What are the recommended muscle relaxants and their dosing regimens?

Recommended Muscle Relaxants and Dosing Regimens

For most clinical scenarios requiring muscle relaxation, suxamethonium is the gold standard for short-acting muscle relaxant therapy, with non-depolarizing agents like baclofen and tizanidine recommended for specific indications based on patient characteristics. 1

General Recommendations by Clinical Scenario

Electroconvulsive Therapy

• Suxamethonium is the first-line muscle relaxant for electroconvulsive therapy to prevent complications related to generalized convulsions 1
• If contraindications to suxamethonium exist, rocuronium combined with sugammadex is an alternative option 1
• Short-acting agents are preferred to produce brief muscle relaxation during seizures 1

Obese Patients (BMI ≥ 40 kg/m²)

• Suxamethonium at 1.0 mg/kg based on actual body weight is recommended for tracheal intubation in severely obese patients 1
• Non-depolarizing muscle relaxants should be dosed based on lean body weight in obese patients 1
• Sugammadex is preferred over neostigmine for reversal of steroid muscle relaxants in obese patients due to faster recovery time 1

Patients with Neuromuscular Disease

• Suxamethonium is contraindicated in patients with primary muscle damage (myopathies) or up-regulation of nicotinic acetylcholine receptors 1
• For patients with myasthenia, non-depolarizing muscle relaxants require 50-75% dose reduction 1
• Sugammadex is recommended for reversal of steroidal muscle relaxants in patients with neuromuscular disease 1
• Neuromuscular blockade monitoring is essential when using muscle relaxants in patients with neuromuscular disease 1

Patients with Renal/Hepatic Failure

• Benzylisoquinoline muscle relaxants (atracurium/cisatracurium) are recommended in cases of renal/hepatic failure 1
• Sugammadex efficacy is decreased in patients with severe renal failure (creatinine clearance < 30 mL/min) 1

Elderly Patients

• Baclofen is preferred for elderly patients, starting at 5 mg three times daily with maximum tolerated dose of 30-40 mg per day 2
• Tizanidine is another option for elderly patients, starting at 2 mg three times daily with careful monitoring for orthostatic hypotension 2
• Avoid carisoprodol and orphenadrine in elderly patients due to high risk of sedation, falls, and anticholinergic effects 2

Specific Muscle Relaxant Dosing

Suxamethonium (Succinylcholine)

• Standard dose: 1.0 mg/kg based on actual body weight 1
• For obese patients: 1.0 mg/kg based on actual body weight 1
• Contraindicated in myopathies and conditions with up-regulation of nicotinic acetylcholine receptors 1

Baclofen

• Starting dose: 5 mg three times daily 2
• Maximum tolerated dose in elderly: 30-40 mg per day 2
• Enhanced muscle relaxant effect when combined with glucocorticoids 3

Tizanidine

• Starting dose: 4 mg, can be repeated at 6-8 hour intervals 4
• Maximum daily dose: 36 mg 4
• For elderly patients: Start at 2 mg three times daily 2
• Food has complex effects on tizanidine pharmacokinetics that may alter clinical response 4

Cyclobenzaprine

• Dosing: 5-10 mg three times daily 5
• For patients with mild hepatic impairment: Start with 5 mg and titrate slowly 5
• Not recommended for patients with moderate to severe hepatic impairment 5

Monitoring and Safety Considerations

• Neuromuscular blockade monitoring is crucial to adjust dosing and identify potential recurarization 1
• Sugammadex dosing must be adjusted based on the degree of blockade at time of reversal 1
• Muscle relaxants should be used for the shortest duration necessary in elderly patients 2
• Abrupt discontinuation of baclofen should be avoided due to risk of withdrawal symptoms 2
• Most muscle relaxants have limited evidence of efficacy for chronic pain management 6, 7

Common Pitfalls to Avoid

• Failing to distinguish between antispasticity agents (baclofen, tizanidine, dantrolene) and antispasmodic agents (cyclobenzaprine) 7, 8
• Using inappropriate dosing calculations in obese patients (actual vs. lean body weight) 1
• Overlooking the need for neuromuscular blockade monitoring in special populations 1
• Combining muscle relaxants with other medications that have anticholinergic properties in elderly patients 2
• Underestimating the risk of adverse effects, particularly drowsiness and dizziness, which can lead to falls 9