Glentek (Riluzole)
Glutamate Antagonist for Amyotrophic Lateral Sclerosis (ALS)
Quick Facts About Glentek
Key Takeaways About Glentek (Riluzole)
- First approved ALS treatment: Riluzole was the first drug specifically approved for ALS and remains the most widely prescribed treatment for the disease worldwide
- Extends survival: Clinical trials have demonstrated that riluzole extends survival by approximately 2–3 months, with greater benefit when treatment is started early in the disease course
- Liver monitoring required: Regular liver function tests are mandatory – monthly for the first 3 months, then every 3 months for the first year, and periodically thereafter
- Twice-daily dosing: Take one 50 mg tablet every 12 hours at the same times each day, preferably on an empty stomach for optimal absorption
- Oral suspension available: For patients with swallowing difficulties (dysphagia), a common ALS symptom, a 5 mg/ml oral suspension formulation is available
What Is Glentek and What Is It Used For?
Glentek contains riluzole, a medicine that acts on the nervous system to slow the progression of amyotrophic lateral sclerosis (ALS). It is the first drug approved specifically for ALS and works by reducing the toxic effects of excess glutamate on motor neurons in the brain and spinal cord.
Glentek is used to treat patients with amyotrophic lateral sclerosis (ALS), a devastating progressive neurodegenerative disease also known as motor neuron disease (MND) or, in some countries, Lou Gehrig's disease. ALS affects the nerve cells (motor neurons) responsible for sending instructions from the brain and spinal cord to the muscles. As these motor neurons degenerate and die, the muscles they control gradually weaken, waste away (atrophy), and eventually become paralysed.
The active substance in Glentek, riluzole, is a benzothiazole compound that exerts its neuroprotective effects through multiple mechanisms. Its primary action is to inhibit the release of glutamate, a chemical messenger (neurotransmitter) in the brain and spinal cord. In ALS, there is evidence that glutamate accumulates to excessive levels around motor neurons, causing a process known as excitotoxicity – essentially overstimulating the nerve cells until they are damaged and destroyed. By blocking glutamate release, riluzole helps to reduce this excitotoxic damage and slow the rate of motor neuron degeneration.
In addition to inhibiting glutamate release, riluzole also blocks certain glutamate receptors (NMDA and kainate receptors) on the postsynaptic neuron and stabilises voltage-dependent sodium channels in an inactivated state. These combined actions provide a broad neuroprotective effect that reduces the excitotoxic cascade. However, the exact mechanism by which riluzole extends survival in ALS patients is not fully understood, and the disease's pathophysiology is complex and multifactorial.
Clinical trials have demonstrated that riluzole extends survival by approximately 2–3 months compared with placebo. While this may seem modest, it represents a clinically meaningful benefit for patients and families living with ALS, particularly when treatment is initiated early in the disease course. Riluzole appears to be more effective in the bulbar-onset form of ALS (where symptoms begin in the muscles controlling speech and swallowing) and when started while the patient still has relatively preserved respiratory function.
Riluzole was first approved for the treatment of ALS in 1995, making it the first drug ever approved specifically for this disease. It is included on the World Health Organization's List of Essential Medicines, underscoring its global importance. Glentek is manufactured by Glenmark Pharmaceuticals and is approved across the European Economic Area (EEA), including Denmark, Germany, Sweden, and the Netherlands.
It is important to understand that riluzole does not cure ALS, nor does it reverse existing nerve damage. It slows the progression of the disease but cannot restore lost motor function. Treatment with riluzole is typically part of a comprehensive, multidisciplinary ALS management plan that may include physiotherapy, occupational therapy, speech therapy, nutritional support, respiratory management, and psychological support.
What Should You Know Before Taking Glentek?
Before starting Glentek, your doctor must check your liver function, as riluzole can cause liver damage. Do not take Glentek if you have liver disease, are pregnant, or are breastfeeding. Tell your doctor about all other medications you are taking, as some drugs can interact with riluzole.
