Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AMRIX vs EMVERM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Centrally acting muscle relaxant; it is the R-enantiomer of baclofen. Agonist at GABA-B receptors in the spinal cord, leading to inhibition of monosynaptic and polysynaptic spinal reflexes, thereby reducing muscle spasticity.
Mebendazole binds to tubulin, inhibiting microtubule polymerization, which disrupts glucose uptake and causes energy depletion leading to parasite death.
Treatment of spasticity due to multiple sclerosis, spinal cord injury, or other spinal cord disorders
Treatment of trichuriasis (whipworm infection),Treatment of enterobiasis (pinworm infection),Treatment of ascariasis (roundworm infection),Treatment of hookworm infections (Ancylostoma duodenale and Necator americanus),Off-label: Treatment of capillariasis, toxocariasis, and other helminth infections
15 mg orally once daily. May increase to 30 mg once daily if needed, after at least 1 week. Maximum 30 mg/day.
Mebendazole 100 mg orally twice daily for 3 days for adults and children over 2 years.
Terminal elimination half-life approximately 32 hours (range 28–40 hours); clinically relevant for once-daily dosing in chronic muscle spasm
2-8 hours; clinical context: the short half-life supports once-daily dosing; metabolites may persist longer.
Hepatic via deamination; primarily metabolized by monoamine oxidase B (MAO-B) to inactive metabolites.
Primarily hepatic; metabolized by microsomal enzymes (CYP450) to major metabolite 2-aminomebendazole, which is less active; also undergoes further metabolism.
Renal: approximately 40% as unchanged drug and metabolites; biliary/fecal: minimal; total clearance: 2.5 L/min
Primarily fecal (approx. 90%) as unchanged drug and metabolites; <10% excreted renally.
40–45% bound to serum proteins, primarily albumin
~90-95% bound to plasma proteins, primarily albumin.
5–8 L/kg; suggests extensive tissue distribution, including skeletal muscle
~1-2 L/kg; indicates extensive tissue distribution.
Oral: 85–95% (extended-release formulation)
Oral: ~22-40% due to first-pass metabolism; improved with food.
No specific dose adjustment recommended; use with caution in severe renal impairment (Cr Cl < 30 m L/min).
No adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment (Cr Cl <30 m L/min); use with caution.
Contraindicated in Child-Pugh class C. For Child-Pugh class A or B: initiate at 15 mg once daily; do not increase dose. Use with caution.
No adjustment for mild (Child-Pugh A) or moderate (Child-Pugh B) impairment. Avoid use in severe hepatic impairment (Child-Pugh C) due to increased risk of toxicity.
Safety and efficacy not established in pediatric patients under 12 years. For ages 12 and older, same as adult dosing.
Children ≥2 years: 100 mg orally twice daily for 3 days. Children <2 years: safety not established; use only if potential benefit outweighs risk.
Initiate at 15 mg once daily. Due to higher incidence of anticholinergic effects and falls, monitor closely; consider lower doses in frail elderly.
No specific adjustment required; use standard adult dosing. Monitor for adverse effects due to potential age-related renal or hepatic decline.
None
None.
Abrupt discontinuation may precipitate withdrawal syndrome including hallucinations, seizures, autonomic instability.,May cause sedation, dizziness, and muscle weakness; caution with activities requiring alertness.,Use with caution in patients with impaired renal function due to reduced clearance.,May exacerbate seizures in patients with epilepsy.,Avoid concomitant use with other CNS depressants.
Risk of neutropenia and agranulocytosis, especially with high doses or prolonged use,May cause bone marrow suppression; monitor blood counts in prolonged therapy,Hepatotoxicity reported; use caution in hepatic impairment,Seizures have occurred, particularly in patients with history of seizures,Not recommended in pregnancy (pregnancy category C); embryotoxic and teratogenic in animals
Hypersensitivity to amrix or baclofen.,Abrupt withdrawal is contraindicated; must be tapered.,Concomitant use with MAO inhibitors is contraindicated due to risk of hypertensive crisis.
Hypersensitivity to mebendazole or any component of the formulation,Absolute contraindication: Known hypersensitivity
Avoid grapefruit and grapefruit juice during treatment as they may increase cyclobenzaprine levels. Taking AMRIX with or without food does not significantly affect absorption. Alcohol should be strictly avoided as it potentiates CNS depression.
No significant food interactions; absorption is enhanced by fatty foods but not required for efficacy in enterobiasis. Avoid alcohol due to potential hepatotoxicity.
