How risky is stopping epilepsy drugs?
Q A patient who has been fit-free for five years has asked if he can stop his anti-epilepsy drug. How should I advise him?
A About 1 per cent of the population have epilepsy, but about 70 per cent become seizure-free on medication. Exhaustive studies show that after a mean of 3.2 years of seizure freedom, 78 per cent of patients would still be seizure-free after a further two years if they stayed on medication, whereas
59 per cent would if they withdrew. Peak risk is
about nine months after withdrawal.
The longer a person has been seizure-free on anti-epileptic drugs, the better their prognosis.
Seizure freedom for five to 10 years gives two-thirds
of the risk of seizure recurrence associated with seizure freedom of two to three years.
Factors that increase the risks of recurrence include age of onset (over 16); taking more than one anti-epileptic drug (AED); seizures occurring after initiation of an AED; a history of tonic-clonic seizures; a history of myoclonic seizures; an abnormal EEG.
A relative risk of recurrence can be roughly worked out on the basis of these factors.
At five years seizure-free, on one AED and with one or two of the above risk factors, the likelihood of recurrent seizures on withdrawal is about 20 to 30 per cent, compared with 10-15
per cent risk without withdrawal.
At 10 years the risk would drop to perhaps 10 per cent and 5 per cent.
The patient can then be counselled to take into account the need to be seizure-free as far as possible for, say, work or driving.
Dr Jonathan Bird is consultant neuropsychiatrist,
Burden Centre for Neuropsychiatry, Frenchay Hospital, Bristol