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We report an apparent withdrawal reaction to venlafaxine, a
recently introduced serotonin noradrenaline reuptake inhibitor
antidepressant whose use is increasing.
A 42 year old man with a first episode of major depression
was treated with venlafaxine after unsuccessful trials with
fluoxetine and imipramine. He fully recovered over four weeks
while taking a dose of 37.5 mg twice daily. This dose was
maintained for 6 months and his mental state was stable. The
dose was reduced to 37.5 mg once daily, which he tolerated
well. However, within 36 hours after stopping venlafaxine
treatment he developed positional vertigo, which caused him
significant incapacity, in addition to nausea and light
headedness. The symptoms resolved rapidly on reintroduction of
the drug. The dose was reduced to 18.75 mg daily for three
weeks and then discontinued. He had ongoing symptoms of
vertigo, which resolved slowly over three weeks. The patient's
determination enabled him to discontinue taking the drug, but
he did so with difficulty. He had no previous history of
adverse drug reactions or withdrawal symptoms.
Other antidepressants have been reported to have withdrawal
syndromes. Attention was drawn to withdrawal of tricyclic
antidepressants by Dilsalver, who showed that cholinergic and
noradrenergic hypersensitivity were important mechanisms for
these symptoms.1
Selective serotonin reuptake inhibitors, particularly
paroxetine, also cause withdrawal syndromes, possibly through
adaptation to the effects of serotonin reuptake
inhibition.2
Withdrawal of venlafaxine may share a similar mechanism, and
its short half life (5 hours) may add to its potential to
cause withdrawal symptoms.
At the time of writing, three reports had been published
about five similar cases, but the patients in all five cases
were taking higher doses of venlafaxine before treatment was
discontinued.3–5
The possibility of a withdrawal reaction is mentioned in the
manufacturer's data sheet, but it implies that such reactions
are observed with doses of 150 mg daily and above. Given the
possibility of a withdrawal reaction with low doses of
venlafaxine, we suggest that this drug is used with caution
and that care is taken to gradually taper any dose before
discontinuing
treatment. |
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