Striascan (Ioflupane I-123): Uses, Dosage & Side Effects

What Is Striascan and What Is It Used For?

Striascan belongs to a group of medicines known as radiopharmaceuticals, which combine a very small pharmacologically inactive amount of chemical substance (ioflupane) with a short-lived radioactive label (iodine-123). Unlike therapeutic drugs, radiopharmaceuticals are not intended to exert any pharmacological effect on the body – their purpose is to emit gamma photons that can be detected by specialized imaging equipment, creating high-resolution maps of specific biological targets. In the case of Striascan, the target is the presynaptic dopamine transporter (DAT), a protein located on the terminals of dopaminergic neurons that project from the substantia nigra into the striatum.

After slow intravenous injection, the iodine-123-labeled ioflupane rapidly distributes throughout the circulation, crosses the blood-brain barrier, and accumulates preferentially in the caudate nucleus and putamen (collectively, the striatum). Binding to DAT is specific and reaches a plateau approximately 3 hours after injection, providing a stable imaging window for SPECT acquisition. In a healthy adult, the resulting SPECT images show a characteristic symmetrical comma-shaped or crescent-shaped pattern of radiotracer uptake in each hemisphere. In disorders characterized by nigrostriatal dopaminergic degeneration, this pattern becomes asymmetrical, fragmented, or reduced to a dot-shaped appearance, reflecting the loss of functioning dopaminergic terminals.

Striascan is clinically indicated in two principal scenarios. First, it is used to help differentiate essential tremor from parkinsonian syndromes. Essential tremor is a common movement disorder in which tremor occurs without any underlying loss of dopaminergic neurons, and the Striascan image remains normal. In contrast, idiopathic Parkinson's disease, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD) all involve dopaminergic cell loss and typically show abnormal reduced striatal uptake on Striascan. This distinction is clinically important because management, prognosis, and family counseling differ substantially between essential tremor and a degenerative parkinsonian syndrome.

Second, Striascan is indicated as an aid in differentiating probable dementia with Lewy bodies (DLB) from Alzheimer's disease. DLB is associated with alpha-synuclein pathology and loss of nigrostriatal dopaminergic neurons, producing a reduced-uptake pattern on Striascan similar to Parkinson's disease. Alzheimer's disease, in contrast, predominantly affects cortical and hippocampal structures and generally preserves the nigrostriatal pathway, so DAT SPECT typically appears normal. An abnormal DAT SPECT in the context of cognitive decline with fluctuating attention, visual hallucinations, REM sleep behavior disorder, or parkinsonism is regarded by international consensus criteria as a supportive biomarker for the diagnosis of DLB.

It is important to emphasize that Striascan is exclusively a diagnostic tool. It does not treat or slow the progression of any disease, and it is not routinely used to monitor therapy. Its value lies in providing objective imaging information about the integrity of the dopaminergic system at a single point in time. The results must always be interpreted by an experienced nuclear medicine physician in conjunction with the referring neurologist or memory clinic team, and always in the context of the patient's full clinical picture: history, neurological examination, cognitive assessment, and other investigations such as MRI of the brain. An abnormal Striascan does not identify which specific parkinsonian syndrome is present, and a normal scan does not entirely exclude very early-stage disease in rare instances.

What Should You Know Before Receiving Striascan?

Contraindications

Striascan must not be administered in certain clearly defined situations. It is contraindicated in patients with a known hypersensitivity to ioflupane or to any of the excipients in the solution (acetic acid, sodium acetate trihydrate, ethanol, and water for injections). Although true hypersensitivity reactions to ioflupane (123I) are rare, nuclear medicine departments are equipped to recognize and manage such reactions, including anaphylaxis, should they occur.

Striascan is also contraindicated during pregnancy. Any radiopharmaceutical administered during pregnancy carries a potential radiation dose to the developing embryo or fetus, and for a diagnostic investigation that is not time-critical, pregnancy must be ruled out or alternative non-radiation imaging strategies must be considered. If there is any possibility that you could be pregnant, inform the nuclear medicine team immediately so that a pregnancy test can be arranged or the appointment postponed.

Warnings and Precautions

Before receiving Striascan, have a detailed conversation with the nuclear medicine physician or technologist about your full medical history. Particular care is required in patients with moderate or severe kidney or liver impairment, because these conditions can alter the elimination and redistribution of ioflupane and its metabolites and therefore the radiation dose delivered. Your physician will weigh the expected diagnostic benefit against these pharmacokinetic considerations, and may adjust the hydration protocol or imaging schedule accordingly.

