Leucovorin oral suspension is a compounded, prescription liquid form of leucovorin calcium — also called folinic acid. Folinic acid is a reduced, already-active form of folate (vitamin B9). Because it is a liquid, a dose can be measured in milliliters with an oral syringe instead of split from a tablet, which matters a great deal when the dose is based on body weight or is divided over the day.
Leucovorin is FDA-approved as 5 mg and 25 mg tablets and as an injection. There is no FDA-approved oral liquid. A licensed compounding pharmacy prepares the suspension in the concentration your prescriber orders. Compounded preparations are not FDA-approved, and a valid prescription is required.
How does it work?
Folate has to be in an active, reduced form before the body can use it to build DNA and to make the methyl groups the brain and blood cells depend on. Ordinary folate and folic acid must first be converted by an enzyme called dihydrofolate reductase (DHFR). Folinic acid is different: it is 5-formyl-tetrahydrofolate, historically called “citrovorum factor,” and it is already reduced, so it does not need DHFR to become usable.
That single difference explains both of its main jobs. First, when methotrexate blocks DHFR, folinic acid supplies the active folate that the blocked enzyme can no longer produce — this is what “leucovorin rescue” means. Second, folinic acid can get into the central nervous system by routes that depend less on the folate receptor alpha (FRα) transport system at the choroid plexus, the doorway that normally carries folate from the blood into the spinal fluid.
That second point is the reason leucovorin is used in cerebral folate deficiency (CFD). In CFD, the level of active folate in the spinal fluid (CSF 5-MTHF) is low even though the folate level in the blood is normal, because FRα transport is blocked — by variants in both copies of the FOLR1 gene, by autoantibodies against FRα, or by mitochondrial disease. High-dose folinic acid can partly get around that block and raise folate levels in the spinal fluid.
What is it used for?
Leucovorin has several long-established uses. It is FDA-approved to rescue normal cells after high-dose methotrexate and to treat methotrexate overdose or impaired methotrexate elimination — these uses are well established and supported by strong evidence. It is also used for megaloblastic anemia caused by folate deficiency when oral folate cannot be used, and as an adjunct to fluorouracil (5-FU) in colorectal cancer.
As of March 10, 2026, leucovorin calcium tablets (Wellcovorin) are FDA-approved for cerebral folate transport deficiency in adults and children with a confirmed FOLR1 variant. A compounded oral suspension is not an FDA-approved product, but prescribers order one when a patient with this or a related condition needs a liquid.
Leucovorin is also discussed as a possible treatment for language and communication difficulties in some autistic children, and this is where care is needed. The best study to date is a randomized, double-blind, placebo-controlled trial by Frye and colleagues published in Molecular Psychiatry in 2018: 48 children received 2 mg/kg/day (up to 50 mg/day) or placebo for 12 weeks. Verbal communication scores improved by 5.7 standardized points (95% confidence interval 1.0–10.4; Cohen's d 0.70), and by 7.3 points in children who tested positive for FRα autoantibodies (d 0.91). The rest of the supporting work is largely open-label or retrospective. This is promising, but it is not established treatment.
How do the concentrations compare?
The suspension is compounded at whatever concentration your prescriber orders. The concentration does not change how the medicine works — it changes how many milliliters make up a dose. Lower concentrations suit small infant doses that need to be measured precisely; higher concentrations keep the volume manageable for larger doses. The table below is for education only.
| Concentration | Notes |
|---|---|
| 2.5 mg/mL | A dilute strength; useful for very small or finely divided doses, typically dispensed in larger bottles |
| 5 mg/mL | A common pediatric strength; balances precise measuring against bottle size |
| 10 mg/mL | The most frequently dispensed strength; the 30 mL starting size uses this concentration |
| 15 mg/mL | Keeps volume down for mid-size doses |
| 20 mg/mL | For larger doses, so each dose stays a small number of milliliters |
| Custom | Other concentrations as your prescriber orders |
Concentrations are described for education only and are not a statement that any strength is better for a particular person. Your prescriber selects the concentration, the dose, and the schedule.
