Arava (Page 5 of 7)

8.2 Lactation

Risk Summary

Clinical lactation studies have not been conducted to assess the presence of ARAVA in human milk, the effects of ARAVA on the breastfed child, or the effects of ARAVA on milk production. Because of the potential for serious adverse reactions in a breastfed infant from ARAVA, advise a nursing woman to discontinue breastfeeding during treatment with ARAVA.

8.3 Females and Males of Reproductive Potential

ARAVA may cause fetal harm when administered during pregnancy. Advise females of the potential risk to the fetus. Advise females to notify their healthcare provider immediately if pregnancy occurs or is suspected during treatment [see Use in Specific Populations (8.1)] .

Women receiving ARAVA treatment who wish to become pregnant should discontinue ARAVA and undergo an accelerated drug elimination procedure to achieve plasma teriflunomide concentrations of less than 0.02 mg/L (0.02 mcg/mL) [see Warnings and Precautions (5.3)] .

Pregnancy Testing

Exclude pregnancy in females of reproductive potential before starting treatment with ARAVA.

Contraception

Females

Advise females of reproductive potential to use effective contraception during treatment with ARAVA and while undergoing a drug elimination procedure until verification that the plasma teriflunomide concentration is less than 0.02 mg/L [see Warnings and Precautions (5.3)] .

8.4 Pediatric Use

The safety and effectiveness of ARAVA in pediatric patients have not been established.

The safety and effectiveness of ARAVA in the treatment of polyarticular course juvenile idiopathic arthritis (JIA) was evaluated in a single multicenter, double-blind, active-controlled trial in 94 pediatric patients (1:1 randomization) with polyarticular course juvenile idiopathic arthritis (JIA) as defined by the American College of Rheumatology (ACR). In this population, ARAVA treatment was found not to be effective.

The safety of ARAVA was studied in 74 patients with polyarticular course JIA ranging in age from 3–17 years (47 patients from the active-controlled study and 27 from an open-label safety and pharmacokinetic study). The most common adverse events included abdominal pain, diarrhea, nausea, vomiting, oral ulcers, upper respiratory tract infections, alopecia, rash, headache, and dizziness. Less common adverse events included anemia, hypertension, and weight loss. Fourteen pediatric patients experienced ALT and/or AST elevations, nine between 1.2 and 3-fold the upper limit of normal, and five between 3 and 8-fold the upper limit of normal.

8.5 Geriatric Use

Of the total number of subjects in controlled clinical trials (Trials 1, 2, and 3) of ARAVA, 234 subjects were 65 years and over [see Clinical Studies (14)] . No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out. No dosage adjustment is needed in patients over 65.

8.6 Hepatic Impairment

Dedicated studies of the effect of hepatic impairment on leflunomide pharmacokinetics have not been conducted. Given the need to metabolize leflunomide into the active species, the role of the liver in drug elimination/recycling, and the possible risk of increased hepatic toxicity, the use of ARAVA in patients with hepatic impairment is not recommended.

8.7 Renal Impairment

Dedicated studies of the effect of renal impairment on leflunomide pharmacokinetics have not been conducted. Given that the kidney plays an important role in drug elimination, caution should be used when ARAVA is administered to these patients.

10 OVERDOSAGE

There have been reports of chronic overdose in patients taking ARAVA at daily dose up to five times the recommended daily dose and reports of acute overdose in adults and children. Adverse events were consistent with the safety profile for ARAVA [see Adverse Reactions (6)] . The most frequent adverse events observed were diarrhea, abdominal pain, leukopenia, anemia, and elevated liver function tests.

In the event of a significant overdose or toxicity, perform an accelerated drug elimination procedure to accelerate elimination [see Warnings and Precautions (5.3)] .

Studies with both hemodialysis and CAPD (chronic ambulatory peritoneal dialysis) indicate that teriflunomide, the primary metabolite of leflunomide, is not dialyzable [see Clinical Pharmacology (12.3)] .

11 DESCRIPTION

ARAVA (leflunomide) is a pyrimidine synthesis inhibitor. The chemical name for leflunomide is N-(4´-trifluoromethylphenyl)-5-methylisoxazole-4-carboxamide. It has an empirical formula C 12 H 9 F 3 N 2 O 2 , a molecular weight of 270.2 and the following structural formula:

Chemical Structure

ARAVA is available for oral administration as tablets containing 10, 20, or 100 mg of active drug. Combined with leflunomide are the following inactive ingredients: colloidal silicon dioxide, crospovidone, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone, starch, talc, titanium dioxide, and yellow ferric oxide (20 mg tablet only).

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Leflunomide is an isoxazole immunomodulatory agent that inhibits dihydroorotate dehydrogenase (a mitochondrial enzyme involved in de novo pyrimidine synthesis) and has antiproliferative activity. Several in vivo and in vitro experimental models have demonstrated an anti-inflammatory effect.

12.3 Pharmacokinetics

Following oral administration, leflunomide is metabolized to an active metabolite, teriflunomide, which is responsible for essentially all of leflunomide’s in vivo activity. Plasma concentrations of the parent drug, leflunomide, have been occasionally seen at very low concentrations. Studies of the pharmacokinetics of leflunomide have primarily examined the plasma concentrations of the active metabolite, teriflunomide.

