Issues for surgery
Loss of control of spasticity if omitted.
Risk of potentially fatal withdrawal symptoms if baclofen omitted (see Further information).
Risk of CNS depression if continued (see Interactions with common anaesthetic agents and Interactions with other common medicines used in the perioperative period).
For intrathecal baclofen – risk of withdrawal (with Medtronic Synchromed II ® pump) or overdose (with Flowonix Prometra® pump), both of which could be fatal, if precautions not followed prior to magnetic resonance imaging (see Further information).
Advice in the perioperative period
Elective and emergency surgery
Continue.
Intrathecal baclofen
Baclofen indwelling infusion pumps MUST NOT be stopped (see Further information). Inform anaesthetist either in advance of admission for elective procedures or as soon as possible for emergency procedures, so consideration can be given to the position of the diathermy plate.
For patients requiring magnetic resonance imaging – liaise with Specialist centre and follow recommendations in Further information.
For patients requiring lumbar puncture – see Further information
Post-operative advice
Restart post-operatively as soon as next dose is due.
Monitor renal function – dose reduction may be necessary if renal function is impaired (consult current product literature).
Interactions with common anaesthetic agents
Hypotension
Baclofen can increase the risk of hypotension when used concomitantly with inhalational or intravenous anaesthetics. A case report noted hypotension with concurrent administration of morphine and intrathecal baclofen.
CNS depression (see also Interactions with other common medicines used in the perioperative period)
Baclofen has CNS depressant effects which may be additive with other medicines that also have CNS depressant effects, such as:-
- benzodiazepines
- inhalational anaesthetics and intravenous anaesthetics
- local anaesthetics
- opioids*
*Baclofen is also thought to increase the analgesic effect of fentanyl and morphine.
(Consult British National Formulary for available drugs in each class)
Antimuscarinic action
Antimuscarinic action of baclofen may be additive with agents that also have antimuscarinic effects, such as atropine and glycopyrronium.
Seizure threshold
Baclofen may lower the seizure threshold; a case report describes severe seizures during induction of anaesthesia, which were attributed to both baclofen and propofol.
Interactions with other common medicines used in the perioperative period
Hypotension
Baclofen can increase the risk of hypotension when used concomitantly with the antiemetics droperidol and prochlorperazine.
CNS depression (see also Interactions with common anaesthetic agents)
Baclofen has CNS depressant effects which may be additive with other medicines that also have CNS depressant effects, such as:-
- antiemetics (e.g. cyclizine, prochlorperazine)
- opioids*
*Baclofen is also thought to increase the analgesic effect of fentanyl and morphine.
(Consult British National Formulary for available drugs in each class)
Antimuscarinic action
Antiemetics
Antimuscarinic action of baclofen may be additive with antiemetics that also have antimuscarinic effects, such as cyclizine, haloperidol, levomepromazine or prochlorperazine.
Nefopam
Antimuscarinic action of baclofen may be additive with nefopam, which also has antimuscarinic effects.
Seizure threshold
Baclofen may lower the seizure threshold; concurrent use with other drugs that lower the seizure threshold (e.g., tramadol) might result in additive effects.
Non-steroidal anti-inflammatory drugs (NSAIDs)
An isolated case report describes baclofen toxicity secondary to ibuprofen-induced acute renal impairment. Whilst the manufacturers note that drugs or medicinal products that can significantly affect renal function may reduce baclofen excretion, leading to toxic effects, concurrent use is not contraindicated. It would be prudent to monitor renal function and adjust the baclofen dose in the event of a decline in renal function.
Further information
Withdrawal
Anxiety, confusional state, delirium, hallucinations, psychotic disorders, mania or paranoia, seizures, dyskinesia, tachycardia, hyperthermia, rhabdomyolysis, and temporary aggravation of spasticity have been reported after abrupt withdrawal of baclofen, especially after long-term use. Gradual dose reduction over at least 1-2 weeks is advised.
Intrathecal baclofen
With intrathecal baclofen, withdrawal symptoms occur after a few hours and can resemble autonomic dysreflexia, infection, malignant hyperthermia, and neuroleptic malignant syndrome; in rare cases, this has progressed to status epilepticus, rhabdomyolysis, coagulopathy, multiple organ failure, and death.
Magnetic resonance imaging (MRI)
MRI requires careful planning in patients with intrathecal baclofen pumps, as the procedure will affect the functioning of the pump. Patients with Flowonix Prometra® pumps are at risk of overdose, so it is recommended to empty the pump prior to MRI. Patients with Medtronic Synchromed II ® pumps, the standard pump used in the UK, do not need the pump emptying but are at risk of pump failure and subsequent withdrawal. Liaise with the patients' Specialist centre and follow the recommendations below:-
- Before an MRI, it is essential to examine the pump site to ensure the pump is not oriented axially, as this may cause permanent pump failure
- Inform radiographer of the pump, as scanning parameters may need to be altered to keep a low specific absorption rate, which may increase scanning duration
- Pump should be interrogated 20 minutes after MRI to ensure normal function has returned. Interrogation can be arranged at the patient’s Specialist centre or via the manufacturer
- Intrathecal baclofen pumps usually restart within 2 hours of pump stall; however, it can take up to 24 hours. If the pump has not restarted after 4 hours, close neurological monitoring is needed, and seek advice from Specialist about starting oral baclofen to avoid withdrawal
Lumbar puncture
Lumbar punctures should be performed under radiological guidance to avoid catheter damage and under strict sterile conditions to avoid introducing infection to the intrathecal baclofen delivery system.
References
- Balaratnam M. Stevenson V. intrathecal baclofen pumps: what the neurologist needs to know. Pract Neurol. 2022; 22:241-246 doi:10.1136/practneurol-2021-003184
- Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 27th May 2024]
- Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 27th May 2024]
- Petsas A, Drake J. Perioperative management for patients with a chronic spinal cord injury. BJA Education. 2015; 15(3):123-130
- Summary of Product Characteristics – Baclofen Tablets 10mg. Mylan. Accessed via www.medicines.org.uk 27/05/2024 [date of revision of the text February 2024]
- Summary of Product Characteristics – Baclofen 0.5mg/ml solution for infusion. Aguettant Ltd. Accessed via www.medicines.org.uk 27/05/2024 [date of revision of the text October 2014]