How is it used?
Use it exactly as your prescriber directs. Shake the bottle well before every dose, then draw the dose up with the oral syringe the pharmacy provides — kitchen spoons are not accurate enough for a weight-based dose. If the dose is given through a feeding tube, follow the flushing instructions your prescriber or nurse gave you.
For reference, the FDA-approved dosing for Wellcovorin tablets in FOLR1-confirmed cerebral folate transport deficiency starts at 1 to 2 mg/kg per day, with a maximum of 8.5 mg/kg per day for patients under 40 kg or 330 mg per day for patients 40 kg and over. Single doses are preferably 25 mg or less and should not exceed 75 mg, given once daily or divided into as many as six doses a day. Dividing a dose into small pieces several times a day is exactly the situation where a liquid is easier and more accurate than tablets.
In the autism research setting, the dosing described in published studies has been roughly 0.5 to 2 mg/kg per day divided into two doses, up to about 50 mg per day. The AAP notes that clinicians who choose to prescribe generally start low — around 5 mg twice daily or less — and increase gradually over several weeks; the published trials ran 12 weeks. This is descriptive only and is not a recommendation. Do not start, stop, or change a dose on your own. A Bayview pharmacist is happy to answer questions about your prescription, but dosing decisions belong to your prescriber.
Side effects & safety
Leucovorin is generally well tolerated. The prescribing information warns about hypersensitivity reactions, including anaphylaxis and urticaria (hives), which can involve itching, rash, shortness of breath, or rigors. Get emergency care for a rash with swelling, trouble breathing, or any reaction that comes on quickly.
The AAP also flags irritability or behavioral activation, trouble sleeping, and stomach upset. These are among the more common reasons a trial is stopped or a dose is lowered — tell your prescriber if you see them.
Leucovorin also interacts with two other medicines in important ways. It can antagonize antifolate therapy, so it must not be taken alongside — or added around — methotrexate used for rheumatologic conditions unless the prescriber specifically directs it. And it increases the toxicity of fluorouracil (5-FU). Tell every one of your prescribers that you are taking leucovorin.
Who should not use it?
Leucovorin is not appropriate for everyone. It should not be used by anyone with a known allergy to leucovorin, folinic acid, or folic acid. It should not be taken with methotrexate prescribed for a rheumatologic condition, or adjusted around methotrexate dosing, without direct instruction from the prescriber, because it can work against that therapy. Anyone receiving fluorouracil needs their oncology team to manage leucovorin, since it increases 5-FU toxicity. Tell your prescriber the full health history, all allergies, and every medication and supplement the person takes — including folic acid — so they can determine whether leucovorin is appropriate.
How should it be stored?
Store it exactly as directed on the label the pharmacy assigns, and protect it from light. Shake well before each dose, keep the bottle tightly closed, and use only the oral syringe provided. Keep it out of the reach of children and do not share it with anyone. Your label carries a beyond-use date assigned under USP <795> standards — do not use the suspension after that date, and dispose of any unused medication as your pharmacist directs.
Why is this compounded?
The approved dosage forms of leucovorin are 5 mg and 25 mg tablets and an injection. There is no FDA-approved oral liquid at all. That leaves a real gap for infants, young children, people with dysphagia or other trouble swallowing, and anyone who takes medication through a G-tube — and for the divided, weight-based dosing that leucovorin regimens often call for, where a tablet simply cannot be split accurately enough.
Bayview compounds the suspension in a non-aqueous (anhydrous) vehicle. That is a stability decision, not a preference: leucovorin degrades in water, so a water-based liquid would not hold up. As a 503A compounding pharmacy, Bayview prepares each order to the prescriber's concentration as a nonsterile oral liquid under USP <795> standards — not USP <797>, which governs sterile preparations — using quality ingredients. Compounded preparations are not FDA-approved.
