EXSERVAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EXSERVAN (EXSERVAN).
Exservan (riluzole) is a benzothiazole derivative that modulates glutamatergic neurotransmission. Its mechanism of action involves inhibition of glutamate release, inactivation of voltage-dependent sodium channels, and interference with neurotransmitter binding to excitatory amino acid receptors.
| Metabolism | Riluzole is extensively metabolized in the liver via N-hydroxylation (CYP1A2) and glucuronidation (UGT1A1, UGT1A3, UGT1A8, UGT1A9, UGT2B7). |
| Excretion | Primarily renal excretion as unchanged drug: 80% excreted unchanged in urine; approximately 20% as metabolites; biliary/fecal <5%. |
| Half-life | Terminal elimination half-life is approximately 3–4 hours in patients with normal renal function; prolonged in renal impairment (up to 8–10 hours in ESRD). |
| Protein binding | Approximately 40% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Volume of distribution (Vd) is approximately 1.0 L/kg; moderate distribution suggests limited tissue binding. |
| Bioavailability | Sublingual film (EXSERVAN): bioavailability is 100% relative to oral disintegrating tablet; oral tablets exhibit approximately 30% bioavailability due to extensive first-pass metabolism. |
| Onset of Action | Oral: onset occurs within 15–30 minutes; sublingual film (EXSERVAN): onset within 5–15 minutes due to rapid absorption via oral mucosa. |
| Duration of Action | Duration of clinical effect is 3–5 hours for sublingual film; may be shorter with oral tablets (2–4 hours). Individual variability exists; careful titration required. |
| Molecular Weight | 197.2 |
Adults: 15 mg orally once daily in the morning; increase to 30 mg after 2 weeks if needed. Maximum 30 mg/day.
| Dosage form | FILM |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (eGFR<30 mL/min/1.73 m²). |
| Liver impairment | Mild hepatic impairment (Child-Pugh A): 15 mg once daily. Moderate to severe hepatic impairment (Child-Pugh B or C): not recommended. |
| Pediatric use | Not approved for use in pediatric patients. |
| Geriatric use | No specific dose adjustment; use with caution due to increased sensitivity and potential for adverse effects. |
| 1st trimester | EXSERVAN (levodopa/carbidopa) is not recommended in the first trimester due to potential teratogenic effects observed in animal studies. Use only if benefit outweighs risk. |
| 2nd trimester | Limited data; use with caution. Animal studies show developmental toxicity but human data insufficient. |
| 3rd trimester | May be used if clinically necessary. Monitor for potential effects on fetal development and maternal side effects. |
Clinical note
Comprehensive clinical and safety monograph for EXSERVAN (EXSERVAN).
| Placental transfer | Levodopa crosses the placenta; carbidopa is likely transferred to a lesser extent. Animal studies show fetal exposure. |
| Breastfeeding | Levodopa is excreted into breast milk in small amounts. Clinical significance unknown. Carbidopa likely excreted but data lacking. Caution advised; monitor infant for potential effects (e.g., drowsiness, agitation). |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to levodopa, carbidopa, or any componentConcurrent use with nonselective MAO inhibitors (e.g., MAO-A and MAO-B) or within 14 days of stopping such therapyNarrow-angle glaucoma (for carbidopa component)Suspected undiagnosed skin lesions (history of melanoma)
| Precautions | Hepatotoxicity: Elevation of serum aminotransferases; monitor LFTs regularly. Discontinue if ALT > 5x ULN or clinical jaundice develops., Neutropenia: Rare; monitor CBC with differential., Interstitial lung disease: Discontinue if respiratory symptoms develop., Embryo-fetal toxicity: May cause fetal harm; advise females of reproductive potential to use effective contraception., Renal impairment: Not recommended if CrCl < 30 mL/min. |
| Food/Dietary | High-fat meals can decrease absorption; take on an empty stomach (1 hour before or 2 hours after meals). Avoid alcohol due to potential hepatotoxicity. No known specific food interactions beyond fat content. |
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| Lactation Rating | L3 |
| Teratogenic Risk | Pregnancy Category C. No adequate studies in pregnant women. In animal studies, oxycodone (active metabolite) caused fetal harm at high doses. First trimester: risk of neural tube defects (?). Second/third trimesters: risk of neonatal opioid withdrawal syndrome, respiratory depression, low birth weight, preterm birth. |
| Fetal Monitoring | Monitor for fetal growth restriction via ultrasound; assess for neonatal abstinence syndrome after delivery; monitor maternal respiratory status and sedation. |
| Fertility Effects | Opioids may impair fertility by disrupting hypothalamic-pituitary-gonadal axis, causing irregular menstruation and decreased libido. Reversible upon discontinuation. |
| Clinical Pearls | Exservan (riluzole oral film) is indicated for ALS. The oral film formulation bypasses swallowing issues; place on tongue for rapid dissolution. Monitor liver function (ALT/AST) monthly for 3 months, then quarterly; discontinue if elevated >5x ULN. Avoid concomitant hepatotoxic drugs. Neutropenia risk; instruct patients to report fever or infection. Slow acetylators may have higher exposure; no dose adjustment recommended but caution. |
| Patient Advice | Place the film on your tongue and let it dissolve; do not chew or swallow whole. · Take Exservan at the same time each day, at least 1 hour before or 2 hours after a meal. · Avoid alcohol and limit consumption of high-fat meals as they may affect absorption. · Report any signs of liver problems (yellowing skin/eyes, dark urine, abdominal pain) or infection (fever, sore throat) immediately. · Do not stop taking Exservan without consulting your doctor. |