Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
AMITRIPTYLINE HYDROCHLORIDE 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
Inhibits reuptake of serotonin and norepinephrine, leading to increased concentrations at synaptic cleft; also blocks histamine H1, alpha-1 adrenergic, and muscarinic cholinergic 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
Oral: 25-150 mg daily in divided doses or as a single bedtime dose; 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 is 15-35 hours (range 9-46 hours); clinical context: steady-state concentrations achieved within 7-10 days; may be prolonged in elderly, hepatic impairment, or CYP2D6 poor metabolizers.
Hydrocodone: 3.8-4.5 hours (immediate-release). Acetaminophen: 2-3 hours. Clinical note: Half-life prolonged in hepatic impairment; requires dose adjustment.
Primarily hepatic via CYP2D6, CYP3A4, CYP1A2, and CYP2C19; active metabolite nortriptyline; undergoes demethylation, hydroxylation, and conjugation.
Hydrocodone: CYP3A4 and CYP2D6; Acetaminophen: primarily via glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation, with minor oxidation by CYP2E1.
Primarily renal (approximately 30-50% as unchanged drug and metabolites, mainly glucuronide conjugates and hydroxylated metabolites). Fecal excretion accounts for <5%. Enterohepatic recirculation may occur.
Renal: ~90-100% as hydrocodone metabolites (conjugated) and unchanged hydrocodone; ~60% as acetaminophen metabolites (glucuronide, sulfate, cysteine); <5% unchanged acetaminophen. Biliary/fecal: <5%.
Approximately 94-96%; primarily bound to alpha-1-acid glycoprotein (AAG), with minor binding to albumin and lipoproteins.
Hydrocodone: ~20-30% (albumin). Acetaminophen: ~10-25% (albumin).
10-20 L/kg (large Vd due to extensive tissue binding); clinical meaning: high tissue penetration, especially CNS, and slow redistribution from tissues.
Hydrocodone: 3-4 L/kg (extensive tissue distribution). Acetaminophen: ~1 L/kg (uniformly distributed).
Oral: 30-60% due to extensive first-pass metabolism (CYP2C19, CYP3A4, CYP2D6); significant interindividual variability.
Oral: Hydrocodone ~70% (high first-pass metabolism); Acetaminophen ~85-90% (minimal first-pass).
GFR 10-50 m L/min: use 50% of normal dose; GFR <10 m L/min: use 25% of normal dose.
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: avoid use.
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.
Adolescents: 10-50 mg daily in divided doses; children under 12 years (for enuresis): 6-10 years: 10-20 mg, 11+ years: 25-50 mg at bedtime.
Not recommended for pediatric patients; safety and efficacy not established for children under 18 years. For adolescents ≥18 years: adult dosing.
Start at 10-25 mg at bedtime; increase by 10-25 mg every 3-7 days as tolerated; maximum 75-100 mg daily; monitor for CNS 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.
Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants. Close monitoring for clinical worsening, suicidality, or unusual changes in behavior is recommended.
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.
Cardiotoxicity (QT prolongation, arrhythmias), serotonin syndrome, activation of mania/hypomania, angle-closure glaucoma, urinary retention, seizures, increased intraocular pressure, orthostatic hypotension, drowsiness, withdrawal symptoms upon abrupt discontinuation.
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.
Concurrent use with MAOIs (risk of serotonin syndrome), recent myocardial infarction, hypersensitivity to tricyclic antidepressants, during acute recovery phase of MI, use with cisapride or other QT-prolonging drugs.
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 alcohol and tyramine-rich foods (e.g., aged cheese, cured meats, soy sauce) due to risk of hypertensive crisis. Limit caffeine intake; may increase CNS stimulation. Grapefruit juice may increase plasma levels; avoid or limit consumption.
