Clinical toxicology deals with the assessment and treatment of persons exposed acutely or chronically to potentially harmful toxic chemicals. Optimal management requires an interdisciplinary approach due to the diversity of substances and clinical manifestations.

Poison centers are medical facilities specializing in treatment of toxic exposures. The first was established in Chicago, USA (1953).

Roles:

• Receive calls regarding drugs, substance abuse, chemicals, plants, household/personal care products, animal/fish toxins, food poisoning, etc.
• Provide 24/7 telephone information using comprehensive sources/protocols.
• Offer regional treatment referral, transportation.
• Provide poisoning care, public/health professional education, data collection, reporting.
• Staffed by clinical pharmacists/nurses, specialists in poison information.
• Rapid information retrieval due to emergency nature.

• Dispense prescription drugs in Child-Resistant Containers (CRCs) unless exempted.
• Pharmacists should promote distribution of syrup of ipecac (1 oz per young child) but advise calling poison center/physician before use.
• Health professionals should review dosing, follow up, and provide instructions/side effect warnings.

Obtain the following information:

1. Substance: Ingredients, percentages; identify unknown substances (comatose patient, unmarked container, plants).
2. Amount: If unknown, assume potentially toxic amount was ingested.
3. Time since exposure: Influences symptoms consistency and treatment (e.g., stomach emptying).
4. Symptoms: Consistency with substance; severe symptoms (respiratory/cardiovascular collapse) need immediate treatment.
5. Age and weight of patient: Determine toxicity and antidote dosing.
6. Past medical history and prior therapy: May influence intoxication severity or treatment complications.

Major toxicology information sources include secondary sources for rapid retrieval of toxicity/management data.

Poisindex: Computer-generated system on commercial products, biologicals (plants, venomous animals). Available as CD-ROM, mainframe, microfiche.

Includes: manufacturer, product type, ingredients, percentages, tablet imprint, toxicity info, management protocols, overviews, clinical effects, kinetics, lab values, treatment, references.

Advantages: Ease of use, large data storage, up-to-date, detailed protocols, cross-referenced product info. Essential for poison centers.

Minimize absorption from GIT by:

1. Emptying stomach (emesis, gastric lavage).
2. Administering adsorbent (activated charcoal).
3. Inducing catharsis.

Most effective if done within 4h of ingestion (extended to 10-12h for salicylates, anticholinergics, phenytoin).

Activated charcoal is primary treatment; ipecac or lavage may be used if charcoal ineffective. Ipecac is first choice in children; lavage if contraindicated (CNS depression).

Emetics induce vomiting by acting on GIT or centrally (chemoreceptor trigger zone/vomiting center).

Contraindications:

• CNS depression (lethargy, loss of gag reflex, unconsciousness) – risk of aspiration.
• Seizing patients.
• Caustic ingestion – re-exposure causes further damage, risk of perforation.
• Drugs with anti-emetic properties may render emetics ineffective.

Note: Ipecac may be used under medical supervision after hydrocarbon ingestion.

Obtained from ipecacuanha plant; emetic of choice (home/hospital). Local and centrally acting. Available OTC in 15/30 mL containers.

Dose: 10 mL (children 3h) in 4.2% of patients. Large doses cause cardiotoxicity (T-wave depression, bradycardia, fibrillation, hypotension).

Tube inserted into stomach via nose/mouth; patient in left lateral decubitus position. Stomach contents aspirated, fluid instilled and removed. Takes 20–30 min; hospital-only procedure.

Indications: Comatose patients (with cuffed endotracheal tube to prevent aspiration); seizure patients after control.

Contraindicated in caustic ingestions – tube may cause additional damage.

Tube size: 1/2 inch oral in adults; smaller nasogastric tubes less effective. In children, use smaller tubes.

Solution: Tap water or normal saline (in children, use normal/half-normal saline to avoid electrolyte-free solution risks – water intoxication, seizures, coma).

Wash volume: 200–300 mL (adults), 50–100 mL (children). Several liters total.

Odorless, tasteless, fine black powder; nonspecific adsorbent of many drugs/chemicals.

Characteristics for effectiveness: Small particle size, large surface area, low mineral content (vegetable origin).

