http://bmj.com/cgi/content/full/323/7304/85
BMJ 2001;323:85 ( 14 July )
B D M Ratnayaka, H Dhaliwal, S Watkin.
Department of Neonatal Medicine,
City Hospital, Nottingham NG5 1PB
Baclofen is a skeletal muscle relaxant
used for the relief of chronic severe spasticity resulting from disorders
such as multiple sclerosis or traumatic injury to the spinal cord. We report
convulsions in a 7 day old girl who had been exposed to baclofen during
intrauterine life.
A paraplegic mother had been taking
baclofen 20 mg four times daily (Lioresal, Novartis, Surrey), oxybutanin
3 mg three times daily, and trimethoprim 100 mg daily, which she continued
throughout her pregnancy. The pregnancy was uneventful, but the baby was
delivered by ventouse extraction owing to fetal tachycardia. The Apgar
score was 10 at one and five minutes (cord pH: arterial 7.33, venous 7.3).
Seven days later the baby was admitted
with generalised convulsions. In retrospect the mother had noticed abnormal
movements from the second day after birth. Investigations included a full
septic screen for bacteriology and virology; a full blood count; serum
electrolytes; liver function tests; a metabolic screen of blood, urine,
and cerebrospinal fluid; urine for toxicology; and cranial ultrasonography.
All gave negative results. The convulsions did not respond to phenobarbitone,
phenytoin, clonazepam, lignocaine, or pyridoxine, which were tried according
to our hospital's guidelines for the management of neonatal seizures. The
baby received broad spectrum antibiotics until the cultures gave negative
results. Electroencephalography on day 11 showed prolonged episodes of
epileptic activity.
We thought that the convulsions could
be due to withdrawal of baclofen. Baclofen, 1 mg/kg daily in four divided
doses, was started. Thirty minutes after the first dose the convulsions
stopped. Baclofen was withdrawn slowly over the next two weeks. Magnetic
resonance imaging of the brain on day 17 suggested a short hypoxic ischaemic
insult during the perinatal period.
Because the baby was in good condition
at birth and because the convulsions were controlled within 30 minutes
of starting baclofen, we concluded that the convulsions had been caused
by its withdrawal. The change shown by the magnetic resonance image may
have been secondary to the convulsions.
In adults the half life of baclofen
is 2-6 hours (mean 3.5 hours). A previous report of baclofen overdose showed
a secondary increase in baclofen concentrations into the therapeutic range
after an initial decrease, probably due to its slow release from the central
nervous system and lipid stores.5 This may explain the delay in presentation
of our patient.
Convulsions after withdrawal of baclofen
are well reported in adults.1-4 Convulsions after withdrawal of exposure
to baclofen during intrauterine life have not been reported; this is the
first such report to the Committee on Safety of Medicines.
References