Gabapentin


  Issues for Surgery


For treatment of epilepsy – precipitation of rebound seizures or status epilepticus if omitted.

For peripheral neuropathic pain – loss of pain management if omitted.

For migraine prophylaxis [unlicensed] – risk of acute migraine attack if omitted.

For menopausal symptoms in women with breast cancer – loss of symptom control if omitted (particularly hot flushes).


  Advice in the Perioperative period


Elective and Emergency Surgery

Continue.

Patients should be advised to take their regular medications on the day of surgery1, 2, 3.

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).

Post-operative Advice

Regular dosing of the patient’s usual oral medication should be re-established as early as possible post-operatively2, 3.

Gabapentin is only available as oral preparations. For epilepsy patients, if they 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.


  Interaction(s) with Common Anaesthetic Agents


For general information regarding the use of anaesthetic agents used in epilepsy patients – see Antiepileptics – A General Overview.

Central Nervous System (CNS) Depression (also see under Interaction(s) with other Common Medicines used in the Perioperative Period)

Gabapentin has CNS depressant effects which may be additive with other medicines that also have CNS depressant effects such as1: -

  • benzodiazepines
  • inhalational anaesthetics and intravenous anaesthetics
  • local anaesthetics
  • opioids* – see also Opioids and Respiratory Depression below

*NB: Tramadol should be avoided in patients with a history of epilepsy due to an increase in seizure risk1

(Consult British National Formulary for available drugs in each class)

Opioids and Respiratory Depression

Gabapentin has been reported to enhance the analgesic effects of opioids. There might be an additive effect of gabapentin and opioids on respiratory depression (see Further Information) – monitor for signs of CNS depression (such as somnolence, sedation, respiratory depression), and adjust the dose of gabapentin or the opioid appropriately2, 4, 5, 6.


  Interaction(s) with other Common Medicines used in the Perioperative Period


For general information regarding the use of antiemetics in epilepsy patients – see Antiepileptics – A General Overview.

CNS Depression (also see under Interaction(s) with Common Anaesthetic Agents for information on opioids)

Gabapentin has CNS depressant effects which may be additive with antiemetics that also have CNS depressant effects such as cyclizine, droperidol and prochlorperazine*1.

*NB: see Antiepileptics – A General Overview

Opioids and Respiratory Depression (see under Interaction(s) with Common Anaesthetic Agents and Further Information)

Non-Steroidal Anti-inflammatory Drugs (NSAIDs)

Gabapentin and NSAIDs can increase the risk of hyponatraemia1.


  Further Information


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

Gabapentin is a category 3 antiepileptic; hence it is usually unnecessary to ensure that patients are maintained on a specific manufacturer’s product as therapeutic equivalence can be assumed. However, other factors are important when considering if switching is appropriate such as patient anxiety, risk of confusion or dosing errors. (For more information see Antiepileptics – A General Overview).

MHRA/CHM Advice: Gabapentin (Neurontin): Risk of severe respiratory depression (October 2017)

Gabapentin has been associated with a rare risk of severe respiratory depression even without concomitant opioid medicines. Patients with compromised respiratory function, respiratory or neurological disease, renal impairment, concomitant use of CNS depressants, and elderly people might be at higher risk of experiencing severe respiratory depression and dose adjustments may be necessary in these patients1.


  References


  1. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press http://www.medicinescomplete.com [Accessed on 15th July 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
  4. Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 15th July 2019]
  5. Gabapentin. In: Brayfield A (Ed), Martindale: The Complete Drug Reference. London: The Royal Pharmaceutical Society of Great Britain. http://www.medicinescomplete.com [Accessed 15th July 2019]
  6. Summary of Product Characteristics –Gabapentin 300mg Capsules. Rivopharm. Accessed via www.medicines.org.uk 15/07/2019 [date of revision of the text May 2019]