Organophosphate Poisoning
Description Diagnostic criteria General and supportive measures Medicine treatment Referral ICD-10 code: T60.0 *Notifiable condition DESCRIPTION Organophosphates are potent inhibitors of acetylcholinesterase. Note: Where the history is of an unspecified rat poison or pesticide ingestion, consider other active ingredients such as amitraz and ‘super-warfarin’ anticoagulants. DIAGNOSTIC
Description
Diagnostic criteria
General and supportive measures
Medicine treatment
Referral
ICD-10 code: T60.0
*Notifiable condition
DESCRIPTION
Organophosphates are potent inhibitors of acetylcholinesterase.
Note:
Where the history is of an unspecified rat poison or pesticide ingestion, consider other active ingredients such as amitraz and ‘super-warfarin’ anticoagulants.
DIAGNOSTIC CRITERIA
Clinical
- Acute cholinergic toxidrome has central and peripheral effects.
Peripheral effects:
- Muscarinic: diarrhoea, vomiting, urinary incontinence, lacrimation, pinpoint pupils, bronchorrhoea, bronchoconstriction, hyper-salivation, sweating, bradycardia, hypotension.
- Nicotinic: tachycardia, hypertension, dilated pupils, muscle weakness and fasciculations.
Cardiac features of bradycardia and tachycardia depend on whether muscarinic or nicotinic effects predominate.
Central effects:
- Nicotinic: confusion, coma, convulsions.
- Intermediate syndrome can occur within 1–4 days after recovery from cholinergic crisis. Patients develop weakness or paralysis predominantly affecting the muscles of respiration (including the neck flexors and bulbar muscles) and proximal limb muscles, sparing the distal muscles. Cranial nerves may also be affected. Supportive care is the mainstay of therapy.
- Signs depend on dose and route of exposure (vapour or liquid) as well as the time exposed (vapour).
Investigations
- Decreased levels of pseudocholinesterase.
- Use for confirmation only.
- Do not wait for levels before treating.
GENERAL AND SUPPORTIVE MEASURES
- Ensure use of personal protective equipment.
- Remove all patient’s clothing and wash clothes thoroughly.
- Wash affected skin with soap and water.
- Suction secretions frequently.
- Monitor respiratory function closely and ventilate if necessary. If using suxamethonium or mivacurium for intubation, consider that metabolism may be delayed and prolonged respiratory support may be required. Use alternative agents if possible.
- Also monitor heart rate, pupillary size and level of consciousness.
MEDICINE TREATMENT
For bradycardia, bronchorrhoea or bronchospasm:
- Atropine bolus, IV, 0.05 mg/kg over 1 minute.
- Reassess after 3-5 minutes for evidence of atropinisation as indicated by reduced bronchial secretions, dry skin, increasing heart rate and blood pressure, and dilating pupils (note: pupil dilatation may be delayed).
- If no evidence of atropinisation after bolus, give repeated atropine boluses every 3-5 minutes, incrementally doubling the dose of atropine until atropinisation is achieved, e.g.:
- For a 10kg child: 0.5 mg, 1 mg, 2 mg, 4 mg, 8 mg, (no maximum dose). - If there is some evidence of atropinisation after initial bolus, give the same or reduced dose.
- Once atropinisation achieved, follow with atropine infusion. Calculate the total dose of atropine required to achieve atropinisation (as described above). Give 10-20% of this dose per hour.
Undiluted infusion:- Prepare 20 mL of undiluted atropine (0.5 mg/ml).
- Calculate infusion rate to deliver 10-20% of the total bolus dose per hour.
- Example: If the patient required 15 mg of atropine bolus dose to clear respiratory secretions, then start infusion at 1.5 mg - 3 mg per hour = 3-6 mL/hour of atropine [0.5 mg/mL].
Undiluted atropine infusion must be given via a syringe driver. If not available, continue with bolus dosing.
If high dose of atropine is required, use undiluted atropine 1mg/mL. Calculate infusion rate accordingly.
- Reassess frequently and adjust atropine infusion/bolus dosing as follows:
- Bronchial secretions, bronchospasm or bradycardia recur—increase dose.
- Good control of bronchial secretions and signs of atropine toxicity (tachycardia, dilated pupils, agitation, pyrexia, reduced bowel sounds and urinary retention): decrease dose rapidly or stop infusion.
- No recurrence of bronchial secretions and no signs of atropine overdose: reduce dose slowly.
Note:
Atropine will not improve focal areas of chest crackles that are due to aspiration.
Do not stop atropine infusion abruptly, but wean over at least 24 hours. Tachycardia and dilated pupils are not contraindications for giving atropine in the acute resuscitation setting.
Glycopyrrolate is not a substitute for atropine. However, it does not penetrate the CNS and therefore, may be useful in patients who are suffering from central cholinergic toxicity as a result of atropine but still require control of peripheral muscarinic symptoms.
- Glycopyrrolate, 0.025 mg/kg, IV.
Patients with organophosphate poisoning may be extremely agitated or develop seizures due to central toxicity. Treat both with a benzodiazepine. See: The Nervous System, Status epilepticus (convulsive).
REFERRAL
- All severe cases for ICU care.
Standard Treatment Guidelines and Essential Medicines List for South Africa, Hospital Level, Paediatrics, 2023 Edition
Chapter 18: Poisoning, 18.1 Poisoning, 18.1.9 Organophosphate Poisoning
Erratum for Medicine Treatment update (08 April 2026): Click here to access pdf.