Issues for Surgery
For treatment of epilepsy – precipitation of rebound seizures or status epilepticus if omitted.
For migraine prophylaxis [unlicensed] – risk of acute migraine attack if omitted.
Risk of metabolic acidosis if continued (see Further Information).
Risk of nephrolithiasis if continued without adequate hydration (see Further Information).
Advice in the Perioperative period
Elective and Emergency Surgery
Abrupt withdrawal of any anticonvulsant drug should be avoided1.
Confirm with the patient if they need to be maintained on a specific manufacturer’s product (see Further Information).
Regular dosing of the patient’s usual oral medication should be re-established as early as possible post-operatively2, 3.
Topiramate is only available as oral preparations. If patients with epilepsy cannot resume their usual oral medication post-operatively, the advice of a Neurologist should be sought to determine the most appropriate antiepileptic preparation, dose, route and frequency to be used.
Monitor renal and hepatic function post-operatively since any impairment may lead to reduced clearance and the need to alter the dose of topiramate1, 4. Consult relevant product literature where necessary.
Interaction(s) with Common Anaesthetic Agents
For general information regarding the use of anaesthetic agents in patients with epilepsy – see ‘Antiepileptics – A General Overview’.
One study suggests that topiramate might attenuate the effects of ketamine, whereas another did not find an interaction5.
The manufacturer of topiramate predicts that it will inhibit the metabolism of diazepam (by cytochrome P450 enzyme CYP2C19). Bear the possibility in mind should any unexpected increase in diazepam adverse effects occur5.
Central Nervous System (CNS) Depressants
Concomitant administration of topiramate and CNS depressants has not been evaluated in clinical studies6. There may be potential for additive CNS depressant effects with administration of other CNS depressant medicines e.g. benzodiazepines, inhalational and intravenous anaesthetics, local anaesthetics, opioids and some antiemetics.
Interaction(s) with other Common Medicines used in the Perioperative Period
For general information regarding the use of antiemetics in patients with epilepsy – see ‘Antiepileptics – A General Overview’.
CNS Depressants – see Interaction(s) with Common Anaesthetic Agents
Proton Pump Inhibitors (PPIs)
The manufacturer of topiramate predicts that it will inhibit the metabolism of some PPIs by the cytochrome P450 enzyme CYP2C19 (lansoprazole, omeprazole, rabeprazole). Bear this in mind should any unexpected increase in PPI adverse effects occur5.
MHRA/CHM Advice: Antiepileptic Drugs: updated advice on switching between different manufacturer’s products (November 2017)1
Ensure adequate hydration throughout the perioperative period to maintain a good urine output, to try to reduce the risk of developing renal calculi, especially in predisposed patients1, 4, 6.
Hyperchloremic, non-anion gap, metabolic acidosis (i.e. decreased serum bicarbonate below the normal reference range in the absence of respiratory alkalosis) is associated with topiramate treatment1, 4, 6. This decrease in serum bicarbonate is due to the inhibitory effect of topiramate on renal carbonic anhydrase4, 5. Surgery can predispose to acidosis and this may be additive to the bicarbonate lowering effects of topiramate. If there are signs or symptoms indicative of metabolic acidosis, measurement of serum bicarbonate is recommended6. If metabolic acidosis develops and persists, consideration should be given to reducing the dose or discontinuing topiramate (using dose tapering)4, 6 – discuss with a Neurologist where appropriate.