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No drug-drug interactions are known but there are suggestions of pharmacodynamic
interaction with traditional sodium channel blockers such as carbamazepine and
oxcarbazepine.

Lacosamide commonest side effects are dizziness, headaches, nausea, and diplopia. It seems
better tolerated if no traditional sodium channel blockers are used concomitantly. No
idiosyncratic side effects have yet been associated with this drug. It should be used with
caution in people with a history of cardiac conduction problems as it is known to increase the
PR interval in some people.

Levetiracetam
Levetiracetam, a piracetam derivative, is a broad-spectrum drug indicated both as a first-line
drug and as an add-on drug. Its mode of action is not fully understood. It has a binding site
in the brain for which the natural ligand is the synaptic vesicle protein SV2A but it is not
known if this is related to its mode of action.

The recommended doses are between 1000 and 3000 mg/day divided into two doses although
some people respond to doses outside this range. Levetiracetam should be started at 500
mg/day divided into two doses and increased by 250500 mg/day every week up to
10001500 mg/day in the first instance.

Levetiracetam is well tolerated overall and no idiosyncratic side effects have yet been
described. Somnolence, dizziness, asthenia, ataxia, insomnia, behavioural problems
(particularly irritability, usually of a transient nature) and mood changes are the most
common side effects. No definite pharmacokinetic interactions have yet been identified.

Oxcarbazepine
Oxcarbazepine, the 10-keto analogue of carbamazepine, has a similar mechanism of action
to carbamazepine. Its indications are very similar to those of carbamazepine; it is effective in
focal seizures with or without secondary generalisation and may worsen absences and
myoclonic seizures.

The recommended doses are between 600 and 2400 mg/day divided into two doses.
Oxcarbazepine should be started at 300 mg/day and increased by 300 mg/day each week, up
to 900 mg/day in the first instance.

Oxcarbazepine weakly induces hepatic enzymes, and so is likely to have fewer drug
interactions than carbamazepine. A high dose of the oral contraceptive pill is advised to give
protection against pregnancy. Oxcarbazepine exhibits less autoinduction than
carbamazepine. Its safety profile is very similar to that of carbamazepine apart from
hyponatraemia, which is more pronounced with oxcarbazepine and allergic skin reactions
which are less common. Cross-sensitivity is seen in less than one-third of people
hypersensitive to carbamazepine. There are indications of teratogenicity in animal models,
particularly at high doses but to date no concerns have been raised in humans.

Perampanel
Perampanel has been licenced for the adjunctive treatment of refractory focal epilepsy. It is
the first licenced drug that interacts with glutamate receptors. Its effective dose is likely to be
somewhere between 4 and 12 mg/day. The commonest treatment emerging events so far seen
are drowsiness, ataxia, lethargy, irritability, weight gain and blurred vision. No clinically
significant pharmacokinetic interaction has yet been seen. It has a very prolonged half-life
and can be given in a once-a-day regimen.