Fansidar

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Fansidar

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Medically reviewed

Marina Burgos

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 Fansidar

Quick Facts

Property Description
Active ingredients Sulfadoxine, Pyrimethamine
Form Oral tablets
Pharmacological class Antimalarial drug, Antimicrobial combination
General purpose Inhibition of susceptible microbe/parasite growth
Origin Synthetic compound

What is the Drug Fansidar and Its Pharmacological Class?

Fansidar is the recognized trade name for a fixed-dose combination (FDC) medication, classified primarily as an antimalarial drug and a specialized antimicrobial combination. This medication, a synthetic compound, is supplied for ingestion as oral tablets. This specific combination is categorized as an essential medicine, signifying its role in managing specific global infectious diseases. This particular combination is clinically recognized for its ability to target and impede the development of drug-resistant strains of certain parasites, a key feature that differentiates it from single-agent therapies.


Composition of Fansidar: Sulfadoxine and Pyrimethamine

The product is defined by its two distinct active ingredients: Sulfadoxine and Pyrimethamine, which are intentionally paired to form this combination product. Sulfadoxine belongs to the sulfonamide class, while Pyrimethamine is categorized as an antifolate agent. This specific FDC offers the advantage of streamlined administration compared to taking two separate medications. The combination targets and impedes the metabolic processes of certain protozoal organisms.


How Does the Sulfonamide/Antifolate Combination Achieve Its Purpose?

The drug achieves its therapeutic purpose through a cooperative mechanism known as sequential metabolic blockade, resulting in a powerful synergistic effect. This action stems from the two ingredients simultaneously interrupting two separate, sequential steps required by the target organism to synthesize folic acid. By blocking this critical biosynthesis pathway, the combination effectively arrests the parasite’s ability to produce the DNA and proteins necessary for growth and reproduction, thereby inhibiting the propagation of susceptible microbes and parasites.

Regulatory References

  1. List of Essential Medicines

What side effects are possible with Fansidar?

Possible Side Effects and Safety Information

The official safety profile for Fansidar (Sulfadoxine/Pyrimethamine) outlines adverse reactions across multiple system-organ classes, as documented in government regulatory sources. These effects are classified by frequency based on clinical reporting data.

Reactions classified as very common include gastrointestinal disturbances like nausea, vomiting, and diarrhea, as well as headache and common skin rash. Effects classified as common include dizziness, thrombocytopenia, and leucopenia.

Serious Adverse Reactions and System-Specific Concerns

The regulatory labeling highlights potential for rare, serious adverse reactions which include life-threatening cutaneous events such as Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN). Fatalities have been associated with these severe skin reactions, as well as with blood dyscrasias like agranulocytosis and aplastic anemia, and fulminant hepatic necrosis. The drug's safety profile focuses heavily on the potential for disorders of the blood and lymphatic system, nervous system, and liver function.

Population-Specific Safety Constraints

The official safety documents include specific constraints for certain groups. The medication is contraindicated in infants less than 2 months of age and is not recommended during the first trimester of pregnancy, nor near term. Patients with severe, pre-existing renal or hepatic failure are contraindicated for repeated prophylactic use. Caution is also noted for individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as this may lead to hemolysis.

Furthermore, the safety documents note that hematologic risks, such as leucopenia, have been reported specifically with prophylactic treatment durations of two months or longer.

Overdose and Emergency Response

Overdose and When to Seek Help

The official regulatory profile addresses overdose and severe reactions by identifying specific critical risks and mandated actions. Overdose is officially documented to be especially dangerous in children.

Key manifestations associated with overexposure include neurological disturbances such as convulsions (seizures), primarily linked to the pyrimethamine component. Non-specific overdose presentations may also involve gastrointestinal effects like nausea and vomiting.

Immediate Medical Attention Required

Stop use of Fansidar and seek medical attention immediately is the mandated action at the first appearance of a skin rash, due to the risk of life-threatening outcomes such as Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN). Urgent medical treatment must also be sought if early indications of serious systemic disorders appear, including fever, sore throat, arthralgia, pallor, or jaundice.

Overdose Management

Management generally consists of symptomatic and supportive treatment. No specific antidote is known for the combination. However, the administration of folinic acid (leucovorin) is documented for managing drug-induced folic acid deficiency, which is a key toxic effect of the pyrimethamine component in an overdose scenario. Due to the potential for severe reactions, close hospitalization and monitoring are often required.

