Bylvay (Odevixibat)
Ileal bile acid transporter (IBAT) inhibitor for progressive familial intrahepatic cholestasis (PFIC)
Quick Facts About Bylvay
Key Takeaways About Bylvay
- First-in-class IBAT inhibitor: Bylvay (odevixibat) is a selective inhibitor of the ileal bile acid transporter, approved specifically for progressive familial intrahepatic cholestasis (PFIC)
- Weight-based dosing: Starting dose is 40 mcg/kg once daily, which may be increased to 120 mcg/kg/day (max 7,200 mcg) after 3 months if response is insufficient
- Flexible administration: Capsules can be swallowed whole or opened and sprinkled on soft food or into age-appropriate drinks, making it suitable for young children
- Regular monitoring required: Liver function tests, fat-soluble vitamin levels (A, D, E), and INR should be checked before and during treatment
- Most common side effects: Diarrhoea, vomiting, and abdominal pain are the most frequently reported adverse effects; adequate hydration is important
What Is Bylvay and What Is It Used For?
Bylvay (odevixibat) is a prescription medicine that reduces bile acid levels in the body by blocking their reabsorption in the intestine. It is used to treat progressive familial intrahepatic cholestasis (PFIC) in patients aged 6 months and older — a rare genetic liver disease that causes a build-up of bile acids, progressive liver damage, and severe itching.
Bylvay contains the active substance odevixibat, which belongs to a class of medicines known as ileal bile acid transporter (IBAT) inhibitors. Bile acids are essential components of bile, a digestive fluid produced by the liver and secreted into the intestines to aid in the digestion and absorption of dietary fats. Under normal circumstances, after performing their digestive function, approximately 95% of bile acids are reabsorbed in the terminal ileum (the final section of the small intestine) through a specific transport protein called the ileal bile acid transporter (IBAT), also known as the apical sodium-dependent bile acid transporter (ASBT).
Odevixibat selectively and reversibly blocks this IBAT transporter. By inhibiting the reabsorption of bile acids in the intestine, odevixibat allows them to pass through to the colon and be excreted in the faeces. This mechanism reduces the amount of bile acids being recycled back to the liver through the enterohepatic circulation, ultimately lowering the overall bile acid pool and decreasing serum bile acid concentrations.
Progressive familial intrahepatic cholestasis (PFIC) is a group of rare autosomal recessive genetic disorders that impair bile formation or bile flow from the liver. These conditions are characterised by progressive cholestasis — the accumulation of bile acids in the liver and bloodstream. The most prominent and debilitating symptom in many PFIC patients is severe, relentless pruritus (itching), which can be extremely distressing and significantly impair quality of life, particularly in children. Over time, PFIC leads to progressive liver damage, fibrosis, and eventually may necessitate liver transplantation.
By reducing circulating bile acid levels, Bylvay addresses the underlying pathophysiology of cholestasis-related pruritus and may slow the progression of liver damage. Clinical trials have demonstrated that odevixibat significantly reduces serum bile acid levels and improves pruritus scores compared to placebo in PFIC patients. The European Medicines Agency (EMA) granted marketing authorisation for Bylvay in July 2021, and the U.S. Food and Drug Administration (FDA) approved it in the same year, making it one of the first pharmacological treatments specifically developed for PFIC.
Bylvay acts locally in the gut and has minimal systemic absorption. It does not directly treat liver damage but reduces bile acid levels that contribute to disease progression and symptoms. If your condition does not improve after 6 months of continuous daily treatment, your doctor will recommend an alternative treatment approach.
What Should You Know Before Taking Bylvay?
Before starting Bylvay, you must discuss your complete medical history with your doctor, particularly any liver conditions, digestive disorders, or current medications. Bylvay is contraindicated in patients with known hypersensitivity to odevixibat or any of its excipients, and it is not recommended during pregnancy or in women of childbearing potential not using contraception.
