AtroPen (Atropine) - Intramuscular

What Is AtroPen?

AtroPen (atropine) is an injectable medication used to treat certain poisonings in adults and children, including insecticide and nerve agent poisonings. AtroPen belongs to a group of drugs called anticholinergics. It blocks the effects of a neurotransmitter (or chemical messenger) called acetylcholine.

Acetylcholine affects many functions in the body, including heart rate, secretion production, and smooth muscle contraction. During an insecticide or nerve agent poisoning, levels of acetylcholine become too high.

Atropine, the active ingredient in AtroPen, is also used to increase heart rate when the heart is beating too slowly.

Healthcare providers may also administer atropine during surgery to help limit excessive secretions, such as saliva.

Drug Facts

Generic Name: Atropine sulfate

Brand Name(s): Atropen

Drug Availability: Prescription

Therapeutic Classification: Anticholinergic; antimuscarinic

Available Generically: No

Controlled Substance: No

Administration Route: Intramuscular

Active Ingredient: Atropine sulfate

Dosage Form(s): Auto-injector

What Is AtroPen Used For?

AtroPen is an injectable medication used in adults and children to treat specific insecticide (organophosphorus or carbamate) and nerve agent (chemical warfare agent) poisonings.

Accidental or intentional exposure to these chemicals through inhalation, ingestion, or skin contamination can lead to toxic effects. Farm workers and people working in manufacturing facilities that make these products are at an increased risk of exposure. They need additional protection on the job.

Insecticide or nerve agent poisonings can cause mild to severe and deadly symptoms. Examples of mild symptoms include:

  • Blurred vision
  • Small pupils
  • Excessive tear production
  • Excessive runny nose
  • Increased saliva production and drooling
  • Chest tightness or difficulty breathing
  • Tremors or muscle twitching
  • Nausea or vomiting
  • Wheezing, coughing, or increased airway secretions
  • Stomach cramps
  • Fast or slow heart rate

Severe symptoms include:

  • Confusion or strange behavior
  • Severe difficulty breathing or excessive airway/lung secretions
  • Severe muscle twitching and weakness
  • Uncontrollable urination or defecation
  • Seizures
  • Coma

AtroPen may be used along with other medicines, such as pralidoxime, to reverse these symptoms.

Healthcare providers may also use other injectable forms of atropine (the active ingredient in AtroPen) to treat:

  • Symptomatic bradycardia, a slowed heartbeat with symptoms such as low blood pressure, chest pain, difficulty breathing, or dizziness
  • Excessive secretions, such as saliva, during surgery

How to Take AtroPen

AtroPen is available as an intramuscular (into the muscle) auto-injector. In general, AtroPen should be administered (given) by a professional trained to recognize insecticide or nerve agent poisoning symptoms. However, your healthcare provider may prescribe AtroPen for self-administration, depending on your situation and risk of exposure.

Follow these steps to ensure you are using AtroPen safely and accurately:

  • Depending on your symptoms, you may need one to three AtroPen injections.
  • Talk with your healthcare provider to see if your symptoms are mild or severe.
  • Check with your healthcare provider about what to do in different situations.
  • Follow your healthcare provider's instructions.
  • Inject AtroPen into the outer part of your thigh.
  • AtroPen may be given through clothing, but be sure that pockets near the injection site are empty.
  • Hold the AtroPen injector firmly against your thigh for 10 seconds to ensure the entire dose is delivered.
  • Remove the AtroPen injector and massage the injection site for several seconds.
  • Using a hard surface, bend the needle back against the AtroPen injector.
  • Save the used injector(s) to show medical professionals how many doses were given.
  • Immediately seek medical help after administering AtroPen.


Store AtroPen injectors at room temperature (68 to 77 degrees F) and protect them from light. Do not allow AtroPen to freeze.

Keep AtroPen and all your medications in a safe location, out of the reach of children and pets.

How Long Does AtroPen Take to Work?

AtroPen should begin to improve symptoms within 10 to 15 minutes. If symptoms get worse, additional doses of AtroPen may be needed. Always seek immediate emergency medical care after administering an AtroPen injection.

What Are the Side Effects of AtroPen?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at or 800-FDA-1088.

