Jawaharlal Nehru Technological University Hyderabad Pharm. D IV Year CLINICAL TOXICOLOGY Previous Question Paper (July/August - 2021 - R08)

The management of a poisoned patient follows a systematic approach prioritizing life-saving interventions and the prevention of further toxin absorption. The primary goal is to stabilize the patient and limit systemic toxicity.

The general principles are categorized into the following steps:

1. Resuscitation (ABCDE): Immediate assessment and stabilization of the Airway, Breathing, and Circulation are paramount. This includes establishing intravenous access, monitoring vital signs, and addressing cardiac arrhythmias or respiratory depression.
2. Risk Assessment: A clinical evaluation is performed to identify the toxic agent, the dose, the time of ingestion, and the patient's current clinical status. This helps determine the severity and the need for specific interventions.
3. Decontamination: This aims to reduce the absorption of the toxin. Methods include:
   • Ocular: Irrigation with copious amounts of saline or water.
   • Dermal: Removal of contaminated clothing and washing the skin with soap and water.
   • Gastrointestinal: Use of activated charcoal to adsorb toxins, or in rare, specific cases, whole-bowel irrigation. Gastric lavage is now reserved only for life-threatening ingestions occurring within one hour.
4. Enhanced Elimination: For specific toxins, techniques such as multiple-dose activated charcoal, urinary alkalinization, or extracorporeal removal (hemodialysis or hemoperfusion) may be employed to accelerate the removal of the toxin from the body.
5. Antidotal Therapy: Administration of specific pharmacological antagonists to neutralize the toxin's effect, such as N-acetylcysteine for acetaminophen toxicity or naloxone for opioid overdose.
6. Supportive Care: Continuous monitoring and management of complications, including fluid therapy for hypotension, temperature control, and management of seizures or agitation.
7. Psychiatric Evaluation: For intentional ingestions, a thorough psychiatric assessment is mandatory before discharge to prevent recurrence.

Elimination enhancement refers to clinical interventions designed to accelerate the removal of a toxicant from the body after absorption has occurred. These techniques are indicated in cases of severe poisoning where the toxicant has a low volume of distribution, long half-life, or high potential for end-organ damage.

The primary methods for enhancing elimination include:

• Forced Diuresis: This involves the administration of fluids and diuretics to increase urine output, thereby promoting the renal excretion of water-soluble toxins. Alkaline diuresis is specifically used for weak acids (e.g., salicylates, phenobarbital) by raising urinary pH, which traps the ionized form of the drug in the renal tubule, preventing reabsorption.
• Extracorporeal Techniques: These are used for toxins that are not easily removed by endogenous processes. Hemodialysis is effective for small, water-soluble molecules with low protein binding and low volume of distribution, such as methanol, ethylene glycol, and lithium. Hemoperfusion involves passing blood through a column containing activated charcoal or resin to adsorb toxins, which is useful for substances with high protein binding or large molecular weight, such as theophylline or carbamazepine.
• Multiple-Dose Activated Charcoal (MDAC): This technique involves repeated oral administration of activated charcoal to interrupt the enterohepatic circulation of certain drugs. It is effective for substances that undergo significant biliary excretion or diffuse back into the gut lumen, such as carbamazepine, dapsone, and quinine.
• Peritoneal Dialysis: Though less efficient than hemodialysis, it may be utilized in pediatric patients or settings where hemodialysis is unavailable to remove toxins like lithium or salicylates through the peritoneal membrane.

The choice of method depends on the toxicokinetic properties of the specific poison, including its protein binding, molecular weight, and volume of distribution. Clinical stability and the risk-benefit ratio of the procedure must always be assessed before implementation.