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# Organophosphate and carbamate poisoning

Poisoning by common insecticides that block an enzyme in nerves, flooding the body with acetylcholine. It can stop breathing and is often intentional.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Main bronchi](https://durgical.com/en/anatomy/right-main-bronchus/)
- [Diaphragm](https://durgical.com/en/anatomy/diaphragm/)
- [Medulla oblongata](https://durgical.com/en/anatomy/medulla-oblongata/)
- [Lacrimal gland](https://durgical.com/en/anatomy/lacrimal-gland/)
- [Lobar bronchi](https://durgical.com/en/anatomy/lobar-bronchus/)
- [Sinoatrial (SA) node](https://durgical.com/en/anatomy/sinuatrial-node/)
- [Atrioventricular (AV) node](https://durgical.com/en/anatomy/atrioventricular-node/)

## Why it happens

- [The neuromuscular junction](https://durgical.com/en/physiology/the-neuromuscular-junction/)
- [Adrenergic and cholinergic receptors](https://durgical.com/en/physiology/adrenergic-and-cholinergic-receptors/)
- [Sympathetic and parasympathetic effects on each organ](https://durgical.com/en/physiology/sympathetic-and-parasympathetic-effects-on-each-organ/)
- [Types of enzyme inhibition](https://durgical.com/en/biochemistry/topics/types-of-enzyme-inhibition/)
- [Neuromuscular junction: motor end plate and acetylcholine receptors](https://durgical.com/en/histology/neuromuscular-junction-motor-end-plate-and-acetylcholine-receptors/)

## What it is

Poisoning by insecticides that inhibit acetylcholinesterase, so acetylcholine builds up at nerve endings and produces the cholinergic toxidrome. Organophosphates bind the enzyme almost permanently; carbamates bind reversibly and usually cause shorter illness.

## Who gets it

Pesticide self-poisoning is a major cause of suicide deaths in rural low- and middle-income countries. In Colombian surveillance (INS, 2008–2015), insecticides were the pesticides most often involved, mainly organophosphates and carbamates; most cases were men of working age, and more than half had suicidal intent.

## Causes

- Intentional ingestion (self-harm) of agricultural insecticides
- Occupational exposure through skin or inhalation during spraying or mixing
- Accidental ingestion by children or from food or containers contaminated with pesticide
- Nerve agents act by the same mechanism

## Risk factors

- Agricultural work and easy access to pesticides at home
- Depression, alcohol use and previous self-harm
- Spraying without protective equipment
- Storing pesticides in unlabelled drink bottles

## Pathophysiology

Inhibited acetylcholinesterase cannot break down acetylcholine, which overstimulates muscarinic receptors (glands, smooth muscle, heart), nicotinic receptors (skeletal muscle, autonomic ganglia) and the central [nervous system](https://durgical.com/en/anatomy/system/nervous-system/). Organophosphate-enzyme complexes undergo 'ageing', after which oximes can no longer reactivate the enzyme. Death usually comes from respiratory failure caused by bronchorrhoea, bronchospasm, respiratory muscle weakness and central depression.

## Classification

- Acute cholinergic crisis (minutes to hours)
- Intermediate syndrome (about 1–4 days): weakness of neck flexors, proximal limb and respiratory muscles
- Organophosphate-induced delayed polyneuropathy (weeks later)

## Symptoms and signs

- Muscarinic: salivation, tearing, sweating, bronchorrhoea, wheeze, vomiting, diarrhoea, urinary incontinence
- Miosis (pinpoint pupils) and blurred vision
- Bradycardia and hypotension (tachycardia can also occur from nicotinic effects)
- Nicotinic: muscle fasciculations, cramps and weakness progressing to paralysis
- Central: anxiety, confusion, seizures and coma
- Garlic- or solvent-like smell of the breath or clothing

## Red flags

- Copious secretions, crackles and hypoxaemia
- Weak neck flexion or falling tidal volume (impending respiratory failure)
- Seizures or decreasing consciousness
- Marked bradycardia or heart block
- New weakness 1–4 days after apparent recovery (intermediate syndrome)

## Diagnosis

**Clinical**
Diagnosis is clinical: exposure history (container, smell) plus the cholinergic toxidrome; improvement with antimuscarinic treatment supports it. Treatment never waits for laboratory confirmation.

**Tests**
Red blood cell acetylcholinesterase (more specific) and plasma butyrylcholinesterase activity; arterial blood gases, glucose, electrolytes, ECG for bradycardia and QT prolongation, and screening for co-ingestants such as alcohol.

