Ioflupane I-123 (2 brand names, 1 dosage form, 1 route)
Available dosage forms: SOLUTION.
Routes of administration: INTRAVENOUS.
Brand Names
- DATSCAN
- IOFLUPANE I-123
Indications and Usage
DATSCAN is indicated as an adjunct to other diagnostic evaluations for striatal dopamine transporter visualization using single photon emission computed tomography (SPECT) brain imaging in adult patients with: suspected Parkinsonian syndromes (PS) or suspected dementia with Lewy bodies (DLB).
Contraindications
DATSCAN is contraindicated in patients with known serious hypersensitivity to ioflupane I 123 [see Warnings and Precautions (5.1)].
Adverse Reactions
The following clinically significant adverse reaction is described elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions (5.1)]
Drug Interactions
Ioflupane I 123 binds to the dopamine transporter [see Clinical Pharmacology (12.1)]. Drugs that bind to the dopamine transporter with high affinity have the potential to impact DATSCAN image interpretation. These potentially interfering drugs include: amoxapine, amphetamine, armodafinil, benztropine, bupropion, buspirone, cocaine, mazindol, methamphetamine, methylphenidate, modafinil, norephedrine, phentermine, selegiline, and sertraline. Selective serotonin reuptake inhibitors (paroxetine and citalopram) may increase or decrease ioflupane binding to the dopamine transporter. In patients taking venlafaxine or desvenlafaxine prior to DATSCAN administration, there have been cases of altered DATSCAN uptake that impacted image interpretation. The mechanism of interference of these drugs with DATSCAN imaging is not known. Whether discontinuation of any of the above drugs prior to DATSCAN administration may minimize the impact on image interpretation is unknown; however, if use of these drugs can be safely suspended, consider discontinuing for at least 5 biological half-lives before administration of DATSCAN [see Dosage and Administration (2.3)]. The impact of dopamine agonists and antagonists upon DATSCAN imaging results has not been established.
Mechanism of Action
The active drug substance in DATSCAN is N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-[123I]iodophenyl)nortropane or ioflupane I 123. In vitro, ioflupane binds reversibly to the human dopamine transporter (DaT) (Ki = 0.62 nM; IC50 = 0.71 nM). Autoradiography of post-mortem human brain slices exposed to radiolabeled ioflupane shows concentration of the radiolabel in striatum (caudate nucleus and putamen). The specificity of the binding of ioflupane I 125 to dopamine transporter was demonstrated by competition studies with the DaT inhibitor GBR 12909 (a dopamine reuptake inhibitor), the serotonin reuptake inhibitor citalopram, and the norepinephrine reuptake inhibitor desipramine in post-mortem human brain slices exposed to radiolabeled ioflupane. Citalopram reduced binding in the neocortex and thalamus with only minor effects in the striatum. This indicated that the binding in the cortex and thalamus is mainly to the serotonin reuptake sites. Desipramine showed no effect on the level of striatal binding of ioflupane I 125, but reduced extrastriatal binding by 60 to 85%. The binding of ioflupane I 125 to the striatum was abolished in the presence of high concentrations of GBR 12909, indicating selectivity of ioflupane binding for the pre-synaptic DaT. Following administration of DATSCAN to humans, radioactive decay of the iodine-123 emits gamma radiation which can be detected externally using gamma detectors, allowing visualization of the brain striata through SPECT imaging [see Clinical Pharmacology (12.3)].
Overdosage
The risks of overdose relate predominantly to increased radiation exposure, with the long-term risks for neoplasia. In case of overdosage of radioactivity, frequent urination and defecation should be encouraged to minimize radiation exposure to the patient.