Common Side Effects

You may experience side effects from AtroPen. Let your healthcare provider know about any side effects that bother you or don't go away. Common side effects include the following:

  • Pain at the injection site
  • Dry mouth
  • Blurred vision
  • Dry eyes
  • Light sensitivity (eye discomfort when exposed to bright lights)
  • Headache
  • Dizziness
  • Flushing
  • Constipation
  • Stomach pain
  • Nausea or vomiting
  • Sweating less than usual for you
  • Dry nose

Severe Side Effects

AtroPen may cause serious side effects. Let your healthcare provider know right away if you develop any signs of a severe reaction. Call 911 if your symptoms feel life-threatening.

Serious side effects may include the following:

  • Allergic reactions, including a severe form called anaphylaxis. Symptoms may include rash, hives, itching, wheezing, difficulty breathing, swallowing, or talking, or swelling of the mouth, face, lips, tongue, or throat.
  • Trouble urinating
  • Chest pain, chest pressure, a fast or abnormal heartbeat, or palpitations
  • Very dizzy or passing out
  • Trouble breathing or slow or shallow breaths
  • Confusion
  • Difficulty with balance
  • Hallucinations (seeing or hearing things that are not there)
  • Unusual tiredness or weakness
  • Restlessness
  • Shakiness
  • Swelling of the belly
  • Severe constipation or stomach pain
  • Trouble getting or keeping an erection
  • Decreased interest in sex
  • Depression or changes in mood
  • Changes in eyesight, eye pain, or eye irritation
  • Not sweating during physical activity or in warm temperatures

Report Side Effects

AtroPen may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much AtroPen Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For injection dosage form (autoinjector):
    • For treatment of organophosphorus poisoning:
      • Adults and children older than 10 years of age weighing more than 41 kilograms (kg)—2 milligrams (mg) injected into a muscle.
      • Children 4 to 10 years of age weighing 18 to 41 kg—1 mg injected into a muscle.
      • Children 6 months to 4 years of age weighing 7 to 18 kg—0.5 mg injected into a muscle.
      • Children younger than 6 months of age weighing less than 7 kg—0.25 mg injected into a muscle.


The following modifications (changes) should be kept in mind when using AtroPen:

  • Severe allergic reaction: If you've had an allergic reaction to AtroPen (atropine) in the past, your healthcare provider will monitor you closely after receiving AtroPen.
  • Pregnancy: Not enough is known about the safety and effectiveness of AtroPen in pregnant people and their unborn fetuses. Let your healthcare provider know if you're pregnant and discuss the benefits and risks of taking AtroPen during your pregnancy.
  • Breastfeeding: AtroPen is present in human breast milk, but we don't know enough about the safety of AtroPen in nursing babies. Let your healthcare provider know if you're breastfeeding and discuss when it is safe to resume breastfeeding after receiving AtroPen.
  • Adults over 65: Some older adults may be more sensitive to AtroPen's side effects. Your healthcare provider will monitor you closely after receiving AtroPen.
  • Children: AtroPen is safe for children of all ages to treat insecticide poisonings. Young children may be more sensitive to overheating and should be monitored closely.

Missed Dose

AtroPen is used to treat poisonings or other acute problems, usually under the supervision of a healthcare professional. It is not taken regularly, so a missed dose is unlikely.

Overdose: What Happens If I Take Too Much AtroPen?

The symptoms of an AtroPen overdose include:

  • Flushing
  • Dry skin, eyes, nose, or mouth
  • Fast heartbeat
  • Large pupils
  • Blurred vision
  • Fever
  • Trouble walking or difficulties with balance
  • Confusion
  • Hallucinations
  • Agitation
  • Coma
  • Slowed or shallow breathing
  • Death

If you think you're experiencing an overdose or life-threatening symptoms, seek immediate medical attention.

What Happens If I Overdose on AtroPen

If you think you or someone else may have overdosed on AtroPen, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking AtroPen, call 911 immediately.


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Your doctor will check your progress closely while you or your child are receiving this medicine. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to receive it. Blood and urine tests may be needed to check for unwanted effects.

This medicine may cause heart problems. Check with your doctor right away if you or your child have chest pain or discomfort, dizziness, fainting, fast, slow, or irregular heartbeat, lightheadedness, or pounding or rapid pulse.

This medicine may make you sweat less, which can cause your body temperature to rise. Be careful when you exercise and during hot weather. You could overheat or get heat stroke. Check with your doctor right away if you or your child have dizziness, fast, shallow breathing, fast, weak heartbeat, headache, muscle cramps, pale, clammy skin, thirst, or extremely high fever or body temperature.