Therapeutic Uses of Fansidar

What Fansidar Treats: Main Uses and Benefits

Fansidar is commonly used for managing acute, symptomatic disease and providing scheduled prophylactic coverage to vulnerable populations, within its designated therapeutic areas. Its application is primarily focused on addressing the effects of the Plasmodium falciparum parasite, which is commonly associated with acute forms of malaria.

Therapeutic Contexts and Symptom Relief

This medication is generally used to help address symptoms related to systemic imbalance, such as high fever, chills, and headache. The primary therapeutic benefit is centered on providing relief from the symptoms associated with the parasitic infection, which helps ease the overall symptom load and may assist with maintaining functional stability during difficult episodes. It is relevant for managing conditions presenting with systemic or localized discomfort caused by malaria, and for use in prophylactic strategies in contexts like high-risk travel and intermittent preventive management during pregnancy.

Quick Facts

Condition/Context Symptom Domain Primary Benefit
Uncomplicated Malaria High fever, chills, headache Easing the overall symptom load
High-Risk Travel/Residence Risk of acute clinical illness Preventing the onset of disruptive symptoms
Pregnancy (Endemic Areas) Maternal anemia, low birth weight risk Supporting maternal and fetal health stability

Eligibility and Restrictions for Use

The official eligibility profile for Fansidar is strictly defined by regulatory authorities based on specific patient populations and pre-existing conditions.

Populations Excluded from Use

Use is absolutely contraindicated in patients with a history of hypersensitivity to pyrimethamine, sulfonamides, or any excipients. The medicine must not be administered to infants less than 2 months of age. It is also contraindicated for individuals with megaloblastic anemia due to documented folate deficiency. Furthermore, the medicine is contraindicated for prophylactic use in patients already receiving sulfamethoxazole/trimethoprim (co-trimoxazole).

Restricted and Conditional Eligibility

Repeated prophylactic use is contraindicated in patients with renal failure, hepatic failure, or blood dyscrasias. Conditional use requires caution in patients with impaired renal or hepatic function, those with possible folate deficiency (e.g., malabsorption), and individuals with severe allergy or bronchial asthma.

Age and Life Stage Rules

Category Eligibility Status (Regulatory)
Infants Contraindicated for those under 2 months of age.
Pregnancy Contraindicated during the first trimester and for prophylaxis at term. Allowed for Intermittent Preventive Treatment (IPTp) starting in the second trimester.
Lactation Contraindicated for prophylactic use during the nursing period.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The official interaction profile for Fansidar (sulfadoxine/pyrimethamine) is structured around pharmacodynamic and pharmacokinetic patterns, as defined in government regulatory documents.

Pharmacodynamic Reinforcement

Co-administration with other folate inhibitors (e.g., methotrexate, trimethoprim) is officially discouraged or restricted. This is due to an additive antifolate effect, which leads to a cumulative risk of haematological toxicity, including bone marrow suppression. Concomitant use with other sulfonamide drugs may similarly increase the potential for severe adverse cutaneous reactions.

Exposure-Modifying Interactions

Interactions driven by altered drug exposure are documented with highly protein-bound medications. The sulfadoxine component may displace other drugs, such as the anticoagulant Warfarin or the anticonvulsant Phenytoin, from plasma proteins. This displacement results in an increase in the free plasma concentration of the co-administered drug, requiring careful monitoring.

Supplement and Dose Restriction

The efficacy of Fansidar is susceptible to interference from folic acid supplementation. Regulatory guidance specifies that high doses of folic acid, typically those equal to or above 5 mg daily, must be avoided as this level directly counteracts the antifolate action, potentially leading to compromised antimalarial efficacy or treatment failure. Lower doses (e.g., 0.4 mg daily) are noted as safe for concurrent use. Furthermore, conditions such as renal or hepatic failure may increase the severity of potential interactions due to impaired drug clearance.

Mechanism of Action

How Fansidar Works

Fansidar's action is governed by a cooperative strategy known as sequential metabolic blockade, resulting in the inhibition of target parasite growth and replication. The combination targets the parasite’s unique and essential pathway for synthesizing folic acid, a molecule the organism cannot acquire from its host.


Dual Enzyme Inhibition of the Folate Pathway

The drug's mechanism involves simultaneously targeting two separate, sequential enzymes in the parasite's folate biosynthesis pathway. Sulfadoxine acts as a competitive inhibitor of Dihydropteroate Synthase (DHPS), while Pyrimethamine selectively inhibits Dihydrofolate Reductase (DHFR). This synergistic, dual-point attack on the cascade results in an augmented metabolic stress due to the synergy of the two components.


