HEAVY METAL POISONING AND THEIR ANTIDOTES

HEAVY METAL POISONING AND THEIR ANTIDOTES
- March 8, 2018
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HEAVY METAL POISONING AND THEIR ANTIDOTES

Arsenic poisoning

Acute poisoning symptoms:
1. Burning sensation
2. Thirst
3. Difficulty in swallowing
4. Inflammation of gums and mouth
5. Abdominal pain
6. Vomiting and diarrhoea
Treatment:
1. Removal of patient from source of poison
2. Removal of unabsorbed poison ( emesis, gastric lavage, mgso4)
3. Antidote: a. Dimercaprol injection b. Egg and albumin
4. Symptomatic treatment: replacement of fluids by i.v. drips
5. Peripheral vasoconstrictor should be injected
6. Morphine is used for severe pain
Chronic poisoning symptoms :
1. Skin rashes
2. Loss of hair and finger nails
3. Weakness
4. Loss of weight
Treatment:
1. Removal of patient from further exposure to poison
2. Dimercaprol injection helps to improve peripheral neuritis
3. General nutrition must improve
Mercury poisoning

Acute poisoning: symptoms
1. Metallic taste
2. Choking of throat
3. Burning sensation in abdomen associated with diarrhoea
4. Thrombocytopenia and bone marrow depression
5. Whiteness of mucus membrane of mouth with change in voice
6. Appearance of blood in the vomiting and urine may occur
Treatment:
1. White albumin of egg +glucose+ nahco3 is introduced into stomach to convert the mercury into insoluble mercury albuminate
2. Dimercaprol injection should be given to form non toxic complex with unabsorbed mercury
3. Antidote- penicillamine is used
4. Symptomatic treatment – use of morphine, demulcents, i.v. Glucose, cardiac stimulants.
Chronic poisoning: symptoms
1. Nausea, vomiting
2. Loss of appetite
3. Abdominal pain
4. Swollen and inflamed gums
5. Skin eruptions and paralysis of speech muscles
Treatment:
1. Avoid further exposure to poison
2. Regular antiseptic e.g. Borax powder is used
3. A course of dimercaprol/ penicillamine should be given.
Lead poisoning

Acute poisoning: symptoms
1. loss of appetite and sleep
2. 2. Metallic taste, thrist
3. 3. Nausea , vomiting and abdominal pain
4. 4. If large amount of lead has been absorbed a shock like syndrome
5. 5. Pain, paresthesias and muscle weakness
6. 6. Acute hemolysis sometimes leading to hemoglobinuria, oliguria and kidney damage
7. 7. feeling of pain in the joints and muscles
Chronic poisoning: symptoms
1. On git: metallic taste, anorexia, chronic contipation, abdominal pain
2. Neuromusculareffect: muscular weakness, increased fatigability leading to paralysis.
3. Cns: lead encephlopathy, ataxia, vertigo, headache, insomnia, irritability (common in children), delirium, lethargy, convulsions.
4. Hematologic: hypochromic microcyte anemia
5. Renal damage
6. blue lining on the gums
7. in female it cause menstrual disturbance and abortion
Treatment of lead poisoning:
1. in acute phase supportive measures are given.
2. Fluid and electrolyte balance must be maintained.
3. It must be ensured that there is no further exposure
4. Convulsions if present are treated with diazepam
5. Concentration of lead in blood is estimated prior to chelation therapy
6. If blood lead concentration is more than 50-60 micro gram /dl then chelators are administrated.
7. The chelators are commonly used:edetate calcium disodium, dimercaprol and d-penicillamine
8. for lead encephalopathy edetate calcium disodium (5 mg/kg/day) and dimercaprol (4 mg/kg/day) used.
9. calcium gluconate is given if abdominal pain persists
10. magnesium sulphate given for chronic constipation
Heavy metal antagonist

1. Dimercaprol:

Also known as BAL ( BRITISH ANTI LEWISITE)

M.O.A.-
- Dimercaprol forms chelation comlex with sulfhydryl groups and metals (PB, arsenic, antimony, copper, mercury, gold , bismuth).
- It works best in 2:1 complex
Dose:
- Usually 100 mg every 4 hours for 48 hours, then 100 mg eight hourly for 8-10 days.
- In wilson disease, it is given in a dose of 300 mg daily for 10 days.
Uses:
- In poisoning of pb, arsenic, antimony, copper, mercury, gold , bismuth.
- It is also used as an adjuvant to ca- edta in lead poisoning
- Adjuvant to penicillamine in copper poisoning
- Contraindications: in fe and cd poisoning fe- dimercaprol complex and cd- dimecaprol complex itself toxic.
Adverse effects:
- Increased bp, tachycardia
- Vomiting, tingling
- Burning sensation, conjuctivitis, lacrimation, rhinorrhea
- Sweating of hand and forhead, muscle pain.
2. Disodium edetate
- Chelator of calcium
- Used for emergency control of hypercalcaemia
- Causes tetany on rapid i.v. Injection
3. Calcium disodium edetate

It binds to lead , zinc, cadmium, manganese, copper and also some radioactive metals.

M.o.a.-
- It exchanges the calcium ( of calcium disodium edetate) with excess of heavy metals.
- It is excreted through urine
- It is given i.v.
Uses:
- In lead poisoning
- In zinc, cd, cu, mn poisoning
- Not used in hg poisoning
Adverse effect
- It might cause kidney damage and necrosis of pct of the kidney
- Cause acute febrile reaction which is characterised by chills, urticaria, anaphylaxis, myalgia, dermatitis.
4. Penicillamine-
1. Strongly bind to Cu
2. It is obtained as a degradation product of penicillin
3. It has very strong copper chelating property
4. It also bind with hg, pb and zn
5. It is known to occur in two isomers
6. D (+) isomer- can be used therapeutically for chelating property
Uses:
- In Wilson’s disease
- In copper poisoning
- Hg, pb, and zn poisoning
- In cysteine stones
- In scleroderma (excessive fibrosis of the muscles and skin, wooden body
- Rheumatoid arthritis
Adverse effect:
- Cutaneous vasoconstriction
- Renal and haematological problems
- Aplastic anemia, lupus erythematosus, leucopenia.
5. Deferoxamine:

It is isolated as iron chelate from streptomyces pilosus

Dose: the 500 mg injection is continued at four or 12 hour but the total amount of drug should not exceed 6 g in24 hours.

Adverse effect: pruritis, rashes, anaphylaxis, neurotoxicity, diarrhoea, fever, leg cramps, hepatic failure.

Uses: in iron poisoning

6. Acetyl d- penicillamine
- A weak chelator but less toxic drug. It has been shown to be highly effective in mercury poisoning.
- It is administered 1 g daily in three or four divided dose for 10 days
7. Succimer
- Succimer is chemically similar to dimercaprol.
- It is effective in lead poisoning.
- Succimer is less toxic than dimercaprol
- Adverse effect
- Nauses, vomiting, diarrhoea, loss of appetite
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