Cyclobenzaprine (AMRIX) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but adequate well-controlled studies in pregnant women are lacking. Use only if clearly needed. First trimester: no specific teratogenic effects documented; second and third trimesters: avoid near term due to potential neonatal effects (e.g., sedation, withdrawal).
FDA Pregnancy Category C. Animal studies have shown embryotoxicity and teratogenicity at high doses. Human data are limited; therefore, use during pregnancy only if clearly needed. Risk cannot be ruled out, especially in the first trimester.
Cyclobenzaprine is excreted into human milk in small amounts. M/P ratio: not established. Use with caution in nursing mothers; monitor infant for sedation, poor feeding, or hypotonia.
Excretion in human milk unknown. Caution should be exercised when administered to a nursing woman. M/P ratio not available.
No specific dose adjustments are recommended based on pharmacokinetic changes in pregnancy; however, due to potential for increased clearance, lowest effective dose should be used. Avoid use during labor and delivery due to potential neonatal depression.
No dose adjustment is recommended solely due to pregnancy, as pharmacokinetic changes are not well characterized. Use standard dosing: mebendazole 100 mg twice daily for 3 days for pinworm (or single 100 mg dose). For other indications, follow standard protocols.
AMRIX (cyclobenzaprine extended-release) should not be used longer than 2-3 weeks due to lack of evidence for efficacy in muscle spasm beyond that period. It has significant anticholinergic effects; avoid in patients with glaucoma, urinary retention, or those taking MAOIs. Do not crush or chew capsules; administer once daily at same time. Onset of action is delayed compared to immediate-release cyclobenzaprine.
EMVERM (mebendazole) is poorly absorbed systemically, making it ideal for intraluminal helminth infections. Administer with fatty meal to enhance absorption when systemic effect (e.g., for trichinosis) is desired. Avoid in pregnancy (FDA Category C). Tablets may be chewed, swallowed, or crushed. Monitor for rare agranulocytosis, especially with concurrent metronidazole or high doses.
Take AMRIX exactly once daily at the same time each day; do not crush, chew, or open the capsule.,Avoid alcohol and other CNS depressants (e.g., benzodiazepines, opioids) as they increase the risk of severe drowsiness and dizziness.,Do not drive or operate heavy machinery until you know how AMRIX affects you; it may cause drowsiness, dizziness, or blurred vision.,Contact your healthcare provider if you experience symptoms of serotonin syndrome (e.g., agitation, hallucinations, rapid heart rate, fever, muscle stiffness, nausea, diarrhea).,Do not use AMRIX for longer than 2-3 weeks unless specifically directed by your doctor; prolonged use is not recommended.,Inform your doctor if you have a history of urinary retention, glaucoma, thyroid disorders, heart problems, or liver disease.,If you miss a dose, take it as soon as you remember unless it is almost time for your next dose; do not double the dose.
Take exactly as prescribed; a second course may be needed if reinfection occurs.,Tablets can be chewed, crushed, or swallowed whole with or without food.,Mebendazole works by preventing worms from absorbing sugar, causing their death.,Strict hand hygiene and laundering of bedding/clothing to prevent reinfection.,Treat all household members if pinworm outbreak; withhold treatment in pregnancy unless essential.,Notify provider if fever, sore throat, or unusual bleeding/bruising (agranulocytosis warning).
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about AMRIX vs EMVERM, answered by our medical review team.
AMRIX is a Muscle Relaxant that works by Centrally acting muscle relaxant; it is the R-enantiomer of baclofen. Agonist at GABA-B receptors in the spinal cord, leading to inhibition of monosynaptic and polysynaptic spinal reflexes, thereby reducing muscle spasticity.. EMVERM is a Anthelmintic that works by Mebendazole binds to tubulin, inhibiting microtubule polymerization, which disrupts glucose uptake and causes energy depletion leading to parasite death.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AMRIX and EMVERM 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 AMRIX is: 15 mg orally once daily. May increase to 30 mg once daily if needed, after at least 1 week. Maximum 30 mg/day.. The standard adult dose of EMVERM is: Mebendazole 100 mg orally twice daily for 3 days for adults and children over 2 years.. 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 AMRIX and EMVERM 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. AMRIX is classified as Category C. Cyclobenzaprine (AMRIX) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but adequate well-controlled studies in pregnant women are lacki. EMVERM is classified as Category C. FDA Pregnancy Category C. Animal studies have shown embryotoxicity and teratogenicity at high doses. Human data are limited; therefore, use during pregnancy only if clearly needed.. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.