Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORGESIC vs BACLOFEN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
NORGESIC is a combination of orphenadrine citrate, aspirin, and caffeine. Orphenadrine is a centrally acting muscle relaxant with anticholinergic properties; its exact mechanism is not fully understood, but it may act via central atropine-like effects and inhibition of reuptake of norepinephrine and serotonin. Aspirin inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis, leading to analgesic, antipyretic, and anti-inflammatory effects. Caffeine is a central nervous system stimulant that may enhance analgesia via adenosine receptor antagonism.
GABA-B receptor agonist; inhibits monosynaptic and polysynaptic spinal reflexes by hyperpolarizing afferent terminals.
Adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions
Spasticity due to multiple sclerosis (FDA approved),Spinal cord injury (FDA approved),Intrathecal use for severe spasticity of cerebral origin (off-label),Hiccups (off-label),Alcohol withdrawal syndrome (off-label),Trigeminal neuralgia (off-label)
1-2 tablets orally 2-4 times daily. Each tablet contains orphenadrine citrate 100 mg and acetaminophen 325 mg.
Initial: 5 mg orally 3 times daily; increase by 5 mg per dose every 3 days to max 80 mg/day (20 mg 4 times daily). Intrathecal: initial test dose 50-100 mcg; for continuous infusion, daily dose typically 300-800 mcg.
Terminal elimination half-life is 2–4 hours; clinical multiple dosing may require 4–6 hour intervals
Terminal half-life: 2.5-4 hours (young adults), 4-8 hours (elderly); clinical context: requires frequent dosing for spasticity.
Orphenadrine is extensively metabolized in the liver via oxidative N-demethylation and hydroxylation; aspirin is hydrolyzed to salicylic acid, which is primarily metabolized in the liver by conjugation (glucuronidation and glycine conjugation) and oxidation; caffeine is metabolized in the liver via cytochrome P450 1A2 (CYP1A2) to paraxanthine, theobromine, and theophylline.
Metabolized via hepatic deamination by transaminase; primarily excreted unchanged in urine (approximately 70-80%), with minor hepatic metabolism.
Primarily renal (70% as unchanged drug and metabolites; 10% as unchanged) and biliary (30%)
Renal: 70-80% unchanged; fecal: <5%; biliary: minimal.
~90% bound to albumin and alpha-1-acid glycoprotein
30-35% bound to albumin.
1.5–2.0 L/kg; indicates extensive tissue distribution
Vd: 0.5-0.7 L/kg; indicates distribution into total body water.
Oral: ~70% (first-pass metabolism reduces absolute bioavailability); Intramuscular: ~100%
Oral: 70-85% with high variability; intrathecal: 100%.
GFR 30-59 m L/min: reduce dose by 50% (maximum 1 tablet twice daily). GFR <30 m L/min: avoid use due to risk of accumulation.
Cr Cl 30-50 m L/min: reduce dose by 50%; Cr Cl <30 m L/min: avoid use or use with extreme caution, reduce dose by 75%.
Child-Pugh Class B: reduce dose by 50% (maximum 1 tablet twice daily). Child-Pugh Class C: contraindicated.
No specific guidelines; use with caution due to potential for increased sedation/neurotoxicity.
Not recommended for patients under 18 years of age due to lack of safety and efficacy data.
Children 2-7 years: initial 2.5 mg orally 4 times daily, increase by 2.5 mg/dose every 3 days to max 40 mg/day; children ≥8 years: initial 5 mg orally 3 times daily, increase as in adults to max 60 mg/day.
Start with 1 tablet twice daily; titrate slowly due to increased risk of anticholinergic effects (confusion, urinary retention).
Start at low end of dosing range (5 mg twice daily), titrate slowly due to increased risk of sedation, weakness, and cognitive impairment.
No FDA black box warning.
Abrupt discontinuation may cause withdrawal symptoms including hallucinations, seizures, and life-threatening hyperpyrexia; taper dose gradually.
