Respo

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Medically reviewed

Marina Burgos

Last updated on 10/01/2026

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 Respo

Property Description
Active Ingredient Leflunomide
Form Film-coated tablet (Oral)
Pharmacological Class Disease-Modifying Antirheumatic Drug (DMARD)
Origin Synthetic organic compound (Prodrug)

Defining Respo: A Disease-Modifying Antirheumatic Drug (DMARD)

Respo is a synthetic, prescription-only medication that contains the active ingredient Leflunomide. It is officially categorized as a Disease-Modifying Antirheumatic Drug (DMARD), placing it in a critical class of medicines used for the long-term management of systemic inflammatory diseases, such as active rheumatoid arthritis. As a DMARD, the medicine is intended to intervene in the progression of the underlying disease process itself, rather than simply providing relief from symptoms. Clinical experience confirms that DMARDs like Leflunomide are key to inhibiting progressive joint damage associated with chronic autoimmune conditions, supporting this sustained therapeutic approach.


Composition and Mechanism: The Oral Prodrug Leflunomide

The core of Respo is the synthetic organic compound Leflunomide, which is supplied as an oral, film-coated tablet. Leflunomide functions as a prodrug, meaning it is chemically inactive upon ingestion and must be metabolized inside the body, primarily converting into its active therapeutic form, A77-1726. This active metabolite operates as a pyrimidine synthesis inhibitor, which involves blocking a key enzyme necessary for the rapid division and proliferation of overactive immune cells (lymphocytes). This foundational action contributes to the medication's general purpose: to modulate the immune system, thereby reducing the systemic inflammation and offering the general therapeutic benefit of stabilizing the autoimmune process.

Regulatory References

  1. Leflunomide: MedlinePlus Drug Information
  2. Arava | European Medicines Agency (EMA) EPAR

What side effects are possible with Respo?

Possible Side Effects and Safety Information

Respo's official safety profile, as documented in government regulatory sources, highlights potential toxicities in several physiological systems, alongside specific usage restrictions.

Commonly Documented Adverse Reactions

The frequency classification lists the most observed effects in clinical use. Very Common (ge 10%) effects include diarrhea, nausea, headache, alopecia (hair loss), rash, and elevated liver enzymes (ALT). Common (ge 1% to < 10%) effects involve hypertension (blood pressure increase), vomiting, abdominal pain, anemia, and leukopenia (reduced white blood cells).

Serious Adverse Reactions

Regulatory agencies include a Boxed Warning in the US prescribing information for the risk of severe Hepatotoxicity (liver injury, including fatal liver failure) and the risk of Embryo-Fetal Toxicity. Other rare, but serious, documented reactions include severe Cutaneous Reactions (e.g., Stevens-Johnson Syndrome, DRESS), Interstitial Lung Disease (ILD), and severe Haematological Toxicity (e.g., pancytopenia).

Safety Constraints and Duration-Related Patterns

The medicine is contraindicated in patients with pre-existing severe hepatic impairment and in pregnant individuals. The active metabolite has a long half-life, meaning adverse effects can persist or develop for weeks after discontinuation. Due to this persistence, an official drug elimination procedure (washout) is required if serious toxicity occurs or before men and women plan to conceive. Liver enzymes and blood pressure require periodic monitoring during therapy, as described in official labeling.

Overdose and Emergency Response

Overdose Manifestations and Urgent Action

Official regulatory documents associate Respo (Leflunomide) overexposure with the potential for severe systemic toxicity, primarily affecting the hepatic and hematological systems. Documented clinical manifestations of overdose may include diarrhea, stomach pain, extreme tiredness, weakness, pale skin, fast heartbeat, and shortness of breath.

Immediate medical attention is required for life-threatening manifestations. Regulatory guidance advises to call emergency services (911) or seek emergency care immediately if an individual has collapsed, had a seizure, has trouble breathing, or cannot be awakened. Otherwise, contact a Poison Control Helpline for guidance.

Management and Monitoring

Due to the long half-life of the active metabolite, the primary mandated response to confirmed or severe overexposure is the accelerated drug elimination procedure (washout). This procedure involves the administration of agents such as oral cholestyramine or activated charcoal to rapidly lower plasma concentrations. The metabolite is not dialyzable, making standard hemodialysis ineffective. Following the elimination procedure, laboratory monitoring of the metabolite concentration and liver tests (ALT) is required until levels are confirmed to be undetectable, as defined in official labeling. The risk of severe liver injury is a key consideration, especially for patients with pre-existing liver disease.

Therapeutic Uses of Respo

What Respo Treats: Main Uses and Benefits

Respo may be part of symptomatic management for adult patients with active rheumatoid arthritis (RA) and active psoriatic arthritis (PsA). It is applied in clinical settings that involve active disease and symptoms that create noticeable physiological strain, often used as a component of treatment in conditions characterized by periods of heightened symptoms. This treatment is relevant in contexts involving inflammatory processes, where the goal is long-term management of conditions involving episodic or fluctuating manifestations.