Contraindications
You must not take Bylvay if you are allergic (hypersensitive) to odevixibat or any of the other ingredients in this medicine. The excipients include microcrystalline cellulose, hypromellose, titanium dioxide (E171), yellow iron oxide (E172), and in certain capsule strengths, red iron oxide (E172). If you have experienced any allergic reaction to these substances in the past, inform your doctor before starting treatment.
Warnings and Precautions
Talk to your doctor or pharmacist before taking Bylvay if any of the following apply to you:
- Complete absence or deficiency of BSEP function: If you have been diagnosed with a complete absence of or deficient bile salt export pump (BSEP) function, odevixibat may have reduced efficacy. BSEP is the protein responsible for exporting bile salts from liver cells into the bile ducts, and its complete absence (as seen in PFIC type 2 with certain biallelic mutations) means that interrupting the enterohepatic circulation may have a limited therapeutic effect.
- Severely impaired liver function: Patients with severe hepatic impairment should exercise caution, as the altered liver function may affect the overall benefit-risk profile of the treatment.
- Reduced gastrointestinal motility: Conditions that slow gastric or intestinal motility, or any disruption to the normal enterohepatic circulation of bile acids due to medications, surgical interventions, or other diseases besides PFIC, may decrease the effectiveness of odevixibat.
Diarrhoea monitoring: If you develop diarrhoea while taking Bylvay, it is important to maintain adequate fluid intake to prevent dehydration. Diarrhoea is one of the most common side effects and may include bloody stools or loose stools. Your doctor may adjust your dose or provide supportive measures if diarrhoea is severe or persistent.
Liver function monitoring: Elevated liver enzyme levels may be observed during treatment with Bylvay. Before starting treatment, your doctor will assess your liver function through blood tests. Regular liver function monitoring will continue throughout your treatment to detect any changes early and adjust therapy if needed.
Vitamin and coagulation monitoring: Because Bylvay reduces bile acid reabsorption, it can also affect the absorption of fat-soluble vitamins (vitamins A, D, and E). Before and during treatment, your doctor may check blood levels of these vitamins and supplement them if necessary. Your INR (international normalised ratio), which measures blood clotting ability, should also be monitored, as vitamin K absorption may be affected.
Children and Adolescents
Bylvay is approved for use in patients aged 6 months and older. It is not recommended for infants under 6 months of age because the safety and efficacy of the medicine have not been established in this age group. Clinical trials have included paediatric patients from 6 months of age, and dosing is weight-based to ensure appropriate exposure across different age groups and body sizes.
Interactions with Other Medicines
Tell your doctor or pharmacist if you are taking, have recently taken, or might take any other medicines. Treatment with odevixibat may affect the absorption of fat-soluble vitamins, including vitamins A, D, and E, as well as certain medications that rely on bile acid-mediated absorption pathways. Your doctor will take this into account when prescribing Bylvay alongside other treatments.
Pregnancy and Breastfeeding
If you are pregnant, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before using this medicine. Bylvay is not recommended during pregnancy or in women of childbearing potential not using contraception, as there is insufficient data on the effects of odevixibat on pregnancy outcomes.
It is not known whether odevixibat passes into breast milk or could affect a breastfed infant. Your doctor will help you decide whether to stop breastfeeding or to avoid treatment with Bylvay, weighing the benefits of breastfeeding for the child against the therapeutic benefits of Bylvay for the mother.
Driving and Using Machines
Bylvay has no or negligible influence on the ability to drive and use machines. No dose adjustments or special precautions are needed in this regard.
How Does Bylvay Interact with Other Drugs?
Bylvay may interact with fat-soluble vitamin supplements and medications that rely on bile acid-mediated absorption. Because odevixibat acts locally in the gut with minimal systemic absorption, the potential for systemic drug-drug interactions is limited, but monitoring of fat-soluble vitamin levels is recommended during treatment.
Odevixibat works locally in the gastrointestinal tract and is minimally absorbed into the systemic circulation. This means that its potential for systemic drug interactions is relatively low compared to many other medications. However, because it fundamentally alters bile acid homeostasis in the gut, certain interactions should be considered.
