Lead

(USAN, rINN)

💊 Chemical information

Blei; Plomb; Plomo; Plumbum.
Pb = 207.2.
CAS — 7439-92-1.

Description.

Lead is a grey, malleable and ductile metal.

💊 Adverse Effects

Lead poisoning (plumbism) may be due to inorganic or organic lead and may be acute or, more often, chronic. It has followed exposure to a wide range of compounds and objects from which lead may be absorbed following ingestion or inhalation. Some of those that have been incriminated include paint, pottery glazes, crystal glassware, domestic water supplies, petrol, poteen, cosmetics (particularly home-made or traditional forms such as kohl or surma), herbal or folk remedies, including traditional Chinese medicines, newsprint, and retained bullets. Children are often the victims of accidental poisoning and may be vulnerable to chronic exposure to lead from environmental pollution. Acute effects of lead poisoning include metallic taste, abdominal pain, diarrhoea, vomiting, hypotension, muscle weakness and cramps, fatigue, abnormal liver function tests, and acute interstitial nephritis. Encephalopathy may occur and is more common in children. Symptoms of chronic poisoning with inorganic lead include anorexia, abdominal pain, constipation, anaemia, headache, fatigue, irritability, peripheral neuropathy, and encephalopathy with convulsions and coma. There may be kidney damage and impairment of mental function. Children with elevated lead concentrations may be asymptomatic apart from intellectual deficits and behavioural disorders. Organic lead poisoning produces mainly CNS symptoms; there can be gastrointestinal and cardiovascular effects, and renal and hepatic damage.
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💊 Treatment of Adverse Effects

The main aim in the management of both acute and chronic lead poisoning is to control the symptoms and reduce the concentration of lead in the body. Patients should be removed from the source of exposure and iron and calcium deficiencies corrected. Treatment of acute symptomatic poisoning entails supportive therapy including intravenous fluids. Renal and hepatic function should also be monitored and convulsions controlled with a benzodiazepine. Encephalopathy, which is rare in adults but more common in children, requires urgent treatment. Acute ingestion of lead or its salts should be treated if appropriate by activated charcoal or gastric lavage if within 1 hour of ingestion of a potentially life-threatening dose. Emesis is not recommended for organic lead compounds. In severe cases of inorganic or organic lead poisoning, chelation therapy may be required to facilitate removal of lead from the body. A lead mobilisation test that measures urinary excretion of lead after a standard dose of sodium calcium edetate has been widely used as a means of assessing the need for therapy. However, because of difficulties in administering the test and uncertainties in interpreting results, some authorities have recommended blood-lead concentrations as a guide to treatment. The lead mobilisation test in addition to measurement of blood-lead concentrations may be useful in determining the necessity for chelation therapy in children (see below). Blood-lead concentrations should be obtained before starting chelation therapy, and then again after the first course since mobilisation of stored lead from body tissues may cause blood-lead concentrations to rebound after an initial drop; a second course of chelator may then be required. Raised blood-lead concentrations despite chelation therapy could also indicate continued exposure. Chelation therapy is not indicated for children with a blood-lead concentration less than 25 micrograms per 100 mL. Children with a blood-lead concentration of 25 to 44 micrograms per 100 mL and a positive sodium calcium edetate mobilisation test should be considered for treatment with oral succimer; alternative chelators are oral penicillamine, and in the USA but not UK, dimercaprol. For blood-lead concentrations of 45 to 70 micrograms per 100 mL, oral succimer should be given, followed by a second course if necessary. If encephalopathy is present or blood-lead concentrations are over 70 micrograms per 100 mL, parenteral sodium calcium edetate should be given with monitoring of renal and hepatic function, followed by a second course of chelator if necessary. In the USA, dimercaprol is given with sodium calcium edetate and 4 hours before the first dose; While dimercaprol has been used in the UK, it is not currently recommended as first-line treatment for lead poisoning. It is considered that asymptomatic adults do not generally require chelation therapy. Symptomatic adults without encephalopathy may be treated with succimer; alternatives are unithiol, penicillamine or sodium calcium edetate. Adults with severe toxicity or encephalopathy should be treated with parenteral sodium calcium edetate followed by a second course if necessary. As with children (see above), dimercaprol is given with sodium calcium edetate in the USA but not in the UK. Lead foreign bodies may need to be removed surgically or endoscopically to prevent further exposure. Long-term management of chronic lead poisoning involves eliminating environmental lead exposure. Chelation therapy is not a substitute for environmental controls in those suffering occupational exposure. The authors suggested that, since succimer is as effective a chelator as any other currently available, chelation therapy in general may not be beneficial in children with these blood-lead levels.
1. Rogan WJ, et al. The effect of chelation therapy with succimer on neuropsychological development in children exposed to lead. N Engl J Med 2001; 344: 1421–6.

💊 Lead in the Environment

Many countries have taken action to reduce lead exposure from environmental sources, including food, paint, and petrol, by limiting or banning altogether the use of lead compounds in such sources. Such measures have been of value in reducing childhood exposure to lead. Screening of all children to detect those at risk of chronic lead poisoning and developmental deficit has been advocated, but selective screening in areas perceived as high risk may be more appropriate in countries where the overall level of lead contamination is low.

💊 Pharmacokinetics

Lead is absorbed from the gastrointestinal tract. It is also absorbed by the lungs from dust particles or fumes. Inorganic lead is not absorbed through intact skin, but organic lead compounds may be absorbed rapidly. Lead is distributed in the soft tissues, with higher concentrations in the liver and kidneys. In the blood it is associated with the erythrocytes. Over a period of time lead accumulates in the body and is deposited in calcified bone, hair, and teeth. Lead crosses the placental barrier. It is excreted in the faeces, urine, and sweat, and also appears in breast milk.

💊 Uses and Administration

Lead compounds were formerly used as astringents, but the medicinal use of preparations containing lead is no longer recommended. The lead salts or compounds that have been used have included lead acetate and lead subacetate (for lead lotion, still known sometimes as lotio plumbi), lead carbonate, lead monoxide, and lead oleate (for lead plaster-mass).

💊 Preparations

Proprietary Preparations

Multi-ingredient: Austria: Vulpuran; Mex.: Emplasto Monopolis.
Published May 08, 2019.