Adequate hydration is important both before and after the scan. Drink plenty of water on the day of the appointment, and continue to drink fluids and urinate frequently during the first 48 hours after the injection. Frequent voiding accelerates elimination of the radiotracer from the body and reduces the cumulative radiation dose to the bladder wall and surrounding pelvic organs. There are no dietary restrictions before or after Striascan other than maintaining good hydration.

The interpretation of Striascan images requires expert knowledge of the normal appearance and of the patterns seen in various neurodegenerative conditions. An abnormal scan confirms loss of functioning dopaminergic terminals but does not by itself differentiate between Parkinson's disease and other degenerative parkinsonisms such as MSA or PSP. Conversely, a scan interpreted as normal does not rule out a non-degenerative cause of tremor or rare very early-stage disease. Striascan is therefore always used as one component of a broader diagnostic assessment; it is not a stand-alone test for any specific condition.

Children and Adolescents

Striascan is not recommended for use in children and adolescents aged 0 to 18 years. The safety and diagnostic efficacy of ioflupane (123I) have not been established in the pediatric population, and the clinical conditions in which Striascan is indicated are overwhelmingly disorders of later adult life. Pediatric DAT imaging is confined to extremely rare research settings and specialized referral centers.

Pregnancy and Breastfeeding

Striascan must not be used during pregnancy. If you are of childbearing age, the nuclear medicine department may request a pregnancy test before proceeding. Any possibility of pregnancy should be disclosed, even if considered unlikely; in such cases, the examination should be postponed until pregnancy can be reliably excluded or alternative non-ionizing imaging methods should be considered where clinically appropriate.

If you are breastfeeding, the nuclear medicine physician will generally postpone Striascan administration when clinically feasible. When the examination cannot be delayed, breastfeeding must be interrupted for at least 3 days after injection, as it is not fully known whether and to what extent ioflupane (123I) is excreted into human breast milk. During this 3-day interruption, express milk at regular intervals and discard it to maintain milk supply. Feed your infant with formula or previously stored expressed milk during this period. After 72 hours, the radioactive decay of iodine-123 is sufficiently advanced for breastfeeding to be safely resumed.

Driving and Operating Machinery

Striascan has no known effect on the ability to drive or use machines. The injection does not produce sedation, drowsiness, or cognitive impairment, and the SPECT procedure itself does not require anesthesia. Patients usually drive themselves home after the imaging acquisition, unless their underlying neurological condition (the very condition being investigated) independently affects driving ability.

How Does Striascan Interact with Other Drugs?

Striascan works by binding to the dopamine transporter (DAT). Any substance that also binds to DAT can compete with ioflupane (123I) for these binding sites, thereby reducing the amount of radiotracer visible in the striatum and potentially obscuring or simulating a pattern of dopaminergic deficit. This competition is the main source of potential interaction: it is pharmacokinetic rather than pharmacodynamic in the conventional sense, and it affects image interpretation rather than causing any systemic adverse effect.

For this reason, the full medication history – including prescription drugs, over-the-counter products, herbal supplements, and any history of illicit drug use – should be disclosed to the nuclear medicine team prior to imaging. Reassuringly, the medications most commonly prescribed in the differential diagnosis of parkinsonian syndromes – namely levodopa, dopamine agonists (pramipexole, ropinirole, rotigotine), MAO-B inhibitors (selegiline, rasagiline, safinamide), COMT inhibitors (entacapone, opicapone, tolcapone), and amantadine – have not been shown to produce clinically relevant effects on DAT imaging and generally do not need to be stopped. Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine, used in Alzheimer's disease and DLB, are also not considered to interfere with Striascan.

Major Interactions

Minor or Possible Interactions

What Is the Correct Dosage of Striascan?

Because Striascan is a radiopharmaceutical, its preparation, dispensing, and administration are subject to strict national regulations and local institutional protocols for handling radioactive materials. You will never receive Striascan to take home. All handling is performed by authorized nuclear medicine personnel (physicians, physicists, radiopharmacists, and technologists) within designated facilities equipped with radiation shielding, dose calibrators, and dedicated waste-management procedures. The prescribing nuclear medicine physician determines the individual dose based on the indication, the patient's body weight and age, the SPECT camera characteristics, and the planned interval between injection and imaging.

Adults

The exact activity within the 111–185 MBq range is selected by the nuclear medicine physician, taking into account the sensitivity of the SPECT system, the expected counts per unit time, and the interval between injection and imaging. Higher activities within the range may be preferred when imaging systems are less sensitive or when image acquisition must be shorter to accommodate a patient who has difficulty remaining still. A single injection is sufficient for the entire examination, and no repeat dosing is normally required.