The primary concern relates to the absorption of fat-soluble substances. By reducing bile acid levels in the intestinal lumen, odevixibat may decrease the solubilisation and subsequent absorption of fat-soluble vitamins (A, D, E, and K) and potentially other lipophilic compounds. This is a class effect of IBAT inhibitors and is an expected pharmacological consequence of their mechanism of action.
| Interacting Substance | Type | Effect | Recommendation |
|---|---|---|---|
| Vitamin A supplements | Pharmacokinetic | Reduced absorption due to decreased bile acid-mediated solubilisation | Monitor serum levels; supplement as needed |
| Vitamin D supplements | Pharmacokinetic | Reduced absorption due to decreased bile acid-mediated solubilisation | Monitor serum levels; supplement as needed |
| Vitamin E supplements | Pharmacokinetic | Reduced absorption due to decreased bile acid-mediated solubilisation | Monitor serum levels; supplement as needed |
| Vitamin K / Warfarin | Pharmacokinetic | Potential decrease in vitamin K absorption, affecting anticoagulation | Monitor INR regularly; adjust warfarin dose if necessary |
| Ursodeoxycholic acid (UDCA) | Pharmacodynamic | Both affect bile acid metabolism; combined effects not fully characterised | Can be used concomitantly; monitor clinical response |
| Other bile acid sequestrants | Pharmacodynamic | Additive reduction of bile acid pool; may increase risk of fat-soluble vitamin deficiency | Use with caution; enhanced vitamin monitoring |
Patients taking Bylvay concurrently with any lipophilic medications should discuss potential absorption changes with their healthcare provider. Regular monitoring of therapeutic drug levels may be advisable for medications with narrow therapeutic windows that are absorbed via bile acid-dependent pathways.
What Is the Correct Dosage of Bylvay?
The recommended starting dose of Bylvay is 40 micrograms per kilogram of body weight, taken once daily in the morning. If the response is insufficient after 3 months, the dose may be increased to 120 micrograms per kilogram per day, up to a maximum of 7,200 micrograms once daily. The dose is the same for children (from 6 months), adolescents, and adults.
Always take Bylvay exactly as your doctor or pharmacist has told you. Treatment should be initiated and supervised by a physician experienced in the management of progressive cholestatic liver disease. The dose is calculated based on your body weight, and your doctor will determine the appropriate number of capsules and capsule strengths for your individual needs.
Starting Dose
40 micrograms (mcg) per kg body weight, taken once daily in the morning. This dose applies to all patients regardless of age (from 6 months onwards).
Dose Escalation
If the medicine has not shown sufficient effect after 3 months of treatment, the dose may be increased to 120 mcg per kg body weight once daily (maximum 7,200 mcg per day).
Treatment Duration
If the medicine has not improved your condition after 6 months of continuous daily treatment, your doctor will recommend an alternative treatment.
| Body Weight | Starting Dose (40 mcg/kg) | Increased Dose (120 mcg/kg) | Capsule Combination |
|---|---|---|---|
| 5 kg | 200 mcg | 600 mcg | 1 × 200 mcg / 1 × 600 mcg |
| 10 kg | 400 mcg | 1,200 mcg | 1 × 400 mcg / 1 × 1200 mcg |
| 15 kg | 600 mcg | 1,800 mcg | 1 × 600 mcg / 1 × 600 mcg + 1 × 1200 mcg |
| 30 kg | 1,200 mcg | 3,600 mcg | 1 × 1200 mcg / 3 × 1200 mcg |
| 60 kg | 2,400 mcg | 7,200 mcg | 2 × 1200 mcg / 6 × 1200 mcg |
How to Take Bylvay
Take all capsules once daily in the morning, with or without food. There are two ways to take Bylvay capsules:
- Swallow whole: Swallow capsules whole with a glass of water. The smaller capsules (400 mcg and 1,200 mcg) are primarily intended to be swallowed whole, but can also be opened if needed.
- Open and sprinkle: The larger capsules (200 mcg and 600 mcg) are primarily intended to be opened and sprinkled on soft food (such as yoghurt, applesauce, banana or carrot puree, chocolate pudding, rice pudding, or porridge at or below room temperature) or into an age-appropriate drink (breast milk, formula, or water). Hold the capsule horizontally at both ends, twist in opposite directions, pull apart, and empty the granules into the food or drink.
