Anticonvulsants used for Partial Seizures

Partial seizures originate in a focal region of the cortex and can be subdivided into those that do not impair consciousness (simple partial) and those that do (complex partial). Both types of partial seizure can spread rapidly to other cortical areas, resulting in secondary generalised tonic-clonic seizures.

See relevant articles on:

Managing Epilepsy in Primary Care
Epilepsy in Children and Young People
Epilepsy in Adults
Epilepsy in Elderly People

• Simple partial seizures:
  • Presentation depends on the site of origin of the discharge, e.g. those arising from the motor cortex cause rhythmic movements of the contralateral face, arm or leg (Jacksonian seizures).
  • Seizures arising from sensory regions or areas responsible for emotions and memory may produce olfactory, visual or auditory hallucinations, feelings of déjà vu or jamais vu, fear, panic or euphoria.
• Complex partial seizures: an epileptic seizure that is limited to one cerebral hemisphere and causes impairment of awareness or responsiveness.
• Temporal lobe epilepsy may be simple partial seizures without loss of awareness (with or without aura) or complex partial seizures (with loss of awareness).

• Carbamazepine, lamotrigine, oxcarbazepine, or sodium valproate are the drugs of choice for partial (focal) seizures with or without secondary generalisation; second-line drugs include clobazam, gabapentin, levetiracetam, pregabalin, tiagabine, topiramate, and zonisamide.²
• Where a single drug has failed to control the seizures, combination therapy can be tried but this increases the risk of adverse effects and drug interactions.

• Interactions between anti-epileptics are complex and may enhance toxicity without a corresponding increase in anti-epileptic effect.
• These interactions are very variable and unpredictable. Plasma monitoring is often advisable with combination therapy.

• First-line drugs for partial seizures with or without secondary generalisation include carbamazepine, lamotrigine, oxcarbazepine, sodium valproate or topiramate.
• Second-line drugs include clobazam, gabapentin, levetiracetam and tiagabine.

Indications for drug monitoring include:

• When drug therapy is initiated and after dosage adjustments (sampling at trough level at steady state).
• Suspected therapeutic failure; identify inappropriate dosage, non-compliance, altered absorption, altered clearance (sampling at trough level at steady state).
• Therapeutic confirmation after optimum seizure control so that a drug level can serve as a reference point in the event that seizure control is lost or side-effects occur (sampling at trough level at steady state).
• Signs of clinical intoxication (sampling at peak level or when symptoms are present).
• Suspected drug interaction (sampling at trough level).
• Monitoring of pharmacologically active metabolites.
• Special risk groups where drug pharmacokinetics is altered: neonates, elderly patients, pregnant women, patients with compromised elimination, e.g. renal, hepatic disease (sampling at trough level).
• Suspected drug overdose.

• At 9 years after diagnosis of epilepsy about 70% of people will have been seizure-free for the preceding 3 years and only about 30% will still be on medication.⁵
• Because of the possible long-term side-effects of the drugs, it is common clinical practice to consider drug withdrawal after a patient has been seizure-free for three or more years.
• The probability of relapse is greatest within the first year of treatment reduction or withdrawal.
• The more severe and long-lasting the patient's epilepsy before remission, the greater the risk of relapse.
• Juvenile myoclonic epilepsy or the presence of a structural lesion underlying the epilepsy also increase the risk of relapse.
• Social complications of failed drug withdrawal increase with adulthood and trials of drug withdrawal should ideally take place before school-leaving age. After this a number of factors may influence the decision, e.g. employment, driving, leisure activities, contraception and pregnancy.
• The final decision to come off drug treatment should be taken by the patients and their families following advice from the physician. If a decision to withdraw medication is made, discontinuation of treatment should be undertaken slowly, over a period of 2-3 months, to minimise the risks of relapse.⁵