Drugs

Acute poisoning

Common medical emergency
Its incidence varies in different countries
Substances involved in poisoning vary as well
Paracetamol poisoning is very common in UK (48% of all cases of poisoning), while it is rare in Iraq.
Organophosphorus poisoning on the other hand is very common in developing countries including Iraq.

Acute poisoning

First aid measure
History taking
Standard clinical examination
Laboratory investigation
Assessment of an acutely poisoned patient

First aid measure should ensure that:

Airway is clear
Breathing is adequate
Circulation is not compromised


First aid measure

History taking should include:

Establishing the diagnosis of poisoning
Calculating the duration since exposure to the toxic substance
Identification of the drug or substance abused
Asking about the cause of poisoning
Considering the symptoms since poisoning
Asking about past medical and psychiatric history

History taking

Start standard clinical examination esp. considering:
State of consciousness (better assessed by Glasgow coma scale)
Most cases of poisoning can lead to disturbance of consciousness, but this is especially true in case of psychotropic drugs.
In an unconscious patient, carefully exclude stroke, hypoglycemia, diabetic ketoacidosis, CNS infection (meningitis and encephalitis), uraemia, hepatic encephalopathy, and brain injury.

Clinical examination

Pupil size:
Small (miosis): Opioids (narcotics)
OP (organophosphorus)


Large (midriasis): Anticholenergics
TCAD
Alcohol
Antihistaminics

Clinical examination

Respiratory rate:
Reduced: Opioids
Benzodiazapines

Increased Salicylates

Clinical examination

Blood pressure:

Hypotension TCAD
Salicylates
Phenthiazines

Hypertension  agonists


Clinical examination

Heart rate:

Tachycardia (or tachyarrhythmia): TCAD,
Digoxine
Theophylline
Anticholenergics
Antihistamines
Bradycardia (or bradyarrhythmia): Digoxine
CCB (calcium channel blockers)
 Blockers
Opioids

Clinical examination

Temperature:
Fever: Anticholenergic
Salicylates
SSRI

Hypothermia: CNS depressants
Phenthiazines


Clinical examination

Cerebellar signs (esp. nystgmus): Anticonvulsants

Alcohol
Extrapyramidal signs: Phenthiazines
Metoclopromide

Convulsions: TCAD

Theophylline
Anticonvulsants
NSAIDs

Clinical examination

Sweating: Salicylates
OP
Cyanosis: CNS depressants
Methaemoglobinaemia

Jaundice: Paracetamol

Needle tracts: Drug abuse

Clinical examination

Urea, creatinine and electrolytes should be measured in most patients.
Arterial blood gases and acid base balance should be checked in those with significant respiratory or circulatory symptoms and when the poison is likely to affect acid base balance
Toxicology laboratory is needed for
The measurement of serum level of paracetamol (and to a lesser extent of aspirin) to plan subsequent management.
Other types of poisoning are diagnosed by urine or gas chromatography (only in difficult cases and for medico-legal indications).

Toxicology study

A. Prevention of further absorption
B. Supportive care
C. Antidotes
D. Psychiatric consultation

General management of acute poisoning

Removal of clothing and skin washing with soap and water in case of contamination by chemicals or pesticides.
Eye irrigation by normal saline for 15 min. in case the eye is contaminated.
Patients breathless or wheezy because of inhaling toxic gases or fumes should receive oxygen and bronchodilator nebulization


A. Prevention of further absorption

Ingested poisons are removed by:

Gastric lavage
Activated char coal
Whole bowel irrigation
Urinary alkalization
Haemodialysis and haemoperfusion
A. Prevention of further absorption

Gastric lavage:

Only if potentially life threatening amounts are ingested (not to be used for acids, alkalis, or petroleum distillates poisoning).
No gastric lavage should be attempted in unconscious patient unless the airways are protected by cuffed endotracheal tube.

A. Prevention of further absorption

Activated charcoal:
it adsorbs most toxins and is the method of choice to prevent further drug absorption.
For patients poisoned within one hour, 50 gm is given orally.
The dose can be repeated every 4 hours for carbamazepine, theophylline poisoning.
For patients with disturbed consciousness or those who can not swallow, activated charcoal is administered through nasogastric tube and the airway should be protected to avoid aspiration pneumonitis.
If multiple doses are needed, a laxative (like sorbitol) is given to avoid intestinal obstruction.
Certain poisons are not adsorbed by charcoal, including iron, lithium, acids, alkalis, ethanol, methanol and petroleum distillates


A. Prevention of further absorption

Whole bowel irrigation:

Polyethylene glycol is administered orally for potentially toxic ingestion of iron, lithium, and theophylline.
One litre is ingested every hour until the rectal effluent is clear.
Contraindications include GI bleeding or ulceration
Urinary alkalinization:
Indicated for severe salicylate poisoning
Haemodialysis or haemoperfusion:
Effective methods of treating severe poisoning by salicylate, theophylline, carbamazepine, and methanol

A. Prevention of further absorption

1. Unconscious patients are better treated in intensive care units with general treatment of comatose patient provided. Regular recording of Glasgow coma scale is important.
2. Convulsions are treated with IV diazepam 10mg IV repeated as necessary.
3. If cardiac complications are present or expected, the patient is put under continuous ECG monitoring.
4. Ventilatory support may be needed for those with respiratory depression.

B. supportive care

Antidote
Poison
Vitamin K, fresh frozen plasma
Anticoagulants (warfarine, rodenticides)
IV glucagon, adrenaline
 blockers
Calcium gluconate (or chloride)
Calcium channel blockers
Cobalt edetate, Sodium thiosulphate, Nitrites, Hydroxycobalamine
Cyanide
Ethanol, 4 methylpyrazol
Methanol,
Ethylene glycol
Naloxone
Opioids (narcotic analgesics)
Atropine, Oximes
OP (organophosphorus compounds)
N. acetylcysteine, Methionine
Paracetamol
Digoxine specific Ab fragments
Digoxine
Desferrioxamine
Iron salts
C. Antidotes


:
This is essential for patients who have attempted suicide.
The psychiatrist should be consulted as soon as the patient recovers.

D. psychiatric consultation

Certain substances are of very low toxicity even if ingested in high doses. Examples include:
most antibiotics (except antiTB, and tetracyclines)
antiulcer drugs (H2 blockers and PPIs)
oral contraceptive pills
chalk
paper glue
washing liquids

Substances of low toxicity