Contraindications
You should not take Glentek if any of the following apply to you:
- Allergy to riluzole or any of the other ingredients in Glentek (listed in the Contents section below) – symptoms may include rash, itching, swelling, or difficulty breathing
- Liver disease or elevated blood levels of liver enzymes (transaminases) above 3 times the upper limit of normal – riluzole is extensively metabolised by the liver and can cause further liver damage
- Pregnancy – the safety of riluzole has not been established in pregnant women, and animal studies have raised concerns about potential harm to the developing foetus
- Breastfeeding – it is not known whether riluzole passes into breast milk, and the potential risk to the nursing infant has not been assessed
Warnings and Precautions
Talk to your doctor before taking Glentek if you have or have had any of the following:
- Liver problems: If your skin or the whites of your eyes turn yellow (jaundice), you experience generalised itching, feel nauseous, or have unexplained vomiting, these may be signs of liver damage. Contact your doctor immediately. Your doctor will perform liver function tests before starting treatment, monthly for the first 3 months, every 3 months for the first year, and periodically thereafter
- Kidney problems: If your kidneys do not function well, your doctor may need to adjust your dose or monitor you more closely, as impaired renal function can affect the elimination of riluzole metabolites
- Fever or signs of infection: Riluzole can, in rare cases, reduce the number of white blood cells (neutropenia), which are essential for fighting infections. If you develop a fever, sore throat, mouth ulcers, or other signs of infection, contact your doctor immediately. A blood test may be needed to check your white blood cell count
Liver function tests (ALT/GPT and AST/GOT) must be measured before starting treatment, every month for the first 3 months, every 3 months during the remainder of the first year, and periodically thereafter. Treatment must be discontinued if ALT or AST levels rise to 5 times the upper limit of normal. Patients should be advised to report any febrile illness to their prescribing physician.
Children and Adolescents
Glentek is not recommended for use in children and adolescents under 18 years of age, as there is insufficient data on the safety and efficacy of riluzole in this age group. ALS is extremely rare in the paediatric population, and no clinical trials have been conducted in patients under 18.
Pregnancy and Breastfeeding
You must not take Glentek if you are pregnant or think you might be pregnant. Animal reproduction studies have shown adverse effects on embryonic and foetal development. The safety of riluzole during human pregnancy has not been established. If you are of childbearing potential, you should use effective contraception during treatment with riluzole.
You must not take Glentek if you are breastfeeding. It is not known whether riluzole is excreted in human breast milk, but given its lipophilic nature and extensive tissue distribution, excretion into breast milk is considered likely. If treatment with riluzole is necessary, breastfeeding should be discontinued.
Driving and Operating Machinery
Glentek may cause dizziness or light-headedness in some patients. If you experience these effects, you should not drive or operate machinery until the symptoms have resolved. It is your responsibility to assess whether you are fit to drive or perform tasks requiring alertness. The underlying condition (ALS) itself may also affect your ability to drive safely, and you should discuss this with your doctor.
Other Medicines and Glentek
Tell your doctor if you are taking, have recently taken, or might take any other medicines. This includes prescription medicines, over-the-counter products, and herbal supplements. Some medications can interact with riluzole by affecting how it is metabolised in the liver (see the Drug Interactions section below for details).
How Does Glentek Interact with Other Drugs?
Riluzole is primarily metabolised by the liver enzyme CYP1A2. Drugs that inhibit CYP1A2 (such as fluvoxamine and ciprofloxacin) can significantly increase riluzole blood levels, while CYP1A2 inducers (such as rifampicin and cigarette smoke) can reduce its effectiveness. Always inform your doctor about all medications you are taking.
Riluzole is extensively metabolised in the liver, primarily by the cytochrome P450 enzyme CYP1A2. Any drug or substance that inhibits or induces this enzyme can alter riluzole blood levels, potentially increasing toxicity or reducing efficacy. Additionally, riluzole is a substrate of multiple CYP enzymes to a lesser extent, including CYP2D6, CYP2C19, CYP3A4, and CYP2E1. The following tables summarise the most clinically important interactions.
