FM13.{1-10,21} | Toxicology: General Principles — Practice Quiz

Correct. A poison is defined as any substance that, in relatively small quantities, causes injury, illness, or death through its chemical action. Route of administration is not part of the definition.

The forensic definition of poison focuses on chemical action at small doses, distinguishing it from mechanical injury.

A poison is defined by its ability to cause harm through chemical action in small quantities — route and class of compound are not defining characteristics.

Correct. The Poisons Act 1919 governs the import, possession, and sale of poisons in India. IPC Section 328 relates to the criminal use of poison.

Poisons Act 1919 + IPC Section 328 (administering poison to cause harm) are the two key legal provisions in Indian toxicology law.

The Poisons Act 1919 specifically regulates possession and sale of poisons. NDPS Act 1985 governs narcotic drugs and psychotropic substances.

Correct. A high Vd (>1 L/kg) indicates extensive tissue binding. Lipophilic toxins like organochlorines can have Vd of 100+ L/kg, making forced diuresis and dialysis ineffective.

Volume of distribution determines the utility of dialysis: large Vd → dialysis ineffective (e.g., digoxin, tricyclics); small Vd → dialysis effective (e.g., lithium, methanol).

High tissue distribution → high Vd (>1 L/kg). Low Vd (<0.1 L/kg) means the poison stays in the plasma, making dialysis more effective.

Correct. ABC (Airway, Breathing, Circulation) takes absolute priority before any decontamination or diagnostic steps in poisoning management.

The universal approach to acute poisoning: Resuscitate → Decontaminate → Diagnose → Treat specifically. Never skip resuscitation.

In any acute poisoning, ABC (Airway, Breathing, Circulation) is always the first step. Decontamination and investigations come after the patient is stabilized.

Correct. Activated charcoal does NOT adsorb metals (iron, lead, lithium), strong acids/alkalis, or alcohols. However, it IS effective for organophosphates and most organic compounds.

Contraindications to activated charcoal: MAILS — Metals (iron, lead, lithium), Alcohols, Inorganic acids/alkalis. All organic pesticides including OP compounds are adsorbed effectively.

Activated charcoal is ineffective for metals (iron, lithium, lead), strong acids/bases, and alcohols. It DOES work for organophosphates.

Correct. Alkalinisation of urine (pH >7.5 with IV sodium bicarbonate) ion-traps the ionised form of salicylate in the tubular lumen, greatly enhancing renal elimination.

Ion trapping principle: alkalinising urine traps weak acids (salicylate, phenobarbital) in ionised form → cannot be reabsorbed → enhanced excretion.

Forced alkaline diuresis is specifically beneficial for salicylate and phenobarbital (weak acids). Methanol needs dialysis; TCAs have large Vd.

Correct. Suspected homicidal poisoning constitutes a medicolegal case. The attending doctor must treat the patient AND report to police. Withholding treatment is unethical and illegal.

Medicolegal duty: treat first, report simultaneously. Delay in reporting or refusal of treatment are both professional misconduct under Indian medical law.

All cases of suspected homicidal/criminal poisoning are medicolegal cases requiring police notification. Treatment must never be withheld while reporting.

Correct. Viscera (stomach, liver, kidney, intestine) must be preserved in saturated common salt (NaCl) solution. Formalin interferes with chemical analysis. Blood goes in sodium fluoride (NaF).

Viscera preservation: saturated NaCl. Blood: NaF (prevents fermentation). Urine: no preservative. Formalin is ONLY for histology, never toxicology.

CRITICAL: NEVER use formalin for viscera preserved for chemical analysis — it destroys the analytes. Use saturated NaCl for viscera, NaF for blood.

Correct. The Reinsch test uses a copper strip inserted into acidified urine/stomach contents. Heavy metals (As, Sb, Bi, Hg) deposit onto the copper strip as a metallic coat.

Reinsch test: copper strip in acidified biological fluid → metallic deposit confirms heavy metal poisoning. Follow with atomic absorption spectroscopy for confirmation.

The Reinsch test is specifically for heavy metals (arsenic, antimony, bismuth, mercury) using a copper strip in acid solution.

Correct. TLV-TWA is the standard for occupational exposure limits: average over 8-hour workday/40-hour week believed safe for repeated lifetime exposure.

Three TLV categories: TWA (8h average), STEL (15-min short-term), Ceiling (instantaneous maximum). All set by ACGIH; adopted by occupational health authorities.

TLV-TWA = 8h/40h week average safe exposure. TLV-STEL = 15-min short-term limit. TLV-C = ceiling that must never be exceeded.

Correct. After oral absorption, drugs/poisons enter the portal circulation and reach the liver before entering systemic circulation — this is the hepatic first-pass effect.

First-pass effect determines oral bioavailability. High first-pass drugs (morphine, GTN, lidocaine) have much lower oral potency. Bypassing oral route (IV, sublingual, rectal) avoids first-pass.

First-pass metabolism occurs in the liver via the portal circulation. This reduces bioavailability of many oral poisons — important when comparing oral vs intravenous toxicity.

Correct. The Marsh test (James Marsh, 1836) converts arsenic compounds to arsine gas (AsH₃), which is burned to deposit a metallic arsenic mirror. It detects as little as 0.02 mg arsenic.

Arsenic tests: Reinsch (screening) → Marsh test (confirmation). The arsenic mirror formed is soluble in hypochlorite (differentiates from antimony mirror, which is insoluble).

Marsh test is specific for arsenic. The Reinsch test detects multiple heavy metals; the Marsh test is the classical confirmatory test for arsenic.