May impair mental and/or physical abilities required for driving or operating machinery due to anticholinergic effects (e.g., drowsiness, blurred vision),Use with caution in patients with glaucoma, prostatic hypertrophy, or gastrointestinal obstruction due to anticholinergic effects,Aspirin component increases risk of bleeding, particularly in patients with bleeding disorders or on anticoagulant therapy,Reye's syndrome risk in children and teenagers with viral infections,Hypersensitivity reactions including anaphylaxis may occur,Renal impairment may increase risk of salicylate toxicity
May cause CNS depression (drowsiness, sedation) and impair ability to drive or operate machinery.,Risk of withdrawal syndrome including fever, altered mental status, and autonomic instability upon abrupt cessation.,Use with caution in patients with renal impairment; dose adjustment required.,May exacerbate psychiatric disorders; monitor for hallucinations, confusion.,Risk of respiratory depression when combined with other CNS depressants.
Hypersensitivity to any component,Peptic ulcer or gastrointestinal bleeding,Severe renal impairment (creatinine clearance <10 m L/min),Severe hepatic impairment,Bleeding disorders (e.g., hemophilia),Concurrent use of anticoagulants or antiplatelet drugs (relative),Children and teenagers with varicella or influenza-like symptoms (due to Reye's syndrome risk),Glaucoma (angle-closure), prostatic hypertrophy, or gastrointestinal obstruction (relative, due to anticholinergic effects)
Hypersensitivity to baclofen.,Intrathecal formulation is contraindicated in patients with active infection or bleeding disorders at lumbar puncture site.,Women who are breastfeeding (relative contraindication).
Avoid alcohol. Take with food or milk to minimize GI irritation. No specific food interactions beyond alcohol and potential for increased gastric irritation with aspirin.
No specific food interactions. Avoid alcohol due to additive CNS depression.
Norgesic contains orphenadrine citrate, aspirin, and caffeine. Aspirin: First trimester: possible increased risk of miscarriage and cardiac defects; third trimester: premature closure of ductus arteriosus and oligohydramnios; avoid in third trimester. Orphenadrine: limited human data; animal studies not sufficient; avoid in pregnancy unless benefit outweighs risk. Caffeine: considered low risk at moderate doses.
First trimester: Limited human data; animal studies show increased fetal malformations (omphalocele, exencephaly) at doses equivalent to human therapeutic range. Second and third trimesters: Risk of neonatal withdrawal (hypertonia, seizures) with chronic maternal use. Avoid unless benefit outweighs risk.
Orphenadrine: excreted in breast milk; M/P ratio unknown; potential for anticholinergic effects in infant. Aspirin: excreted in breast milk; risk of Reye's syndrome if infant has viral illness; avoid breastfeeding while using aspirin. Caffeine: low levels in milk; generally considered safe in moderate amounts. Not recommended during breastfeeding.
Baclofen excreted into breast milk in low concentrations (M/P ratio approximately 0.43). Relative infant dose estimated 0.9% of maternal weight-adjusted dose. Considered compatible with breastfeeding, but monitor infant for sedation and hypotonia.
No standard dosing adjustments established. Avoid use in pregnancy, especially third trimester, due to aspirin component. If necessary, use lowest effective dose for shortest duration. Increased renal clearance in pregnancy may affect caffeine elimination, but no specific dose adjustment recommended.
No specific dose adjustments recommended. Increased renal blood flow and GFR in pregnancy may reduce baclofen levels; monitor clinical effect and adjust dose as needed. Avoid abrupt discontinuation due to risk of maternal withdrawal and rebound spasticity.
Norgesic (orphenadrine/aspirin/caffeine) is used for musculoskeletal pain. Orphenadrine has anticholinergic properties; use cautiously in elderly, glaucoma, or prostatic hypertrophy. May cause drowsiness and impair motor skills. Avoid in myasthenia gravis. Monitor for GI bleeding due to aspirin.
Abrupt withdrawal can cause severe rebound spasticity, fever, and rhabdomyolysis; taper by 5-10 mg/week. Intrathecal baclofen pumps require careful monitoring for overdose (respiratory depression) or withdrawal. Use with caution in renal impairment (dose adjust for Cr Cl <30 m L/min).
