Mercury (Quick silver)

It is a liquid metal, bright silvery in appearance and is volatile at room temperature. Metallic mercury is not poisonous if swallowed, for it is not absorbed. If the mercury is breathed of swallowed as vapour, or if applied to the skin or mucous membrane in finely divided state it is absorbed.

Poisonous compounds:
1} Mercuric Chloride {HgCl2, corrosive sublimate}, occurs as colowebsiteess masses of prismatic crystals or as white crystalline powder. It has no smell but a styptic nauseous metallic taste.
2} Mercuric oxide {brick red crystalline powder}
3} Mercuric iodide {scarlet red powder}
4} Mercuric cyanide {white prismatic crystals}
5} Mercuric sulphide {cinnabar, sindoor} Artificial preparation occurs as red crystalline powder and is known as vermillion.
6} Mercurous chloride {calomel}
7} Mercuric nitrite.
8} Mercuric sulphate {white crystalline powder}
9} Sulphate of mercury {lemon-yellow powder}
10} Ammoiomercuric chloride
11} Organic compounds of mercury

Route :
Ingestion
Fatal Dose :
1-2 g. of mercuric chloride(corrosive sublimate)
Fatal Period :
3-5 days
Mechanism of action :
The mercuric ion binds with sulphydryl groups of enzymes and cellular proteins, nucleic acids and mitotic apparatus interfering with enzyme and cellular transport functions. It is rapidly converted to mercuric ions in the blood which can lead to renal tubular damage {nephrotoxic poison}. In the CNS, mercury acts mainly upon cerebellum, temporal lobe, basal ganglia and corpus callosum.
Acute exposure to elemental mercury vapour may produce corrosive bronchitis with fever, chills and dyspnoea. It may progress to pulmonary oedema and fibrosis. Sometimes manifestations similar to Kawasaki disease {mucocutaneous lymph node syndrome} are seen especially in children.

Clinical Picture :
A. Acute Poisoning-
1. First phase – Acrid metallic taste and feeling of constriction in the throat, hoarse voice, difficulty in breathing. The mouth tongue and fauces become corroded, swollen and show a greyish white coating. Hot burning pain in the mouth extending down to the stomach and abdomen` followed by nausea, retching and vomiting.
The vomit contains greyish slimy mucoid material with blood and shreds of mucous membrane. This is followed by diarrhoea with blood-stained stools and tenesmus. Circulatory collapse occurs soon. Inhalation of fumes produces nervous symptoms, e.g. ataxia, restriction of visual field, paresis and delirium.
2. Second phase – If the person survives, the second phase begins in 1-3 days, Glossitis and ulcerative gingivitis appear within 24-36 hours. Severe infection, loosening of the teeth and necrosis of the jaw may occur. In 2-3 days the renal tubules show necrosis and transient polyuria, albuminuria, cylindruria, uraemia and acidosis. Recovery may occur within 10-14 days. After many days, membranous colitis develops and produces dysentery, ulceration of the colonic mucosa and haemorrhage.
Intramuscular injection produces abscess with ulceration. I.V. may cause mercurialism with thrombophlebitis, granuloma formation, pulmonary wmbolism and repeated haemoptysis is seen.
Organic material such as phenyl and methoxylmethyl mercury, ethyl and methyl mercury are more toxic. Symptoms are mainly CNS and include ataxia, dysarthria, paraesthesias, neuropathies, mental deterioration and chorea.

B. Chronic Poisoning {Hydrargyrism}
This may result from
a. continuous accidental absorption by workers
b. excessive therapeutic use
c. recovery from a large dose
d. if ointment is used as an external application for a long time.

Chronic exposure to elemental mercury yields a classic triad of gingivitis and salivation, tremors and neuropsychiatric changes. The symptoms are salivation, inflammation of the gums and occasionally a blue line at their junction with the teeth {diagnostic}, sore mouth and throat, loosening of teeth, gastrointestinal disturbances, anaemia, anorexia, loss of weight and chronic inflammation of the kidneys with progressive uraemia. Tremors {sometimes called Danbury tremors} occur first in the hands, then progress to the lips, tongue and finally involve arms and legs. The tremor is moderately course and interspersed by jerky movements. The advanced condition is called as hatter’s shakes or glass-blower’s shakes {diagnostic}, because they are common in persons working in glass-blowing and hat industries. The patient then becomes unable to dress himself, write legibly or walk properly. The most sever form is known as concussion mercurialis, in which no activity is possible. Mercurial Erethism is seen in persons working with mercury in mirror manufacturing firms. This term refers to the psychological effects of mercury toxicity. These include anxiety, depression, shyness, timidity, irritability, loss of confidence, delusions and hallucinations, or suicidal melancholia or manic-depressive psychosis, emotional instability, loss of memory and insomnia. Mercurialentis {diagnostic} is a peculiar eye change due to exposure to vapour of mercury. It is due to brownish deposit of mercury through the cornea on the anterior lens capsule. Slit-lamp examination demonstrates a malt-brown reflex from the anterior lens capsule. It is bilateral and has no effect on visual acuity. Renal damage results in membranous glomerulonephritis with hyaline casts and fatty casts in the urine. Kidney is the primary target.
Acrodynia or pink disease {because it is characterised by a generalized body rash} is thought to be an idiosyncratic hypersensitivity reaction particularly seen in children. The onset is insidious with anorexia, insomnia, sweating, skin rash and photophobia. Hands and feet become puffy, pinkish, painful, paraesthetic with peeling of skin. Teeth may be shed.

Treatment :
A. Acute poisoning
1} Give egg-whites, milk or activated charcoal to precipitate mercury. Gastric lavage with egg-white solution or 2-5 percent solution of sodium bicarbonate is of uncertain benefit.
2} Activated charcoal or 5 percent sodium formaldehyde sulphoxylate solution is used to bind the mercury.
3} BAL is the chelating agent of choice. Dosage regimen is same as for arsenic.
4} Penicillamine is an alternative given orally in 4 divided doses of 100mg, kg, day for 3-7 days, repeated after 10 days if necessary.
5} Ca-EDTA should not be used as it is nephrotoxic with mercury.
6} Urine must be kept alkaline.
7} High colonic lavage with 1:1000 solution of sulphoxylate twice daily.
8} Haemodialysis is indicated if there is significant kidney damage.

B. Chronic poisoning

1} Removal of patient from further exposure.
2} Demulcents
3} Saline purgatives
4} Oral hygiene
5} Chelation therapy: D-Penicillamine 25040 mg, kg, day{maximum 1g.} for children in 2 divided doses and 250 mg 4 times a day for adults is given until urinary mercury levels are less than 5micrograms per litre OR BAL 100 mg i.m. 4th howebsitey for 2 days, followed by 100 mg every 8 hours for 8-10 days, OR DMPS 5 mg, kg i.v. or six infusions of 250 mg, day, followed by 100 mg orally twice a day for 24 days OR DMSA 30 mg, kg, day orally for 5 days, followed by 20 mg, day for 14 days.
6} For organic mercurials chelation is not very effective.

Mercury (Quick silver)

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