Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AMITRIL vs ANEXSIA 7.5/325
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Amitriptyline inhibits the reuptake of serotonin and norepinephrine, thereby increasing their synaptic concentrations. It also blocks histamine H1, alpha-1 adrenergic, and muscarinic receptors.
Hydrocodone is a mu-opioid receptor agonist, producing analgesia and euphoria. Acetaminophen inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and providing analgesic and antipyretic effects.
Major depressive disorder,Neuropathic pain,Fibromyalgia,Migraine prophylaxis,Chronic tension-type headache,Insomnia (off-label),Irritable bowel syndrome (off-label)
Management of moderate to moderately severe pain where treatment with an opioid is appropriate and for which alternative treatments are inadequate
Adults: Initial 25 mg PO once daily at bedtime, increase by 25 mg every 3-7 days as tolerated to typical maintenance 75-150 mg/day PO divided doses or single dose at bedtime. Maximum 300 mg/day.
1 tablet (hydrocodone 7.5 mg / acetaminophen 325 mg) orally every 4 to 6 hours as needed for pain; maximum 6 tablets per day (hydrocodone 45 mg / acetaminophen 1950 mg).
Terminal elimination half-life: 15–25 hours (mean 20 h); may extend to >40 h in elderly or hepatic impairment.
Hydrocodone: 3.8-4.5 hours (immediate-release). Acetaminophen: 2-3 hours. Clinical note: Half-life prolonged in hepatic impairment; requires dose adjustment.
Hepatic, primarily via CYP2D6 and CYP3A4, with contributions from CYP1A2 and CYP2C19. Amitriptyline is metabolized to nortriptyline (active) and other metabolites.
Hydrocodone: CYP3A4 and CYP2D6; Acetaminophen: primarily via glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation, with minor oxidation by CYP2E1.
Renal: ~70% as metabolites, <5% unchanged; fecal: ~30% via bile.
Renal: ~90-100% as hydrocodone metabolites (conjugated) and unchanged hydrocodone; ~60% as acetaminophen metabolites (glucuronide, sulfate, cysteine); <5% unchanged acetaminophen. Biliary/fecal: <5%.
90–95% bound to albumin and alpha-1-acid glycoprotein.
Hydrocodone: ~20-30% (albumin). Acetaminophen: ~10-25% (albumin).
Vd: 15–30 L/kg; extensive tissue distribution, including CNS.
Hydrocodone: 3-4 L/kg (extensive tissue distribution). Acetaminophen: ~1 L/kg (uniformly distributed).
Oral: 30–60% due to first-pass metabolism.
Oral: Hydrocodone ~70% (high first-pass metabolism); Acetaminophen ~85-90% (minimal first-pass).
GFR 30-59 m L/min: Reduce dose by 50%. GFR 15-29 m L/min: Reduce dose by 75%. GFR <15 m L/min: Contraindicated. Hemodialysis: Not dialyzable; avoid use.
For GFR 30-59 m L/min: administer every 6 hours; maximum 4 tablets per day. For GFR 15-29 m L/min: administer every 8 hours; maximum 3 tablets per day. For GFR <15 m L/min: not recommended due to accumulation of metabolites.
Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Use contraindicated or reduce dose by 75% with extreme caution.
Child-Pugh Class A: no adjustment necessary. Child-Pugh Class B: reduce dose by 25-50% and extend dosing interval to every 6-8 hours; maximum 4 tablets per day. Child-Pugh Class C: contraindicated due to risk of hepatotoxicity.
Children ≥12 years: Initial 25-50 mg/day PO, increase gradually to 100 mg/day in divided doses. Children 6-11 years: 1-3 mg/kg/day PO in divided doses, not to exceed 100 mg/day. Not recommended under 6 years.
Not recommended for pediatric patients; safety and efficacy not established for children under 18 years. For adolescents ≥18 years: adult dosing.
