Axumin: Uses, Dosage & Side Effects

What Is Axumin and What Is It Used For?

Axumin contains the active substance fluciclovine (18F), also known by its chemical name anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid (abbreviated FACBC). It is a synthetic amino acid analog, meaning it is a molecule that resembles the natural amino acids used by cells for growth and function, but with a crucial modification: it is labeled with the radioactive isotope fluorine-18. This radiolabel allows the molecule to be detected by a PET scanner, which creates detailed three-dimensional images of the body showing where the tracer has accumulated.

The fundamental principle behind Axumin lies in the biology of prostate cancer cells. Cancer cells, in general, have increased metabolic demands compared to normal tissue. In particular, prostate cancer cells overexpress certain amino acid transporters on their surface – primarily LAT-1 (L-type amino acid transporter 1) and ASCT2 (alanine-serine-cysteine transporter 2). These transporters actively pump amino acids into the cell to support rapid protein synthesis and cellular proliferation. Because fluciclovine structurally mimics natural amino acids, it is recognized and transported into cells by these same pathways. However, once inside the cell, fluciclovine is not significantly metabolized or incorporated into proteins. Instead, it accumulates, creating a detectable signal. Areas of high tracer uptake on the PET scan suggest the presence of metabolically active prostate cancer cells.

Axumin was approved by the U.S. Food and Drug Administration (FDA) in May 2016 and by the European Medicines Agency (EMA) in May 2017. Its primary clinical indication is for PET imaging in men with suspected prostate cancer recurrence based on elevated blood PSA levels following prior curative treatment. Prostate cancer recurrence after radical prostatectomy (surgical removal of the prostate) or definitive radiation therapy is a significant clinical challenge. A rising PSA – termed biochemical recurrence – is often the first sign that the cancer has returned, but conventional imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy frequently fail to localize the site of recurrence, especially at low PSA levels (below 1.0 ng/mL). This is where molecular imaging with PET tracers like Axumin provides a critical advantage.

By identifying the location and extent of recurrent disease, Axumin PET/CT helps clinicians make more informed treatment decisions. For example, if the recurrence is localized to the prostate bed (the area where the prostate was removed), the patient may benefit from salvage radiation therapy targeted to that specific area. If the scan reveals disease in distant lymph nodes or bones, a systemic approach with hormonal therapy or other treatments may be more appropriate. In clinical studies, Axumin PET/CT has been shown to change the intended management in a substantial proportion of patients – up to 60% in some series – highlighting its significant clinical impact.

It is important to understand that Axumin is a diagnostic tool only. It does not treat prostate cancer, nor does it cure or slow the progression of disease. Its sole purpose is to provide imaging information that supports clinical decision-making. Axumin is always used in combination with a PET or PET/CT scanner and is administered in a nuclear medicine department or PET imaging center under the supervision of a qualified nuclear medicine physician or radiologist.

What Should You Know Before Receiving Axumin?

Contraindications

There are relatively few absolute contraindications to Axumin administration, as it is a diagnostic agent with a favorable safety profile. The primary contraindication is hypersensitivity (allergy) to fluciclovine (18F) or to any of the excipients in the formulation. If you have previously experienced an allergic reaction to Axumin, you must not receive it again.

Axumin is specifically developed and approved for imaging in men with suspected prostate cancer recurrence. It has not been evaluated or approved for use in women, and there are no data supporting its use for the detection of other cancer types in routine clinical practice, although research into additional indications is ongoing.

Warnings and Precautions

Before receiving Axumin, inform your doctor or nuclear medicine specialist about the following:

• Risk of image misinterpretation: Axumin uptake is not specific to prostate cancer. Other conditions with increased amino acid metabolism – such as certain benign tumors, infections, inflammation, bone fractures, degenerative bone disease, and other malignancies – can also show increased tracer uptake (false positives). Conversely, some prostate cancer lesions may not accumulate enough tracer to be detected (false negatives), particularly very small metastases or low-grade tumors. Clinical correlation with other diagnostic findings is always necessary.
• Kidney impairment: Although fluciclovine is primarily eliminated through minimal renal excretion (only about 3% in the first 4 hours) and no dose adjustment is generally required for renal impairment, you should inform your doctor if you have significant kidney problems.
• Hepatic impairment: The liver shows physiological uptake of fluciclovine. While no specific dose adjustment is required for liver impairment, inform your doctor if you have liver disease, as this may affect image interpretation.
• Adequate hydration: You should be well hydrated before and after the scan. After the procedure, frequent urination is encouraged to reduce radiation exposure to the bladder.
• Sodium content: Axumin solution contains sodium. One dose may contain up to 39 mg of sodium per vial, which may be relevant for patients on a sodium-restricted diet.