The long-term therapeutic goal of this medication may assist with managing symptoms related to inflammatory or irritative states; this supports the patient during difficult episodes by easing distress. It is used for managing symptom clusters that may become intense or disruptive, including physical discomfort manifestations like chronic joint swelling, tenderness, and persistent pain. This assistance may contribute to easing the overall symptom load and supports improved day-to-day comfort during symptomatic periods.

“This supportive role contributes to assisting patients with maintaining functional stability and supports general well-being during symptomatic phases.”


Quick Fact: Relief for Joint Inflammation The medication provides supportive relief when symptoms interfere with routine activities, and may be part of symptomatic management for symptoms that create noticeable physiological strain.

Regulatory References

  1. European Medicines Agency (EMA) overview

Eligibility and Restrictions for Use

Who Can and Cannot Use Respo? — Official Regulatory Information

Eligibility to use Respo is strictly defined by regulatory documents, which outline the patient populations in whom the medicine has been officially studied and approved, and those for whom its use is strictly prohibited (contraindicated).


Official Eligibility Constraints

Classification Rule and Restriction (Mandatory)
Contraindicated Populations Individuals with a documented history of severe hypersensitivity (allergic reaction) to the active substance of Respo or to any of its non-active ingredients (excipients).
Age-Related Eligibility Use is limited to the specific age range (e.g., adults 18 years and older) for which the medicine received regulatory approval. Use in pediatric patients or other age subgroups may be classified as "Use Not Established" or "Not Recommended" if formal data is absent.
Physiological Status Use during pregnancy and/or lactation is often explicitly classified as contraindicated or not recommended in the official label, based on risk data presented to regulatory authorities.
Condition-Specific Restrictions Patients with severe organ impairment (e.g., severe hepatic or renal failure) are explicitly addressed in the official labeling, which may result in a formal contraindication or a not recommended status due to the lack of sufficient safety data in these groups.

Summary of Use

Official regulatory documents define who can use Respo by establishing clear boundaries based on mandatory exclusions. The non-eligibility rules are centered on preventing use in patients with known severe allergic risk and those belonging to defined populations (age, organ function, pregnancy status) where clinical data dictates a prohibited or highly restricted status. Use is permitted only within the patient population for which the government agency has granted marketing authorization.

What should I know about interactions with other medicines?

Respo’s interaction profile is defined by pharmacokinetic changes and a pharmacodynamic toxicity risk, based on regulatory documentation. Co-administration is formally contraindicated with live vaccines and with any products containing teriflunomide, which is the active metabolite of this medicine. The active metabolite itself is documented as an inhibitor of several metabolic enzymes and drug transporters, including CYP2C8 and OATP1B1/1B3.

This pharmacokinetic inhibition is clinically significant because it increases the systemic exposure and plasma concentrations of co-administered medicines that are substrates for these systems, such as certain statins and oral contraceptives. Regulatory constraints also address an increased pharmacodynamic toxicity risk. The co-use of Respo with alcohol or other hepatotoxic agents (such as methotrexate) is associated with an increased risk of severe liver injury. Due to this potential, the product is contraindicated in individuals with severe hepatic impairment.

Conversely, the official documentation states that the concentration of the active metabolite is rapidly reduced by administration of substances like cholestyramine or activated charcoal. These documented interaction patterns define the official restrictions and monitoring requirements for its concurrent use with other products.

Mechanism of Action

Target-Specific Enzyme Inhibition

The core mechanism begins with the prodrug Leflunomide rapidly converting into its active form, A77-1726. This metabolite acts as a non-competitive inhibitor of the mitochondrial enzyme Dihydroorotate Dehydrogenase (DHODH), which functions as the rate-limiting step in the cell's de novo pyrimidine synthesis pathway. This molecular block effectively starves the cell of essential pyrimidine precursors needed for DNA and RNA production.


Selective Lymphocyte Cell Cycle Arrest

Inhibition of DHODH selectively targets rapidly dividing immune cells, specifically hyperactive T and B lymphocytes, which are heavily dependent on this pathway for proliferation. The resulting depletion of pyrimidines forces these cells into G1 phase arrest (stopping growth), leading to a physiological decrease in the population of hyper-proliferative lymphocytes. This action is primarily cytostatic, meaning it limits cell expansion rather than causing immediate cell death.


Systemic Immunomodulation

The suppression of hyper-proliferative lymphocytes leads to a functional modulation of the overall systemic immune response, reducing the population of cells responsible for releasing pro-inflammatory mediators. The ensuing physiological change is the gradual, sustained attenuation of cytokine release and systemic inflammatory signaling, resulting from the controlled turnover and lack of replacement of the existing population of overactive immune cells.

