Antiepileptics – A General Overview

For further information on individual agents, please refer to specific monographs

  Antiepileptic Drugs (AEDs)

  Withdrawal

  Agents Use in Anaesthesia

Many of the agents used in anaesthesia possess both pro-convulsant and anticonvulsant properties, which could impact on the choice of anaesthetic.

Inhalational Anaesthetics
Nitrous oxide provokes seizures in animal models, but this has not been replicated in humans^{2, 3}. There are multiple case reports of sevoflurane-provoking seizure-like activity, particularly in children and where high concentrations are used in conjunction with hypocapnea². Both isoflurane, which has anticonvulsant properties, and desflurane, can be used in refractory status epilepticus².

Intravenous (IV) Anaesthetics
IV anaesthetics have been found to have both pro-convulsant and anticonvulsant properties, depending on the agent and the dose used^{2, 3}. The barbiturates (e.g. thiopental) and propofol are well-established agents for the treatment of refractory status epilepticus^{2, 3}. Etomidate has been reported to be more frequently associated with post-operative seizures and prolongs seizures when used for electroconvulsive therapy (ECT), and is generally avoided³. As with other IV agents, ketamine also facilitates seizures at low doses but at doses that produce sedative or anaesthetic effects, it shows anticonvulsant properties^{2, 3}.

Local Anaesthetics
Regional techniques with local anaesthetics are safe in patients with epilepsy³. However, close attention should be paid to safe dosing as local anaesthetic agents readily cross the blood-brain barrier and result in seizures if plasma levels are too high³, even in patients without epilepsy.

Neuromuscular Blocking Drugs (NMBDs)
None of the NMBDs appear to have any pro-convulsant or anticonvulsant effects for anaesthesia^{2, 3}. Non-depolarising NMBDs are safe, but the enzyme-inducing effects of some antiepileptics may cause resistance to the effects of agents such as pancuronium, rocuronium and vecuronium – monitor the effects of the NMBD and adjust the dose as necessary³.

Anticholinergics and Anticholinesterases
The increase in acetylcholine via administration of atropine or scopolamine can produce central cholinergic blockade (or central cholinergic syndrome). This can sometimes lead to seizures, which may be mistaken for epilepsy associated seizures and delay appropriate diagnosis and management. Glycopyrrolate does not cross the blood-brain barrier, so does not produce these effects².

Opioids
All opioid analgesics possess some degree of pro-convulsant activity³. Fentanyl, alfentanil, sufentanil, and morphine have been reported to cause generalised seizures after low-to-moderate doses². The addition of alfentanil to propofol anaesthesia for electroconvulsive therapy (ECT) also increases seizure duration²; hence alfentanil is usually avoided or used with caution³. Tramadol should be avoided as it lowers the seizure threshold³. Most other opioids have a long history of safe use in patients with epilepsy³.

Benzodiazepines
All benzodiazepines possess potent anticonvulsant properties and are safe to use^{2, 3}.

  Antiemetics

MHRA/CHM Advice: Antiepileptic Drugs: updated advice on switching between different manufacturer’s products (November 2017)¹

The following advice relates only to antiepileptic drugs used for treatment of epilepsy; it does not apply to other indications (e.g. mood stabilisation, neuropathic pain):-

• Different antiepileptic drugs vary considerably in their characteristics, which influences the risk of whether switching between different manufacturers’ products of a particular drug may cause adverse effects or loss of seizure control
• All epileptic agents have been divided into three risk-based categories to help healthcare professionals decide whether it is necessary to maintain continuity of supply of a specific manufacturer’s product.
• If it felt desirable for a patient to be maintained on a specific manufacturer’s product this should be prescribed by specifying the brand name, or by using the generic name and the name of the manufacturer.

If the prescribed product is unavailable, it may be necessary to dispense a product from a different manufacturer to maintain continuity of treatment. Such cases should be agreed with both the prescriber and the patient (or carer).

  References

1. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press http://www.medicinescomplete.com [Accessed on 29^th June 2019]
2. Perks A, Cheema S, Mohanraj R. Anaesthesia and epilepsy. BJA: British Journal of Anaesthesia. 2012; 108(4):562-571
3. Carter EL, Adapa RM. Adult epilepsy and anaesthesia. BJA Education. 2015; 15(3):111-117, 15(3): 111-117