Fostemsavir
Fostemsavir is an HIV-1 attachment inhibitor used, in combination with other antiretroviral medicines, to treat HIV-1 infection in heavily treatment-experienced adults whose virus has become resistant to multiple other therapies.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Fostemsavir: Patient Information Guide
A plain-language walkthrough of Fostemsavir — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Fostemsavir is used to treat HIV-1 infection in adults who have exhausted many prior treatment options. Here is what the FDA-approved evidence supports:
- Rukobia (fostemsavir extended-release tablet), taken by mouth in combination with other antiretroviral medicines, is approved for HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 whose current regimen is failing — due to resistance, intolerance, or safety issues.
⚙️How it works▾
Fostemsavir is a prodrug, meaning it is inactive until the body converts it into its active form, temsavir. Temsavir is an HIV-1 attachment inhibitor — it binds to a protein on HIV's outer coat called gp120, which the virus normally uses to grab onto and enter CD4+ T cells (key immune cells). By blocking that attachment step, temsavir prevents the virus from getting inside the cell and making copies of itself.
This mechanism is distinct from most other HIV drugs, which act at later stages of the viral life cycle. That's why it can be effective even when the virus has developed resistance to multiple other antiretroviral classes. However, certain HIV subtypes — particularly subtype AE, common in Southeast Asia — show naturally reduced sensitivity to temsavir.
💊How it's taken▾
Rukobia extended-release tablets are taken by mouth twice daily, with or without food. The tablets must be swallowed whole — do not chew, crush, or split them, as this can affect how the medicine is released. Always take Rukobia alongside other antiretroviral medicines as prescribed.
- Can be taken with or without food at a standard meal; a high-fat meal significantly increases drug exposure, so consistency in how you take it may be helpful
- Swallow tablets whole — do not crush, chew, or split
- No dose adjustment is needed for kidney problems or liver impairment
🤒Side effects — in detail▾
Most side effects reported with Rukobia are mild to moderate. Common ones include:
- Nausea
- Diarrhea
- Headache
- Stomach pain or discomfort
- Upset stomach (dyspepsia)
- Fatigue or weakness
- Rash
- Sleep disturbances
- Drowsiness (somnolence)
- Vomiting
Serious reactions to watch for include signs of immune reconstitution syndrome (new or worsening infections or inflammation after starting therapy), liver enzyme elevations (especially with hepatitis B or C co-infection), and heart rhythm changes. Contact your doctor right away if you notice jaundice, severe fatigue, irregular heartbeat, or sudden flares of illness.
⚠️Warnings & precautions▾
- Immune reconstitution syndrome: As your immune system recovers with HIV treatment, it can overreact to previously hidden infections (like tuberculosis, CMV, or PCP), causing inflammation. Autoimmune conditions (e.g., Graves' disease, Guillain-Barré syndrome) can also emerge, sometimes months after starting therapy.
- Heart rhythm (QTc prolongation): Very high doses of Rukobia significantly prolong the QT interval — a measure of heart electrical activity — raising the risk of a dangerous arrhythmia called Torsade de Pointes. Use with caution if you have a history of QT prolongation, heart disease, or if you take other QT-prolonging drugs. Elderly patients are more vulnerable.
- Liver enzyme elevations with hepatitis co-infection: If you also have hepatitis B or C, your liver enzymes should be monitored regularly. Some cases reflected hepatitis B reactivation, especially when anti-hepatitis therapy was stopped.
- Drug interactions causing loss of HIV control: Several common medicines can dramatically lower Rukobia's effectiveness. Using Rukobia with strong CYP3A inducers can cause the HIV treatment to fail entirely.
🔀What it interacts with▾
Fostemsavir interacts with a number of commonly used medicines. Key interactions to know about:
- Strong CYP3A inducers (rifampin, carbamazepine, phenytoin, enzalutamide, mitotane, St. John's wort) — contraindicated; these drugs lower temsavir levels enough to cause HIV treatment failure
- Hepatitis C antivirals grazoprevir and voxilaprevir — Rukobia raises their levels, increasing risk of liver enzyme elevations; switch to an alternative HCV regimen if possible
- Ethinyl estradiol-containing oral contraceptives — Rukobia raises estrogen levels; limit daily ethinyl estradiol to no more than 30 mcg and be extra cautious if you have risk factors for blood clots
- Statins (rosuvastatin, atorvastatin, fluvastatin, pitavastatin, simvastatin) — Rukobia increases statin exposure; use the lowest effective statin dose and monitor for muscle pain or weakness
- QT-prolonging drugs — combining with Rukobia may add to the risk of dangerous heart rhythm problems; use with caution
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Do not take Rukobia if you have had a serious allergic reaction to fostemsavir or any component of the tablet
- Do not take Rukobia with strong CYP3A inducers (rifampin, carbamazepine, phenytoin, enzalutamide, mitotane, St. John's wort) — this combination is contraindicated
- Tell your doctor if you have hepatitis B or C — liver monitoring is recommended throughout treatment
- Tell your doctor about any heart conditions or history of QT interval prolongation before starting
- Tell your doctor about all medicines, vitamins, and herbal supplements you take
- Pregnancy: Human safety data are limited; animal studies showed fetal harm at very high doses. A pregnancy registry exists — call 1-800-258-4263 if you become pregnant while taking Rukobia
- Breastfeeding: Not recommended — HIV can be passed through breast milk, and drug exposure to the infant is also a concern
- Children: Safety and effectiveness in pediatric patients have not been established
- Older adults: Use with extra caution — elderly patients are more susceptible to QT interval effects and may have reduced kidney, liver, or heart function
- No dose adjustment is needed for kidney impairment, hemodialysis, or mild to severe liver impairment
🚑If you take too much▾
There is no specific antidote for a Rukobia overdose. If too much is taken, the heart rhythm (QT interval) should be monitored along with vital signs and overall clinical status. Because fostemsavir binds strongly to proteins in the blood, dialysis is unlikely to remove a meaningful amount of the drug.