When mixing with a drink, add one teaspoon (5 ml) of liquid, let the granules soak for approximately 5 minutes, then use an oral dosing syringe to draw up and administer the mixture. The granules do not dissolve in liquids. Do not administer via a bottle or sippy cup as the granules cannot pass through the opening. Take the entire dose immediately after mixing — do not save the mixture for later use.
Missed Dose
If you miss a dose of Bylvay, do not take a double dose to make up for the missed one. Simply take your next dose at the usual time. Maintaining a regular daily schedule helps ensure consistent therapeutic effect.
Overdose
If you think you have taken too much Bylvay, tell your doctor immediately. Possible symptoms of overdose include diarrhoea and gastrointestinal discomfort. Treatment is supportive, focusing on managing symptoms and maintaining adequate hydration. There is no specific antidote for odevixibat overdose.
Do not stop taking Bylvay without first discussing it with your doctor. Abrupt discontinuation may lead to a rebound increase in bile acid levels and worsening of symptoms. Your doctor will advise you on the best course of action if treatment needs to be modified or stopped.
What Are the Side Effects of Bylvay?
Like all medicines, Bylvay can cause side effects, although not everyone gets them. The most common side effects are gastrointestinal in nature, including diarrhoea (which may include bloody stools), vomiting, and abdominal pain. An enlarged liver (hepatomegaly) is a common but less frequent side effect.
The side effect profile of Bylvay has been characterised through clinical trials involving patients with PFIC. The gastrointestinal effects are largely a consequence of the medicine's mechanism of action — by increasing bile acid excretion through the faeces, it can cause changes in bowel habits. Most side effects are manageable and tend to improve over time as the body adjusts to the altered bile acid balance.
It is important to distinguish between side effects and symptoms of the underlying disease. PFIC itself can cause abdominal discomfort, liver enlargement, and various gastrointestinal symptoms. Your doctor will monitor you regularly to differentiate between drug-related adverse effects and disease-related symptoms.
Very Common
- Diarrhoea (including bloody stools and loose stools)
- Vomiting
- Abdominal pain (stomach pain)
Common
- Hepatomegaly (enlarged liver)
Diarrhoea management: Diarrhoea is the most frequently reported side effect and is a direct result of increased bile acid excretion in the stool. If you experience diarrhoea, it is crucial to drink plenty of fluids to prevent dehydration, especially in young children and infants. Contact your doctor if diarrhoea is severe, persistent, or accompanied by signs of dehydration such as reduced urination, dry mouth, or excessive thirst.
Liver enzyme elevations: Although not classified as a common adverse event in frequency terms, elevated liver enzymes (transaminases) may be observed during routine monitoring. Your doctor will perform regular liver function tests to detect any changes early. In some cases, transient elevations normalise without the need for dose adjustment, but persistent or significant increases may require treatment modification.
Fat-soluble vitamin deficiency: Due to the mechanism of action, there is a potential for reduced absorption of fat-soluble vitamins (A, D, E, and K). While not always presenting as overt side effects, subclinical deficiencies can develop over time. Regular monitoring and supplementation as directed by your doctor help prevent these complications.
It is important to report any suspected side effects after the medicine has been authorised. This helps to continuously monitor the benefit-risk balance of the medicine. Healthcare professionals and patients can report suspected adverse reactions to their national medicines regulatory authority or through the EMA pharmacovigilance system.
How Should You Store Bylvay?
Store Bylvay in its original packaging to protect from light, at a temperature not exceeding 25°C (77°F). Keep the medicine out of sight and reach of children, and do not use it after the expiry date printed on the carton and bottle.
Proper storage of medicines is essential to maintain their efficacy and safety. Bylvay capsules are sensitive to light and should always be kept in the original plastic bottle with its tamper-evident, child-resistant polypropylene closure. Each bottle contains 30 hard capsules.
- Temperature: Store at or below 25°C (77°F). Do not freeze. Avoid exposing the capsules to excessive heat or direct sunlight.
