Drug Interactions in Imaging Dopamine Transporters with 123I-FPCIT
Page 1 of 4
or 123I-Beta-CIT
SPECT images of pre-synaptic dopamine transporters obtained using the radioligands 123I-FPCIT or
123I-Beta-CIT can be affected by a number of neuro-active drugs. Such drugs may cause a misleading
scan or misleading data in a clinical trial.
Prior to administration of 123I-FPCIT (DATSCAN) or 123I-Beta-CIT check the patient’s present and recent
past medication record against the drugs shown below.
Some of the drugs remain “active” for many days and even weeks later. Where withdrawal of a drug is
necessary to ensure a valid scan the time required for adequate washout in days is shown in square
brackets.
The decision to withdraw any medication must be made by the specialist in charge of the patient’s care.
(Important Note: This information relates to the action of drugs on the pre-synaptic transporter, and
hence on the imaging ligand. It does not relate to drugs which induce the symptoms of parkinsonism
(so-called reversible drug-induced parkinsonism), usually by acting on the post-synaptic receptor.
These latter drugs do not alter transporter ligand uptake.)
This Procedure Note has 3 sections
Drugs for which there is strong evidence, often obtained from
imaging studies, that uptake of the radioligands IS NOT ALTERED
by the drug.
OK
Many of these drugs are used in the treatment of parkinsonsim and
dementia and they can be continued with no fear of them affecting
the scan.
Drugs for which there is strong evidence, often obtained from
imaging studies, that uptake of the radioligands WILL BE
ALTERED by the drug.
STOP
All of these drugs must be stopped to prevent a misleading result.
OK,
except in
research
Drugs for which either
a. there is strong evidence of a small effect on uptake (less
than 20%)
or
b. the evidence is much weaker, and often shown only in nonhuman studies, of some effect on uptake
It is unlikely that any of these drugs will affect a routine scan but
their use in clinical trials should be monitored carefully to prevent
misleading data.
Version 2.1
May 2009
Prepared by
J. Patterson, J. Booij, P. Kemp
Review Date
May 2011
Drug Interactions in Imaging Dopamine Transporters with 123I-FPCIT
Page 2 of 4
or 123I-Beta-CIT
Levodopa and combination drugs with peripheral DC inhibitors, these
OK.
From the mechanism of action of
include
these drugs none are expected to
levodopa (L-DOPA)
THESE DRUGS
Comments
co-beneldopa (Madopar)
influence radioligand uptake and for
co-careldopa (Sinemet, Duodopa, Stalevo)
many there is direct evidence that
this is correct.
WILL NOT
Dopamine agonists, these include
AFFECT A
SCAN.
DO NOT STOP
However, acute high dose
apomorphine (APO-go)
bromocriptine (Parlodel)
administration of dopaminergic
cabergoline (Cabaser)
lisuride
drugs (e.g. for a challenge test),
pergolide (Celance)
pramipexole (Mirapexin)
ropinirole (Requip)
rotigotine (Neupro)
especially in previously untreated
patients, should be avoided in the
24 hours prior to the scan.
MAO-B, COMT inhibitors
selegiline (Deprenyl, Eldepryl, Zelapar)
entacapone (Comtess)
Non-SSRI antidepressants can also
rasagiline (Azilect)
have serotonin reuptake inhibiting
tolcapone (Tasmar)
potency next to another primary
action e.g. norepinephrine reuptake
inhibition. Decreased cortical
Anticholinergics (see 2 exceptions in drugs to STOP)
biperiden (Akineton)
uptake and possibly also increased
orphenadrine (Biorphen, Disipal)
procyclidine (Arpicolin, Kemadrin)
striatal uptake might be expected in
dexetimide (Tremblex)
theory from this type of medication
as well, but this is likely to be to a
trihexyphenidyl/benzhexol (Broflex)
lesser extent than with SSRIs (see
comments on SSRIs below).
Other medication commonly used in the treatment of parkinsonism
domperidone (Motilium)
amantadine (Symmetrel, Lysovir)
Medication commonly used in the treatment of essential tremor
atenolol (Tenormin, Kalten, Tenoret, Tenif, Beta-Adalat)
propranolol (Inderal)
primidone (Mysoline)
metoprolol (Lopresor, Betaloc)
Cholinesterase Inhibitors
donepezil [5] (Aricept)
galantamine [5] (Reminyl)
rivastigmine [5] (Exelon)
Tricyclic Antidepressants
amitriptyline (Triptafen)
amoxapine (Asendis)
dosulepin (Prothiaden)
doxepin (Sinequan)
lofepramine (Gamanil)
trimipramine (Surmontil)
maprotiline (Ludiomil)
mianserin
nortriptyline (Allegron, Motival) trazodone (Molipaxin)
MAO inhibitors and other antidepressants
phenelzine (Nardil)
moclobemide (Manerix)
tranylcypromine
isocarboxacid
mirtazapine (Zispin)
reboxetine (Edronax)
There is no evidence that the following classes of drugs will affect
radioligand uptake:
Antiemetics, Antihistamines, Anxiolytics, Barbiturates,
Benzodiazepines, Beta blockers, Calcium channel blockers,
Hypnotics, Sedatives, Neuroleptics (see single exception in drugs to
STOP)
Version 2.1
May 2009
Prepared by
J. Patterson, J. Booij, P. Kemp
Review Date
May 2011
Drug Interactions in Imaging Dopamine Transporters with 123I-FPCIT
Page 3 of 4
or 123I-Beta-CIT
STOP!
