mg or more of iron is generally required,
particularly for patients with significant ongoing transfusion
requirements (each unit of blood contains about 220 mg of iron).
- Patients should be warned that their urine will become orange. This
is the iron-Desferal® complex (ferrioxamine)
which is being excreted.
- Daily use the pump maximizes iron excretion. A minimum of about 5
days per week is needed to get adequate excretion in general, however.
- Ascorbic acid can be used to increase iron excretion by patients
using Desferal®. Ascorbic acid increases
the chances of serious cardiac complications of iron toxicity,
including congestive heart failure, conduction defects, and arrythmia.
Generally, these problems are seen in patients who use 1 to 2 g of
ascorbate per day with their Desferal®. The
following precautions should be taken when ascorbic acid is used by a
patient on Desferal® chelation therapy:
- The maximum dose of ascorbic acid should be 250 to 500 g/day.
- Ascorbic acid should not be started until the patient has been
on Desferal® for a couple of months to ensure that the medication
is being used properly.
- Ascorbic acid should be used only on those days when Desferal®
infusion is performed.
   
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