Patient Preparation for the Scan

Proper patient preparation is essential for obtaining high-quality Axumin PET images. Inadequate preparation can lead to suboptimal images and potential misinterpretation. Your nuclear medicine center will provide specific instructions, which typically include the following:

• Fasting: You must not eat or drink anything (except small amounts of water) for at least 4 hours before the injection. This reduces background amino acid transport activity in normal tissues, improving the contrast between tumor and normal tissue.
• Avoid strenuous exercise: You must avoid any significant physical exercise for at least 24 hours before the scan. Muscular activity markedly increases amino acid uptake in skeletal muscles, which can interfere with image interpretation and potentially obscure tumor uptake, particularly in the pelvic region.
• Empty the bladder: You should urinate immediately before the scan begins. The bladder can accumulate radioactivity that may obscure adjacent structures in the pelvis, including the prostate bed, which is a key area of interest.
• Avoid high-protein meals: In the 24 hours before the scan, it is advisable to avoid meals very high in protein, as elevated circulating amino acids can compete with fluciclovine for transporter uptake.

Pregnancy and Breastfeeding

Axumin is indicated exclusively for use in men with suspected recurrent prostate cancer. It has not been studied in women, and there are no data on its use during pregnancy or breastfeeding. If a female family member or caregiver is pregnant, she should be informed about radiation precautions and should avoid prolonged close contact with the patient for a period after the scan, as advised by the nuclear medicine department.

Children and Adolescents

There is no relevant use of Axumin in the pediatric population. Prostate cancer does not occur in children, and the safety and efficacy of Axumin have not been established in patients under 18 years of age.

How Does Axumin Interact with Other Drugs?

Axumin has a distinct pharmacological profile compared to therapeutic drugs. It is administered as a single intravenous injection at a very low mass dose (the actual mass of fluciclovine in a diagnostic dose is in the microgram range), and it is not metabolized by cytochrome P450 enzymes or other common drug-metabolizing pathways. For these reasons, traditional pharmacokinetic drug-drug interactions – where one drug alters the blood levels of another – are not expected with Axumin.

However, certain clinical factors can influence the accuracy of Axumin PET imaging and should be considered:

Factors That May Affect Scan Accuracy

Because Axumin is not a therapeutic agent and does not interact with other drugs at the pharmacokinetic level, you do not need to stop any of your regular medications before the scan unless specifically instructed by your nuclear medicine physician. However, always provide a complete list of all medications, supplements, and herbal products you are taking so that the interpreting physician can account for any potential influence on image findings.

It is also worth noting that Axumin should not be confused with other PET tracers such as fluorodeoxyglucose (FDG), which measures glucose metabolism, or PSMA-based tracers (such as 68Ga-PSMA-11 or 18F-DCFPyL), which target the prostate-specific membrane antigen. Each tracer has different uptake mechanisms and clinical applications, and they are not interchangeable without careful clinical consideration.

What Is the Correct Dosage of Axumin?

Axumin is not a medication that you take at home or self-administer. It is always prepared and administered in a nuclear medicine department or PET imaging center by trained professionals who are authorized to handle radioactive materials. The dosing is standardized and does not require adjustment based on body weight, age, or organ function in most cases.

Adults

Timing of Imaging

Elderly

Renal and Hepatic Impairment

Children

Missed Dose and Overdose

Because Axumin is administered as a single injection in a clinical setting, a missed dose is not applicable in the traditional sense. If the procedure is cancelled or postponed, a new appointment will be scheduled. There is no issue with “missing” a dose.

In the event of an overdose (administration of a higher-than-intended radioactivity), the absorbed radiation dose to the patient will be proportionally higher. The nuclear medicine physician will encourage the patient to drink fluids and urinate frequently to accelerate clearance and reduce the overall radiation exposure. No specific pharmacological antidote exists for Axumin overdose; management is supportive, focused on reducing radiation exposure through enhanced hydration and frequent voiding.

What Are the Side Effects of Axumin?

Like all medicines, Axumin can cause side effects, although not everybody experiences them. Because Axumin is administered as a single low-mass diagnostic injection and is not a therapeutic agent, the overall incidence and severity of side effects are considerably lower than those associated with most therapeutic drugs. In clinical trials involving over 900 patients, the majority of reported adverse events were mild and self-limiting.