- Light protection: Keep the capsules in the original packaging at all times. The outer carton and bottle provide the necessary light protection.
- Expiry date: Do not use Bylvay after the expiry date stated on the carton and bottle after “EXP”. The expiry date refers to the last day of that month.
- Disposal: Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines that are no longer needed. These measures help protect the environment.
If you notice any change in the appearance of the capsules, such as discolouration, cracking, or an unusual odour, do not use them and consult your pharmacist. Once the bottle has been opened, use the capsules within the period specified by your pharmacist or as indicated on the packaging, and ensure the bottle is always tightly sealed after each use.
What Does Bylvay Contain?
Bylvay capsules contain the active substance odevixibat (as sesquihydrate). The capsules are available in four strengths: 200 mcg, 400 mcg, 600 mcg, and 1,200 mcg. Inactive ingredients include microcrystalline cellulose and hypromellose.
Understanding the composition of your medicine can be important, particularly if you have known allergies or sensitivities to specific excipients. Below is a detailed breakdown of what each Bylvay capsule contains.
Active Substance
- Bylvay 200 mcg: Each hard capsule contains 200 micrograms of odevixibat (as sesquihydrate)
- Bylvay 400 mcg: Each hard capsule contains 400 micrograms of odevixibat (as sesquihydrate)
- Bylvay 600 mcg: Each hard capsule contains 600 micrograms of odevixibat (as sesquihydrate)
- Bylvay 1,200 mcg: Each hard capsule contains 1,200 micrograms of odevixibat (as sesquihydrate)
Inactive Ingredients (Excipients)
Capsule contents: Microcrystalline cellulose, hypromellose.
Capsule shell (200 mcg and 600 mcg): Hypromellose, titanium dioxide (E171), yellow iron oxide (E172).
Capsule shell (400 mcg and 1,200 mcg): Hypromellose, titanium dioxide (E171), yellow iron oxide (E172), red iron oxide (E172).
Printing ink: Shellac, propylene glycol, black iron oxide (E172).
Capsule Appearance
| Strength | Size | Appearance | Imprint |
|---|---|---|---|
| 200 mcg | Size 0 (21.7 mm × 7.64 mm) | Ivory opaque cap and white opaque body | A200 (black) |
| 400 mcg | Size 3 (15.9 mm × 5.82 mm) | Orange opaque cap and white opaque body | A400 (black) |
| 600 mcg | Size 0 (21.7 mm × 7.64 mm) | Ivory opaque cap and ivory opaque body | A600 (black) |
| 1,200 mcg | Size 3 (15.9 mm × 5.82 mm) | Orange opaque cap and orange opaque body | A1200 (black) |
All Bylvay capsules are packaged in a plastic bottle with a tamper-evident, child-resistant polypropylene closure. Each pack contains 30 hard capsules. The marketing authorisation holder is Ipsen Pharma, 70 rue Balard, 75015 Paris, France. The manufacturer is Almac Pharma Services Limited, Seagoe Industrial Estate, Portadown, Craigavon, County Armagh, BT63 5UA, United Kingdom (Northern Ireland).
Frequently Asked Questions About Bylvay
Bylvay (odevixibat) is used to treat progressive familial intrahepatic cholestasis (PFIC) in patients aged 6 months and older. PFIC is a rare genetic liver disease that causes a build-up of bile acids (cholestasis), leading to severe itching (pruritus) and progressive liver damage. Bylvay works by blocking the reabsorption of bile acids in the intestine, allowing them to be excreted in the stool, which reduces bile acid levels in the blood and alleviates symptoms.
Bylvay contains odevixibat, an ileal bile acid transporter (IBAT) inhibitor. It works locally in the gut by blocking the protein (IBAT/ASBT) that normally reabsorbs bile acids from the intestine back into the body. By preventing this reabsorption, bile acids pass through to the colon and are excreted in the faeces instead of being recycled to the liver. This reduces circulating bile acid levels and relieves cholestasis-associated symptoms, particularly severe pruritus.