Chemical Structure
(click image for full-size original)

Absorption

Following oral administration, peak teriflunomide concentrations occurred between 6 to 12 hours after dosing. Due to the very long half-life of teriflunomide (18–19 days), a loading dose of 100 mg for 3 days was used in clinical studies to facilitate the rapid attainment of steady-state teriflunomide concentrations. Without a loading dose, it is estimated that attainment of steady-state plasma concentrations would require about two months of dosing. The resulting plasma concentrations following both loading doses and continued clinical dosing indicate that plasma teriflunomide concentrations are dose proportional.

Distribution

Teriflunomide is extensively bound to plasma protein (>99%) and is mainly distributed in plasma. The volume of distribution is 11 L after a single intravenous (IV) administration.

Elimination

Teriflunomide, the active metabolite of leflunomide, has a median half-life of 18 to 19 days in healthy volunteers. The elimination of teriflunomide can be accelerated by administration of cholestyramine or activated charcoal . Without use of an accelerated drug elimination procedure, it may take up to 2 years to reach plasma teriflunomide concentrations of less than 0.02 mg/L, due to individual variation in drug clearance [see Warnings and Precautions (5.3)] . After a single IV administration of the metabolite (teriflunomide), the total body clearance of teriflunomide was 30.5 mL/h.

Metabolism

In vitro inhibition studies in human liver microsomes suggest that cytochrome P450 (CYP) 1A2, 2C19 and 3A4 are involved in leflunomide metabolism. In vivo, leflunomide is metabolized to one primary (teriflunomide) and many minor metabolites. In vitro, teriflunomide is not metabolized by CYP450 or flavin monoamine oxidase enzymes. The parent compound is rarely detectable in plasma.

Excretion

Teriflunomide, the active metabolite of leflunomide, is eliminated by direct biliary excretion of unchanged drug as well as renal excretion of metabolites. Over 21 days, 60.1% of the administered dose is excreted via feces (37.5%) and urine (22.6%). After an accelerated elimination procedure with cholestyramine, an additional 23.1% was recovered (mostly in feces).

Studies with both hemodialysis and CAPD (chronic ambulatory peritoneal dialysis) indicate that teriflunomide is not dialyzable.

Gender. Gender has not been shown to cause a consistent change in the in vivo pharmacokinetics of teriflunomide.

Smoking. A population based pharmacokinetic analysis of the clinical trial data indicates that smokers have a 38% increase in clearance over nonsmokers; however, no difference in clinical efficacy was seen between smokers and nonsmokers.

Specific Populations

The potential effect of other drugs on ARAVA

  • Potent CYP and transporter inducers:

Following concomitant administration of a single dose of ARAVA to subjects receiving multiple doses of rifampin, teriflunomide peak concentrations were increased (~40%) over those seen when ARAVA was given alone [see Drug Interactions (7)].

  • An in vivo interaction study with ARAVA and cimetidine (nonspecific weak CYP inhibitor) has demonstrated a lack of a significant impact on teriflunomide exposure.

The potential effect of ARAVA on other drugs

  • CYP2C8 Substrates

There was an increase in mean repaglinide C max and AUC (1.7 and 2.4-fold, respectively), following repeated doses of teriflunomide and a single dose of 0.25 mg repaglinide, suggesting that teriflunomide is an inhibitor of CYP2C8 in vivo. The magnitude of interaction could be higher at the recommended repaglinide dose [see Drug Interactions (7)].

  • CYP1A2 Substrates

Repeated doses of teriflunomide decreased mean C max and AUC of caffeine by 18% and 55%, respectively, suggesting that teriflunomide may be a weak inducer of CYP1A2 in vivo.

  • OAT3 Substrates

There was an increase in mean cefaclor C max and AUC (1.43 and 1.54-fold, respectively), following repeated doses of teriflunomide, suggesting that teriflunomide is an inhibitor of organic anion transporter 3 (OAT3) in vivo [see Drug Interactions (7)].

  • BCRP and OATP1B1/1B3 Substrates

There was an increase in mean rosuvastatin C max and AUC (2.65 and 2.51-fold, respectively), following repeated doses of teriflunomide, suggesting that teriflunomide is an inhibitor of BCRP transporter and organic anion transporting polypeptide 1B1 and 1B3 (OATP1B1/1B3) [see Drug Interactions (7)].

  • Oral Contraceptives

There was an increase in mean ethinylestradiol C max and AUC 0–24 (1.58 and 1.54-fold, respectively) and levonorgestrel C max and AUC 0–24 (1.33 and 1.41-fold, respectively) following repeated doses of teriflunomide [see Drug Interactions (7)] .

  • Teriflunomide did not affect the pharmacokinetics of bupropion (a CYP2B6 substrate), midazolam (a CYP3A4 substrate), S-warfarin (a CYP2C9 substrate), omeprazole (a CYP2C19 substrate), and metoprolol (a CYP2D6 substrate).

Drug Interaction Studies

Drug interaction studies have been conducted with both ARAVA (leflunomide) and with its active metabolite, teriflunomide, where the metabolite was directly administered to the test subjects.

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