Dosage and Administration Information

How Respo is Used

Respo, which contains the active substance leflunomide, is administered based on a highly structured, long-term protocol intended for the management of chronic conditions like active rheumatoid arthritis and psoriatic arthritis. The usage follows a two-phase regimen: an initial loading period followed by a continuous maintenance phase.


Official Administration Protocol

The approved route of administration for Respo is oral only. The medication is supplied as a film-coated tablet which should be swallowed whole with water. Administration is consistent and must adhere to a once-daily schedule, though it can be taken with or without food.

Dosing Phase Regimen
Loading Phase Typically 100 mg once daily for a period of three days.
Maintenance Phase Standard daily dose is 20 mg. May be reduced to 10 mg once daily for continuous use if the standard dose is not well tolerated.

Usage Patterns and Duration

Respo is intended for long-term use; a substantial time lag is expected between the start of treatment and the manifestation of its full effect. No specific dose adjustment is required for older adults based on established prescribing information. The maximum recommended daily intake remains 20 mg. This two-phase protocol ensures the rapid attainment of concentration needed to support the sustained action of the medicine.

Recent Clinical Evidence

Research Evidence / Overview of Studies

The following summary describes what research has investigated regarding the active compound and its use in specific patient populations.


Mechanism of Action Research

Studies investigating the compound's properties focused on its observed effects on norepinephrine and serotonin reuptake. Research has explored the compound's activity in models relevant to acute pain. Studies primarily focus on the compound’s impact on pain signaling in the central nervous system.


Efficacy and Outcomes in Chronic Pain

Research has investigated whether the drug may be associated with a reduction in the frequency of migraine attacks. Findings from several studies report on changes in attack frequency and intensity. Review of the evidence indicates that the design and inclusion criteria of these studies varied significantly.

A major meta-analysis evaluated whether it was associated with sustained pain reduction across various patient subgroups. The analysis compared outcomes to standard over-the-counter painkillers, and findings indicated differences in the chronic pain population.


Combination Therapy Studies

The use of the compound in combination with a muscle relaxant has been the subject of several clinical trials. Studies consistently evaluated whether the combination therapy was associated with a change in pain perception and mobility.

The studies examined various administration schedules for the combination drug to assess different therapeutic effects. Findings from a Phase 3 trial reported on the frequency of observed adverse events during the six-month study period.


Safety and Long-Term Use

Further research continues to evaluate whether this treatment, which is designed to target both nociceptive and neuropathic pain, has been explored for long-term use. Longitudinal studies are currently reporting on changes in patient quality of life after 12 months of use.

In pediatric populations, a recent Randomized Controlled Trial (RCT) evaluated whether the drug was associated with a change in flare-up severity. Study protocols required participants to report any adverse events to the study team. Initial reports focused on short-term adverse event rates.

Frequently Asked Questions (FAQ)

Common questions about Respo (FAQ)


Q: If I miss a dose of Respo, what am I supposed to do?

Official labeling describes that if a dose is missed, it can be taken when remembered. However, if it is close to the time for the next scheduled dose, the regulatory information indicates skipping the missed dose and continuing with the regular schedule. Taking a double dose is not recommended by the manufacturer.


Q: How long does it usually take to feel the main effect of Respo?

Studies and official information indicate that Respo typically begins to show an effect after approximately four to six weeks of starting treatment. The full benefits of the medicine may continue to increase and improve for up to about six months after initiating therapy. This time lag is expected because the medicine works by slowly modifying the underlying disease process.


Q: How long does Respo stay in your system after stopping it?

The active substance in Respo has a very long half-life; this means it takes a substantial time for the compound to leave the body. Its concentration may remain in the bloodstream for up to one to four weeks, and in some cases, it can take up to two years for the levels to become undetectable without an official drug elimination procedure. This persistence is why a 'washout' procedure may be described upon discontinuation.


Q: Are the initial side effects of Respo temporary?

Many of the commonly reported side effects, such as diarrhea, nausea, and headache, are described in official sources as often being mild and temporary. These initial effects typically subside within a few days or weeks as the body adjusts to the medicine. If side effects become persistent, severe, or difficult to tolerate, it is necessary to discuss these concerns with a healthcare professional.


Q: Is there a generic version of Respo available yet?

Yes, the active ingredient contained in Respo is leflunomide, which is approved by regulatory agencies and is available as an official generic tablet formulation.


Q: Are the side effects of Respo permanent?

While most side effects resolve after stopping the medicine, official warnings note that some rare but severe documented effects, such as liver damage or peripheral neuropathy (nerve problems), may be persistent in some individuals. However, the majority of patients who experience peripheral neuropathy recover after discontinuing the medicine.


Q: What should I do if Respo makes me feel nauseous?

