Baclofen and tizanidine

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.

Baclofen and tizanidine (brand names Lioresal, Zanaflex) — Centrally acting muscle relaxants; GABA-B agonist (baclofen); alpha-2 agonist (tizanidine).

Identification

• Therapeutic class: Centrally acting muscle relaxants.
• Pharmacologic class: GABA-B agonist (baclofen); alpha-2 agonist (tizanidine).

Pharmacology

• Mechanism of action: Reduce spasticity by inhibiting spinal reflexes (baclofen) or central alpha-2 stimulation (tizanidine).
• Onset / peak / duration: Onset within hours; tizanidine short acting.
• Half-life / therapeutic level: Baclofen 2 to 4 hours, tizanidine 2.5 hours; level not routine.

Clinical use

• Indications: Spasticity from multiple sclerosis, spinal cord injury, and other neurologic disease.
• Usual dose, route, frequency: PO divided doses, titrated; baclofen also intrathecal.
• Maximum dose / adjustments: Reduce in renal (baclofen) or hepatic (tizanidine) impairment; taper to stop.

Safety

• Contraindications: Tizanidine with potent CYP1A2 inhibitors (ciprofloxacin, fluvoxamine).
• Black box warning: Intrathecal baclofen carries a boxed warning that abrupt discontinuation can cause life-threatening withdrawal (high fever, rigidity, organ failure); oral forms also should not be stopped abruptly.
• Interactions: CNS depressants and alcohol, antihypertensives (tizanidine hypotension), CYP1A2 inhibitors (tizanidine).
• Pregnancy / lactation: Use only if clearly needed.
• High-alert: No.

Adverse effects

• Common side effects: Drowsiness, dizziness, weakness, dry mouth (tizanidine).
• Serious effects to report: Severe withdrawal if stopped abruptly, hypotension (tizanidine), hepatotoxicity (tizanidine).
• Antidote / reversal: Supportive care; restart drug for withdrawal.

Nursing process

• Assessment before administration: Spasticity baseline, blood pressure (tizanidine), renal and hepatic function.
• Interventions during therapy: Never stop abruptly; rise slowly; check LFTs for tizanidine.
• Monitor: Spasticity, sedation, blood pressure, LFTs (tizanidine).
• Evaluation / expected outcome: Reduced spasticity with preserved function.

Patient teaching

• Patient teaching: Do not stop suddenly; avoid alcohol; report severe weakness or fever.
• Notify provider if: Sudden high fever or rigidity, fainting, yellowing of skin.
• Administration tips: Taper to discontinue; tizanidine consistent timing relative to food.