Take with food or milk to reduce GI upset.,Avoid alcohol and other CNS depressants.,Do not drive or operate machinery until you know how this medication affects you.,Report signs of bleeding (bruising, black stools) or anticholinergic effects (dry mouth, blurred vision, constipation).,Do not exceed recommended dose; orphenadrine can cause serious anticholinergic toxicity.
Do not stop taking baclofen suddenly; sudden discontinuation can cause serious withdrawal symptoms including hallucinations, seizures, and high fever.,Avoid alcohol and CNS depressants as they increase sedation and risk of falls.,May cause dizziness or drowsiness; avoid driving or operating machinery until you know how it affects you.,Take exactly as prescribed; missed doses can lead to muscle spasms or withdrawal.,Report any unusual muscle stiffness, rapid heart rate, or dark urine immediately.
No interactions on record
"Sevoflurane enhances the inhibitory effects of baclofen on the central nervous system by potentiating GABA-B receptor activity, leading to an increased risk of profound sedation, respiratory depression, and hypotension. This synergistic interaction can result in prolonged recovery from anesthesia and the need for ventilatory support. Clinically, patients may exhibit exaggerated muscle relaxation and a delayed emergence from anesthesia, particularly at higher doses of either agent."
"Concomitant use of etidocaine, an amide-type local anesthetic that blocks voltage-gated sodium channels, and baclofen, a GABAB receptor agonist used for muscle spasticity, may lead to additive central nervous system (CNS) depression and respiratory depression. This interaction results from synergistic depressant effects on the brainstem and spinal cord, increasing the risk of sedation, dizziness, ataxia, and impaired consciousness. Clinically, patients may experience excessive drowsiness, respiratory compromise, and impaired motor coordination, particularly in the elderly or those with pre-existing renal impairment where baclofen accumulation is more likely."
"The coadministration of Baclofen and Metaxalone results in additive central nervous system (CNS) depression due to their shared pharmacodynamic effects on GABAergic and sedative pathways. This combination can potentiate sedation, dizziness, ataxia, and respiratory depression, particularly in elderly patients or those with renal impairment. Clinical outcomes may include increased risk of falls, cognitive impairment, and impaired motor coordination, necessitating cautious dose titration."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about NORGESIC vs BACLOFEN, answered by our medical review team.
NORGESIC is a Muscle Relaxant that works by NORGESIC is a combination of orphenadrine citrate, aspirin, and caffeine. Orphenadrine is a centrally acting muscle relaxant with anticholinergic properties; its exact mechanism is not fully understood, but it may act via central atropine-like effects and inhibition of reuptake of norepinephrine and serotonin. Aspirin inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis, leading to analgesic, antipyretic, and anti-inflammatory effects. Caffeine is a central nervous system stimulant that may enhance analgesia via adenosine receptor antagonism.. BACLOFEN is a Skeletal Muscle Relaxant that works by GABA-B receptor agonist; inhibits monosynaptic and polysynaptic spinal reflexes by hyperpolarizing afferent terminals.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NORGESIC and BACLOFEN depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of NORGESIC is: 1-2 tablets orally 2-4 times daily. Each tablet contains orphenadrine citrate 100 mg and acetaminophen 325 mg.. The standard adult dose of BACLOFEN is: Initial: 5 mg orally 3 times daily; increase by 5 mg per dose every 3 days to max 80 mg/day (20 mg 4 times daily). Intrathecal: initial test dose 50-100 mcg; for continuous infusion, daily dose typically 300-800 mcg.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between NORGESIC and BACLOFEN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. NORGESIC is classified as Category C. Norgesic contains orphenadrine citrate, aspirin, and caffeine. Aspirin: First trimester: possible increased risk of miscarriage and cardiac defects; third trimester: premature clos. BACLOFEN is classified as Category C. First trimester: Limited human data; animal studies show increased fetal malformations (omphalocele, exencephaly) at doses equivalent to human therapeutic range. Second and third t. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.