General Warnings

Drugs That Can Cause Neutropenia and Agranulocytosis

Neutropenia is a medical condition that arises when the number of neutrophils (white blood cells) in the bloodstream falls below the normal range. Neutrophils are a type of white blood cell and a crucial component of the body’s immune system. Their primary function is to combat bacterial infections by engulfing and destroying bacteria. A typical reference range for neutrophil count in adults is around 1,500 to 8,000 neutrophils per microliter of blood. Neutropenia is often categorized into mild (1,000 to 1,500 neutrophils per microliter), moderate (500 to 1,000 neutrophils per microliter), and severe (less than 500 neutrophils per microliter) based on the severity of the decrease. It’s important to note that neutropenia can result from various factors, including medical conditions, medications, chemotherapy, radiation therapy, and even some genetic disorders.

Agranulocytosis, on the other hand, is an extreme and severe form of neutropenia where the neutrophil count drops precipitously, often falling below 100 neutrophils per microliter of blood. This drastic reduction in neutrophils has a profound impact on the body’s immune defense mechanisms. Individuals with agranulocytosis are at exceptionally high risk of developing serious bacterial infections. Even a minor infection that would typically be easily handled by a healthy immune system can become life-threatening for someone with agranulocytosis. Given the severity of this condition, prompt medical attention, including hospitalization and aggressive treatment with antibiotics, is essential to manage and potentially reverse agranulocytosis and its associated risks.

Both neutropenia and agranulocytosis involve a deficiency in neutrophils, which are vital in defending the body against bacterial infections. Neutropenia is a broader term referring to any reduction in neutrophil count, while agranulocytosis represents an extreme and highly dangerous form of neutropenia characterized by a significant depletion of neutrophils. Both conditions pose a serious threat to the immune system’s ability to protect the body from infections, underscoring the importance of vigilant monitoring and appropriate medical management when they occur.

While these conditions can have various causes, including medical conditions and genetic factors, certain medications are known to be associated with the development of neutropenia and agranulocytosis. In this article, we will explore the drugs that can cause these conditions, their mechanisms, and the importance of monitoring and awareness.

Medications That Can Cause Neutropenia and Agranulocytosis

The following drugs can cause neutropenia and agranulocytosis:

1.      Antithyroid Medications (e.g., Methimazole and Propylthiouracil): These drugs are used to treat hyperthyroidism. Agranulocytosis is a rare but severe side effect associated with their use. Regular blood monitoring is essential for patients taking these medications.

2.      Chemotherapy Drugs: Certain chemotherapy agents, such as carboplatin, cisplatin, and methotrexate, can suppress bone marrow function, leading to neutropenia. This effect is usually temporary but can increase the risk of infections during treatment.

3.      Antibiotics (e.g., Trimethoprim-Sulfamethoxazole): Some antibiotics, particularly trimethoprim-sulfamethoxazole (Bactrim), have been linked to neutropenia and agranulocytosis, especially in patients with underlying kidney disease or compromised immune systems.

4.      Antipsychotic Medications (e.g., Clozapine): Clozapine, used to treat schizophrenia and bipolar disorder, is known for its potential to cause agranulocytosis. Patients taking clozapine require frequent blood monitoring to detect and manage this risk.

5.      Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Although rare, some NSAIDs like diclofenac have been associated with neutropenia, emphasizing the importance of monitoring when using these medications.

6.      Anticonvulsants (e.g., Carbamazepine): Certain anticonvulsants, including carbamazepine, have been linked to neutropenia and agranulocytosis, though these reactions are infrequent.

Monitoring and Risk Mitigation for Neutropenia and Agranulocytosis

1.      Regular Blood Monitoring: Patients taking medications associated with the risk of neutropenia and agranulocytosis should undergo regular blood tests to monitor their neutrophil levels. These tests, which can be done through a simple blood draw, help healthcare providers detect any abnormalities in the white blood cell count. The frequency of monitoring may vary depending on the specific medication and the patient’s individual risk factors, but close monitoring is essential, especially during the initial stages of treatment.

2.      Patient Education: Healthcare providers play a crucial role in educating patients about the potential side effects of medications and the signs and symptoms of neutropenia and agranulocytosis. Patients should be aware of common symptoms, such as fever, sore throat, chills, and the development of skin sores or infections. Encouraging patients to report any of these symptoms promptly is essential for early detection and intervention.

3.      Medication Management: In cases where neutropenia or agranulocytosis is detected or strongly suspected, healthcare providers may need to adjust the patient’s medication regimen. This could involve reducing the dosage, discontinuing the offending medication, or switching to an alternative treatment option that does not carry the same risk of neutropenia. The decision will depend on various factors, including the severity of the condition and the patient’s overall health.

4.      Hospitalization and Treatment: Severe cases of neutropenia or agranulocytosis, especially those associated with life-threatening infections, may require hospitalization. In the hospital setting, patients can receive intravenous antibiotics to combat existing infections and support the body’s immune system. Growth factors, such as granulocyte colony-stimulating factor (G-CSF), may be administered to stimulate the production of white blood cells, including neutrophils.

5.      Preventative Measures: In some situations, healthcare providers may consider prophylactic measures to reduce the risk of neutropenia or agranulocytosis in high-risk patients. This could involve using medications to stimulate white blood cell production or carefully selecting alternative drugs with a lower risk of these adverse effects.

6.      Continued Monitoring: Even after the resolution of neutropenia or agranulocytosis, patients may need ongoing monitoring to ensure that their blood cell counts return to normal and remain stable. This long-term follow-up helps ensure the patient’s safety and well-being.


While many medications provide significant benefits for various medical conditions, some can pose the risk of neutropenia and agranulocytosis. Healthcare providers must be vigilant in monitoring patients on these medications and educating them about potential side effects. Patients should also play an active role in their care by reporting any concerning symptoms to their healthcare team. Through awareness and proactive management, the risks associated with these medications can be minimized, allowing patients to safely benefit from their therapeutic effects.


Dr. Oche Otorkpa PG Cert, MPH, PhD

Dr. Oche is a seasoned Public Health specialist who holds a post graduate certificate in Pharmacology and Therapeutics, an MPH, and a PhD both from Texila American University. He is a member of the International Society of Substance Use Professionals and a Fellow of the Royal Society for Public Health in the UK. He authored two books: "The Unseen Terrorist," published by AuthorHouse UK, and "The Night Before I Killed Addiction."
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