Poisoning by Therapeutic Substances Chapter Notes | Forensic Medicine and Toxicology (FMT) - NEET PG PDF Download

Introduction

• There are numerous pharmaceutical substances, known as therapeutic drugs, that can be harmful or even deadly if consumed in large quantities or over extended periods.
• Toxic reactions and fatal incidents typically occur by accident or in cases of suicide, as the use of these drugs for murder is uncommon.
• While it is not feasible to enumerate all such drugs, there are certain medicinal compounds that are frequently associated with poisoning, including:
• Analgesics: medications like aspirin, codeine, phenacetin, paracetamol, phenylbutazone, and amidopyrine.
• Antidepressants and sedatives
• Benzodiazepines
• Barbiturates
• Chloral
• Insulin
• Among these, aspirin, paracetamol, and insulin are particularly emphasized, as the other substances have been discussed earlier in the text.

Aspirin

Aspirin, also known as acetyl salicylic acid, is a non-addictive medication used to relieve pain and reduce fever.

Signs and Symptoms

• Flushed face
• Swelling of the face
• Skin rash
• Tinnitus (ringing in the ears)
• Deafness
• Fast breathing
• Nausea
• Vomiting
• Vomiting blood
• Black stools
• Low levels of clotting proteins
• Acute kidney failure
• Fluid in the lungs
• Breathing arrest

Fatal dose: 5 to 10 grams.

Fatal period: Few minutes to a few hours.

Treatment

• Gastric lavage
• Leaving some dilute NaHCO₃ (sodium bicarbonate) in the stomach
• Restoring normal electrolyte levels
• Achieving acid-base balance
• Administering Vitamin K
• Blood or platelet transfusion
• Forced diuresis

Medicolegal Importance

Accidental idiosyncrasy and suicidal tendencies.

Paracetamol

Paracetamol, also known as acetaminophen, is a medication used to relieve pain and reduce fever. Unlike narcotic pain relievers, paracetamol is non-narcotic, making it a safer option for many individuals.

Mode of Action

• Prostaglandin Inhibition: Paracetamol works by inhibiting the production of prostaglandins in the body. Prostaglandins are chemicals that promote inflammation, pain, and fever. By reducing their levels, paracetamol helps alleviate pain and lower fever.
• Overdose and Liver Damage: In cases of overdose, paracetamol can cause severe liver damage. This is due to the formation of a toxic by-product called N-acetyl-p-benzoquinone (NAPQ). Under normal circumstances, NAPQ is detoxified by a substance called glutathione. However, when paracetamol is taken in excessive amounts, the liver's capacity to detoxify NAPQ is overwhelmed, leading to potential liver injury.

Some Preparations Sold in India

• Alkasol-P
• Beserol
• Calpol
• Cosavil
• Crocin
• Cyclopam
• Metacin
• Noragesic
• Robinaxol

Initial Symptoms (First 24 Hours)

• Anorexia: Loss of appetite.
• Nausea: Feeling sick to the stomach.
• Vomiting: Expelling contents of the stomach.
• Epigastric Pain: Pain in the upper abdomen.

False Sense of Recovery (24 to 48 Hours)

• After the initial symptoms, there may be a temporary improvement in condition, leading to a misleading feeling of recovery.

Severe Symptoms (48 to 96 Hours)

• Hepatic Encephalopathy: Severe brain dysfunction due to liver failure.
• Jaundice: Yellowing of the skin and eyes due to liver damage.
• Hepatic Pain: Pain in the liver area, often in the right upper abdomen.
• Confusion: Altered mental status and disorientation.
• Coma: Loss of consciousness and responsiveness.
• Asterixis: Coarse flapping tremors of the hands, a sign of liver failure.
• Gastrointestinal Bleeding: Bleeding in the digestive tract.
• Cerebral Swelling: Increased pressure in the brain.
• Kidney Damage: Impairment of kidney function.

Complications

• Heart Arrhythmias: Irregular heartbeats.
• Haemorrhagic Pancreatitis: Inflammation of the pancreas with bleeding.
• Disseminated Intravascular Coagulation: Serious condition affecting blood clotting.

Prognosis

• Death: Often occurs during the severe symptom stage.
• Recovery: If the patient survives, recovery typically starts after 5-7 days, with full recovery expected in 2 to 3 months.

Toxicity and Treatment of Poisoning

• The fatal dose of the substance is estimated to be between 10 to 25 grams.
• The toxicity rating is classified as 4, indicating a high level of toxicity.
• The fatal period can extend up to five days after exposure.

Initial Treatment:

• Gastric lavage may be performed to cleanse the stomach.

Specific Antidotes and Medications:
N-acetyl cysteine (NAC) is the specific antidote for the poisoning. It should be administered:

• Orally at a dose of 1330 mg/kg over 3 days.
• Intravenously at a dose of 300 mg/kg over 20 hours.

Cysteamine may be administered intravenously:

• 1 gram in 10 minutes.
• 400 mg in 5% dextrose over 4 to 8 hours.

Supportive Measures:

• Intravenous (IV) electrolytes and rehydration are essential for supportive care.
• Vitamin K may be administered to manage bleeding tendencies.
• Mannitol can be used to treat cerebral edema.

Adjuncts for Toxicity Management:

• Charcoal and hypertonic glucose are adjuncts used for managing toxicity.

Postmortem Findings

• Jaundice and petechial hemorrhages in the skin are present.
• There is congestion of the gastrointestinal tract.
• Centrilobular hepatic necrosis and acute tubular necrosis of the kidney are observed.
• Cerebral edema is another internal finding.

Paracetamol is commonly used as a medication to reduce fever and relieve pain. While most cases of poisoning are accidental, there have been instances of intentional self-harm with paracetamol. 

Insulin

• Homicide and Suicide: Insulin has been used in several cases for homicide and occasionally for suicide, particularly by individuals who have access to large quantities.
• Method of Murder: In the absence of suspicion, insulin can serve as an effective method for murder. Modern postmortem assays exist, but complex investigations are unlikely without suspicion in cases that appear natural.
• Hypoglycemic Agent: Insulin is a powerful hypoglycemic agent. Prolonged and severe lowering of blood sugar levels can lead to brain damage and death.
• Rapid Onset: In massive doses, especially when administered intravenously, death can occur within a few hours.
• Needle Marks: If insulin-related death is suspected, whether from suicide, homicide, or accidental overdose (often in hospitals), it is crucial to look for recent needle marks.
• Sample Collection: The surrounding skin, subcutaneous tissue, and underlying muscle should be excised and sent unfixed for assay. Blood samples are also necessary, as modern analytical methods can differentiate between human, bovine, and porcine insulin.
• Adjuvants Detection: These methods can detect adjuvants like zinc, helping trace the source of extrinsic insulin.
• Timing of Samples: Postmortem samples should be collected as soon as possible after death. Plasma should be separated from cells and kept deep-frozen until analysis.
• Blood Glucose Levels: Postmortem blood glucose levels are generally not useful in confirming hypoglycemia, while vitreous humour may provide more helpful information.
• Oral Hypoglycemic Agents: Overdoses of oral hypoglycemic agents such as sulfonylureas and biguanides can occur, either suicidally or accidentally. These overdoses can lead to hypoglycemia, hypokalemia, and acidosis.