GE Healthcare announced the US Food and Drug Administration (FDA) has approved DaTscan (Ioflupane I 123 Injection), a radiopharmaceutical agent intended for use with Single Photon Emission Computed Tomography (SPECT) imaging, for the detection of dopamine transporters (DaT) in the brains of adult patients with suspected Parkinsonian Syndromes (PS). The first FDA-approved diagnostic imaging agent to help physicians evaluate neurodegenerative movement disorders, such as idiopathic (of unknown cause) Parkinson’s Disease (PD), DaTscan may be used as an adjunct to other diagnostic evaluations to help differentiate essential tremor (an involuntary shaking of the hands, head, and face) from tremor due to PS. DaTscan cannot differentiate between the different types of PS.
“Ioflupane [DaTscan] may be an important new imaging agent for physicians in differentiating diseases such as Parkinson’s disease from Essential Tremor,” said Mark Stacy, MD, neurologist and director of the Duke Movement Disorders Clinic at Duke University Medical Centre in Durham, NC. “Understanding exactly what you are dealing with is important in selecting the appropriate treatments for patients with movement disorders.”
The FDA’s action, following a priority review, marks the approval of the first radiopharmaceutical agent to detect DaT distribution within the brain (dopamine is a brain chemical that is classified as a neurotransmitter and is found in regions of the brain that regulate activities such as movement and emotion). Visualization of DaT distribution within the brain may help decrease diagnostic uncertainty in adult patients with suspected PS.
The FDA granted DaTscan Priority Review due to an unmet clinical need for an imaging agent to assist physicians in managing patients according to their dopaminergic status. Parkinsonian syndromes are a group of neurodegenerative disorders (including multiple system atrophy, progressive supranuclear palsy and idiopathic Parkinson’s disease) characterized by rigidity, tremor and an impaired ability to walk.
“Currently, movement disorders are diagnosed through clinical examinations, blood tests and neuropsychological evaluations, which are not conclusive and may lead to misdiagnosis,” Dr Stacy said. “A new diagnostic adjunct to existing clinical assessments represents a meaningful contribution to the movement disorders field.”
The FDA’s approval of DaTscan was based on two phase III clinical trials confirming the efficacy of DaTscan for the visualization of DaT distribution within the striata, an interior part of the brain. These studies, evaluating 284 adult patients with tremor, demonstrated the consistent performance of DaTscan in the visual detection of DaT distribution in the brain when compared with a reference clinical diagnosis.
“We are confident that DaTscan, an objective and accurate marker of dopamine transporters, will better inform physicians’ diagnostic decisions,” said Stephen Lightfoot, MI-SPECT Segment Leader, GE Healthcare Medical Diagnostics. “By potentially enabling better disease management, we expect that DaTscan will greatly benefit the patient community.”
DaTscan is a radiopharmaceutical imaging agent that works by binding to dopamine transporters (DaT) in the brain. A specific marker for DaT, DaTscan produces images that provide visual evidence of the presence of dopamine transporters. DaTscan has been available in Europe since 2000 and has been used in nearly 300,000 patients in 32 countries. DaTscan is classified as a Schedule II controlled substance. A Schedule II controlled substance is a substance with a currently accepted medical use in the US (with or without severe restrictions) that has a high potential for abuse that may lead to severe psychological or physical dependence, as determined by the Controlled Substances Act.
DaTscan is a radiopharmaceutical indicated for striatal dopamine transporter visualization using Single Photon Emission Computed Tomography (SPECT) brain imaging to assist in the evaluation of adult patients with suspected Parkinsonian Syndromes (PS). DaTscan may be used to help differentiate essential tremor from tremor due to PS (idiopathic Parkinson’s disease, multiple system atrophy and progressive supranuclear palsy). DaTscan is an adjunct to other diagnostic evaluations. DaTscan is contraindicated in patients with known hypersensitivity to the active substance, any of the excipients, or iodine.
Hypersensitivity reactions, generally consisting of skin erythema and pruritis, have been reported following DaTscan administration. For thyroid accumulation DaTscan injection may contain up to 6% of free iodide (iodine 123 or I-123). To decrease thyroid accumulation of I-123, block the thyroid gland at least 1 hour before administration of DaTscan; failure to do so may increase the long term risk for thyroid neoplasia.
In clinical trials, headache, nausea, vertigo, dry mouth or dizziness of mild to moderate severity were reported. In post-marketing experience, hypersensitivity reactions and injection site pain have been reported. Drugs that bind to the dopamine transporter with high affinity may interfere with the DaTscan image. The impact of dopamine agonists and antagonists upon DaTscan imaging results has not been established.
It is unknown whether DaTscan can cause fetal harm or increase risk of pregnancy loss in pregnant women. DaTscan should be given to pregnant women only if clearly needed. Like all radiopharmaceuticals, DaTscan may cause fetal harm depending on the stage of fetal development, and the magnitude of the radionuclide dose. Radioactive iodine products cross the placenta and can permanently impair fetal thyroid function.
It is not known whether DaTscan is excreted into human milk, however, I-123 is excreted into human milk. Because many drugs are excreted into human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to interrupt nursing after administration of DaTscan or not to administer DaTscan. Nursing women may consider interrupting nursing and pump and discard breast milk for 6 days after DaTscan administration to minimize risks to a nursing infant.
The safety and efficacy of DaTscan have not been established in paediatric patients. There were no differences in responses between the elderly and younger patients that would require a dose adjustment. The effect of renal or hepatic impairment upon DaTscan imaging has not been established. DaTscan is excreted by the kidney; patients with severe renal impairment may have increased radiation exposure and altered DaTscan images.
Ioflupane I 123 Injection is a DEA Schedule II controlled substance. A DEA license is required for handling or administering this controlled substance. It is unknown whether or not ioflupane is dialyzable. The major risks of overdose relate to increased radiation exposure and long-term risk for neoplasia. In case of radioactivity over-dosage, frequent urination and defecation should be encouraged to minimize radiation exposure to the patient. DaTscan emits radiation and must be handled with safety measures to minimize radiation exposure to clinical personnel and patients.
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