Chelating Agents & Treatment of Poisoning 397Chronic iron overload: 0.5 to 1 g IM
daily. In addition 2 g IV infusion given
separately with each unit of blood
transfused.
CALCIUM DISODIUM EDETATE
It is the calcium chelate of disodium
edetate having high affinity for metals like
lead, zinc, cadmium, copper, manganese
and some radioactive metals. Given by IV
route, it is distributed extracellularly and
excreted unchanged in urine by glomerular
filtration carrying the toxic metal along.
It is primarily indicated in lead
poisoning. It is also useful in iron, zinc,
copper, manganese and radioactive metal
but not mercury poisoning.
Adverse effects include nephrotoxic-
ity, anaphylactoid reaction, chills, bodyache
and malaise.
DEFERIPRONE
It is an orally active iron chelator. It is
useful in acute iron poisoning, iron
overload in cirrhosis, transfusion siderosis
in thalassemia patients. Adverse effects
are anorexia, vomiting, altered taste, joint
pain and neutropenia.
DISULFIRAM (ESPERAL)
It is relatively nontoxic, used as an
adjunct in the treatment of chronic
alcoholism.
It exerts its action by inhibiting alde-
hyde dehydrogenase enzyme. Disulfiram
thus increases the concentration of acetal-
dehyde in body when ethanol is ingested
by an individual pretreated with disul-
firam. The symptoms and signs produced
are flushing, pulsating headache, nausea,
vomiting, thirst, marked uneasiness, ver-
tigo, weakness, confusion, hypotension and
circulatory collapse.
After oral administration it is rapidly
absorbed from gastrointestinal tract.
Adverse effects include urticaria,
allergic dermatitis, restlessness, tremor,
dizziness, metallic taste, fatigue, decrease
in sexual potency and lassitude.
It is indicated in chronic alcoholism
in a dose range of 1 g on 1st day, 0.75 g on
2nd day, 0.5 on 3rd day, decreasing to
0.125-0.25 g/day. Sensitization to alcohol
develops after two to three hours of first
dose and lasts for 7 to 14 days after
stopping it.
LEUCOVORIN
It is used as leucovorin calcium
(calcium folinate). It is 5-formyl derivative
of tetrahydrofolic acid and it acts as an
antidote to folic acid antagonists like
methotrexate or pyrimethamine which
inhibit the enzyme dihydrofolate
reductase.
Well absorbed by the oral or IM route
and is rapidly converted to biologically
active folate. Distribution occurs to all body
tissues and it is concentrated in the CSF. It
is excreted in the urine.
Adverse effects include pyrexia which
occurs rarely.
It is indicated in overdose of
methotrexate, folic acid antagonists and as
adjuvant treatment of colorectal carcinoma.
Dose: NYRIN; 120 mg per day by IM
or IV infusion.