Initial 10-25 mg PO at bedtime, with gradual titration. Maintenance often 50-100 mg/day. Monitor for orthostatic hypotension, falls, and anticholinergic effects.
Initiate at 1 tablet (hydrocodone 5 mg / acetaminophen 325 mg) every 6 hours as needed; titrate cautiously due to increased sensitivity, decreased renal function, and risk of respiratory depression. Maximum 4 tablets per day.
Amitriptyline is not approved for use in pediatric patients. Clinical worsening and suicide risk: Monitor for clinical worsening, suicidality, or unusual changes in behavior during initial therapy. Serotonin syndrome: Serotonin syndrome has been reported with SSRIs and SNRIs.
Addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or other CNS depressants; hepatotoxicity due to acetaminophen.
Suicidality in children, adolescents, and young adults; serotonin syndrome; activation of mania/hypomania; seizures; angle-closure glaucoma; urinary retention; cardiovascular effects (QT prolongation, arrhythmias); impaired cognitive/motor performance.
Risk of opioid addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risks from concomitant use of alcohol, benzodiazepines, or other CNS depressants; hepatotoxicity; severe hypotension; adrenal insufficiency; seizures; GI obstruction; impaired mental/physical abilities; use in elderly, cachectic, or debilitated patients; renal impairment; hepatic impairment; pregnancy; labor and delivery; nursing mothers; pediatric use; driving and operating machinery.
Hypersensitivity to amitriptyline or any component; concomitant use with MAOIs or within 14 days of MAOI use; recent myocardial infarction; during acute recovery phase after MI; concomitant use with cisapride.
Significant respiratory depression; acute or severe bronchial asthma; known or suspected GI obstruction; hypersensitivity to hydrocodone or acetaminophen; concomitant use of MAOIs or within 14 days of such therapy.
Avoid grapefruit and grapefruit juice as they may increase serum levels of amitriptyline. Limit tyramine-rich foods (aged cheeses, cured meats, fermented products) if taking MAOIs concurrently (contraindicated). Alcohol consumption may enhance sedative effects and is not recommended. High-fat meals may delay absorption but do not significantly alter overall exposure.
Avoid alcohol consumption due to increased risk of acetaminophen hepatotoxicity and CNS depression. No specific food restrictions, but grapefruit juice may theoretically affect hydrocodone metabolism via CYP3A4 inhibition; however, clinical significance is uncertain.
First trimester: Possible increased risk of cardiovascular malformations (OR ~1.2-1.5). Second/third trimester: Risk of neonatal withdrawal syndrome (irritability, feeding difficulties) and direct toxic effects (tachycardia, urinary retention). Late third trimester: Possible persistent pulmonary hypertension of the newborn (PPHN) with SSRI-like effects, though data limited for tricyclics.
FDA Category C (hydrocodone) and Category D (acetaminophen) in third trimester. First trimester: Acetaminophen associated with rare gastroschisis; hydrocodone risk of neural tube defects. Second trimester: No major malformations except with prolonged opioid use. Third trimester: Acetaminophen safe; hydrocodone risk of neonatal opioid withdrawal syndrome (NOWS). Avoid near term.
M/P ratio approximately 1.0-1.5. Excreted in breast milk in low amounts. Infant serum levels are usually subtherapeutic but cases of drowsiness, irritability reported. Use with caution; monitor infant for sedation and feeding difficulties. American Academy of Pediatrics considers compatible with breastfeeding if infant is healthy and full-term.
Hydrocodone/acetaminophen excreted in breast milk. M/P ratio unknown. Hydrocodone relative infant dose <3% of weight-adjusted maternal dose. Acetaminophen relative infant dose <2%. Use with caution; monitor infant for sedation, apnea, poor feeding. Highest risk in CYP2D6 ultrarapid metabolizers.
Due to increased plasma volume and hepatic metabolism in pregnancy, lower serum concentrations may occur. Monitor clinical response; dose adjustments may be needed but no standard guidelines. Use lowest effective dose. Taper if discontinuing to avoid withdrawal.