This medicine may cause eye problems, including acute glaucoma. Check with your doctor right away if you or your child have blindness, blurred vision, decreased vision, eye pain, headache, nausea or vomiting, or tearing. Your doctor may want you to have your eyes checked by an ophthalmologist (eye doctor).

This medicine may cause urinary retention (trouble passing urine or not fully emptying the bladder). Check with your doctor right away if you or your child have decreased in urine volume, decreased in frequency of urination, difficulty in passing urine, or painful urination.

Check with your doctor right away if you or your child have constipation, nausea, vomiting, or stomach pain. These may be symptoms of a serious stomach or bowel problem (eg, blockage).

This medicine may cause lung or breathing problems. Tell your doctor right away if you have an increase or thickening of mucous from the lungs.

This medicine may cause serious allergic reactions, including anaphylaxis, which can be life-threatening and require immediate medical attention. Check with your doctor right away if you or your child have cough, difficulty swallowing, dizziness, fast heartbeat, hives, itching, puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue, skin rash, tightness in the chest, trouble breathing, or unusual tiredness or weakness.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take AtroPen?

If you've had an allergic reaction to AtroPen or atropine products, let your healthcare provider know. They will need to monitor you closely after receiving AtroPen.

What Other Medications Interact With AtroPen?

Use caution when taking AtroPen with the following medications:

  • Pralidoxime is often used with AtroPen to treat insecticide or nerve agent poisoning symptoms. However, side effects may occur sooner when using these products together. Monitor for signs of flushing, large pupils, dry mouth or nose, or a fast heartbeat.
  • Barbiturates, such as phenobarbital.

What Medications Are Similar?

AtroPen is the only anticholinergic medicine used to treat insecticide and nerve agent poisonings.

Frequently Asked Questions

  • What is AtroPen used for?

    AtroPen treats specific insecticide and nerve agent poisonings in adults and children. Healthcare providers may also use other injectable forms of atropine (the active ingredient in AtroPen) for treating other conditions. These include treatment of a slow heartbeat that is causing symptoms or preventing excess secretions, like saliva production, during surgery.

  • How does AtroPen work?

    AtroPen works by blocking the effects of acetylcholine. Acetylcholine is a chemical messenger in the body that affects many functions, including heart rate, secretion production (i.e., saliva), and smooth muscle contraction. During an insecticide or nerve agent poisoning, acetylcholine builds up in the body and causes toxicity.

  • How long does it take for AtroPen to work?

    AtroPen should begin to improve symptoms within 10 to 15 minutes. If symptoms worsen, it may be necessary to administer additional doses of AtroPen. Always be sure to seek emergent medical care immediately after administering AtroPen.

  • What are the side effects of AtroPen?

    The most common side effects of AtroPen include pain at the injection site, dry mouth, blurred vision, dry eyes, light sensitivity, headache, dizziness, flushing, constipation, stomach pain, nausea or vomiting, reduced sweating, and dry nose.

How Can I Stay Healthy While Taking AtroPen?

AtroPen can be a life-saving antidote if exposed to specific insecticides and nerve agent chemicals. But if your job requires you to work with these substances regularly, it is vital to take protective measures to limit exposure.

  • Talk with your employer about appropriate personal protective equipment (PPE), including masks. Be sure you understand the risks associated with the chemicals you work with and the equipment needed to protect yourself. It could save your life and protect the health of your loved ones.
  • The most common route for pesticide poisoning among people who regularly work with these substances is absorption through the skin. Wearing protective gloves, hats, long sleeve shirts, and chemical-resistant coveralls can help limit exposure. In one study, skin exposure was reduced by 65% among U.S. citrus farmers when they wore gloves and coveralls.
  • If you have children at home, it's essential to protect them too. Change your clothes before coming home and leave your shoes outside if you can.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. DailyMed. Atropen auto-injector- atropine injection.

  2. DailyMed. Atropine sulfate - atropine sulfate injection, solution.

  3. Vale A, Lotti M. Organophosphorus and carbamate insecticide poisoningHandb Clin Neurol. 2015;131:149-168. doi:10.1016/B978-0-444-62627-1.00010-X

  4. Damalas CA, Koutroubas SD. Farmers' exposure to pesticides: toxicity types and ways of preventionToxics. 2016;4(1):1. doi:10.3390/toxics4010001

  5. Protecting children from pesticides: information for parents.

By Christina Varvatsis, PharmD
Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.