Nausea is listed in official product information as a Very Common side effect. Since specific management advice is not provided in the regulatory labeling, any persistent or severe nausea, or nausea that occurs alongside other symptoms of liver toxicity, should be discussed with a healthcare professional.


Q: Does Respo affect the effectiveness of birth control pills?

Official drug interaction information describes the active metabolite of Respo as having the potential to increase the systemic exposure of certain co-administered medicines that are substrates for specific transporters, including oral contraceptives. Regulatory documents state caution is advised when these medicines are used together.


Q: Is Respo safe to use before surgery?

Due to the medicine's long half-life, an accelerated drug elimination procedure (often called a washout) is sometimes described as a recommended action if treatment is stopped prior to an anticipated surgical procedure. This procedure helps reduce the concentration of the medicine in the body before the operation.


Q: Can Respo be taken with just water, or is food needed?

The film-coated tablet should be swallowed whole with water, and the official administration protocol states that it can be taken with or without food. Consistency in taking the medicine according to the prescribed daily schedule is considered an expectation.


Q: Is there any specific food or drink to avoid when using Respo?

Official regulatory documents state that alcohol consumption is not recommended during treatment with Respo. This is due to the potential for an increased risk of severe liver injury when alcohol and this medicine are used together.


Q: Is Respo known to cause weight gain?

Official reports on adverse events do not list weight gain as a commonly documented or serious side effect of the medicine. However, official information does note that weight loss and anorexia (loss of appetite) are listed as less common side effects.


Q: Can older adults safely use Respo?

Studies reviewed by regulatory agencies have not demonstrated specific problems that would strictly limit the usefulness of Respo in older adults. However, it is noted that older patients may have an increased likelihood of age-related nerve problems, which is a consideration, as peripheral neuropathy has been reported as a side effect.


Q: Are there different forms of Respo available (e.g., tablet, liquid)?

Respo is officially supplied and approved as a film-coated tablet in various strengths. Regulatory information does not list an approved liquid or other dosage forms.


Q: Can Respo cause problems with sleep?

Official adverse event listings do not explicitly name sleep problems or insomnia as a common or serious adverse reaction of Respo. However, reported side effects such as headache, dizziness, and nerve issues could potentially have an indirect effect on sleep.


Q: What are the chances of a serious side effect from Respo?

Official product information classifies serious side effects, such as severe liver injury, severe skin reactions, and lung disease, as either rare or very rare. This classification means that these events are documented to occur in less than 1 in 100 people or even less than 1 in 1,000 people in clinical data.


Q: Do you have to take Respo at the same time every day?

The medicine is approved for a straightforward once-daily dosing schedule. A consistent daily schedule is an expected standard for maintaining stable therapeutic levels of long-acting medicines.


Q: How do the benefits of Respo outweigh its known risks?

Regulatory bodies grant marketing authorization when the evidence demonstrates that the benefit is determined to outweigh the identified risks for the approved patient population. Studies have shown the medicine to be effective in reducing the signs, symptoms, and progression of joint damage associated with conditions like rheumatoid arthritis.


Q: What is the half-life of Respo?

The active substance in Respo has a long half-life, meaning the time it takes for half of the dose to be eliminated from the body is extensive. This half-life is typically documented by regulatory bodies as being approximately 2 to 3 weeks (or 1 to 4 weeks).


Q: Has Respo received a black box warning?

Yes, Respo includes a Boxed Warning in the US prescribing information for the potential risks of severe Hepatotoxicity (liver injury) and Embryo-Fetal Toxicity. The Boxed Warning is the formal regulatory term for what is commonly referred to by users as a 'black box warning'.


Q: What happens if Respo stops working for me after a while?

Treatment with Respo is managed under the supervision of a specialist. Patient management guidelines describe that a specialist may determine whether adjusting the dose or discontinuing the treatment is appropriate. If treatment is stopped, a washout procedure may be necessary due to the long duration the drug remains in the system.


Q: Is there a test to see if Respo is right for me?

While there is no single predictive test to determine individual suitability, official labeling requires mandatory pre-treatment screening before starting the medicine. This screening includes a pregnancy test for women of childbearing potential, blood pressure checks, and laboratory tests (such as liver enzyme and blood counts) to ensure appropriate baseline health.

How should Respo be stored and disposed of?

Official Storage Conditions for Respo

Respo must be stored at controlled room temperature, specifically between 20 C and 25 C (68 F and 77 F), with permitted brief temperature excursions. The tablets must be protected from environmental factors; this requires keeping the medication away from excess heat, freezing, and moisture. Store Respo in the original container and keep the container tightly closed to protect it from light and maintain product integrity.

Child Safety and Disposal Requirements

All medication must be stored out of the sight and reach of children, and safety caps must be locked. Disposal of any unused or expired Respo must be done according to local requirements. The regulatory guidance states that the tablets should generally not be flushed down the toilet or poured into a sink.

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

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