JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D IV Year CLINICAL TOXICOLOGY Previous Question Paper (April/May - 2023 - R08)

Lead poisoning, or plumbism, occurs due to the accumulation of lead in the body, primarily affecting the nervous, hematological, and renal systems. Lead is a systemic toxicant that mimics calcium, allowing it to cross the blood-brain barrier and deposit in bones, where it has a long half-life.

Key clinical features include:

• Neurological: Encephalopathy, irritability, cognitive impairment, and peripheral neuropathy (wrist drop).
• Hematological: Microcytic hypochromic anemia caused by the inhibition of delta-aminolevulinic acid dehydratase and ferrochelatase, leading to impaired heme synthesis.
• Gastrointestinal: Lead colic, characterized by severe abdominal pain, constipation, and a characteristic blue-black "lead line" on the gums.

Diagnosis is confirmed by measuring blood lead levels. Management involves removing the source of exposure and, in severe cases, chelation therapy using agents such as Dimercaprol (BAL), Calcium Disodium EDTA, or Succimer (DMSA) to facilitate the excretion of lead.

Opioid toxicity results from the overstimulation of mu-opioid receptors, leading to central nervous system depression, respiratory depression, and miosis. It is a medical emergency characterized by the classic triad of coma, pinpoint pupils, and respiratory depression.

Management strategies include:

1. Airway and Ventilation: The primary goal is to ensure adequate oxygenation and ventilation, often requiring bag-valve-mask ventilation or endotracheal intubation.
2. Pharmacological Antidote: Naloxone, a competitive opioid receptor antagonist, is the specific treatment. It is administered intravenously, intramuscularly, or intranasally.
3. Dosing Considerations: Naloxone has a shorter half-life than many opioids, necessitating careful observation for the recurrence of respiratory depression (re-narcotization) and potential repeat dosing or continuous infusion.
4. Supportive Care: Monitoring for complications such as non-cardiogenic pulmonary edema, aspiration pneumonia, and rhabdomyolysis is essential during the recovery phase.