Major Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Fluvoxamine | SSRI antidepressant | Potent CYP1A2 inhibitor – can increase riluzole blood levels by up to 5-fold | Avoid combination; if essential, close monitoring and dose reduction are required |
| Ciprofloxacin | Fluoroquinolone antibiotic | Moderate CYP1A2 inhibitor – can significantly increase riluzole exposure | Use with caution; monitor for increased side effects and liver enzymes |
| Rifampicin | Antibiotic (TB treatment) | Potent CYP1A2 inducer – can significantly reduce riluzole blood levels and efficacy | Avoid combination if possible; alternative antibiotics should be considered |
| Smoking (tobacco) | CYP1A2 inducer | Polycyclic aromatic hydrocarbons in cigarette smoke induce CYP1A2, reducing riluzole levels | Patients should be advised to stop smoking; if they continue, higher riluzole levels may occur on cessation |
Moderate Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Theophylline | Bronchodilator | Also metabolised by CYP1A2 – competition for metabolism may alter levels of both drugs | Monitor theophylline levels; dose adjustment may be needed |
| Caffeine | Stimulant | CYP1A2 substrate – riluzole may inhibit caffeine metabolism, leading to increased caffeine effects | Moderate caffeine intake during riluzole treatment |
| Omeprazole | Proton pump inhibitor | Mild CYP1A2 inducer – may modestly reduce riluzole blood levels | Monitor clinical response; dose adjustment usually not required |
| Carbamazepine / Phenytoin | Anticonvulsants | CYP enzyme inducers – may reduce riluzole blood levels through enhanced metabolism | Monitor for reduced riluzole efficacy; consider dose adjustment |
| Other hepatotoxic drugs | Various | Additive risk of liver damage when combined with riluzole | More frequent liver function monitoring; avoid unnecessary hepatotoxic medications |
If you consume charcoal-grilled food regularly, be aware that charcoal grilling produces polycyclic aromatic hydrocarbons that can induce CYP1A2, potentially reducing riluzole blood levels. Similarly, cruciferous vegetables (broccoli, Brussels sprouts, cauliflower) in large quantities may have mild CYP1A2-inducing effects, though this is generally not clinically significant.
What Is the Correct Dosage of Glentek?
The recommended dose of Glentek is one 50 mg tablet twice daily, taken every 12 hours at the same times each day. The dose is the same for all adults, regardless of age or body weight. Do not take more than 100 mg per day.
Always take Glentek exactly as your doctor has instructed. Do not change the dose without first consulting your doctor. If you are unsure about the correct dose, ask your doctor or pharmacist for advice.
Adults
Amyotrophic Lateral Sclerosis (ALS)
Recommended dose: 50 mg (one tablet) twice daily
Dosing interval: Every 12 hours, at the same times each day (e.g., morning and evening)
Maximum daily dose: 100 mg (two tablets per day)
The tablets should be swallowed whole with a glass of water. There is no dose titration – the full dose of 50 mg twice daily is started from the beginning of treatment. Treatment should be continued for as long as it provides clinical benefit, as determined by your treating neurologist.
Oral Suspension (for patients with swallowing difficulties)
Recommended dose: 10 ml (50 mg) twice daily using the oral syringe provided
Concentration: 5 mg/ml
The oral suspension formulation (marketed as Teglutik) is particularly important for ALS patients, as dysphagia (difficulty swallowing) is a common and progressive symptom of the disease. It allows patients to continue riluzole treatment when they can no longer swallow tablets safely.
Children and Adolescents
Not Recommended
Glentek is not recommended for patients under 18 years of age, as safety and efficacy data are lacking in the paediatric population. ALS is exceedingly rare in children and adolescents.
Elderly Patients
No dose adjustment is required for elderly patients based on age alone. However, liver and kidney function may decline with age, and your doctor may perform more frequent monitoring. The pharmacokinetic profile of riluzole in elderly patients is not significantly different from that in younger adults, though clearance may be slightly reduced.
Patients with Liver or Kidney Impairment
Glentek is contraindicated in patients with liver disease or pre-existing elevated transaminase levels. For patients with mild hepatic impairment, the doctor may decide to treat with close monitoring and more frequent liver function tests. In patients with renal impairment, no specific dose adjustment is recommended, but monitoring may be intensified as metabolite accumulation is possible.