Arrest of Parasite DNA and RNA Synthesis

The enzyme inhibition rapidly depletes the parasite of Tetrahydrofolate (THF), a critical cofactor needed to produce nucleic acid precursors (purines and pyrimidines). The resulting metabolic disruption impairs the synthesis of DNA and RNA, which functionally arrests the division and replication of the asexual erythrocytic stages. This action results in the cessation of parasitic multiplication.

Dosage and Administration Information

Fansidar is administered exclusively via the oral route as a fixed-dose combination tablet containing 500 mg of sulfadoxine and 25 mg of pyrimethamine. Standardized administration patterns exist based on the context of use, whether it is for acute management or preventive regimens.

Administration Principles

Context of Use Standard Adult Dose Frequency and Duration
Acute Treatment 2 to 3 tablets as a single dose Single course only.
Malaria Prophylaxis 1 tablet (weekly) or 2 tablets (bi-weekly) Continued during exposure and for 4 to 6 weeks after departure; should not exceed two years.

All tablets must be swallowed whole and should not be chewed. Administration is instructed to occur after a meal to facilitate proper intake and absorption, along with plenty of fluids, such as a full glass of water.

Use in Specific Populations

For Intermittent Preventive Treatment in Pregnancy (IPTp), the regimen consists of three tablets given as a single course per visit, starting in the second trimester. These doses must be spaced by at least one month.

Pediatric dosing for children older than 2 months is determined using fractions of the tablet based on the patient’s body weight in kilograms. The drug is contraindicated for use in infants less than 2 months of age. In cases where a prophylactic dose is missed, common practice involves taking it as soon as possible, continuing the subsequent doses on the regularly scheduled day.

Recent Clinical Evidence

Research evidence / Overview of studies for Fansidar


Evidence for Treating Malaria

Research has evaluated Fansidar for treating active malaria infections in different parts of the world. These studies have primarily examined short-term changes in symptoms and have monitored outcomes related to systemic or functional imbalance. In locations where research describes the parasite strain as potentially responsive to the medicine's components, research describes patterns where the parasite levels were observed to change in the short-term. However, research shows the patterns observed in the studies can vary significantly depending on the location and the specific type of malaria.

Evidence is limited in current studies from areas experiencing high levels of drug resistance. Subgroup findings are uncertain regarding how people respond in areas of low versus high malaria transmission. Comparative evidence is lacking against other treatment approaches that were not included in the studies, and certainty remains low for long-term success in individuals studied in these high-resistance areas. The limitations highlighted suggest the need for further research.


Evidence for Preventing Malaria (Prophylaxis)

Fansidar was studied for preventing malaria in people visiting high-risk areas, and was evaluated in specific public health programs, such as Intermittent Preventive Treatment (IPT). These studies explored how the medicine might affect the risk of episodic or acute changes related to infection.

Research highlights changes measured during the study period suggesting that using the drug periodically was associated with a reduction in malaria episodes that was observed in the monitored groups. This pattern was observed in some studies that focused on people living in areas where malaria is common. The reduction in malaria episodes that was observed may change over time as local parasite resistance changes.


Long-Term Studies and Follow-Up

Research has examined the durability of the effect after individuals have completed their course. Studies monitored outcomes related to daily functioning or activity level over extended periods. Follow-up durations were limited in many of the initial studies conducted on Fansidar. Long-term effects are not fully established, and there is limited information for long-term outcomes beyond the initial study periods. The evidence highlights what is known—and what is still uncertain—about whether an individual will maintain an observed change over a prolonged time.


Evidence in Special Populations

Fansidar was evaluated in studies focused on specific groups, primarily children and pregnant individuals in regions where malaria is common. Research describes its role in specific preventative programs for pregnant individuals, a scenario associated with acute or disruptive episodes. Data for certain groups remain insufficient, such as older adults or individuals who also have other serious, existing health issues. Subgroup findings are uncertain for these less-studied populations.


What Is Still Uncertain About Fansidar

This section focuses on synthesizing the areas where the research evidence is limited. The main challenges that research has explored are related to the development of drug resistance in the malaria parasite. This was associated with differences in the patterns observed in specific locations. Comparative evidence is lacking against all currently available treatments for malaria. Findings were mixed regarding the optimal use of the drug in individuals traveling from non-endemic areas.

