Which medications, such as selective serotonin reuptake inhibitors (SSRIs) and monoamine oxidase inhibitors (MAOIs), need to be stopped before a Dopamine Transporter (DAT) scan in a patient with a history of Parkinson's disease or other conditions affecting the dopaminergic system?

Medications to Discontinue Before DAT Scan

Amphetamines and stimulants (including dextroamphetamine, methylphenidate, and ADHD medications) must be stopped at least 2 weeks before DAT scanning, as they directly interfere with dopamine transporter binding and cause false-positive results. 1, 2

Primary Medications Requiring Withdrawal

Stimulants and Amphetamines

• Amphetamines (dextroamphetamine, mixed amphetamine salts, lisdexamfetamine) should be discontinued at least 14 days before imaging 1, 2
• These medications directly compete with the radiotracer at dopamine transporter sites, reducing striatal uptake and mimicking neurodegenerative parkinsonism 2
• A documented case showed complete normalization of a false-positive DAT scan after amphetamine withdrawal 2

Monoamine Oxidase Inhibitors (MAOIs)

• MAOIs (phenelzine, tranylcypromine, selegiline) require discontinuation with appropriate washout periods 3, 1
• Standard washout is 2 weeks for most MAOIs 3
• These medications affect dopamine metabolism and can alter DAT binding 1

Selective Serotonin Reuptake Inhibitors (SSRIs)

• SSRIs may influence DAT binding, though evidence is mixed 1, 4
• The 2023 systematic review identified SSRIs as potential confounders requiring consideration for withdrawal 1
• However, paroxetine has been studied in PD patients without significant motor worsening, suggesting the decision must weigh clinical stability 4

Critical Clinical Considerations

Medication History Requirements

• Obtain a complete and accurate medication list including over-the-counter stimulants, weight loss supplements, and decongestants containing sympathomimetics 1, 2
• Document exact timing of last dose for all dopaminergic and serotonergic medications 1

Withdrawal Decision-Making

• The specialist managing the patient's care must make the final decision to withdraw medications, weighing diagnostic accuracy against clinical deterioration risk 1
• For patients with established PD on dopaminergic therapy, medication withdrawal may worsen motor symptoms but is necessary for accurate imaging 1, 5
• In patients taking medications for psychiatric conditions (ADHD, depression), coordinate withdrawal with the prescribing psychiatrist to avoid destabilization 3, 2

Common Pitfalls to Avoid

• Failure to identify amphetamine use is a leading cause of false-positive DAT scans in clinical practice 2
• Over-the-counter cold medications containing pseudoephedrine or phenylephrine may interfere with results 3, 1
• Inadequate washout periods (less than 2 weeks for stimulants and MAOIs) will compromise scan accuracy 3, 1, 2

Medications That Can Be Continued

• Dopaminergic medications (levodopa, dopamine agonists) do not need to be stopped, as they do not significantly interfere with DAT binding at the presynaptic transporter 1, 5
• Anticholinergics and amantadine can be continued 1

Expected Impact on Clinical Management

• DAT scanning changes diagnosis in 37% of patients and alters clinical management in 42% of cases 5
• Proper medication withdrawal reduces false-positive reporting and improves diagnostic accuracy 1, 5
• Pre-scan diagnosis correlates with scan results in 71% of neurodegenerative cases and 64% of non-neurodegenerative cases when proper protocols are followed 5