Ineffective for: Cyanide, ethanol, methanol, caustic alkalis/acids.

Dose: ~10× ingested agent amount. Usual: 60–100 g (adults), 15–30 g (children). One tablespoon ≈ 5–6 g.

Administration: Mixed with water to slurry; given orally or via lavage tube. Must be shaken vigorously. Commercial products contain sorbitol/suspending agent.

Important: Give after ipecac-induced vomiting; otherwise, charcoal adsorbs ipecac and reduces efficacy. Store in sealed glass/metal containers; exposure to air reduces adsorption.

Used with activated charcoal to speed GI transit, reducing absorption.

Types: Saline (magnesium sulfate, magnesium citrate) or hyperosmotic (sorbitol). Irritant (aloes, cascara) and oil-based (castor oil) not recommended.

Doses:

• MgSO4: 250 mg/kg or 15–20 g adult, as 10% solution.
• Mg citrate: 200 mL adult, 5 mL/kg child.
• Sorbitol: 1–3 g/kg adult (35–70% solution); 1–1.5 g/kg child (35%).

Sorbitol has fastest onset, then Mg citrate, then MgSO4. Charcoal stool indicates passage.

Caution: Avoid Mg cathartics in renal impairment (risk of Mg accumulation).

If dangerous amounts absorbed:

1. Multiple-dose activated charcoal: Enhances elimination for drugs secreted into stomach/bile. Effective for theophylline, phenobarbital, dapsone, phenylbutazone, quinine, phenytoin, salicylates. Given every 4–6h; cathartic only with first dose.
2. Forced diuresis – increases urine output.
3. Alteration of urine pH:
   • Alkalinization (NaHCO3) helps eliminate phenobarbital, salicylates (urine pH 7–8).
   • Acidification (no longer recommended) increased amphetamine/strychnine elimination but risk of rhabdomyolysis/myoglobinuria → acute renal failure.
4. Dialysis & Hemoperfusion: For severe intoxication with dialyzable/hemoperfusable drugs not responding to conservative therapy.
   • Dialysis: Removes toxins by diffusion across semipermeable membrane. Indicated for ethanol, isopropanol, lithium, phenobarbital, theophylline, salicylates, methanol, ethylene glycol (to prevent toxic metabolite formation).
   • Hemoperfusion: Blood pumped through charcoal/resin cartridge. Effective for theophylline.

Blood passed through cartridge containing coated/uncoated activated charcoal or resin. Toxin must be adsorbed; removal must significantly reduce total body burden. Extremely effective for theophylline. Limited to severely intoxicated patients not responding to conservative therapy.

Act by antagonizing systemically absorbed toxins. Do not replace supportive measures.

Naloxone: Pure opiate antagonist; reverses CNS/respiratory depression. Duration shorter than some opiates (methadone, diphenoxylate) – may require infusion. Dose: 0.4–2 mg IV adult; 0.1–0.4 mg child. Up to 10 mg total before ruling out opiates.

Deferoxamine: Chelates ferric iron; complex (ferrioxamine) excreted. Pink-red urine indicates chelation. Indicated at serum iron >63–90 µmol/L or severe symptoms (vomiting, coma, hypotension, acidosis). Dose: 90 mg/kg every 8h IV at 15 mg/kg/h. Side effects: erythema, urticaria, hypotension.

Digoxin Immune Fab (Digibind): Binds digoxin/digitoxin; complex excreted renally. Indicated in life-threatening arrhythmias, conduction defects, severe hyperkalemia. Each vial (40 mg) binds 0.6 mg digoxin. Risk: heart failure in patients dependent on digoxin's inotropic effect.

N-acetylcysteine (NAC): For acetaminophen overdose. Acts as glutathione substitute/precursor. Initiate if: adult ingested ≥7.5 g, child ≥200 mg/kg, or unknown amount. Most effective within 8h, can start up to 24h. Side effects: nausea/vomiting. If vomited within 1h, readminister. Remove charcoal via lavage 2h before NAC loading dose if given orally. IV regimen (Europe/Canada): 300 mg/kg over 20h.

Conclusion: Clinical toxicology involves supportive care, terminating exposure, hastening excretion, administering antidotes. Thorough patient evaluation and application of principles essential.