Skeletal muscle relaxants (cyclobenzaprine, methocarbamol, carisoprodol)

Skeletal muscle relaxants (cyclobenzaprine, methocarbamol, carisoprodol)

Drug monograph · NCLEX study reference
Trade names	Flexeril, Robaxin, Soma
Therapeutic class	Skeletal muscle relaxant
Pharmacologic class	Centrally acting muscle relaxants (carisoprodol is controlled C-IV)
Onset / peak / duration	Onset within an hour; cyclobenzaprine ER once daily.
Half-life / level	Cyclobenzaprine 18 hours; no routine level.
Routes	PO (oral), IV, IM
High-alert (ISMP)	No
Black box warning	None
Antidote / reversal	Supportive care.
Pregnancy / lactation	Use only if clearly needed.

Nursing pharmacology study reference (NCLEX-style monograph). Numeric values are standard teaching ranges for study and must be verified against current manufacturer labeling before clinical use. This is educational content, not prescribing guidance.

Skeletal muscle relaxants (cyclobenzaprine, methocarbamol, carisoprodol) (brand names Flexeril, Robaxin, Soma) — Skeletal muscle relaxant; Centrally acting muscle relaxants (carisoprodol is controlled C-IV).

Identification

• Therapeutic class: Skeletal muscle relaxant.
• Pharmacologic class: Centrally acting muscle relaxants (carisoprodol is controlled C-IV).

Pharmacology

• Mechanism of action: Reduce muscle spasm through central nervous system depression; cyclobenzaprine is structurally related to tricyclics.
• Onset / peak / duration: Onset within an hour; cyclobenzaprine ER once daily.
• Half-life / therapeutic level: Cyclobenzaprine 18 hours; no routine level.

Clinical use

• Indications: Short-term relief of acute musculoskeletal spasm and pain (typically up to 2 to 3 weeks).
• Usual dose, route, frequency: PO two to three times daily; methocarbamol also IV or IM.
• Maximum dose / adjustments: Short-term use; reduce in elderly and hepatic impairment; carisoprodol risk of dependence.

Safety

• Contraindications: Cyclobenzaprine with recent MI, arrhythmias, heart block, hyperthyroidism, MAO inhibitor use.
• Black box warning: None.
• Interactions: CNS depressants and alcohol (sedation), cyclobenzaprine with serotonergic drugs (serotonin syndrome) and anticholinergics.
• Pregnancy / lactation: Use only if clearly needed.
• High-alert: No.

Adverse effects

• Common side effects: Drowsiness, dizziness, dry mouth, anticholinergic effects (cyclobenzaprine).
• Serious effects to report: Excessive sedation, serotonin syndrome, dependence (carisoprodol).
• Antidote / reversal: Supportive care.

Nursing process

• Assessment before administration: Pain and spasm, cardiac history (cyclobenzaprine), sedation risk.
• Interventions during therapy: Combine with rest and physical measures; avoid alcohol; short courses.
• Monitor: Pain relief, sedation, dependence (carisoprodol).
• Evaluation / expected outcome: Reduced muscle spasm.

Patient teaching

• Patient teaching: Causes drowsiness; avoid alcohol and driving; use short term.
• Notify provider if: Severe drowsiness, palpitations, agitation with fever.
• Administration tips: Often dosed at bedtime due to sedation.