Elderly Patients

No dose adjustment is required for older adults. The standard 111–185 MBq range applies across all adult age groups. Because the principal indications for Striascan – parkinsonian syndromes and dementia with Lewy bodies – are overwhelmingly conditions of later life, the majority of patients referred for this scan are elderly. Decades of clinical experience with ioflupane (123I) support the safety and diagnostic reliability of the standard dose in this population, and there is no evidence that increased age alters the kinetics or target binding of the radiotracer in any clinically relevant way.

Patients with Renal or Hepatic Impairment

No dosimetric data have been formally derived for patients with moderate-to-severe kidney or liver disease. Because a significant proportion of the radiotracer is excreted via the urinary tract, severe renal impairment may slow elimination and marginally increase the radiation dose to the bladder and whole body. In such cases the nuclear medicine physician may emphasize extra hydration and more frequent voiding post-injection. The decision to proceed, and any protocol adjustments, are made on an individualized risk-benefit basis.

Children

The Striascan Procedure Step by Step

Understanding the sequence of events on the day of your Striascan appointment can help reduce anxiety and ensure the best possible diagnostic outcome. Although local protocols may vary slightly, the essential steps are standardized and follow practice guidelines published by the European Association of Nuclear Medicine (EANM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI).

1. Arrival and preparation. On arrival at the nuclear medicine department you will be identified, your weight may be recorded, and your understanding of the procedure will be confirmed. You will be given thyroid-blocking medication (typically potassium iodide tablets) at least one hour before the injection. You should be well hydrated and you may be asked to empty your bladder.
2. Intravenous injection. A small intravenous cannula is inserted into a vein in your arm by a trained technologist or physician. The Striascan solution is then injected slowly and steadily over approximately 15 to 20 seconds, followed by a flush of saline. The injection itself feels similar to a routine blood draw. You may be asked to remain seated and quiet for a short time afterwards.
3. Waiting interval (3–6 hours). During this window the radiotracer distributes in the brain and binds progressively to striatal dopamine transporters. You can leave the department or wait in a designated area; you can eat, drink, read, and use your phone as normal. Continue to drink fluids and urinate regularly to minimize unnecessary radiation to the bladder.
4. SPECT image acquisition. At the scheduled time you return to the scanner room and lie supine on the imaging table with your head gently but firmly supported in a head-holder to minimize motion. A gamma camera with two detector heads rotates slowly around your head over approximately 30 to 45 minutes, recording gamma photons emitted by iodine-123 in your brain. The scanner does not emit any radiation itself; it only detects radiation coming from you. The acquisition is completely painless, and the room is well ventilated and lit.
5. After the scan. You can leave the department immediately after image acquisition and resume your normal daily activities. Continue to drink fluids and urinate often during the next 48 hours to help clear any residual tracer. No special isolation, distance, or sleeping arrangements are required. The images are subsequently reconstructed and analyzed by a nuclear medicine physician, often with semiquantitative software that compares striatal uptake to background, and a report is sent to your referring doctor.

Missed Dose

The concept of a "missed dose" does not apply to Striascan in the usual sense because it is a one-time diagnostic injection rather than a chronic therapy. If you miss your appointment, simply contact the nuclear medicine department to reschedule. Because each patient's dose is compounded specifically for a planned examination time (the iodine-123 activity decays by about half every 13 hours), rescheduling generally requires ordering a fresh dose for the new appointment.

Overdose

Because Striascan is administered by qualified medical professionals using calibrated dose measurements, accidental overdose is extremely unlikely. In the rare event that a dose exceeding the intended activity is administered, the nuclear medicine physician will recommend measures to accelerate elimination: increased oral fluid intake, frequent voiding, and occasionally mild laxatives to reduce intestinal transit of excreted material. There is no specific antidote to ioflupane (123I), and none is required: the short physical half-life of iodine-123 (13.2 hours) means that any excess radioactivity will decay to negligible levels within a few days. Standard hygienic precautions around urine should be followed for the first 48 hours as instructed by the medical team.

What Are the Side Effects of Striascan?

Like any medicinal product, Striascan can cause adverse reactions, although most patients experience none. Because Striascan is given only once for a diagnostic purpose, the opportunity for cumulative or long-term adverse effects is limited. The reactions observed in clinical trials and in post-marketing surveillance have been mostly mild, transient, and self-limiting, resolving without specific treatment.