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: Limited data suggest a small increased risk of congenital malformations, particularly cardiovascular defects. Second trimester: No specific malformation risk, but possible effects on fetal growth. Third trimester: Risk of neonatal withdrawal syndrome (irritability, feeding difficulties) and anticholinergic effects (constipation, urinary retention). Overall risk is low; benefits may outweigh risks in severe depression.
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.
Amitriptyline and its metabolite nortriptyline are excreted in breast milk with an M/P ratio of approximately 1.0 for amitriptyline. Infant daily dose is about 1-2% of maternal weight-adjusted dose. No adverse effects reported in most infants; however, monitor for drowsiness, poor feeding. American Academy of Pediatrics considers amitriptyline compatible with breastfeeding.
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.
Pregnancy increases clearance of amitriptyline by 30-50% due to expanded plasma volume and enhanced hepatic metabolism. Serum levels may decrease, potentially requiring dose increase of 30-50% to maintain efficacy. Consider therapeutic drug monitoring (target trough 100-250 ng/m L) for dose titration. Postpartum dosing should be reduced to prepregnancy levels.
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.
Do not discontinue abruptly; taper over 2-4 weeks to prevent withdrawal symptoms. Use with caution in patients with cardiac conduction defects (prolongs QTc interval). Serum levels >500 ng/m L are associated with toxicity. Start at 10-25 mg at bedtime for neuropathic pain. May precipitate mania in bipolar disorder.
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 at bedtime to minimize daytime sedation.,Avoid alcohol and other CNS depressants.,Report symptoms of urinary retention, vision changes, or rapid heartbeat.,May cause dry mouth; use sugar-free gum or candy.,Avoid abrupt discontinuation; follow your doctor's tapering plan.,Notify your doctor if you experience suicidal thoughts or worsening depression.
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.
"Amitriptyline, a tricyclic antidepressant, may inhibit the metabolism of captopril, an ACE inhibitor, leading to increased serum concentrations of captopril. This elevation can potentiate captopril's antihypertensive effects and increase the risk of adverse effects such as hypotension, renal impairment, and hyperkalemia. Patients should be monitored closely for signs of exaggerated hypotensive response and electrolyte disturbances."
"Rifapentine, a potent inducer of cytochrome P450 (CYP) enzymes, specifically CYP3A4 and CYP2C19, significantly increases the hepatic metabolism of amitriptyline, a tricyclic antidepressant primarily metabolized by CYP2C19 and CYP3A4. This induction leads to markedly reduced plasma concentrations of amitriptyline and its active metabolite nortriptyline, potentially resulting in loss of antidepressant efficacy or relapse of depressive symptoms. Additionally, abrupt withdrawal of rifapentine without dose adjustment of amitriptyline may cause increased tricyclic levels and toxicity."
"Dapiprazole, an alpha-1 adrenergic receptor antagonist, and amitriptyline, a tricyclic antidepressant with significant anticholinergic properties, can have additive anticholinergic and sympatholytic effects when coadministered. This may lead to enhanced central nervous system depression, hypotension, urinary retention, and constipation. Patients should be monitored for excessive sedation, orthostatic hypotension, and anticholinergic toxicity."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about AMITRIPTYLINE HYDROCHLORIDE vs ANEXSIA 7.5/325, answered by our medical review team.
AMITRIPTYLINE HYDROCHLORIDE is a Tricyclic Antidepressant that works by Inhibits reuptake of serotonin and norepinephrine, leading to increased concentrations at synaptic cleft; also blocks histamine H1, alpha-1 adrenergic, and muscarinic cholinergic 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 AMITRIPTYLINE HYDROCHLORIDE 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 AMITRIPTYLINE HYDROCHLORIDE is: Oral: 25-150 mg daily in divided doses or as a single bedtime dose; 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 AMITRIPTYLINE HYDROCHLORIDE 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. AMITRIPTYLINE HYDROCHLORIDE is classified as Category C. First trimester: Limited data suggest a small increased risk of congenital malformations, particularly cardiovascular defects. Second trimester: No specific malformation risk, but . 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.