Side effects are classified below by frequency based on available clinical data:

Radiation-Related Considerations

The primary safety consideration with Axumin relates to radiation exposure rather than chemical toxicity. Like all radiopharmaceuticals, Axumin exposes the patient and, to a lesser extent, those in close contact with the patient to ionizing radiation. The estimated effective dose from a standard 370 MBq injection in a 70 kg adult is approximately 5.3 mSv (millisieverts). To put this in perspective, this is roughly equivalent to about 1.5 to 2 years of natural background radiation exposure, or approximately the dose from 2–3 standard CT scans of the chest.

The organs receiving the highest absorbed doses are the uterine/bladder wall, the pancreas, the liver, and the bone marrow, although all remain within internationally accepted limits for diagnostic nuclear medicine procedures. The benefit of identifying the location and extent of recurrent prostate cancer is considered to outweigh this small radiation risk in the appropriate clinical setting.

After the scan, you will emit low levels of radiation for several hours due to the decay of fluorine-18 (physical half-life approximately 110 minutes). Your nuclear medicine center will provide specific advice on precautions to take after the scan, which may include limiting prolonged close contact with young children and pregnant women for a few hours following the procedure.

When to Contact Your Doctor

Although serious side effects from Axumin are extremely rare, you should contact your doctor or nuclear medicine department if you experience any of the following after your scan:

• Signs of an allergic reaction such as hives, swelling of the face, lips, tongue, or throat, or difficulty breathing
• Persistent pain, swelling, or redness at the injection site that worsens over time
• Persistent headache, dizziness, or nausea that does not resolve within a few hours
• Any other symptoms that concern you following the procedure

You can also report side effects directly to your national medicines regulatory authority (e.g., the FDA MedWatch program in the United States or the Yellow Card Scheme in the United Kingdom) to contribute to ongoing pharmacovigilance monitoring.

How Should Axumin Be Stored?

Axumin is a radioactive medicinal product that is prepared, stored, and handled exclusively within authorized nuclear medicine facilities. As a patient, you will never need to store or handle this product yourself. The following information is provided for completeness and transparency about how the product is managed:

• Temperature: Store below 25°C (77°F). Do not freeze.
• Shielding: Must be stored in a radiation-shielded container (typically lead) that provides adequate protection for surrounding personnel and the environment.
• Shelf life: Axumin must be used within 8 hours from the time of calibration (the reference time for the stated radioactivity). After this period, the remaining product must be disposed of safely according to national regulations for radioactive waste.
• Labeling: Each vial is labeled with the radioactive content, batch number, expiry date and time, and calibration information.
• Handling: All handling of Axumin must comply with local regulations governing radioactive materials. Only healthcare professionals trained and authorized in the use of radiopharmaceuticals may prepare and administer Axumin.

Unused product or waste material should be disposed of in accordance with local regulatory requirements for radioactive waste. The short half-life of fluorine-18 (approximately 110 minutes) means that the radioactivity decays rapidly, and the product becomes non-radioactive within approximately 20 hours (about 10 half-lives).

What Does Axumin Contain?

Active Substance

The active ingredient in Axumin is fluciclovine (18F), a synthetic amino acid analog radiolabeled with fluorine-18. Its chemical name is anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid. Each milliliter of solution contains 1600 MBq of fluciclovine (18F) at the date and time of calibration. Because fluorine-18 undergoes radioactive decay, the actual radioactivity per milliliter decreases continuously over time with a half-life of 109.77 minutes.

The molecular structure of fluciclovine is based on a cyclobutane ring, which distinguishes it from the natural amino acids that use open-chain or aromatic ring structures. This cyclobutane framework makes fluciclovine resistant to metabolic breakdown by the enzymes that normally process amino acids, which is why the tracer accumulates in cells rather than being rapidly broken down and excreted.

Other Ingredients (Excipients)

• Sodium citrate: Used as a buffer to maintain the pH of the solution within an acceptable range
• Hydrochloric acid: Used for pH adjustment
• Sodium hydroxide: Used for pH adjustment
• Water for injections: The solvent in which the active ingredient and other excipients are dissolved

Axumin is a clear, colorless solution provided in a single-use glass vial. Each vial contains a variable volume of solution depending on the manufacturing batch, but the radioactive concentration is standardized at 1600 MBq/mL at the reference calibration time. The product does not contain preservatives, which is standard for single-dose radiopharmaceutical preparations.

The sodium content of Axumin may be up to 39 mg per maximum recommended dose, corresponding to approximately 2% of the WHO recommended maximum daily dietary sodium intake of 2 g for an adult. This information is relevant for patients on severely sodium-restricted diets, although for a single diagnostic injection this is unlikely to be clinically significant.