Missed Dose
If you forget to take a dose of Glentek, skip the missed dose and take the next dose at the usual time. Do not take a double dose to make up for the one you missed. Missing occasional doses should not significantly affect the overall therapeutic benefit, but regular, consistent dosing is important for maintaining steady blood levels of riluzole.
Overdose
Taking too much Glentek can be dangerous. Symptoms of overdose may include nausea, vomiting, drowsiness, and liver toxicity. There is no specific antidote for riluzole overdose. If you suspect an overdose, seek immediate medical attention by calling your local emergency services or poison control centre. Treatment is supportive and symptomatic, with particular attention to liver function and respiratory status.
What Are the Side Effects of Glentek?
The most common side effects of Glentek are fatigue, nausea, and elevated liver enzymes. Common side effects include dizziness, tingling in the mouth, increased heart rate, vomiting, diarrhoea, and headache. Serious side effects requiring immediate medical attention include signs of liver damage and fever (possible low white blood cell count).
Like all medicines, Glentek can cause side effects, although not everybody gets them. Some side effects may be difficult to distinguish from the symptoms of ALS itself, particularly fatigue and muscle weakness. If any side effect becomes severe or persistent, or if you notice effects not listed here, contact your doctor or pharmacist.
- Fever (elevated temperature) – Glentek can reduce the number of white blood cells, increasing your risk of serious infections. Your doctor may need to perform a blood test to check your white blood cell count
- Yellowing of the skin or eyes (jaundice), generalised itching, nausea, or vomiting – these may be signs of liver disease (hepatitis). Your doctor should perform liver function tests urgently
- Persistent cough or difficulty breathing – in rare cases, riluzole has been associated with interstitial lung disease, a serious condition affecting the lungs
- Severe abdominal pain – may indicate inflammation of the pancreas (pancreatitis)
Very Common
May affect more than 1 in 10 people
- Fatigue (tiredness)
- Nausea (feeling sick)
- Elevated liver enzymes (transaminases – detected by blood test)
Common
May affect up to 1 in 10 people
- Dizziness
- Tingling or numbness in the mouth (oral paraesthesia)
- Increased heart rate (tachycardia)
- Vomiting
- Diarrhoea
- Headache
- Abdominal pain
- Drowsiness (somnolence)
- Pain (general)
Uncommon
May affect up to 1 in 100 people
- Anaemia (low red blood cell count)
- Allergic reactions (hypersensitivity)
- Pancreatitis (inflammation of the pancreas)
Frequency Not Known
Cannot be estimated from available data
- Skin rash
- Hepatitis (inflammation of the liver)
- Interstitial lung disease
- Neutropenia (low white blood cell count)
It is important to note that many ALS patients experience symptoms such as fatigue, weakness, and difficulty breathing as part of their underlying disease. If you are uncertain whether a new symptom is a side effect of Glentek or a progression of ALS, discuss this with your neurologist. Reporting suspected side effects is important and helps authorities continuously monitor the benefit-risk balance of the medicine.
How Should You Store Glentek?
Store Glentek tablets at room temperature in the original packaging, out of the reach and sight of children. No special storage conditions are required. Do not use after the expiry date printed on the packaging.
Keep Glentek out of the sight and reach of children. Do not use this medicine after the expiry date stated on the carton and blister after "EXP". The expiry date refers to the last day of the stated month. No special storage conditions are required for this medicine – store at room temperature away from excessive heat and moisture.
Do not throw away any medicines via household waste or wastewater. Ask your pharmacist how to dispose of medicines you no longer use. These measures help to protect the environment from pharmaceutical contamination.
For the oral suspension formulation, specific storage instructions may differ. Check the label on the bottle for any additional storage requirements, such as "store in the refrigerator" or "use within X days of opening". Always check the manufacturer's instructions provided with the oral suspension.
What Does Glentek Contain?
Each Glentek film-coated tablet contains 50 mg of riluzole as the active substance. The tablets are white to off-white, capsule-shaped, with bevelled edges, marked "381" on one side and "G" on the other.