Key Studies & References

  1. WHO Guidelines for the treatment of malaria (MTG) (Section on Sulfadoxine-Pyrimethamine as part of combination therapy)
  2. Revised Recommendations for Preventing Malaria in Travelers to Areas with Chloroquine-Resistant Plasmodium falciparum (Early Safety/Efficacy/Long-Term Use Context)
  3. Therapeutic Efficacy Study of Pyrimethamine/Sulfadoxine (Fansidar®) for the Treatment of Uncomplicated Falciparum Malaria in the Peruvian Amazon (Trial Follow-up)

Frequently Asked Questions (FAQ)

Common questions about Fansidar (FAQ)


Q: Is Fansidar primarily used for malaria prevention or treatment?

Official guidance on Fansidar's use has evolved due to changes in drug resistance. It is currently primarily reserved for the treatment of specific strains of resistant malaria. It is also used in certain structured preventive programs, such as those for pregnant women in endemic areas. However, regulatory bodies generally do not recommend it for routine malaria prevention in most travelers due to the risk of severe side effects.


Q: Are there any documented long-term health effects from using Fansidar?

Official product information notes that when the drug is used for prophylaxis (prevention) for periods longer than three months, official guidance recommends periodic laboratory monitoring. This monitoring typically involves checks of blood cell counts, liver enzyme tests, and urinalysis. The purpose is to monitor for potential side effects and track progress during extended use.


Q: What are the primary medical conditions that preclude someone from using Fansidar?

Regulatory documents strictly define who should not use this medication. Absolute contraindications include a history of a severe reaction to the drug’s components (hypersensitivity), and a specific condition called megaloblastic anemia caused by folate deficiency. Furthermore, it must not be used in infants less than two months of age. Repeated use for prevention is also restricted for individuals with pre-existing severe kidney or liver failure or certain blood disorders.


Q: What major food or dietary supplement interactions are noted in the drug's leaflet?

Official documents recommend the medication be taken after a meal along with plenty of fluids. Regarding supplements, regulatory guidance specifies that taking high doses of folic acid (typically defined as 5 mg or more daily) is recommended to be avoided. This is because high doses of folic acid can interfere with the way the drug works, potentially reducing its overall effectiveness.


Q: What did the key research studies conclude about Fansidar's effectiveness?

Studies have shown that Fansidar has demonstrated effectiveness against susceptible parasite strains, notably those causing chloroquine-resistant P. falciparum malaria. However, official information also indicates that drug resistance is prevalent in many regions. Because of this variability, the medication cannot be recommended as the sole drug for preventing all species of human malaria.


Q: What are the key signs of a serious allergic reaction to Fansidar described in regulatory documents?

According to regulatory warnings, a serious reaction often begins with a skin rash. The appearance of any rash, hives, or swelling should be reported to a healthcare provider immediately, as these may indicate a severe adverse event. Other important signs to watch for include difficulty breathing, sore throat, fever, or chills.


Q: Can Fansidar be used by people who have a history of blood disorders?

Official eligibility rules state that the drug is contraindicated (should not be used) in patients with documented megaloblastic anemia due to folate deficiency. Additionally, using it repeatedly for prevention is contraindicated for those with pre-existing blood dyscrasias, which are disorders affecting blood components.


Q: Where can I find the complete official prescribing information or patient leaflet for Fansidar?

The complete official prescribing information and patient labeling can be found through resources provided by government regulatory agencies. Individuals can search official sites like the FDA's Drugs@FDA database or DailyMed by searching for the brand name or the generic combination of sulfadoxine/pyrimethamine.


Q: Why is Fansidar generally not the initial treatment choice for malaria in non-endemic countries?

Official guidance, such as that from the CDC, generally restricts the use of Fansidar. This is because severe and sometimes fatal reactions have been reported more frequently when the medication is used for prevention in travelers. Therefore, it is typically reserved for treatment or specific, high-risk preventive situations rather than routine prophylaxis.


Q: What are the risks associated with Fansidar use versus its potential benefit for the approved uses?

The official FDA label includes a prominent WARNING that notes fatalities have occurred due to severe reactions like SJS and TEN. The documents state that because the drug is prescribed to help prevent or treat a life-threatening infection (malaria), the potential benefit of the medication must always justify the potential risks associated with its use.


Q: What does the term 'folate antagonist' mean in the context of Fansidar?

The term folate antagonist describes how the pyrimethamine component of the medication works. It is a compound that inhibits the parasite’s unique and essential pathway for synthesizing folic acid, also known as folate. By disrupting this process, the drug effectively stops the parasite from producing the necessary materials for growth and reproduction.


Q: Is Fansidar effective against all known species of the malaria parasite?

