Drugs that bind the ions of heavy metals to form a stable non-toxic compound which can be easily excreted by kidney are?

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2016

Explanation

Chelating agents are a class of drugs specifically designed to treat heavy metal poisoning.
They work by forming a stable chemical ring structure around a metal ion, a process likened to a 'crab's claw' (chele).
This binding creates a new compound (a chelate) that is non-toxic and water-soluble.
The water-soluble nature of the chelate allows it to be efficiently filtered by the kidneys and eliminated from the body in urine, thus removing the toxic metal.

Option A: Antimetabolites are cytotoxic drugs that disrupt cell division by interfering with the synthesis of nucleic acids (DNA/RNA). Their mechanism is unrelated to binding heavy metals.
Option C: Antibodies are proteins of the immune system that specifically target and neutralize pathogens (like viruses and bacteria) or foreign proteins. They do not have a mechanism for binding to and removing metal ions.
Option D: TNF (Tumor Necrosis Factor) agents are biologic drugs that suppress the immune system by blocking the action of TNF-alpha, a pro-inflammatory cytokine. They are used for autoimmune diseases.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology of Chelating Agents as background academic context rather than a clinical decision trigger.
During chelation therapy, a key nursing responsibility is to ensure the patient is well-hydrated. Maintaining a high urine output helps flush the metal-chelate complexes through the kidneys, reducing the risk of nephrotoxicity.
Nurses must closely monitor renal function (e.g., BUN, creatinine, urine output) and liver function tests, as both the heavy metal and the chelating agent can be toxic to these organs.
Patient education is crucial. The nurse should explain the purpose of the therapy, potential side effects (like flushing or nausea), and the importance of completing the full course of treatment.

How to Approach the Question

First, break down the question stem to identify the core function being described: a drug that 'binds' to 'heavy metals' to create a 'non-toxic compound' that is 'excreted by the kidney'.
This is a factual recall question requiring knowledge of different drug classifications.
Evaluate each option based on its primary pharmacological action.
Recall that 'Antimetabolites' are for cancer, 'Antibodies' are for immunity, and 'TNF agents' are for autoimmune diseases.
Recognize that the definition provided in the stem perfectly matches the mechanism of a 'Chelating agent'. The word 'chelate' itself refers to this claw-like binding action.
Select 'Chelating agent' as the only option that fits the described mechanism of action for treating heavy metal poisoning.

Concept Tested & Keywords

Concept Tested: Pharmacology of Chelating Agents
Stem keywords: drugs, bind, heavy metals, stable non-toxic compound, excreted by kidney
Lead-in keywords: are

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E6 Pharmacology KD Tripathi Essentials 9e Part 3 pp. 260-262, 261-263

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