Oxalic Acid (Acid of sugar, Salt of Sorrel)

It occurs as colowebsiteess, transparent prismatic crystals and resembles in appearance the crystals of magnesium sulphate and zinc sulphate. On long standing the crystals obtain a dirty grey colour.
Route :
Ingestion, Contact
Fatal Dose :
15 to 20 g.
Fatal Period :
1 to 2 hours
Mechanism of action :
1} Local: Corrosive action {though corrosion is not marked}. Prolonged contact may produce cyanosis and even gangrene.
2} Systemic:
a. Shock
b. Hypocalcaemia
c. Nephrotoxicity

Clinical Picture :
A} Fulminating poisoning: A large concentrated dose produces immediate symptoms and death within minutes.
1} Burning, sour, bitter taste in the mouth with a sense of constriction around the throat and burning pain from the mouth to the stomach.
2} Pain is very severe, begins in the epigastrium` but soon radiates all over the abdomen` there may be tenderness.
3} Nausea and eructations are immediately followed by vomiting which may be persistent.
4} Vomitus usually contains blood and mucus and has a ‘coffee-ground’ appearance.
5} Thirst may be present
6} Death usually occurs before bowels are affected, but if life is prolonged, diarrhoea will occur.

B} Acute poisoning: It occurs by a large dose when the patient survives for a few hours and is characterised by symptoms of hypercalcaemia and less by digestive upset.
1} Muscle irritability and tenderness, tetany or usually convulsions.
2} There may be numbness and tingling of the fingertips and legs.
3} Usually signs of cardiovascular collapse occur.
4} In some patients, stupor and coma occur.

C} Delayed Poisoning: It is characterised by symptoms of uraemia.
1} The urine may be scanty or suppressed {oliguria} and may contain traces of blood {haematuria}, albumin {albuminuria} and calcium oxalate crystals. This is known as oxaluria.
2} There may be metabolic acidosis and venricular fibrillation.

Treatment :
1} The stomach is washed out carefully using calcium lactate or gluconate, two teaspoonfuls in each lavage.
2} The antidote is any preparation of calcium which converts the poison into insoluble calcium oxalate e.g. lime water, calcium lactate, calcium gluconate, calcium chloride, a suspension of chalk in water or milk. One and a half g. of chalk will neutralise about 1 g. of acid.
3} Calcium gluconate 10 percent, 10 ml i.v. at frequent intervals.
4} Dialysis or exchange transfusion for renal failure.
5} Parathyroid extract 100 units i.m. in severe cases.
6} Demulcent drinks
7} The bowels may be evacuated by an enema or castor oil.

Oxalic Acid (Acid of sugar, Salt of Sorrel)

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