Official information indicates that Fansidar is indicated for use against susceptible strains of Plasmodia, primarily those causing chloroquine-resistant P. falciparum malaria. It is not the most effective drug for the treatment or prevention of all species, such as P. vivax infections.


Q: Is Fansidar still a commonly recommended drug in international travel guidelines?

Current official guidance, such as that provided by the CDC, generally does not recommend this medication for malaria prevention (prophylaxis) for individuals traveling to high-risk areas. This is due to the potential for severe adverse reactions. The drug is typically reserved for specific clinical and public health programs.


Q: How quickly does Fansidar typically start to take effect after administration?

The drug is described in official documents as being long-acting. When taken orally, one of the active components, sulfadoxine, reaches its highest concentration in the bloodstream in approximately 4 hours, though this can vary between 1.5 to 8 hours.


Q: How long does it take for the active components of Fansidar to be cleared from the body?

Both components of the drug have relatively long elimination half-lives, meaning they remain in the body for an extended time. For sulfadoxine, the average half-life is approximately 169 to 200 hours, and for pyrimethamine, it is approximately 100 to 111 hours.


Q: Does Fansidar interact with common over-the-counter pain relievers?

While specific common non-prescription pain relievers are not named, official interaction reports have noted potential interactions with drugs in the same class as diclofenac (a type of non-steroidal anti-inflammatory drug or NSAID). Regulatory documents emphasize the importance of informing healthcare professionals about all medications, including non-prescription pain relievers.


Q: What is the official information regarding the combination of Fansidar and alcohol?

Patient information cautions that use in individuals with a history of alcohol abuse may lead to potential complications. Beyond this specific warning regarding abuse, there are no official restrictions noted for moderate or social alcohol consumption.


Q: Does Fansidar carry a Black Box Warning in regulatory documents?

Yes, the official US prescribing information contains a prominent warning (sometimes referred to as a Black Box Warning). This warning highlights the risk of fatalities that have occurred due to rare but severe reactions, including the serious skin conditions Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN).


Q: What kind of patient monitoring is officially advised when taking Fansidar for an extended time?

When the medication is used for any purpose lasting longer than three months, official guidance recommends that patients undergo regularly scheduled laboratory tests. This includes checking complete blood counts, monitoring liver enzyme tests, and performing a urinalysis to help detect any potential issues early.


Q: Are there any official restrictions on driving or operating machinery after taking Fansidar?

Patient information advises that the medication may cause side effects such as dizziness. Due to potential side effects like dizziness, caution is noted regarding activities that require mental alertness, such as driving or operating complex machinery.


Q: What is the official guidance if a person experiences blurred vision while taking Fansidar?

While blurred vision is not explicitly listed as a common side effect, the official label does mention related central nervous system effects such as changes in vision, hallucinations, and other serious events. The regulatory label indicates that any change in vision, hallucinations, or related serious events are symptoms that should be reported to a healthcare provider immediately.


Q: Are there official warnings regarding sun sensitivity (photosensitivity) while taking Fansidar?

Yes, the official label includes warnings that the drug may cause photosensitization or phototoxicity (increased sensitivity to sunlight). Due to the potential for photosensitivity, the label recommends limiting excessive sun exposure and using protective measures, such as sunscreen and clothing.


Q: How is the potential for crystalluria with Fansidar addressed in the official information?

The official information notes that the potential for crystalluria (crystals forming in the urine) can be addressed through proper hydration. The label states that adequate fluid intake is necessary throughout the course of treatment to help prevent this and reduce the risk of kidney stone formation.


Q: What are the official recommendations about getting vaccinated while taking Fansidar?

Official drug information indicates that Fansidar may interact with certain live vaccines. For example, a potential interaction has been noted with the typhoid vaccine taken by mouth (oral typhoid vaccine).


Q: Is Fansidar available under a generic name?

Yes, the drug is a combination product whose active ingredients are sold under a generic name. The generic name for this combination is sulfadoxine/pyrimethamine.

How should Fansidar be stored and disposed of?

Fansidar tablets must be stored at controlled room temperature, which is defined by regulatory agencies as 20 C to 25 C. To maintain stability, the medication must be kept in a tightly closed container and protected from heat, moisture, and direct light. Fansidar must not be frozen. For safety, the product must always be stored out of the sight and reach of children.

Disposal should follow official guidelines for unused medicine. If no drug take-back program is available, the tablets should be mixed with an unappealing substance, sealed in a bag or container, and discarded in the household trash. It must not be flushed down the toilet or poured into a drain.

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

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