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Interaction between lamotrigine and contraceptive pill identified

8 July, 2005

Changes to the
prescribing information for the anti-epileptic drug Lamictal
(lamotrigine) have been circulated to health care professionals in the
UK by its manufacturer GlaxoSmithKline.

In
a letter, GlaxoSmithKline said that new research shows an interaction
between lamotrigine and oral contraceptives which may result in the
reduced effectiveness of the contraceptives.

There
also may be reduced seizure control in women on lamotrigine who start
taking an oral contraceptive. In addition, if women taking lamotrigine
stop taking oral contraceptives, there is a risk of the level of
lamotrigine in the body becoming too high, which may cause unwanted
symptoms. GlaxoSmithKline added that that lamotrigine levels may be
decreased during pregnancy and quickly revert after birth.

An Epilepsy Action spokesperson said:

'We
advise women, taking lamotrigine, first of all not to make any changes
to their anti-epileptic treatment until they have sought advice from
their GP or epilepsy specialist. This is because reducing or abruptly
stopping anti-epileptic treatment can cause recurrent or an increasing
number of seizures. Until women have sought advice from their GP they
should consider using an additional form of contraception, such as the
barrier method, to avoid an unwanted pregnancy.

'Women
taking lamotrigine and the contraceptive pill may wish to make an
appointment with their epilepsy specialist to discuss their epilepsy
treatment. They should record and report any changes in their seizure
pattern to their epilepsy specialist as this may be a sign that the
anti-epileptic drug treatment is not effective.

'They
should record any breakthrough bleeding and report this to their GP as
soon as possible as this could be a sign of contraceptive failure.
Women taking lamotrigine and the contraceptive pill could discuss with
their GP suitable alternative contraceptive methods.

'It
is important to bear in mind that several anti-epileptic drugs have a
similar interaction with the contraceptive pill in that the
contraceptive effect may be reduced.'

The new information on lamotrigine comes after a clinical study of 22 women taking Lamictal and a combined oral contraceptive.