Leflunomide

Rheumatoid Arthritis Treatment

Leflunomide is primarily used to treat adults with active rheumatoid arthritis (RA). It belongs to a class of medications known as disease-modifying antirheumatic drugs (DMARDs).

The main goals of treatment with leflunomide include:

• Reducing symptoms: It helps decrease joint pain, swelling, and stiffness associated with RA.
• Slowing joint damage: It is used to inhibit the structural damage caused by the disease, such as joint space narrowing and bone erosions, which can be seen on X-rays.
• Improving physical function: By managing inflammation and protecting the joints, it helps patients maintain or improve their ability to perform daily physical activities.

Leflunomide is often prescribed to manage the long-term progression of the disease and is intended to help prevent permanent disability by protecting joint integrity.

Mechanism of Action

Leflunomide belongs to a class of medications known as disease-modifying antirheumatic drugs (DMARDs). It is used to treat rheumatoid arthritis by targeting the underlying processes that cause joint inflammation and structural damage.

In conditions like rheumatoid arthritis, the immune system mistakenly attacks the body's own joint tissues. Leflunomide works by interfering with the production of specific components needed for immune cells to multiply. Specifically, it inhibits an enzyme required for the creation of DNA in white blood cells called lymphocytes.

By limiting the activity and growth of these overactive immune cells, leflunomide helps to:

• Reduce inflammation: It decreases the swelling, redness, and heat in the joints.
• Relieve symptoms: It helps lower pain and stiffness levels associated with the condition.
• Prevent joint damage: By controlling the immune response, it can slow down the progression of structural damage to the bones and cartilage.

Because this medication works by modifying the immune system's response, it does not provide immediate relief like a painkiller. It may take several weeks or months of consistent use before the full benefits are felt.

Common Side Effects

Leflunomide can cause several common side effects that are usually manageable. These include:

• Diarrhea, nausea, or stomach pain
• Headache or dizziness
• Thinning hair or hair loss
• Skin rash or itching
• Back pain
• Weakness or fatigue
• Cold symptoms, such as a runny nose or sore throat

Serious Side Effects

Some side effects require immediate medical attention. Seek help right away if you notice:

• Liver issues: Yellowing of the skin or eyes (jaundice), dark urine, or pain in the upper right stomach area.
• Lung problems: New or worsening cough, fever, or trouble breathing.
• Severe skin reactions: Blistering, peeling, or a painful rash that spreads.
• Infection signs: Fever, chills, sore throat, or other signs of illness.
• Nerve damage: Numbness, tingling, or weakness in the hands or feet.
• High blood pressure: Severe headache, blurred vision, or pounding in the ears.
• Blood disorders: Unusual bleeding or bruising.

Boxed Warning: Liver Injury

Leflunomide can cause severe liver injury, including fatal liver failure. It is not recommended for individuals with pre-existing liver disease or those with significantly elevated liver enzymes. Healthcare providers typically monitor liver function tests monthly for the first six months of treatment and periodically thereafter.

Pregnancy and Fetal Risk

This medication is contraindicated during pregnancy because it can cause serious birth defects or fetal death. A pregnancy test must be confirmed negative before starting treatment. Effective contraception is required during treatment and until the drug is sufficiently cleared from the body.

Infections and Immune System

Because leflunomide suppresses the immune system, it may increase the risk of serious infections, including pneumonia, sepsis, and opportunistic infections. It is generally not started in patients with active, uncontrolled infections.

Blood and Skin Reactions

• Hematologic effects: It may cause a decrease in blood cell counts, such as pancytopenia or thrombocytopenia. Regular blood tests are used to monitor for these changes.
• Skin reactions: Rare but serious skin reactions, such as Stevens-Johnson syndrome and toxic epidermal necrolysis, have been reported.

Other Precautions

Leflunomide may cause or worsen high blood pressure, requiring regular monitoring. It has also been associated with interstitial lung disease, which can be fatal. Because the drug remains in the body for a long time, a specific washout procedure may be necessary if a patient experiences severe side effects or needs to clear the medication quickly.

Pregnancy Risks

Leflunomide is known to cause serious birth defects or the death of an unborn baby. It must not be started if a person is already pregnant. A pregnancy test is typically required before starting treatment to ensure the patient is not pregnant.

For individuals who can become pregnant:

• Contraception: Reliable birth control must be used during treatment.
• Planning Pregnancy: Because leflunomide stays in the body for a very long time (up to two years), a specific medical procedure called a drug elimination procedure or washout is required before it is safe to become pregnant. This involves taking other medications to help the body clear leflunomide more quickly.
• Emergency: If pregnancy occurs while taking this medication or shortly after stopping it, a healthcare provider must be contacted immediately.

Men who wish to father a child should also talk to their doctor about the potential risks and the drug elimination procedure before attempting to conceive.

Breastfeeding

It is not known whether leflunomide passes into human breast milk. Because the drug could cause serious side effects in a nursing infant, breastfeeding is generally not recommended while using this medication. Patients should discuss the risks and benefits with their healthcare provider to decide whether to stop nursing or stop the medication.

Dosage Forms

Leflunomide is available in the following form:

• Oral Tablet: This medication is supplied as a film-coated tablet for administration by mouth.

FDA Approval and Indications

Leflunomide is approved by the U.S. Food and Drug Administration (FDA) for the treatment of active rheumatoid arthritis (RA) in adults. The medication is used to reduce signs and symptoms, improve physical function, and slow the progression of structural joint damage as evidenced by X-ray results.

Boxed Warnings

The FDA requires a boxed warning for leflunomide due to the following serious risks:

• Hepatotoxicity: Severe liver injury, including cases of fatal liver failure, has been reported. Patients with pre-existing liver disease or those taking other medications that may damage the liver are at increased risk. Regular monitoring of liver enzymes is required.
• Embryo-Fetal Toxicity: Leflunomide can cause major birth defects or fetal death if used during pregnancy. It is strictly contraindicated for pregnant women or women who may become pregnant and are not using reliable contraception.

Safety Communications and Monitoring

In 2010, the FDA issued a safety communication to strengthen the warnings regarding liver injury. Clinical guidelines require baseline liver testing and ongoing monitoring while taking the drug. If liver enzyme levels rise significantly, the medication must be discontinued, and a specific drug elimination procedure using cholestyramine or activated charcoal may be necessary to remove the medication from the body quickly.

Pediatric Use

The safety and effectiveness of leflunomide in pediatric patients have not been established, and it is not FDA-approved for use in children.

Drug Elimination and Washout

Leflunomide is not associated with traditional withdrawal symptoms or physical dependence. However, the medication has an exceptionally long half-life, meaning it stays in the bloodstream for a significant amount of time after the last dose is taken. Without intervention, it can take up to two years for the drug to be fully cleared from the body.

The Washout Procedure

Because the drug lingers, doctors often perform a drug elimination procedure or washout if the medication needs to be removed rapidly. This is often necessary if a patient:

• Becomes pregnant or plans to become pregnant.
• Experiences severe side effects, such as liver toxicity or serious infections.
• Needs to switch to another medication that could interact with leflunomide.

The washout typically involves taking specific medications, such as cholestyramine or activated charcoal, for 11 days. Blood tests are then used to confirm that the levels of the drug have dropped to a safe range. Do not attempt this procedure without direct medical supervision.

Managing Treatment Cessation

If you stop taking leflunomide without a washout procedure, symptoms of rheumatoid arthritis may eventually return or worsen as the drug levels slowly decline. Always consult a healthcare provider before stopping this medication to ensure it is done safely and to discuss alternative treatments for your condition.