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Hematinics:, Daily requirement of iron is, Iron fate after absorption,…
Hematinics:
these are the agents required for the formation of blood and treatment of anemia.
Main hematinics include iron, folic acid and vitamin B 12.
other substances like copper, pyridoxine etc are also required in small quantities for the formation of blood.
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Therapeutics
Iron is used for prophylaxis or treatment of iron deficiency anemia(microcytic hypochromic anemia).
It can be given by oral route or parenteral route.
Parenteral route IV or IM is indicated only when oral iron not tolerated, not absorbed or along with erythropoietin.
Rate of hematopoietic response with parenteral iron is not faster than that with optimal doses of oral iron therapy.
Oral iron preparations
Oral preparations include ferrous sulphate, gluconate, succinate etc.
ferrous sulphate contains 20 % elemental iron.
For the treatment of iron deficiency, the dosage recommended is 200 mg elemental iron daily
that can be obtained by giving 1000 mg of ferrous sulphate in three divided doses
providing around 60 mg elemental iron per dose(maximum tolerated dose).
Iron absorption increases in response to low iron stores or increased iron requirements.
The reticulocyte count should begin to increase in two weeks and peak in four weeks.
This suggests good response to the treatment.
Treatment with oral iron should be continued for 3-6 months.
This will correct the anemia and replenish iron stores.
Folic acid:
It consists of pteridine, paraaminobenzoic acid(PABA) and glutamic acid.
Dietary folic acid is in the form of polyglutamates and these are cleaved off in the intestine before absorption.
Maximum absorption occurs in jejunum.
It is reduced to first dihydrofolic acid(DHFA)
and then to tetrahydrofolic acid(THFA) which is methylated to form methyl tetrahydrofolate.
Latter compound is the main form in which it is transported in blood.
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Iron absorption
Iron is absorbed mostly in the duodenum in the ferrous form fe2+.
Heme contains the iron in ferrous form and
most of the inorganic iron is in ferric form Fe3+.
This must be reduced to ferrous form for absorption.
Thus reducing substances like ascorbic acid and also gastric acid Hcl increases the absorption.
On the other hand, substances like alkalies, phosphates, phytates and tetracyclines decrease the absorption.
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Ferric citrate
Ferric citrate has the capacity to bind phosphate and form non-absorbable complex.
It is indicated to control hyperphosphatemia in patients with chronic kidney disease on dialysis.
It is given orally.
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Z technique
Intramuscular injections are usually given by the Z technique to avoid staining and pigmentation of skin.
Major problem with parenteral route is pain at injection site and pigmentation of skin.
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THFA
THFA participates in many one carbon transfer reactions.
Important among these are conversion of homocysteine to methionine
which releases THFA from its methylated form with vitamin B12 as the intermediary carrier and generation of thymidylate.
Deficiency of folic acid
Deficiency of folic acid results in megaloblastic anemia that is indistinguishable from that due to vitamin B12 deficiency.
Main uses of folic acid are in the treatment of megaloblastic anemia due to folic acid deficiency(dietary, due to malabsorption, phenytoin therapy, chronic alcoholism etc.
Folic acid in pregnancy
It is also indicated in pregnancy to prevent neural tube defects in the fetus.
It should be started as soon as possible as the pregnancy is diagnosed.
Leucovorin
Leucovorin(folinic acid, formyl THFA or citrovorum factor) can be used to prevent the toxicity of methotrexate.
Vitamin B12
Vitamin B12 contains cobalt and cyanocobalamin and hydroxocobalamin are the two forms that are present in the diet.
It is present in animal foods like liver, kidney, meat, cheese and egg yolk etc
and the only vegetable source is legumes(microorganisms in the nodule synthesize it).
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Functions of Vitamin B12
Vitamin B12 serves several functions like conversion of homocysteine to methionine(folic acid is required) which is essential for one carbon transfer reactions,
conversion of methylmalonyl COA to succinyl COA. This reaction is required for myelin formation and methylcobalamin is utilized.
Folic acid is not required for this condition.
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Therapeutics
Vitamin B12 is used for the treatment of megaloblastic anemia(IM or SC) for pernicious anemia due to deficiency of intrinsic factor
and orally for other causes, for correcting neurological abnormalities in diabetics
methylcobalamin is used
and also for treatment of tobacco amblyopia(hydroxocobalamin is used, it combines with cyanide to form cyanocobalamin).
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Iron poisoning:
Acute iron poisoning can occur in children due to accidental intake of large number of the iron tablets.
The antidote of acute iron poisoning is desferrioxamine. It is given by IM injection. DTPA and calcium disodium EDTA may also be used
but dimercaprol(BAL) is contraindicated because its complex with iron is itself toxic.
For chronic iron overload, as occurs in thalassemia patients, oral chelating agent like deferiprone is preferred.
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