The frequency categories used below are standard pharmacovigilance terms defined by the Council for International Organizations of Medical Sciences (CIOMS): very common (>1/10), common (≥1/100 to <1/10), uncommon (≥1/1,000 to <1/100), rare (≥1/10,000 to <1/1,000), very rare (<1/10,000), and not known (frequency cannot be estimated from available data). The radiation dose delivered by Striascan is well below the threshold associated with any deterministic radiation effect; stochastic risk (a very small theoretical long-term cancer risk) is considered to be far outweighed by the diagnostic information provided.

Injection-site reactions are uncommon but may occur, particularly if the Striascan solution is inadvertently injected into a small or fragile peripheral vein. They may take the form of a brief burning sensation, localized pain, or mild bruising, and typically resolve spontaneously within minutes to a few hours. If significant injection-site irritation persists, inform the nuclear medicine staff so that simple measures such as a warm compress can be applied and the event documented.

The small amount of radioactivity introduced by Striascan will decay rapidly in the days following your scan. Because the physical half-life of iodine-123 is approximately 13 hours, only around 3% of the administered activity remains after 72 hours (five half-lives), and the remaining activity is negligible within a week. No special precautions are needed regarding contact with adults, children, or pregnant women in the days after your examination, beyond the standard advice about hydration and urination during the first 48 hours.

How Should Striascan Be Stored?

Because Striascan is a radiopharmaceutical, storage, transportation, use, and disposal are tightly controlled under national and international regulations (in the European Union, for example, the Basic Safety Standards Directive 2013/59/Euratom and applicable national implementing law). Only licensed facilities with appropriate shielding, dosimetry, and waste management infrastructure are permitted to receive and store the product, and only authorized personnel with documented training in radiation safety may handle it.

The recommended storage conditions are simple but strict: the product should be kept at a temperature not exceeding 25 °C, stored in the original container to protect it from light, and must not be frozen. It is stored inside appropriate lead shielding within dedicated radiopharmacy storage areas, kept out of sight and reach of all non-authorized persons, and must never be used after its labeled expiry time. Because iodine-123 decays with a physical half-life of approximately 13.2 hours, the effective shelf life of any given vial of Striascan is short; practical batches are typically ordered and calibrated for specific patient appointments.

Unused product and waste generated during administration – including syringes, needles, dose vials, absorbent materials, and any contaminated personal protective equipment – is handled as radioactive medical waste. It is segregated, labeled, stored for radioactive decay for an appropriate number of half-lives, measured for residual activity, and then disposed of through authorized waste-management channels in accordance with local, national, and international rules. At no point is any unused Striascan transferred into the care of the patient.

What Does Striascan Contain?

Active Ingredient

The active substance in Striascan is ioflupane (123I), also known as 123I-FP-CIT, with the chemical name N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane. Each millilitre of solution contains ioflupane labeled with iodine-123 at an activity of 74 MBq at the reference time stated on the vial label. The actual mass of ioflupane present is extremely small, typically in the nanogram-to-microgram range per millilitre, which is why the substance has no pharmacological effect and is considered to be a pure diagnostic tracer. Iodine-123 itself is produced in a cyclotron, emits gamma photons with a principal energy of 159 keV (ideal for detection by SPECT gamma cameras), and has a physical half-life of approximately 13.2 hours.

Inactive Ingredients (Excipients)

• Acetic acid: used as a pH buffer to stabilize the solution within the required acidity range.
• Sodium acetate: a co-buffer that contributes to maintaining optimal pH and tonicity.
• Ethanol (up to approximately 5% v/v): acts as a co-solvent, keeping the ioflupane in solution over the product's shelf life. Each dose typically contains a small amount of alcohol (up to several hundred milligrams), which is generally not clinically relevant but may warrant mention in patients with alcohol use disorder, liver disease, or epilepsy.
• Water for injections: the principal solvent, meeting pharmacopeial standards for injectable preparations.

Appearance and Packaging

Striascan is a clear, colorless solution for intravenous injection. It is supplied in sterile, pharmaceutical-grade glass vials sealed with an elastomeric stopper and a metal crimp cap. Each vial is contained within appropriate lead or tungsten shielding during storage and transport so that personnel are protected from external radiation exposure. The labeled activity on each vial specifies the megabecquerels per millilitre at a defined reference time and date; activity at injection is calculated accounting for radioactive decay between the reference time and the actual time of patient administration.

Striascan is intended exclusively for diagnostic use and is supplied to licensed nuclear medicine facilities only. It should never be handled or transported by patients, and is subject to all applicable regulatory frameworks for medicinal products containing radioactive isotopes.