Active Ingredient
The active substance is riluzole. Each film-coated tablet contains 50 mg riluzole. Riluzole is a benzothiazole derivative with the molecular formula C8H5F3N2OS and a molecular weight of 234.2 g/mol.
Inactive Ingredients (Excipients)
The other ingredients in the tablet core are: anhydrous calcium hydrogen phosphate, microcrystalline cellulose, croscarmellose sodium, anhydrous colloidal silicon dioxide, and magnesium stearate. The film coating contains: hypromellose, titanium dioxide (E171), and macrogol 400. These are standard pharmaceutical excipients used to ensure proper tablet formation, stability, and absorption.
Tablet Appearance and Packaging
Glentek 50 mg tablets: White to off-white, capsule-shaped, film-coated tablets with bevelled edges. They are marked with "381" on one side and "G" on the other.
Glentek tablets are supplied in PVC/PVDC/aluminium blister packs containing 28, 56, or 98 film-coated tablets. Not all pack sizes may be available in every country.
Manufacturer
Glentek is manufactured by Glenmark Pharmaceuticals s.r.o., Fibichova 143, 566 17 Vysoké Mýto, Czech Republic. The marketing authorisation is held by Glenmark Arzneimittel GmbH, Industriestr. 31, 82194 Gröbenzell, Germany. The medicine is approved within the European Economic Area under the name Glentek in Denmark, Germany, Sweden, and the Netherlands.
How Does Riluzole Work in the Body?
Riluzole works through multiple neuroprotective mechanisms: it inhibits glutamate release from presynaptic neurons, blocks glutamate receptors, and stabilises sodium channels. These actions reduce excitotoxic damage to motor neurons in ALS. It is rapidly absorbed after oral administration with a half-life of 9–15 hours.
The pathophysiology of ALS is complex and not fully understood, but one of the most well-established contributing factors is glutamate-mediated excitotoxicity. Glutamate is the most abundant excitatory neurotransmitter in the central nervous system. Under normal conditions, it plays essential roles in neuronal communication, learning, and memory. However, when glutamate accumulates to excessive levels – as occurs in ALS – it overstimulates motor neurons through sustained activation of glutamate receptors, leading to a cascade of intracellular events that ultimately cause neuronal injury and death.
Riluzole addresses this excitotoxic mechanism through three complementary actions:
- Inhibition of glutamate release: Riluzole blocks the presynaptic release of glutamate, reducing the amount of this neurotransmitter available to overstimulate motor neurons
- Glutamate receptor blockade: Riluzole has non-competitive antagonist activity at NMDA (N-methyl-D-aspartate) and kainate glutamate receptors, further reducing excitotoxic signalling
- Sodium channel stabilisation: By stabilising voltage-dependent sodium channels in their inactivated state, riluzole reduces repetitive neuronal firing, which in turn reduces glutamate release
Some research also suggests that riluzole may have additional neuroprotective properties beyond glutamate modulation, including effects on intracellular signalling pathways and potential modulation of neurotrophic factor expression. However, these additional mechanisms are less well characterised.
Pharmacokinetic Profile
After oral administration, riluzole is rapidly and well absorbed from the gastrointestinal tract. Peak plasma concentrations are reached within approximately 60–90 minutes. The absolute bioavailability is approximately 60%, with first-pass metabolism accounting for the remainder. Food reduces the rate and extent of absorption, so riluzole is ideally taken on an empty stomach, though this is not a strict requirement.
Riluzole is highly protein-bound (approximately 97%), primarily to albumin and lipoproteins. It distributes extensively into tissues. The drug is extensively metabolised in the liver, primarily by CYP1A2, to several metabolites, the main one being N-hydroxyriluzole. This metabolite has some pharmacological activity but is considered to contribute minimally to the overall therapeutic effect.
The elimination half-life of riluzole is approximately 9–15 hours, supporting twice-daily dosing. Approximately 90% of the dose is excreted as metabolites in the urine, with less than 1% excreted unchanged. There is considerable interindividual variability in riluzole pharmacokinetics, influenced by CYP1A2 activity, which can be affected by genetic polymorphisms, smoking status, and concurrent medications.
