When viewing this topic in a different language, you may notice some differences in the way the content is structured, but it still reflects the latest evidence-based guidance.

Organophosphate poisoning

Last reviewed: 4 Sep 2023
Last updated: 02 Dec 2021



History and exam

Key diagnostic factors

  • increased secretions
  • fasciculations
  • pinpoint pupils
  • distinctive odor
  • chest crackles and rhonchi
  • semiconscious/coma
More key diagnostic factors

Other diagnostic factors

  • visual disturbances
  • vomiting
  • influenza-like syndrome
  • urinary or fecal incontinence
  • proximal muscle weakness
  • abnormal deep tendon reflexes
  • abnormal heart rate
  • abnormal blood pressure
  • decreased respiration
  • hypothermia
  • seizures
  • delayed-onset central nervous system and peripheral (predominantly motor) neuropathy
Other diagnostic factors

Risk factors

  • pesticide availability
  • history of self-harm or recent interpersonal conflict
  • mental illness
  • alcohol or drug abuse
More risk factors

Diagnostic investigations

1st investigations to order

  • atropine therapeutic trial
  • plasma cholinesterase
  • red blood cell cholinesterase
More 1st investigations to order

Investigations to consider

  • chest x-ray
  • ECG
  • blood gases
More investigations to consider

Treatment algorithm


suspected poisoning


occupational or accidental poisoning

deliberate ingestion or terrorism/warfare with nerve agent


intermediate syndrome

organophosphate-induced delayed neuropathy



Nicholas Buckley, MD, FRACP

Professor of Clinical Pharmacology

Pharmacology Department

Sydney Medical School

University of Sydney


New South Wales



NB is an author of a number of references cited in this topic.

Peer reviewers

Steven B. Bird, MD, FACEP

Assistant Professor of Emergency Medicine

Division of Medical Toxicology

University of Massachusetts Medical School

North Worcester



SBB declares that he has no competing interests.

Cynthia K. Aaron, MD, FACMT, FACEP

Program Director

Medical Toxicology

Regional Poison Center

Children's Hospital of Michigan




CKA holds stock in Merck Pharmaceuticals and is a paid consultant for ToxEd. She was briefly a paid consultant for Lexi-Comp.

Kent R. Olson, MD

Professor Medical Director

San Francisco Division

California Poison Control System

San Francisco



KRO declares that he has no competing interests.

Ruben Thanacoody, MD, FRCP(Edin)

Consultant Physician and Clinical Toxicologist

National Poisons Information Service (Newcastle)




RT declares that he has no competing interests.

  • Differentials

    • Carbamate poisoning
    • Chlorophenoxy herbicide poisoning
    • Opioid overdose
    More Differentials
  • Guidelines

    • Management of acute organophosphorus pesticide poisoning
    • Clinical management of acute pesticide intoxication: prevention of suicidal behaviours
    More Guidelines
  • Videos

    Radial artery puncture animated demonstration

    Femoral artery puncture animated demonstration

    More videos
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer