Levamisole

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Levamisole

Method of action: Anthelmintic

Treatment option:

Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Levamisole

What is Levamisole?

Levamisole is a synthetic derivative of imidazothiazole that belongs to the class of medications known as anthelmintics. Originally developed for its ability to treat parasitic worm infections, it was later discovered to possess immunomodulatory properties, meaning it can influence the behavior of the immune system.

Primary Characteristics

In a clinical context, levamisole has been utilized for two distinct purposes:

  • Antiparasitic Action: It works by interfering with the neuromuscular system of specific parasites, leading to their paralysis and eventual elimination from the host's body.
  • Immunomodulation: It can stimulate or restore the function of certain immune cells, such as T-lymphocytes and macrophages, which play a role in the body's natural defense mechanisms.

Chemical Properties

Levamisole is the levorotatory isomer of tetramisole. This specific chemical structure is responsible for its biological activity. It is typically prepared as a hydrochloride salt, which is highly soluble in water and appears as a white to pale yellow crystalline powder.

Historical and Current Use

While levamisole was once widely used in human medicine to treat various conditions involving immune dysfunction or parasitic infestation, its application in humans has significantly decreased in many regions. Today, it remains more commonly used in veterinary medicine for the treatment of livestock. In some specialized medical settings, it may still be considered for specific conditions where its immune-altering capabilities are deemed relevant, though such uses are closely monitored.

What side effects are possible with Levamisole?

Possible Side Effects and Safety Information

The safety profile for levamisole, as documented in official government regulatory sources, is characterized by the risk of several serious adverse reactions affecting the blood and central nervous system.

Serious and Clinically Significant Risks

Regulatory documents emphasize two primary areas of serious risk:

  • Hematologic (Blood System) Disorders: The most significant and potentially life-threatening adverse effect documented is agranulocytosis (a severe reduction in white blood cells), which can lead to serious infection. Leukopenia (a low white blood cell count) has also been reported. The risk of these disorders has been associated with prolonged or repeated exposure to the medicine.
  • Nervous System Disorders: Serious effects on the central nervous system include encephalopathy (general brain dysfunction) and leukoencephalopathy (damage to the white matter of the brain).

General Adverse Reactions

Adverse reactions are formally classified by frequency (e.g., Common, Uncommon) and the body system affected (System-Organ Class).

System-Organ Class Common Adverse Reactions (Examples)
Gastrointestinal Disorders Nausea, vomiting, diarrhea, and abdominal pain
Nervous System Disorders Headache, dizziness

Regulatory Status

Due to its serious safety profile, levamisole has been withdrawn or cancelled for human use in several major regulatory jurisdictions, including the United States and Canada. This regulatory action reflects the established, high-risk nature of the serious adverse reactions associated with its use.

Overdose and Emergency Response

An overdose of Levamisole is documented in regulatory labeling as a potentially severe event involving distinct clinical manifestations of neurological and autonomic system overstimulation. Documented signs include nausea, vomiting, muscle tremors, dizziness, headache, anxiety, ataxia (incoordination), and clonic convulsions (seizures). Additional physical findings may include increased salivation, frequent urination, and frequent defecation.

The regulatory profile identifies the risk of severe or life-threatening outcomes. The most serious documented manifestations include profound prostration, respiratory distress (dyspnea), and systemic collapse. In the most severe instances of toxicity, the outcome is documented as death.

Given the severity of the potential outcomes, regulatory guidance mandates immediate action. It is explicitly required to seek emergency medical treatment or contact a doctor immediately in the event of a suspected overdose or if the individual feels unwell. Official documents further note that no specific antidote is known for Levamisole toxicity. Therefore, management consists entirely of symptomatic and supportive treatment. The requirement for emergency attention underscores the necessity of continuous medical monitoring.

Therapeutic Uses of Levamisole

What Levamisole Treats: Main Uses and Benefits

Levamisole is used across two distinct therapeutic domains: managing parasitic infections and as part of symptomatic management in certain conditions requiring immune system support. The medication is commonly applied to help with treating infections caused by parasitic worms in both adults and children.


Relief from Parasitic Worm Infections

This medication is applied in addressing symptom clusters that arise from intestinal parasitic infections (helminths). Levamisole is used to manage infestations by various intestinal parasitic worms and helps to relieve the accompanying symptoms related to physical discomfort, such as abdominal pain. The primary benefit is helping to manage the symptoms associated with the parasitic burden, which may contribute to easing the functional strain on the digestive system.

“Levamisole is relevant for easing symptoms related to systemic imbalance that can be linked to a suppressed immune response.”

Quick Fact: Supports management of symptoms related to Digestive Discomfort and Systemic Imbalance.


Supportive Management in Immune-Related Conditions

Beyond its anti-worm role, Levamisole is relevant when supportive symptom management is appropriate in certain chronic conditions where symptoms related to systemic imbalance are present. This may be part of symptomatic management in situations where supportive symptomatic assistance for systemic issues is needed. This use supports the patient during difficult episodes and may help patients cope more steadily with symptom fluctuations, which contributes to improved comfort during periods of heightened symptoms.

Regulatory References

  1. European Medicines Agency therapeutic overview

Eligibility and Restrictions for Use

The official regulatory profile for Levamisole strictly defines which populations are eligible for use through absolute contraindications and conditional restrictions.

Populations Excluded from Use

Levamisole is contraindicated for patients with pre-existing blood disorders due to the serious risk of agranulocytosis. Use is also strictly prohibited for individuals with a known hypersensitivity to the medicine and for patients who are being treated with organophosphorus compounds. Severe renal impairment also constitutes an absolute eligibility prohibition in official labeling.

Restricted and Conditional Use

Use is not recommended for pregnant or breastfeeding women; these states are defined as absolute contraindications in some jurisdictions. Furthermore, the medicine requires special precaution in patients with a history of hepatic impairment (liver diseases), epilepsy, Rheumatoid Arthritis, or Sjögren Syndrome.

Age-Group Eligibility

The medicine is documented for use in both adults and children for its anti-parasitic indication. For older adults, the medicine is generally not expected to cause unique problems compared to younger adults, although comprehensive comparative safety data for the pediatric population may be limited in certain regulatory contexts.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The official interaction profile for Levamisole identifies specific substances that require mandatory timing separation and medicines that necessitate monitoring. All interaction statements are derived strictly from governmental regulatory documentation.

Interaction Category Interacting Substances Official Regulatory Statement
Contraindicated/Prohibited Organophosphorus compounds Co-administration is formally prohibited due to the risk of enhanced toxicity; requires a mandatory 14-day separation period.
Substance Restriction Alcohol (Ethanol) Consumption is prohibited during administration and for at least 24 hours following the last dose, as this combination is officially documented to induce an "ANTABUSE"-like side effect.
Exposure Monitoring Warfarin May require dosage re-adjustment due to documented potential to prolong prothrombin time.
Exposure Monitoring Phenytoin Requires monitoring of plasma levels due to Levamisole increasing concentrations of the co-administered medicine.
Pharmacodynamic Caution Pyrantel, Morantel Noted for a theoretical risk of enhanced toxic effects due to additive cholinergic activity.

Levamisole co-administration is also documented to alter the clearance of certain other anthelmintics, specifically by increasing the bioavailability of Ivermectin while conversely decreasing the bioavailability of Albendazole. Regulatory cautions further note that interaction risks may be of greater relevance in patients with advanced liver disease, a consideration tied to the drug’s metabolism.

Mechanism of Action

Neuromuscular Activation in Parasites

This domain involves agonist activity at selective nicotinic acetylcholine receptors ( nAChRs) located on the muscle cells of susceptible parasitic nematodes. Levamisole's binding initiates a continuous, high-level cholinergic signaling sequence. The resulting molecular cascade sustains depolarization across the cell membrane, leading to the physiological consequence of spastic paralysis in the nematode's musculature, thereby disrupting motor control.


Modulation of Immune Cell Function

This distinct mechanistic domain centers on immunomodulatory effects that influence key immune cells, primarily T-lymphocytes and macrophages. Levamisole engages mechanisms that modulate activity in specific immune responses, promoting T-cell proliferation and macrophage phagocytosis. This supports a more regulated state within the targeted cellular pathways, leading to predictable physiological adjustments in overall leukocyte function.

Dosage and Administration Information

How Levamisole is Used: Official Administration Guidelines

Levamisole is designated for oral administration only, dispensed as either tablets (e.g., 40 mg and 150 mg strengths) or an oral solution. The medicine's proper use follows administration patterns that are specific to its therapeutic context.

Dosing and Scheduling Patterns

For its short-term anthelmintic purpose, the standard regimen involves a single oral dose for adults, typically ranging from 120 mg to 150 mg. A second standard dose may be prescribed one to three weeks after the initial treatment course if a severe parasitic infection is present.

The former adjuvant use was defined by a cyclic regimen: patients would take 50 mg orally three times per day (every 8 hours) for three consecutive days. This 3-day cycle was repeated at 2-week intervals for maintenance therapy over an overall duration of up to 1 year.

Specific Administration Requirements

Pediatric dosing for anthelmintic use is calculated by body weight, requiring a single dose of approximately 2.5 mg/kg to 3 mg/kg. Liquid formulations must be measured using a calibrated measuring device to ensure accurate administration. Administration is often recommended to occur after a light meal to support intake. A critical procedural constraint is the prohibition of alcohol consumption during the period of administration and for at least 24 hours following the final dose. For fixed schedules, a missed dose should be skipped to avoid doubling the next amount.

Recent Clinical Evidence

Levamisole: Recent Clinical Evidence

Levamisole is primarily known for its role as an anthelmintic (anti-worm) agent and is included in the World Health Organization’s List of Essential Medicines for treating parasitic worm infections like ascariasis and hookworm. While historically investigated across many therapeutic areas, recent clinical research primarily focuses on its immunomodulatory properties in specific conditions.


Studies in Nephrotic Syndrome

Recent randomized clinical trials have assessed levamisole’s use as a maintenance therapy in children with steroid-sensitive idiopathic nephrotic syndrome (SSINS) who experience frequent relapses. One such study indicated that, when compared to placebo, the drug was associated with a statistically significant increase in the time to relapse over a 12-month treatment period. Observed adverse events included asymptomatic moderate neutropenia, which was generally reversible upon discontinuation.

Areas of Ongoing Investigation

While levamisole was previously used as an adjuvant therapy in combination with 5-fluorouracil for certain types of colon cancer, this specific indication has been withdrawn in many regions. Current and ongoing research is evaluating the drug’s potential role in:

  • Parasitic Infections: Assessing multi-day regimens for loiasis to evaluate safety and efficacy in reducing microfilarial densities.
  • Hematologic Conditions: Exploring its use in combination regimens for non-severe aplastic anemia.
  • Dermatological Conditions: Research has noted its historical application for managing conditions such as warts and inflammatory dermatoses, attributed to its effect on immune cell function.

Safety Review

Continuous safety monitoring for levamisole-containing medicines is ongoing. Recent reviews by regulatory bodies have been initiated to specifically assess the potential risk of leukoencephalopathy, a condition affecting the white matter of the brain, following reports of serious cases from post-marketing surveillance and medical literature.

Frequently Asked Questions (FAQ)

Common questions about Levamisole (FAQ)


Q: Why is Levamisole sometimes mentioned in discussions about other diseases?

Levamisole is recognized in official sources as a compound with two primary functions: it acts as an anthelmintic (anti-worm agent) and an immunomodulator. This capacity to influence the immune system has historically resulted in its investigation and discussion across a range of medical conditions beyond its approved use.

Q: Does Levamisole treat the cause of the condition or just the symptoms?

Official documents describe the approved anthelmintic action of Levamisole as directly affecting the parasitic worms themselves by causing spastic paralysis, which is intended to disrupt motor control. Additionally, the drug has known immunomodulatory effects, which means it supports the function of specific immune cells, such as T-lymphocytes and macrophages.

Q: How quickly is Levamisole expected to start working?

According to official product information, Levamisole is rapidly absorbed into the bloodstream after being taken by mouth. The peak plasma concentration of the medicine is typically reported to occur within approximately two hours of administration.

Q: What kind of blood monitoring is sometimes mentioned with Levamisole use?

Regulatory documents emphasize that the use of Levamisole is associated with a risk of serious blood disorders, including agranulocytosis and leukopenia (low white blood cell count). Because of this documented risk, official recommendations often cite the need for blood cell count monitoring to be considered during the period the medicine is administered.

Q: Is it true that Levamisole can interact with alcohol?

Yes, the consumption of alcohol is officially prohibited during the use of Levamisole and for at least 24 hours following the final dose. Regulatory documents state that this combination is documented to induce an "ANTABUSE"-like reaction, which is a specific adverse effect.

Q: What happens if an overdose of Levamisole is suspected?

The effects of a suspected overdose have been described in medical literature as potentially including symptoms similar to organophosphate toxicity. These signs may include excessive salivation, episodes of vomiting, seizures, or increased irritability.

Q: Can Levamisole affect the results of any common lab tests?

Regulatory labeling indicates that Levamisole has the potential to affect the results of certain laboratory tests, particularly those used to monitor other medicines. For example, it is noted that it may prolong prothrombin time (a measure of blood clotting) when taken alongside Warfarin.

Q: What is the general duration of treatment with Levamisole?

The duration of treatment with Levamisole varies depending on its use. For its primary anthelmintic (anti-worm) purpose, the regimen generally involves a single oral dose. In cases of severe parasitic infection, a second dose may be scheduled one to three weeks after the initial treatment.

Q: Does Levamisole have an effect on fertility?

Official information notes that Levamisole may potentially affect fertility. Regulatory documents describe that the medicine may temporarily or permanently impact the ability to have children in both men and women.

Q: Are there any studies looking at Levamisole use in older adults?

According to official sources, Levamisole is generally not expected to cause unique problems for older adults when compared to its use in younger adult populations. However, comprehensive comparative safety data specifically focused on the elderly population may be limited in certain regulatory contexts.

Q: Are there any specific foods or drinks to avoid while taking Levamisole?

Regulatory documentation strictly prohibits the consumption of alcohol while using Levamisole and for at least 24 hours after the final dose because of the risk of a documented drug interaction. Official product information does not note specific food items that must be avoided.

Q: Can Levamisole cause changes in mood or sleep?

Official sources report that adverse effects can include central nervous system and psychological changes. These may involve feelings of anxiety or nervousness, irritability, drowsiness, and trouble in sleeping.

Q: How is Levamisole cleared from the body?

According to official pharmacological data, Levamisole undergoes extensive metabolism (breakdown) in the liver. The substance and its metabolites are then primarily eliminated from the body by excretion through the kidneys.

Q: What is the half-life of Levamisole?

The plasma elimination half-life of Levamisole is typically reported in official documents as being approximately 3 to 4 hours. The half-life refers to the time it takes for the concentration of the medicine in the bloodstream to reduce by half.

Q: Are there different strengths or doses of Levamisole available?

Official product information confirms that Levamisole is available for human use in several pharmaceutical preparations. These preparations commonly include 40 mg and 150 mg tablets, and an oral solution.

Q: Can I drive or operate machinery after taking Levamisole?

The safety profile of the medicine includes the risk of side effects affecting the nervous system, such as dizziness, drowsiness, and confusion. These types of effects are noted as potentially impacting the user's ability to perform skilled tasks such as driving or operating machinery.

Q: What happens if I take Levamisole for longer than prescribed?

Official safety documents emphasize that the risk of serious blood disorders, including agranulocytosis and leukopenia (severe reduction in white blood cells), has been specifically associated with prolonged or repeated exposure to the medicine.

Q: Why is Levamisole restricted in some countries but not others?

Levamisole has been withdrawn or cancelled for human use in some major regulatory jurisdictions, such as the United States and Canada, due to the established risk of serious adverse reactions. However, other countries maintain authorization for its use, typically for its single-dose anthelmintic (anti-worm) purpose.

Q: Does Levamisole have a black box warning in the US?

Levamisole was formally withdrawn from the US market in 2000. Its official safety profile emphasizes severe and life-threatening blood and nervous system disorders, which are risks subject to the most stringent regulatory cautions.

Q: What kind of studies are currently being done on Levamisole?

According to recent clinical evidence, current and ongoing research is evaluating Levamisole’s potential role in conditions such as parasitic infections (like loiasis), certain hematologic (blood) conditions, and inflammatory dermatological (skin) conditions.

Q: Are there long-term follow-up studies on people who have used Levamisole?

Regulatory bodies carry out continuous safety monitoring of the medicine, which includes reviews assessing potential long-term risks such as leukoencephalopathy (damage to white matter in the brain). This process suggests that data relevant to long-term safety is collected and assessed by health authorities.

Q: Is it normal to feel tired after taking Levamisole?

Official adverse reaction reports list both unusual tiredness and drowsiness among the documented side effects of Levamisole. These effects are classified as general adverse reactions.

Q: What are the most commonly reported side effects of Levamisole?

Common adverse reactions are formally classified by regulatory bodies. Examples of these commonly reported effects include gastrointestinal issues such as nausea, vomiting, diarrhea, and abdominal pain, as well as nervous system effects like headache and dizziness.

Q: Is it safe for people who have kidney problems?

According to official labeling, Levamisole is contraindicated (prohibited) for patients who have severe renal impairment (severe kidney problems). This condition is documented as an absolute prohibition of use defined by regulatory bodies.

Q: Is it safe to take Levamisole while breastfeeding?

Levamisole is officially not recommended for use by women who are breastfeeding. In certain regulatory jurisdictions, this condition is listed as an absolute contraindication in the product labeling.

Q: What research evidence supports the approved use of Levamisole?

The approved use of Levamisole is supported by its inclusion in the World Health Organization’s List of Essential Medicines. It is included on this list for treating specific parasitic worm infections, such as ascariasis and hookworm.

Q: Can Levamisole cause any long-term health problems?

Official safety documents state that serious health problems affecting the blood and nervous system have been associated with prolonged or repeated exposure to the medicine. These serious risks include severe blood disorders and nervous system conditions like leukoencephalopathy.

Q: Can Levamisole be used by children?

For its anthelmintic (anti-parasitic) indication, Levamisole is documented for use in both adults and children. The official administration guidelines note that pediatric use involves precise calculation of the dose based on the child's body weight.

How should Levamisole be stored and disposed of?

Storage and Disposal of Levamisole

Official labeling defines strict conditions to maintain Levamisole's stability and ensure safe handling.

Storage Requirements

Detail Condition
Temperature Store below 30°C; Do not freeze.
Protection Must be protected from light and stored in a well-closed, light-resistant container.
Child Safety Must be kept out of the reach of children and stored locked up.

Disposal Instructions

Expired or unused Levamisole must be disposed of in accordance with local regulations and to an approved waste disposal plant. Environmental disposal rules require users to avoid release to the environment and prevent the product from entering water systems.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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