Frequently Asked Questions About Glentek
Glentek contains riluzole and is used to treat amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND). Riluzole is the first drug approved specifically for ALS and works by reducing the release of glutamate, which can damage motor neurons when present in excessive amounts. It has been shown to extend survival by approximately 2–3 months.
Riluzole works by inhibiting the release of glutamate from nerve endings in the brain and spinal cord. In ALS, excessive glutamate causes excitotoxicity, which damages and kills motor neurons. Riluzole blocks this process through multiple mechanisms: it inhibits glutamate release, blocks certain glutamate receptors (NMDA and kainate), and stabilises voltage-dependent sodium channels. This neuroprotective effect slows the rate of motor neuron degeneration.
The most common side effects are fatigue, nausea, and elevated liver enzymes (transaminases). Common side effects affecting up to 1 in 10 people include dizziness, tingling in the mouth, increased heart rate, vomiting, diarrhoea, headache, abdominal pain, and drowsiness. Serious but less common effects include liver damage (hepatitis) and reduced white blood cell count. Regular blood tests are required to monitor liver function throughout treatment.
Regular blood tests are essential because riluzole can cause liver damage and reduce white blood cell counts. Liver function tests (ALT and AST) should be performed before starting treatment, monthly for the first 3 months, every 3 months for the remainder of the first year, and periodically thereafter. If liver enzymes rise above 5 times the upper limit of normal, treatment must be stopped. Blood tests also monitor for neutropenia, which increases infection risk.
No, riluzole does not cure ALS. There is currently no cure for amyotrophic lateral sclerosis. However, riluzole is the first and most established treatment shown to slow disease progression. Clinical trials have demonstrated it extends survival by approximately 2–3 months. It works best when started early and is used as part of a comprehensive multidisciplinary management plan including physiotherapy, speech therapy, nutritional support, and respiratory management.
Riluzole can be taken with or without food, though food may reduce its absorption. For optimal blood levels, it is best taken on an empty stomach. The tablets should be taken every 12 hours at the same times each day, typically morning and evening. For patients with swallowing difficulties (dysphagia), which is common in ALS, an oral suspension formulation (5 mg/ml) is available as an alternative.
References
This article is based on the following international medical guidelines and peer-reviewed sources. All medical claims have evidence level 1A, the highest quality of evidence based on systematic reviews of randomised controlled trials.
- Bensimon G, Lacomblez L, Meininger V. A controlled trial of riluzole in amyotrophic lateral sclerosis. ALS/Riluzole Study Group. New England Journal of Medicine. 1994;330(9):585–591. doi:10.1056/NEJM199403033300901
- Lacomblez L, Bensimon G, Leigh PN, et al. Dose-ranging study of riluzole in amyotrophic lateral sclerosis. The Lancet. 1996;347(9013):1425–1431. doi:10.1016/S0140-6736(96)91680-3
- Miller RG, Mitchell JD, Moore DH. Riluzole for amyotrophic lateral sclerosis (ALS)/motor neuron disease (MND). Cochrane Database of Systematic Reviews. 2012;(3):CD001447. doi:10.1002/14651858.CD001447.pub3
- European Medicines Agency (EMA). Riluzole – Summary of Product Characteristics. EMA product information database. Accessed January 2026.
- National Institute for Health and Care Excellence (NICE). Motor neurone disease: assessment and management. NICE guideline [NG42]. Updated 2022.
- American Academy of Neurology (AAN). Practice Parameter: The care of the patient with amyotrophic lateral sclerosis (an evidence-based review). Neurology. 2009;73(15):1218–1226.
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd list. Geneva: WHO; 2023.
- British National Formulary (BNF). Riluzole. NICE BNF monograph. Accessed January 2026.
Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, a group of licensed specialist physicians with expertise in neurology, clinical pharmacology, and neurodegenerative diseases.
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Board-certified physicians specialising in neurology and clinical pharmacology with documented academic and clinical experience in neurodegenerative disease management.
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