**Imaging**
[Chest](https://durgical.com/en/anatomy/region/chest/) X-ray for aspiration pneumonia or pulmonary oedema.

## Differential diagnosis

- Opioid overdose (miosis and coma, but dry secretions)
- Nicotine or cholinergic mushroom poisoning
- Paraquat or other pesticide poisoning
- Acute asthma or pulmonary oedema
- Guillain-Barré syndrome or myasthenic crisis for the later weakness

## Goal of treatment

Secure breathing, reverse muscarinic effects until the chest is dry, reactivate acetylcholinesterase when possible, stop seizures, limit further absorption and protect staff.

## Treatment

**Acute**
Staff wear protective equipment; contaminated clothing is removed and [skin](https://durgical.com/en/anatomy/skin/) washed with soap and water. Airway and breathing are supported, with early intubation when needed (succinylcholine is avoided because its action is prolonged).

**Medical**
Atropine (an antimuscarinic) given intravenously and repeated, titrated to clear bronchial secretions, adequate heart rate and blood pressure, not to pupil size.

**Medical**
Oximes such as pralidoxime may reactivate the enzyme in organophosphate poisoning if started before ageing; benzodiazepines for seizures and agitation.

**Follow-up**
Close monitoring of secretions, oxygen saturation, neck-flexion strength and ventilation for several days because of the intermediate syndrome; psychiatric assessment after intentional poisoning.

## Drugs for this condition

- [Atropine](https://durgical.com/en/pharmacology/atropine/)

## Complications

- Respiratory failure and aspiration pneumonia
- Intermediate syndrome needing prolonged ventilation
- Arrhythmias including QT prolongation
- Delayed polyneuropathy
- Atropine excess (agitation, hyperthermia, tachycardia)
- Death, especially after large intentional ingestions

## Prognosis

Mortality depends on the compound, amount and speed of care; it is highest in intentional ingestions of highly toxic organophosphates. Carbamate poisoning is usually shorter. Survivors may have weakness or neuropathy for weeks.

## Prevention

- Restricting highly hazardous pesticides and safe, locked storage
- Protective equipment and training for agricultural workers
- Detection and treatment of depression and suicide risk in rural communities

## Test yourself

Think of the answer, then tap the question to see it.

## What enzyme do organophosphates and carbamates inhibit?

Acetylcholinesterase, causing acetylcholine to accumulate at muscarinic, nicotinic and central synapses.

## What is the clinical endpoint for titrating atropine in organophosphate poisoning?

Drying of bronchial secretions with clear lungs and adequate heart rate and blood pressure, not pupil size.

## Why are oximes given early in organophosphate poisoning?

They reactivate acetylcholinesterase only before the enzyme-poison complex 'ages' and becomes permanent.

## What is the intermediate syndrome?

Weakness of neck flexors, proximal limb and respiratory muscles 1–4 days after exposure, which can cause late respiratory failure.

## Which nursing priority protects staff when receiving a pesticide-poisoned patient?

Personal protective equipment and decontamination: removing clothing and washing the skin before or during resuscitation.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/organophosphate-and-carbamate-poisoning/)

## Related conditions

- [Suicidal behaviour and suicide risk](https://durgical.com/en/conditions/suicidal-behaviour-and-suicide-risk/)
- [Acute respiratory failure (hypoxaemic and hypercapnic)](https://durgical.com/en/conditions/acute-respiratory-failure/)
- [Aspiration pneumonia and pneumonitis](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/)
- [Anticholinergic toxicity (incl. scopolamine «burundanga»)](https://durgical.com/en/conditions/anticholinergic-toxicity/)
- [Paraquat poisoning](https://durgical.com/en/conditions/paraquat-poisoning/)
- [Opioid overdose](https://durgical.com/en/conditions/opioid-overdose/)
- [Atrioventricular (heart) block](https://durgical.com/en/conditions/atrioventricular-block/)
- [Status epilepticus](https://durgical.com/en/conditions/status-epilepticus/)
- [Myasthenia gravis](https://durgical.com/en/conditions/myasthenia-gravis/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Insecticide poisoning](https://medlineplus.gov/ency/article/002832.htm) (MedlinePlus, US National Library of Medicine, 2026); [Comportamiento epidemiológico de los casos de intoxicaciones por plaguicidas en Colombia, 2008 - 2015](https://www.ins.gov.co/buscador-eventos/IQEN/IQEN%20vol%2022%202017%20num%206.pdf) (Instituto Nacional de Salud (Colombia), Informe Quincenal Epidemiológico Nacional (IQEN), 2017).

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Source: https://durgical.com/en/conditions/organophosphate-and-carbamate-poisoning/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/organophosphate-and-carbamate-poisoning/