Fir + Glycerol Phenylbutyrate
Glycerol Phenylbutyrate brand name: Ravicti.
We found no known interaction between Fir and Glycerol Phenylbutyrate in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Glycerol Phenylbutyrate states a food rule worth keeping to.
Fir and Glycerol Phenylbutyrate
We checked these two against our interaction database. Here is what we found.
No Known Interaction Found
We did not find a documented interaction between Glycerol Phenylbutyrate and Fir in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.
Worth understanding: our licensed dataset holds no drug-interaction record for Fir at all — not against Glycerol Phenylbutyrate, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.
If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.
Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.
Fir safety at a glance
Safety guidance is general; always confirm with your pharmacist or doctor for your situation.
Some Glycerol Phenylbutyrate Products Have a Food Rule — Fir Should Not Break It
At least one FDA label for a product containing Glycerol Phenylbutyrate says to take it with food. If you take Fir on an empty stomach out of habit, keep them separate — and take Glycerol Phenylbutyrate with a meal where the label says to.
This may not be true of your version. Food instructions belong to the product, not the ingredient: two Glycerol Phenylbutyrate products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.
Instruct patients to take glycerol phenylbutyrate oral liquid with food or formula and to administer directly into the mouth via oral syringe.
From the Dosage and Administration section of the FDA label we read for Glycerol Phenylbutyrate — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›
A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.
See Every Supplement That Interacts With Glycerol Phenylbutyrate
This page covers Fir only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Glycerol Phenylbutyrate page lists 17 supplements it has a documented interaction with, worst first, each one explained.
The most serious there right now: Activated Charcoal (major), Coffee Charcoal (moderate), European Mandrake (moderate), Glucomannan (moderate) and Guar Gum (moderate).
By severity: 1 major · 7 moderate · 9 minor.
From our pharmacist’s overview on the Glycerol Phenylbutyrate page
“Ravicti (glycerol phenylbutyrate) pulls ammonia out of the blood in people with urea cycle disorders, so a dose that never gets absorbed is not a small problem, it can let ammonia climb toward dangerous levels. That is why this list deserves real attention even though it is short.”
Reviewed by 2 · Jul 18, 2026
Taking Fir as Part of a Dietary Supplement Product? Check It for Interactions
We hold 2 real supplement products containing Fir, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fir. Even though Fir itself has no known interaction with Glycerol Phenylbutyrate, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:
Where Fir and Glycerol Phenylbutyrate Sit Against Everything Else
Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.
#1,169 of 1,452 supplements looked up here in the last 7 days
#286 of 2,830 medications looked up here in the last 7 days
Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.
Where does our data come from?
- Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions. Fir is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
- Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Fir reference on this page ↓
- Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Fir and Glycerol Phenylbutyrate records this page draws on were last updated June 22, 2026.
- What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
About Fir
What is Fir?
- Coughs and congestion
- Muscle and joint aches (topical)
- Aromatherapy and inhalation
- Minor wounds and skin care
- Cleaning and air freshening
Fir refers to several evergreen trees whose needles, resin, and essential oil are used traditionally for respiratory comfort, sore muscles, and aromatherapy. Solid human evidence for these uses is limited, and fir essential oil can be irritating or toxic if swallowed. Use it cautiously, mostly diluted and topical or inhaled, and check with a pharmacist or doctor first.
Pinaceae · Needles, young shoots, bark, resin, and essential oil · Essential oil, tea, syrup, extract, balms and inhalant rubs
An interaction check asks whether these two react with each other — it does not ask whether Fir is a good idea for someone in your situation. Here is what our Fir record says about it on its own.
Fir: dosing
There is no well-established standardized dose for fir. Products vary widely in strength, from teas to concentrated essential oils.The safest approach is to follow the directions on the product label and use the smallest amount that works. For the essential oil, dilute it in a carrier oil for skin use or use only a few drops for inhalation.
From our Fir monograph — the full record covers uses, side effects and every documented interaction.
About Glycerol Phenylbutyrate
What Is Glycerol Phenylbutyrate Used For?
Brand name: Ravicti
Glycerol phenylbutyrate oral liquid — available as the brand Ravicti and as a generic — is used for the long-term (chronic) management of urea cycle disorders (UCDs). UCDs are rare inherited conditions where the body cannot properly convert ammonia into urea, causing toxic ammonia levels to build up in the blood and brain.
It is used in patients whose ammonia cannot be controlled by a low-protein diet and/or amino acid supplements alone. It must always be used alongside dietary protein restriction and, in some cases, additional dietary supplements such as essential amino acids, arginine, or citrulline. It is not for treating a sudden, severe spike in ammonia (acute hyperammonemia), and its safety and effectiveness for N-acetylglutamate synthase (NAGS) deficiency have not been established.
Most-Reported Side Effects for Glycerol Phenylbutyrate
From FAERS, the FDA’s public side-effect reporting system (1,358 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.
Other Drugs & Fir
Browse every other medication we’ve checked against Fir — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
No interaction 2,829 drugs checked — show the list
We also checked Fir against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Sertraline ›
- Testosterone ›
- Losartan Potassium ›
- Ivermectin ›
- Metoprolol ›
- Rivaroxaban ›
- Aspirin ›
- Rosuvastatin ›
- Acetaminophen ›
- Escitalopram ›
- Abemaciclib ›
- Clopidogrel ›
- Tadalafil ›
- Atorvastatin ›
- Docusate ›
- Tirzepatide ›
- Valacyclovir ›
- Ibuprofen ›
- Methamphetamine ›
- Hydroxyurea ›
- Warfarin Sodium ›
- Semaglutide ›
- Sumatriptan ›
- Prednisone ›
- Propranolol ›
- Lisdexamfetamine ›
- Metformin ›
- Amoxicillin ›
- Lisinopril ›
- Bupropion ›
- Amitriptyline ›
- Methotrexate ›
- Bendamustine ›
- Acyclovir ›
- Doxycycline ›
- Amphetamine ›
- Fluoxetine ›
- Isotretinoin ›
- Lamotrigine ›
- Pregabalin ›
- Azithromycin ›
- Acetaminophen, Codeine ›
- Gabapentin ›
- Amlodipine Besylate ›
- Dextroamphetamine ›
- Clonazepam ›
- Methylene Blue ›
- Omeprazole ›
- Quetiapine ›
- Letrozole ›
- Duloxetine ›
- Naproxen ›
- Buspirone ›
- Citalopram ›
- Ciprofloxacin ›
Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Fir list.
Fir References
The 1 sources that drive our Fir monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Fir is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.
- Balsam Fir / Conifer needles and oils (herbal information) — MedlinePlus Source
Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
Taking Fir and Glycerol Phenylbutyrate Together: Common Questions
Is it safe to take Fir with Glycerol Phenylbutyrate?
Should I take Fir and Glycerol Phenylbutyrate at the same time of day?
Does Glycerol Phenylbutyrate interact with any supplements?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.