All dopaminergic CNS stimulants, these include
Comments
All of these drugs are likely to
alter (usually decrease)
radioligand uptake by at least
20% and often substantially
more.
cocaine [2]
THESE DRUGS
amfetamine [7]
WILL HAVE A
methylamfetamine [3]
SIGNIFICANT
methylphenidate [1] (Ritalin) [2] (Concerta, Equasym)
EFFECT ON A
SCAN.
There is no evidence that the
mechanisms of action will
preferentially alter uptake in the
putamen and either produce in a
normal subject the characteristic
pattern seen in Parkinson’s
Disease (PD) or make a scan in a
PD patient look normal.
However, image interpretation will
become more difficult.
Dopaminergic stimulants for anorexia and obesity, these include
dexamfetamine [7] (Dexedrine)
mazindol [3]
THEY MAY CAUSE
phentermine [14]
A FALSE VISUAL
INTERPRETATION.
Dopaminergic stimulants for ADHD, narcolepsy and other sleeping
disorders, these include
methylphenidate [1] (Ritalin) [2] (Concerta, Equasym)
They should be
stopped prior to the
dexamfetamine [7] (Dexedrine)
modafinil [3] (Provigil)
scan for the number
of days shown in
square brackets.
One dopaminergic stimulant/antidepressant/anti-smoking drug
The mechanisms by which the
drugs alter the uptake of the
radioligands include:
i. direct blockade of the
transporter and competition with
the ligand
ii. internalisation and trafficking
of the transporter
iii. alteration of dopamine
transporter expression
iv. a change in binding affinity for
the transporter
Methylamphetamine is neurotoxic
and reduction of ligand uptake
with prolonged use may reflect a
true decrease in dopamine
transporter density.
Bupropion or amfebutamone [8] (Zyban)
One Anticholinergic
(exceptional example - usually anticholinergics have no effect)
Phentermine and mazindol have
previously been prescription
drugs but now are not generally
available.
benzatropine [5] (Cogentin
-----------------------------------------------------------------------------------------For the following drugs significant effects with the routes of
administration shown have been reported but their relevance to clinical
practice is less clear.
One Anticholinergic
(exceptional example - usually anticholinergics have no effect)
hyoscine/scopolamine [5]
iv administration
(Buscopan,Scopoderm ) (increased ligand uptake)
Sympathomimetics
phenylephrine [1] (increased ligand uptake)
iv infusion
noradrenaline [1] (increased ligand uptake)
iv infusion
Two Anaesthetics
ketamine [1] (Ketalar) (increased ligand uptake) iv administration
isoflurane [1] (Isoflurane, Aerrane)
inhalation
Three opioid Analgesics
Version 2.1
May 2009
fentanyl [1] (Sublimaze, Actiq, Durogesic)
intrathecal/ acute iv
pethidine [1] (Pamergan)
iv administration
morphine [3]
iv administration
Prepared by
J. Patterson, J. Booij, P. Kemp
Review Date
May 2011
Drug Interactions in Imaging Dopamine Transporters with 123I-FPCIT
Page 4 of 4
or 123I-Beta-CIT
OK, except
in research
These drugs will
have no
SSRI and SNRI Antidepressants
Comments
(causes increased ligand uptake)
From the mechanism of action of
citalopram [8] (Cipramil)
escitalopram [8] (Cipralex)
these drugs none are expected to
fluoxetine [45] (Prozac)
fluvoxamine [5] (Faverin)
influence the visual interpretation of
paroxetine [5] (Seroxat)
sertraline [6] (Lustral)
radioligand uptake. However, they
may have a small effect on uptake
venlafaxine [3] (Efexor)
(at most 15%). This will not affect
duloxetine [3] (Cymbalta, Xeristar, Yentreve)
the characteristic uptake pattern of
normal and abnormal scans. It is
significant effect
on the visual
common practice when reporting to
Tricyclic Antidepressants (causes increased ligand uptake)
Imipramine [5]
make allowance for small variations
in uptake (e.g. loss of 4% per
clomipramine [21] (Anafranil)
decade due to aging).
interpretation of a
scan but may
Two Neuroleptics ( antipsychotics)
In clinical trials allowance would
have to be made for these effects
(exceptional examples - usually neuroleptics have no effect)
need to be
pimozide (Orap) [28]
or the medication would have to be
ziprasidone (Zeldox) [2]
stopped prior to the scan. Note
stopped in clinical
that any medication, particularly
antidepressants, must not be
NMDA receptor antagonists
trials
stopped without specialist advice.
memantine [5] (Ebixa, Namenda)
amantadine [6] (Symmetrel)
Serotonergic antidepressants
budipine [6]
cause an apparent increase in
striatal uptake due to two effects
Sympathomimetics
i. enhanced central availability
(concentration near binding sites)
Since infusions of clinical doses of sympathomimetics have been
of the radioligand, resulting from
shown to increase radioligand uptake it may be prudent to record the
displacement from peripheral
use of similar medications such as nasal decongestants, particularly
and/or central serotonin transporter
those available over the counter eg
binding sites
ii. blocking of the uptake in
Short acting (4 to 6h duration)
serotonin transporters in
Ephedrine
nonspecific regions.
Epinephrine
Phenylephrine (Minims)
Pseudoephedrine (Sudafed, Galpseud)
Longer acting (8 to10h duration)
Xylometazoline (Otrivine, Otradrops, Tixycolds)
Anti-Epileptic
(exceptional example - usually antiepileptics have no effect)
lamotrigine [6] (Lamictal)
Herbal and other medicines
St John’s Wort [6]
Ephedra [1] – check for use in Chinese Medicines
Version 2.1
May 2009
Prepared by
J. Patterson, J. Booij, P. Kemp
Review Date
May 2011