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HEAVY METAL POISONING AND THEIR ANTIDOTES
- March 8, 2018
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HEAVY METAL POISONING AND THEIR ANTIDOTES
Arsenic poisoning
Acute poisoning symptoms:
- Burning sensation
- Thirst
- Difficulty in swallowing
- Inflammation of gums and mouth
- Abdominal pain
- Vomiting and diarrhoea
Treatment:
- Removal of patient from source of poison
- Removal of unabsorbed poison ( emesis, gastric lavage, mgso4)
- Antidote: a. Dimercaprol injection b. Egg and albumin
- Symptomatic treatment: replacement of fluids by i.v. drips
- Peripheral vasoconstrictor should be injected
- Morphine is used for severe pain
Chronic poisoning symptoms :
- Skin rashes
- Loss of hair and finger nails
- Weakness
- Loss of weight
Treatment:
- Removal of patient from further exposure to poison
- Dimercaprol injection helps to improve peripheral neuritis
- General nutrition must improve
Mercury poisoning
Acute poisoning: symptoms
- Metallic taste
- Choking of throat
- Burning sensation in abdomen associated with diarrhoea
- Thrombocytopenia and bone marrow depression
- Whiteness of mucus membrane of mouth with change in voice
- Appearance of blood in the vomiting and urine may occur
Treatment:
- White albumin of egg +glucose+ nahco3 is introduced into stomach to convert the mercury into insoluble mercury albuminate
- Dimercaprol injection should be given to form non toxic complex with unabsorbed mercury
- Antidote- penicillamine is used
- Symptomatic treatment – use of morphine, demulcents, i.v. Glucose, cardiac stimulants.
Chronic poisoning: symptoms
- Nausea, vomiting
- Loss of appetite
- Abdominal pain
- Swollen and inflamed gums
- Skin eruptions and paralysis of speech muscles
Treatment:
- Avoid further exposure to poison
- Regular antiseptic e.g. Borax powder is used
- A course of dimercaprol/ penicillamine should be given.
Lead poisoning
Acute poisoning: symptoms
- loss of appetite and sleep
- 2. Metallic taste, thrist
- 3. Nausea , vomiting and abdominal pain
- 4. If large amount of lead has been absorbed a shock like syndrome
- 5. Pain, paresthesias and muscle weakness
- 6. Acute hemolysis sometimes leading to hemoglobinuria, oliguria and kidney damage
- 7. feeling of pain in the joints and muscles
Chronic poisoning: symptoms
- On git: metallic taste, anorexia, chronic contipation, abdominal pain
- Neuromusculareffect: muscular weakness, increased fatigability leading to paralysis.
- Cns: lead encephlopathy, ataxia, vertigo, headache, insomnia, irritability (common in children), delirium, lethargy, convulsions.
- Hematologic: hypochromic microcyte anemia
- Renal damage
- blue lining on the gums
- in female it cause menstrual disturbance and abortion
Treatment of lead poisoning:
- in acute phase supportive measures are given.
- Fluid and electrolyte balance must be maintained.
- It must be ensured that there is no further exposure
- Convulsions if present are treated with diazepam
- Concentration of lead in blood is estimated prior to chelation therapy
- If blood lead concentration is more than 50-60 micro gram /dl then chelators are administrated.
- The chelators are commonly used:edetate calcium disodium, dimercaprol and d-penicillamine
- for lead encephalopathy edetate calcium disodium (5 mg/kg/day) and dimercaprol (4 mg/kg/day) used.
- calcium gluconate is given if abdominal pain persists
- 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-
- Strongly bind to Cu
- It is obtained as a degradation product of penicillin
- It has very strong copper chelating property
- It also bind with hg, pb and zn
- It is known to occur in two isomers
- 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