📡Pharmacodynamics — effects in the body▾
At the recommended dose, Rukobia does not meaningfully prolong the QT interval — a measure of heart electrical activity. However, at four times the recommended daily dose, a clinically significant QT prolongation was observed, and the degree of prolongation tracked with temsavir blood levels. This means the heart rhythm risk is dose-dependent, which is why staying at the prescribed dose matters.
🔬Pharmacokinetics — how your body processes it▾
Fostemsavir is a prodrug that converts rapidly to its active form, temsavir, after being swallowed — fostemsavir itself is generally undetectable in the bloodstream. Temsavir reaches peak blood levels in about 2 hours and has a half-life of around 11 hours, supporting twice-daily dosing. It is primarily broken down by the liver (through esterases and the CYP3A4 enzyme pathway) and is about 88% bound to proteins in the blood. A high-fat meal substantially increases drug exposure compared to fasting, so consistency in how the medicine is taken may be relevant.
📦How to store it▾
Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F and 86°F) .
📄 Written from Fostemsavir’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Fostemsavir
146 supplements and herbal products have documented interactions with Fostemsavir in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 8
- Moderate · 98
- Minor · 40
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Fostemsavir — the kind of thing our pharmacy team would talk through with you at the counter.
Why am I being prescribed Rukobia instead of one of the more common HIV medications? ▾
Can I take Rukobia with or without food? ▾
What side effects should I watch out for? ▾
Are there any medicines I absolutely cannot take with Rukobia? ▾
Is it safe to take Rukobia if I'm pregnant or planning to get pregnant? ▾
I also have hepatitis C — is there anything special I need to know? ▾
Is Fostemsavir available over the counter? ▾
When was Fostemsavir first available? ▾
Who makes Fostemsavir? ▾
💬 Answers drafted from Fostemsavir’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Fostemsavir comes
Fostemsavir is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Extended-release tablet
How this form is used
- Rukobia is used in combination with other antiretrovirals to treat HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 who are failing their current regimen due to resistance, intolerance, or safety concerns
- Rukobia tablets are taken by mouth twice daily
- Rukobia can be taken with or without food
- Swallow Rukobia tablets whole — do not chew, crush, or split them
- Follow your prescriber's instructions for the full dosing schedule
📊 Fostemsavir across the U.S. market
How Fostemsavir appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Powder (1) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Fostemsavir is used
A general measure of how commonly Fostemsavir is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Fostemsavir is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Fostemsavir prescribed? Of the 1,597 medications we measure, Fostemsavir ranks #1,164 by Medicaid prescriptions — more than 27% of them.
Utilization by Fostemsavir product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
12 HR fostemsavir 600 MG Extended Release Oral Tablet
Summed across the 1 of 1 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2380549
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Fostemsavir, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 1 listed Fostemsavir NDCs with Medicaid activity.
🔍 Compare Fostemsavir products
A representative set of FDA-listed product records for Fostemsavir — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Extended-release tablet | ||||
| 600 mg | Oral | ViiV Healthcare Company × 3 listings | NDA | View NDC → |
| 💊Bulk drug substance | ||||
| 15 kg/15 kg | — | Piramal Healthcare UK Limited | BULK INGREDIENT | View NDC → |
Showing 4 of 4 products — FDA National Drug Code Directory. See every product, package size and price: browse all 4 Fostemsavir NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Fostemsavir — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Fostemsavir in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Fostemsavir went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 2380373 1 dose form · 1 strength
-
Dose form (SCDF) Extended Release Oral Tablet RxCUI 2380538In current FDA listingsClinical drug / strength (SCD) 12 HR fostemsavir 600 MGRxCUI 2380549
Look up RxCUI 2380373 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Fostemsavir is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Fostemsavir belongs to the Other antivirals class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. ViiV Healthcare Company is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.