Elimination enhancement refers to therapeutic strategies that accelerate the removal of toxins from the body. These methods are especially valuable when a poison has already been absorbed into the systemic circulation and continues to exert harmful effects. While supportive care and decontamination remain foundational in poisoning management, elimination enhancement can significantly improve outcomes in selected cases.
Goals of Elimination Enhancement
The primary objective is to reduce toxin concentration in the bloodstream and target organs. This helps minimize ongoing toxicity, prevent complications, and shorten recovery time. The choice of method depends on the physicochemical properties of the toxin, such as molecular weight, protein binding, water solubility, and volume of distribution.
1. Urinary Alkalinization
Urinary alkalinization enhances renal excretion of weak acids by increasing their ionized form, preventing reabsorption and promoting elimination.
Indications
- Salicylate poisoning
- Phenobarbitone toxicity
- Chlorpropamide overdose
Procedure
Intravenous sodium bicarbonate is administered to maintain urine pH between 7.5 and 8.0. Serum electrolytes, particularly potassium, must be monitored closely to prevent hypokalemia, which can impair urinary alkalinization.
Precautions
- Risk of fluid overload
- Electrolyte imbalance
- Contraindicated in renal failure
2. Multiple-Dose Activated Charcoal (MDAC)
MDAC enhances toxin elimination by interrupting enterohepatic and enteroenteric circulation. It also creates a concentration gradient that promotes movement of toxins into the gut for adsorption.
Useful For
- Carbamazepine
- Theophylline
- Dapsone
- Phenobarbitone
- Quinine
Dosage
Typical dosing involves 25–50 g of activated charcoal every 4 hours, with close monitoring of bowel function to prevent obstruction or ileus.
3. Forced Diuresis
Forced diuresis involves administering IV fluids along with diuretics to increase urine output and enhance toxin elimination. However, this method is rarely recommended today due to risks of fluid overload and electrolyte imbalance.
Indications
- Limited modern use
Safer and more effective methods such as MDAC and dialysis have replaced forced diuresis in most clinical settings.
4. Hemodialysis
Hemodialysis is one of the most effective methods of removing toxins with low molecular weight, low protein binding, and small volume of distribution.
Dialyzable Toxins Include
- Methanol
- Ethylene glycol
- Lithium
- Salicylates (severe poisoning)
- Valproic acid (severe toxicity)
- Theophylline
Hemodialysis also corrects metabolic acidosis, electrolyte disturbances, and fluid overload, offering additional clinical benefits.
5. Hemoperfusion
Hemoperfusion involves passing blood through a cartridge filled with charcoal or resin adsorbents. It is particularly useful for toxins that are highly protein-bound and not effectively removed by hemodialysis.
Indications
- Theophylline
- Carbamazepine
- Phenobarbitone
- Paraquat (limited benefit)
Limitations
- Risk of thrombocytopenia
- Hypocalcemia
- Hypothermia
- Requires specialized equipment
6. Exchange Transfusion
This method is rarely used today but may be considered in severe neonatal poisonings, methemoglobinemia, or poisoning with substances that bind strongly to erythrocytes.
Factors Influencing Selection of Elimination Methods
- Narrow therapeutic window of the toxin
- Presence of severe metabolic acidosis
- Renal or hepatic impairment
- Time elapsed since ingestion
- Risk of complications
Limitations of Elimination Enhancement
Not all toxins can be effectively removed by enhancement methods. Substances with large volume of distribution, such as tricyclic antidepressants or benzodiazepines, are poorly dialyzable. Individual patient factors, hemodynamic stability, and resource availability also influence treatment selection.
Detailed Notes:
For PDF style full-color notes, open the complete study material below:
PATH: PHARMD/ PHARMD NOTES/ PHARMD FOURTH YEAR NOTES/ CLINICAL TOXICOLOGY/ ELIMINATION ENHANCEMENT.