Clinical details for prescribers
Regulatory status. Leucovorin is not a controlled substance. FDA-approved dosage forms are 5 mg and 25 mg tablets and injection; there is no FDA-approved oral liquid. On 2025-09-22 FDA announced it was initiating approval of leucovorin for cerebral folate deficiency (press release: “FDA Takes Action to Make a Treatment Available for Autism Symptoms”), working with GSK to relabel Wellcovorin. On 2026-03-10 FDA approved Wellcovorin (leucovorin calcium) tablets for the treatment of cerebral folate transport deficiency in adult and pediatric patients with a confirmed variant in the folate receptor 1 gene (FOLR1-CFTD). FDA did not approve leucovorin for autism; use in FRα-autoantibody-positive autism without FOLR1 confirmation remains off-label. Compounded preparations are not FDA-approved.
Pharmacology. Leucovorin calcium is folinic acid (5-formyl-tetrahydrofolate, “citrovorum factor”), a reduced folate that bypasses DHFR. This underlies both methotrexate rescue and CNS entry by routes less dependent on FRα-mediated transport at the choroid plexus, permitting partial circumvention of the transport block in CFD (biallelic FOLR1 variants, FRα autoantibodies, or mitochondrial disease).
Formulation & SIG. Compounded nonsterile oral suspension in a non-aqueous (anhydrous) vehicle — leucovorin hydrolyzes in water — commonly 2.5, 5, 10, 15, and 20 mg/mL; custom concentrations available; volumes from 30 mL to 360 mL. Prepared under USP <795> standards. Beyond-use date is assigned per USP <795> and printed on the dispensing label. Typical SIG format: state mg per dose and frequency, plus the concentration to be compounded.
Dosing reference:
- FOLR1-CFTD (Wellcovorin label): 1–2 mg/kg/day initially; max 8.5 mg/kg/day (<40 kg) or 330 mg/day (≥40 kg); single doses preferably ≤25 mg and not >75 mg; once daily or divided up to 6 times daily — divided dosing is where a liquid is most useful
- Autism research dosing (descriptive only): 0.5–2 mg/kg/day divided BID, max ~50 mg/day; AAP describes starting at ~5 mg BID or lower with titration over weeks; trials ran 12 weeks
Diagnostics & monitoring:
- CSF 5-MTHF by lumbar puncture is the diagnostic standard for cerebral folate deficiency
- FOLR1 sequencing identifies the FDA-approved indication (FOLR1-CFTD)
- Serum FRAA testing is a laboratory-developed test under CLIA only; per AAP, “there are no FDA cleared or approved tests for FRAAs”
- Obtain baseline vitamin B12 and folate; folate can mask B12 deficiency while neurologic injury progresses
- Monitor response with validated scales (SRS, ABC, Vineland) over at least 12 weeks; monitor for behavioral activation, irritability, and insomnia
Safety & interactions:
- Label warns of hypersensitivity including anaphylaxis and urticaria (pruritus, rash, dyspnea, rigors)
- AAP flags irritability/behavioral activation and GI upset
- Antagonizes antifolate therapy — do not co-administer with or adjust around rheumatologic methotrexate without prescriber direction; increases 5-FU toxicity
Evidence in autism. Frye RE, et al., Molecular Psychiatry 2018: 12-week randomized double-blind placebo-controlled trial, n=48, 2 mg/kg/day up to 50 mg/day; verbal communication improved 5.7 standardized points (95% CI 1.0–10.4; Cohen's d 0.70) and 7.3 points in FRAA-positive children (d 0.91). Supporting literature is largely open-label or retrospective. Per AAP, “current evidence is insufficient to support prescribing leucovorin for autism in the absence of CFD.”
Ordering: e-prescribe or send a prescription to Bayview Pharmacy, 3844 Post Rd, Warwick, RI 02886 (NCPDP 4106882, fax 401-284-4506). Background: FDA approval announcement (March 10, 2026); AAP FAQs for prescribing clinicians.
This is a prescription compounded medication and is not FDA-approved. This information is educational and is not medical advice. Bayview Pharmacy does not provide consultations and does not determine whether a medication is appropriate; your prescriber decides that and sets the concentration, dose, and schedule.
