Removal of the Unabsorbed Portion of Poisons and Mechanisms of Antidotes

CATHARTICS

Agents that cause elimination through feces Indicated after ingestion of coated tablets (release content in the intestines)and the time after ingestion is 1-4 hour

Use only saline or salt cathartics, such as (most common)

Magnesium Sulfate (MgSO4) and Magnesium Phosphate (MgPO4) Sodium Sulfate (NaSO4) and Sodium Phosphate (NaPO4)

MERCURY POISONING

- very toxic Higher oxidation state is absorbed Hg2+ Hg+ is not absorbed Reducing agents should be used to reduce Hg2+, such as Sodium formaldehyde will reduce the Hg2+ → Hg+

2 goals for Treatment of acute poisoning must be prompt

1) To keep the concentration of the toxic agent at the target tissue as low as possible by a) preventing absorption b) enhance elimination 2) To combat the pharmacological/toxicological effect at the injured organ/tissue

ABSOLUTE CONTRAINDICATION

Corrosives: Esophagus is already damaged and you don't want to introduce catheter In the presence of Convulsion/seizure

Removal of unabsorbed or the remaining portion of poison from the site of exposure

Depends on the route of exposure and the type of poison: If PO (ingestion) Gastric emptying Emesis (vomiting): Controversial Gastric Lavage Adsorption of the poison Cathartics (laxatives) Neutralization of the poison Enhance elimination (diuresis, changing urine pH) Artificial/Mechanical removal

oral exposure

Dilution of Poison (Dilute with plain water or milk) Give lots of water Reduces local irritant effect Delays absorption Milk Preferred because it coats stomach It retards absorption of poison, due to adsorption onto proteins and is a demulcent (soothing) to mucous membrane

for corrosives

Don't dilute corrosives unless patient is in act of swallowing Don't dilute corrosives if time has passed because more damage will be done • Esophagus is already damaged (saponification of the fat cells with alkali), some fluid may leak to the lung (corrosives liquefy esophagus)

IODINE POISONING

Starch can be used to prevent absorption of poisons, (prevents absorption of Iodine because it binds to it and neutralizes it). When mixed, iodine and starch produce a BLUE color Potato salad

Do not neutralize

Strong Acid/Alkalis

Immediate action to minimize further intoxication (inhalation)

Take pt. away from that environment to fresh air

Never use oil cathartics such as

castor oil because it adsorbs poison

Acidification of urine by

vitamin C or NH4Cl increases excretion of weak base drugs e.g. amphetamine.

ACID POISONING

when we neutralize weak acids, we use neutralizers that don't generate CO2 (e.g., AlOH, KMnO4, yes. NaHCO3, not)

ABSOLUTE CONTRAINDICATIONS

• Corrosives (strong acid/base solution, e.g. drain solution) • When Pt. has ingested large dose of CNS stimulant, emesis may precipitate convulsion. Because emesis involves many muscles, seizure may be triggered • Volatile substance (if poison has potential to produce vapor and gas). Vapors may be toxic to lungs.

RISK OF EMESIS

• Increase gastric perforation and necrosis of the esophagus • Result in pneumonia in ingestion of petroleum products e.g., kerosene, gasoline or furniture polish may cause chemical pneumonitis For this reason emesis is risky and adsorption is preferred Done in the ER when appropriate.

GASTRIC LAVAGE

(Mechanical way to empty stomach = Physically taking or pumping out) - Adults: Use a catheter that is introduced into stomach through the nasal/oral cavity Catheters - come in different size 16-32 - use depending upon age and should be larger enough so it does not enter trachea Position the Pt correctly Usually aspirate before introducing cleansing fluid of Normal Saline Solution (NSS) 50-250 ml (safer than water specially with children) Then 100-500ml of washing fluid (NSS) Repeat process until return is clear and free of poison (10-12 washings) Total volume between 2-4 L When lavage is complete, stomach may be left empty, or give antidote

WHOLE BOWEL LAVAGE

, used in the case of extended release tablets poisoning-Use PolyEthylene Glycol (PEG) - Colyte®, Golytely®

INSTILL SLURRY OF ACTIVATED CHARCOAL (25%)

Activated fine /pure highly adsorptive powder Administered in the form of Suspension (50g in 8 oz water) with a tube Adsorbs a majority of poison and drugs, poison can stick to charcoal, particularly of organic nature. Total doses: 50 -100g for adults and 20 - 30g for children (2-4 hrs)

Only diluted solution can be used for neutralization of

For very weak alkalis use lemon juice For very weak acids use Mg Oxide/Al hydroxide

Hemodialysis

Involves removal of blood from body, purified, then given back though a vein

NEUTRALIZATION

Not used for strong acids/bases and Not universal Prevent absorption of poisons after we have a clear identification of poison Will not remove local irritant effect but will prevent systemic effects Fe2+ supplements poisoning - ferrous state Use NaHCO3 to form ferrous carbonate which is not absorbed

CATHARTICS

Laxatives Used to minimize absorption by expelling poison rapidly through GI

ADSORPTION OF POISONS

Less risky than emesis. Adsorbents - for whatever gastric contents are left over.

Peritoneal dialysis

Less risky, Easy to perform. Sometimes used in cases of renal failure

Hemoperfusion

Most risky. Blood is perfuse through an absorbing substance, e.g., charcoal)

Gastric Emptying by Emesis (Ipecac);

NOT RECOMMENDED

Alkalinization of urine by

NaHCO3 increases excretion of acidic drugs e.g. aspirin.

skin exposure

Remove cloths, use extensive amount of water or soap and water, debridement (removal of damaged tissue): Don't use solvents

RELATIVE CONTRAINDICATION

Unconsciousness/coma

When the patient is seriously poisoned with seriously-known toxic agent:

Use Artificial method of removal

SORBITOL

Used in children, acts promptly and have minimal toxicity Should not used too much, it can cause dehydration due to diarrhea

requirements

Used only if severe toxicity exists - Ex. if Pt. is in a coma -Used only if high blood levels of poison are present -Used only when high level of poison present systemically

eye exposure

Wash with water (eye irrigation), or normal saline solution (NSS), no eye drops or eye solutions use 2% Fluorescein (orange dye under blue light) to detect corneal damage If damaged cornea - green stain is present If not damaged cornea - will not stain

Gastric emptying should be done ASAP, will be ineffective 4-6 hrs after indigestion of toxin except

When poison caused a delay in gastric emptying (e.g., Tricyclic antidepressants) Drug will remain in GI

In drug poisoning, renal elimination of drugs can be enhanced by changing urinary pH to

increase drug ionization and inhibits tubular re-absorption.