Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AMRIX vs INCRELEX
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.
Insulin-like growth factor 1 receptor agonist; promotes linear growth by stimulating chondrocyte proliferation at epiphyseal plates and exerts anabolic effects on muscle, bone, and other tissues.
Treatment of spasticity due to multiple sclerosis, spinal cord injury, or other spinal cord disorders
Treatment of growth failure in children with severe primary IGF-1 deficiency (primary IGFD) or with growth hormone (GH) gene deletion who have developed neutralizing antibodies to GH
15 mg orally once daily. May increase to 30 mg once daily if needed, after at least 1 week. Maximum 30 mg/day.
Intravenous bolus of 0.1 mg/kg given over 1 minute, followed by continuous intravenous infusion of 0.6 mg/kg/min for 30 minutes. Alternatively, a single intravenous bolus dose of 0.3 mg/kg.
Terminal elimination half-life approximately 32 hours (range 28–40 hours); clinically relevant for once-daily dosing in chronic muscle spasm
Terminal elimination half-life is approximately 8-10 hours in adults; clinically, steady-state is achieved within 2-3 days.
Hepatic via deamination; primarily metabolized by monoamine oxidase B (MAO-B) to inactive metabolites.
Primarily metabolized by proteolysis into smaller peptides and amino acids; not significantly metabolized by CYP enzymes.
Renal: approximately 40% as unchanged drug and metabolites; biliary/fecal: minimal; total clearance: 2.5 L/min
Renal: ~95% of absorbed dose as unchanged drug and metabolites; fecal: <5%.
40–45% bound to serum proteins, primarily albumin
Approximately 90% bound to insulin-like growth factor binding proteins (IGFBPs).
5–8 L/kg; suggests extensive tissue distribution, including skeletal muscle
Vd ~0.3-0.5 L/kg, indicating distribution primarily into extracellular fluid.
Oral: 85–95% (extended-release formulation)
Subcutaneous: 80-100% (high bioavailability).
No specific dose adjustment recommended; use with caution in severe renal impairment (Cr Cl < 30 m L/min).
No specific dose adjustment recommended for renal impairment; use with caution in patients with severe renal impairment (e GFR < 30 m L/min/1.73 m²) due to limited data.
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 specific dose adjustment recommended for hepatic impairment; use with caution in patients with Child-Pugh class C cirrhosis due to potential risk of hypoglycemia.
Safety and efficacy not established in pediatric patients under 12 years. For ages 12 and older, same as adult dosing.
Not approved for use in pediatric patients. Safety and efficacy in children have not been established.
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 dose adjustment recommended; elderly patients may be more sensitive to hypoglycemic effects; monitor blood glucose closely.
None
Increased risk of neoplasms; do not use in patients with active or suspected malignancy. Monitor for progression of pre-existing nevi.
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 malignancy (including intracranial tumors),Lymphoproliferative disorders,Intracranial hypertension (pseudotumor cerebri),Slipped capital femoral epiphysis,Progression of scoliosis,Pancreatitis,Hypoglycemia (especially with fasting or missed meals),Fluid retention (edema, pericardial effusion),Hypersensitivity reactions including anaphylaxis,Thymic hypertrophy
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.
Active or suspected malignancy (including intracranial tumors),Closed epiphyses (skeletal maturity),Acute critical illness (due to increased mortality with ICU use),Hypersensitivity to mecasermin or any component
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.
Must be administered within 20 minutes of a meal or snack containing carbohydrates to reduce risk of hypoglycemia. Avoid fasting or skipping meals. Grapefruit/grapefruit juice may alter CYP3A4 metabolism; avoid concurrent use. Alcohol can increase hypoglycemia risk; limit or avoid.
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).
INCRELEX (mecasermin) is an IGF-1 analog. In animal studies, there is no evidence of teratogenicity; however, data in pregnant women are insufficient. First trimester: No known malformation risk. Second/third trimesters: Fetal overgrowth (macrosomia) may occur if maternal IGF-1 levels are elevated. Caution advised.
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 into human milk unknown; molecular weight (7.5 k Da) suggests minimal transfer. M/P ratio not established. Caution recommended; alternative feeding may be considered until more data 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 established dose adjustments. Physiologic changes in pregnancy (increased renal clearance, plasma volume) may reduce drug levels; however, safety and efficacy data are lacking. Use only if clearly needed with careful monitoring.
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.
INCRELEX (mecasermin) is recombinant human insulin-like growth factor-1 (IGF-1) used for growth failure in severe primary IGF-1 deficiency. Monitor blood glucose closely due to risk of hypoglycemia; administer within 20 minutes of a meal or snack. Do not use in patients with closed epiphyses, active malignancy, or history of malignancy. Can cause intracranial hypertension (pseudotumor cerebri); monitor for headache, visual disturbances. Injection site reactions common.
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.
Do not use INCRELEX if you have cancer or a history of cancer.,Take exactly as prescribed; inject within 20 minutes after a meal or snack to prevent low blood sugar.,Do not inject into the same site repeatedly; rotate injection sites.,Watch for signs of low blood sugar (shakiness, sweating, confusion) and have fast-acting sugar (e.g., juice, glucose tablets) available.,Report severe headache, vision changes, or nausea immediately (possible increased pressure in the skull).,Inform all healthcare providers you are using this medication.
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 INCRELEX, 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.. INCRELEX is a Growth Factor that works by Insulin-like growth factor 1 receptor agonist; promotes linear growth by stimulating chondrocyte proliferation at epiphyseal plates and exerts anabolic effects on muscle, bone, and other tissues.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AMRIX and INCRELEX 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 INCRELEX is: Intravenous bolus of 0.1 mg/kg given over 1 minute, followed by continuous intravenous infusion of 0.6 mg/kg/min for 30 minutes. Alternatively, a single intravenous bolus dose of 0.3 mg/kg.. 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 INCRELEX 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. INCRELEX is classified as Category C. INCRELEX (mecasermin) is an IGF-1 analog. In animal studies, there is no evidence of teratogenicity; however, data in pregnant women are insufficient. First trimester: No known mal. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.