The most common side effects of Bylvay (occurring in more than 1 in 10 patients) are diarrhoea (including bloody stool and soft stool), vomiting, and abdominal pain. A common side effect (occurring in up to 1 in 10 patients) is hepatomegaly (enlarged liver). If you experience persistent diarrhoea, it is important to drink plenty of fluids to prevent dehydration and contact your doctor.
Bylvay is not recommended during pregnancy or in women of childbearing potential who are not using contraception. There is limited data on the safety of odevixibat during pregnancy. If you are pregnant, think you may be pregnant, or are planning to have a baby, you should consult your doctor before using this medicine. Your doctor will weigh the potential risks and benefits to determine the most appropriate course of action.
Bylvay capsules should be taken once daily in the morning, with or without food. They can be swallowed whole with a glass of water, or opened and sprinkled on soft food (such as yoghurt, applesauce, or porridge at room temperature) or mixed into an age-appropriate drink (breast milk, formula, or water). When mixing with a drink, use an oral dosing syringe to administer the mixture. The entire dose must be taken immediately after preparation — do not save the mixture for later use.
Before starting and during treatment with Bylvay, your doctor will regularly monitor liver function through blood tests (liver enzymes). Levels of fat-soluble vitamins A, D, and E should also be checked, as Bylvay may reduce their absorption. INR (international normalised ratio), which measures blood clotting ability, should be monitored as well. These routine checks help ensure the medicine is working safely and allow early detection of any complications.
References
- European Medicines Agency (EMA). Bylvay (odevixibat) – Summary of Product Characteristics. EMA/EPAR. Available at: https://www.ema.europa.eu/en/medicines/human/EPAR/bylvay. Last updated 2025.
- U.S. Food and Drug Administration (FDA). Bylvay (odevixibat) Prescribing Information. FDA Label. Approved July 2021.
- Thompson RJ, Arnell H, Artan R, et al. Odevixibat treatment in progressive familial intrahepatic cholestasis: a randomised, placebo-controlled, phase 3 trial (PEDFIC 1). The Lancet Gastroenterology & Hepatology. 2022;7(9):830-842. doi:10.1016/S2468-1253(22)00178-8.
- Gonzales E, Hardikar W, Gorgé O, et al. Efficacy and safety of odevixibat in progressive familial intrahepatic cholestasis: long-term data from the PEDFIC 2 study. Journal of Hepatology. 2023;78(Suppl 1):S1-S2.
- European Association for the Study of the Liver (EASL). Clinical Practice Guidelines: Management of cholestatic liver diseases. Journal of Hepatology. 2024;80(2):S1-S35.
- Baker A, Kerkar N, Todorova L, et al. Systematic review of progressive familial intrahepatic cholestasis. Clinical Research in Hepatology and Gastroenterology. 2019;43(1):20-36. doi:10.1016/j.clinre.2018.07.010.
- World Health Organization (WHO). WHO Model List of Essential Medicines for Children. 9th List, 2023.
- Davit-Spraul A, Gonzales E, Baussan C, Jacquemin E. Progressive familial intrahepatic cholestasis. Orphanet Journal of Rare Diseases. 2009;4:1. doi:10.1186/1750-1172-4-1.
Editorial Team
This article was written by the iMedic Medical Editorial Team, a group of licensed physicians and pharmacists specialising in hepatology, gastroenterology, paediatric liver disease, and clinical pharmacology. All content is based on current evidence-based guidelines from EMA, FDA, EASL, and peer-reviewed medical literature.
All medical information is reviewed by our independent Medical Review Board, consisting of board-certified hepatologists and clinical pharmacologists with expertise in cholestatic liver diseases and rare disease therapeutics.
We follow the GRADE evidence framework and base our content on systematic reviews, randomised controlled trials (RCTs), and authoritative medical guidelines from EMA, FDA, EASL, and WHO.
iMedic receives no commercial funding from pharmaceutical companies. All content is independently produced and free from commercial influence or advertising.
This article is regularly reviewed and updated to reflect the latest clinical evidence, regulatory updates, and prescribing information changes from EMA and FDA.