Some antidepressants; have been used for the
treatment of bulimia nervosa (BN) with
encouraging results in reducing binge frequency.
Among them, fluoxetine bas been proven effective
in reducing bulimic symptoms in a long-term (52
weeks) double-blind trial. We present a case
report of an injured temporomandibular joint
(TMJ) associated with
fluoxetine-monotherapy-induced repeated
yawning.
1. Case report
A 23-year-old Korean female patient visited
our outpatient department because of recently
developed depressed mood, impulsiveness, sleep
disturbance, and recurrent episodes of binge
eating with purging behavior. She was diagnosed
as having BN, purging type, according to DSM-IV
criteria. She had irregularly visited 2 private
practitioners during the previous 9 months
before visiting our outpatient department.
Examination of her history reveals that
antidepressant treatment and cognitive
behavioral therapy had been recommended
previously, but low motivation for treatment
caused her to drop out early from intervention.
She did not undergo any psychiatric treatment
for about 2 months, even though she experienced
increasing episodes of binge eating with purging
behavior. The ficquency of binge eating with
purging behavior was about 2-3 times per day,
for at least 3 days a week during the previous 4
months. She induced vomiting with the right
second and third fingers, and according to her
history, she did not use laxatives, enemas, or
other medication for compensatory behavior to
prevent weight gain.
Treatment with fluoxetine 20 mg/d every
morning started with the patient's agreement.
After 7 days, the fluoxetine dosage was
increased to 40 mg/d every morning and
maintained. On day 21 after fluoxetine
administration, she carefully asked about the
side effects of fluoxetine and questioned the
treating psychiatrist about the association of
excessive yawning with the medication.
Her yawning, associated with the mild sedation,
started on day 5 after taking fluoxetine.
Initially the frequency was 5-10 times per day,
and the intensity was mild. At that time, the
treating psychiatrist did not consider it an
important symptom because the patient reported
no other adverse effects, and it was not so
severe as to impair routine activity. Therefore,
the patient remained on the same medication, and
observation was recommended.
On day 42, the patient reported that she had
visited a dental clinic due to the progressive
nature of the yawning and the accompanying
pain and movement dysfunction in both TMJ
areas that had been evident since day 35.
According to her report, the frequency and
intensity of excessive and spasmodic
yawning had increased over time. She
experienced popping sounds in the jaw joint when
opening or closing the mouth and suffered from
tenderness in both TMJ areas. The dentist
confirmed her injured TMJ on the basis of TMJ
x-ray and clinical symptoms and signs. She had
no history of trauma on the TMJ or of chronic
mouth breathing. Furthermore, she had no habit
of clenching or grinding her teeth during
stressfül events or when sleeping, except
during a period of wearing dental braces 5 years
previously.
Therefore, we discontinued fluoxetine
administration at that time, although fluoxetine
was effective to control her binge eating. At
that time, her binge eating was reduced to about
3-4 tintes (sometimes none) per week, and
decreasing to about half diet noted on her first
visit. Purging behavior also decreased to less
than the frequency of binge eating, and she did
not feel the impulse to purge for 2 weeks prior
to discontinuation of fluoxetine, based on her
report. Five days after discontinuation of
fluoxetine, the frequency and intensity of
yawning began to decrease, and 17 days after
discontinuation, she was free from
yawning and had diminished pain in both TMJ
areas when opening and closing her mouth.
2. Discussion
Fluoxetine-induced yawning bas been reported
in some studies, as listed in the literature
insert, and fluoxetine has been attributed as
causing TMJ injury due to repeated yawning. The
temporal relationship between her yawning and
the "on-off' administration of the drug seems
clear, justifying the conclusion that TMJ
injury is due to repeated yawning secondary
to administration of fluoxetine. One could raise
the possibility that the TMJ injury was caused
by excessive purging activity prior to treatment
with fluoxetine but not by fluoxetine treatment.
This explanation seems less likely, since she
did not experience any TMJ injury-related
symptoms prior to visiting our clinic, even
while she was actively purging, and the purging
behavior decreased rather than progressed during
treatment with fluoxetine, although marked
coincidence and possible injury might be
speculated.
Comparing our case with previous reports, it
is interesting that the reported onset for our
patients who suffered from more severe yawning,
resulting in injury to both TMJs was somewhat
earlier, while the 2 previous cases exhibited a
relatively mild nature and a late onset. As for
the relationship between yawning and dosage, our
case and another one were started on fluoxetine
at 20 mg/d, while the other was started at 40
mg/d. This might suggest that differences in
fluoxetine-induced yawning could be due to
individual vulnerability. However, we could
not confirm underlying triggers or confounding
factors in our case. Modell [4) emphasizes
that dose seems related to the nature of the
yawning.
Although the serotonin antagonist
cyproheptadine was first used to treat
fluoxetine-induced yawning by Cohen and Modell
[4), suggesting that the serotonergic
mechanism was directly involved, we do not have
strong evidence that fluoxetine-induced yawning
could be caused by serotonergic activity alone.
It has been proposed that the underlying
mechanisms for the yawning are associated with
the interaction of several receptor activities
[6) and with other biological aspects, such
as chronic administration of opiates, rather
than with the simple direct involvement of one
specific neurotransraitter.
In conclusion further systematic information
is needed regarding the relationship between
fluoxetine administration and clinically
significant yawning. Clinicians should listen
carefully to their patients when they describe
an unexpected reaction to ensure that it does
not pass unnoticed.
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