0071643192.pdf

TOXICOLOGY

Most lead toxicity is due to chronic, low-level exposure. Acute toxicity from

single exposures is rare.

MECHANISM/TOXICITY

■ Inhibits a wide variety of cellular enzymes

■ Directly damages peripheral nerves

SYMPTOMS/EXAM

■ Chronic lead toxicityproduces subtle, insidious, and nonspecific symp-

toms, including headache, peripheral motor neuropathy, HTN, anemia,

gout, and cognitive impairment.

■ Acute lead toxicity

■ Nausea/vomiting, abdominal pain

■ Ataxia

■ Encephalopathyand seizures

DIAGNOSIS

■ Diagnosis of lead toxicity requires a high index of suspicion.

■ Lead can be directly measured in whole blood.

■ Ingested lead-containing material is usually visible on X-ray.

TREATMENT

■ Remove the patient from the source of exposure.

■ Activated charcoal does notbind metals.

■ Whole-bowel irrigation is indicated in cases of lead ingestion with visible

material on X-ray.

■ Antidote = BAL (British anti-lewisite, dimercaprol) and Ca-EDTA (calcium

disodium ethylenediaminetetraacetic acid).

■ Use for the severely poisoned patient or level > 70 μG/dL

■ Both are parenteral chelating agents.

■ DMSA(2,3-dimercaptosuccinic acid, succimer) oral chelation therapy if

no acute symptoms and level < 70 μG/dL

Arsenic

Arsenic-containing compounds are used in a wide variety of applications:

■ Pesticides, wood preservatives, metal alloys, chemical synthesis, and glass

manufacturing

■ Arsenic trioxide is used as a chemotherapeutic agent for acute promyelo-

cytic leukemia.

MECHANISM/TOXICITY

■ Inhibits multiple key enzymes in cellular oxidative metabolism

■ Arsine gas causes acute hemolysis by an unknown mechanism.

SYMPTOMS/EXAM

■ Chronic poisoning

■ Peripheral neuropathy, headache, ataxia, confusion

■ Diarrhea, constipation

■ Hyperpigmentation, Mees’ lines (transverse white lines on nails),

alopecia, various rashes

■ Malaise, anorexia, fatigue

Most lead toxicity is chronic

and causes subtle neurologic

changes and anemia.

Indications for immediate IV

chelation therapy (BAL and

Ca-EDTA) in lead toxicity =

level≥70 ug/dL or the

presence of symptoms.

Mee’s lines appear weeks to

months after arsenic

exposure.