Increased clearance of hydrocodone in pregnancy may require dose adjustment; monitor for inadequate analgesia. Acetaminophen pharmacokinetics unchanged. Avoid high doses (hepatotoxicity risk). Consider baseline hepatic function. No specific dose adjustment recommended; titrate to effect.
For neuropathic pain, start at 10-25 mg at bedtime; titrate slowly to reduce sedative effects. Monitor QTc interval at baseline and with dose increases, especially in patients with cardiac risk factors. Anticholinergic effects (dry mouth, constipation) are common; consider prophylactic stool softeners. Avoid abrupt discontinuation; taper over 2-4 weeks to prevent withdrawal symptoms.
ANEXSIA 7.5/325 (hydrocodone/acetaminophen) carries a boxed warning for acetaminophen hepatotoxicity; maximum acetaminophen dose from all sources should not exceed 4 g/day. Hydrocodone is metabolized by CYP2D6 to hydromorphone; ultrarapid metabolizers may experience toxicity. Avoid concurrent use with other CNS depressants including alcohol. Prescribe with caution in patients with renal impairment (hydrocodone accumulation) or hepatic impairment (acetaminophen toxicity). Monitor for signs of respiratory depression, especially at therapy initiation and dose titration. Use the lowest effective dose for the shortest duration.
Take exactly as prescribed, usually once daily at bedtime due to drowsiness.,Do not stop suddenly; taper under doctor's guidance to avoid nausea, headache, or insomnia.,Avoid alcohol and other CNS depressants (e.g., sedatives, opioids) as they increase sedation risk.,Report any signs of serotonin syndrome (e.g., agitation, hallucinations, rapid heart rate) or cardiac symptoms (e.g., palpitations, fainting).,May cause dry mouth, constipation, blurred vision; use sugar-free gum, hydrate, and consider fiber supplements.
Do not exceed 6 tablets per day due to acetaminophen content.,Avoid alcohol while taking this medication.,Do not drive or operate heavy machinery until you know how this medication affects you.,Take exactly as prescribed; do not share with others.,Seek emergency help if you experience difficulty breathing, severe drowsiness, or signs of allergic reaction.,Store securely out of reach of children and dispose of unused medication properly.
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 AMITRIL vs ANEXSIA 7.5/325, answered by our medical review team.
AMITRIL is a Tricyclic Antidepressant that works by Amitriptyline inhibits the reuptake of serotonin and norepinephrine, thereby increasing their synaptic concentrations. It also blocks histamine H1, alpha-1 adrenergic, and muscarinic receptors.. ANEXSIA 7.5/325 is a Opioid Analgesic Combination that works by Hydrocodone is a mu-opioid receptor agonist, producing analgesia and euphoria. Acetaminophen inhibits cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and providing analgesic and antipyretic effects.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between AMITRIL and ANEXSIA 7.5/325 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 AMITRIL is: Adults: Initial 25 mg PO once daily at bedtime, increase by 25 mg every 3-7 days as tolerated to typical maintenance 75-150 mg/day PO divided doses or single dose at bedtime. Maximum 300 mg/day.. The standard adult dose of ANEXSIA 7.5/325 is: 1 tablet (hydrocodone 7.5 mg / acetaminophen 325 mg) orally every 4 to 6 hours as needed for pain; maximum 6 tablets per day (hydrocodone 45 mg / acetaminophen 1950 mg).. 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 AMITRIL and ANEXSIA 7.5/325 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. AMITRIL is classified as Category C. First trimester: Possible increased risk of cardiovascular malformations (OR ~1.2-1.5). Second/third trimester: Risk of neonatal withdrawal syndrome (irritability, feeding difficul. ANEXSIA 7.5/325 is classified as Category C. FDA Category C (hydrocodone) and Category D (acetaminophen) in third trimester. First trimester: Acetaminophen associated with rare gastroschisis; hydrocodone risk of neural tube d. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.