Rilutek (Page 2 of 4)

6.2 Postmarketing Experience

The following adverse reactions have been identified during postapproval use of RILUTEK. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Acute hepatitis and icteric toxic hepatitis [see Warnings and Precautions (5.1)]
Renal tubular impairment


7.1 Agents that may Increase Riluzole Blood Concentrations

CYP1A2 inhibitors

Co-administration of RILUTEK (a CYP1A substrate) with CYP1A2 inhibitors was not evaluated in a clinical trial; however, in vitro findings suggest an increase in riluzole exposure is likely. The concomitant use of strong or moderate CYP1A2 inhibitors (e.g., ciprofloxacin, enoxacin, fluvoxamine, methoxsalen, mexiletine, oral contraceptives, thiabendazole, vemurafenib, zileuton) with RILUTEK may increase the risk of RILUTEK-associated adverse reactions [see Clinical Pharmacology (12.3)].

7.2 Agents that may Decrease Riluzole Plasma Concentrations

CYP1A2 inducers

Co-administration of RILUTEK (a CYP1A substrate) with CYP1A2 inducers was not evaluated in a clinical trial; however, in vitro findings suggest a decrease in riluzole exposure is likely. Lower exposures may result in decreased efficacy [see Clinical Pharmacology (12.3)].

7.3 Hepatotoxic Drugs

Clinical trials in ALS patients excluded patients on concomitant medications which were potentially hepatotoxic (e.g., allopurinol, methyldopa, sulfasalazine). RILUTEK-treated patients who take other hepatotoxic drugs may be at an increased risk for hepatotoxicity [see Warnings and Precautions (5.1)].


8.1 Pregnancy

Risk Summary

There are no studies of RILUTEK in pregnant women, and case reports have been inadequate to inform the drug-associated risk. The background risk for major birth defects and miscarriage in patients with amyotrophic lateral sclerosis is unknown. In the U.S. general population, the background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

In studies in which riluzole was administered orally to pregnant animals, developmental toxicity (decreased embryofetal/offspring viability, growth, and functional development) was observed at clinically relevant doses [see Data]. Based on these results, women should be advised of a possible risk to the fetus associated with use of RILUTEK during pregnancy.


Animal Data

Oral administration of riluzole (3, 9, or 27 mg/kg/day) to pregnant rats during the period of organogenesis resulted in decreases in fetal growth (body weight and length) at the high dose. The mid dose, a no-effect dose for embryofetal developmental toxicity, is approximately equal to the recommended human daily dose (RHDD, 100 mg) on a mg/m2 basis. When riluzole was administered orally (3, 10, or 60 mg/kg/day) to pregnant rabbits during the period of organogenesis, embryofetal mortality was increased at the high dose and fetal body weight was decreased and morphological variations increased at all but the lowest dose tested. The no-effect dose (3 mg/kg/day) for embryofetal developmental toxicity is less than the RHDD on a mg/m2 basis. Maternal toxicity was observed at the highest dose tested in rat and rabbit.

When riluzole was orally administered (3, 8, or 15 mg/kg/day) to male and female rats prior to and during mating and to female rats throughout gestation and lactation, increased embryofetal mortality and decreased postnatal offspring viability, growth, and functional development were observed at the high dose. The mid dose, a no-effect dose for pre- and postnatal developmental toxicity, is approximately equal to the RHDD on a mg/m2 basis.

8.2 Lactation

Risk Summary

It is not known if riluzole is excreted in human milk. Riluzole or its metabolites have been detected in milk of lactating rats. Women should be advised that many drugs are excreted in human milk and that the potential for serious adverse reactions in nursing infants from RILUTEK is unknown.

8.3 Females and Males of Reproductive Potential

In rats, oral administration of riluzole resulted in decreased fertility indices and increases in embryolethality [see Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

Safety and effectiveness of RILUTEK in pediatric patients have not been established.

8.5 Geriatric Use

In clinical studies of RILUTEK, 30% of patients were 65 years and over. 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.

8.6 Hepatic Impairment

Patients with mild [Child-Pugh’s (CP) score A] or moderate (CP score B) hepatic impairment had increases in AUC compared to patients with normal hepatic function. Thus, patients with mild or moderate hepatic impairment may be at increased risk of adverse reactions. The impact of severe hepatic impairment on riluzole exposure is unknown.

Use of RILUTEK is not recommended in patients with baseline elevations of serum aminotransferases greater than 5 times upper limit of normal or evidence of liver dysfunction (e.g., elevated bilirubin) [Clinical Pharmacology (12.3)].

8.7 Japanese Patients

Japanese patients are more likely to have higher riluzole concentrations. Consequently, the risk of adverse reactions may be greater in Japanese patients [see Clinical Pharmacology (12.3)].


Reported symptoms of overdose following ingestion of RILUTEK ranging from 1.5 to 3 grams (30 to 60 times the recommended dose) included acute toxic encephalopathy, coma, drowsiness, memory loss, and methemoglobinemia.

No specific antidote for the treatment of RILUTEK overdose is available. For current information on the management of poisoning or overdosage, contact the National Poison Control Center at 1-800-222-1222 or


RILUTEK (riluzole) is a member of the benzothiazole class. The chemical designation for riluzole is 2-amino-6-(trifluoromethoxy)benzothiazole. Its molecular formula is C8 H5 F3 N2 OS, and its molecular weight is 234.2. The chemical structure is:

Chemical Structure
(click image for full-size original)

RILUTEK is a white to slightly yellow powder that is very soluble in dimethylformamide, dimethylsulfoxide, and methanol; freely soluble in dichloromethane; sparingly soluble in 0.1 N HCl; and very slightly soluble in water and in 0.1 N NaOH.

Each film-coated tablet for oral use contains 50 mg of riluzole and the following inactive ingredients: anhydrous dibasic calcium phosphate, colloidal silicon dioxide, croscarmellose sodium, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, and titanium dioxide.

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