ACETAMINOPHEN AND HYDROCODONE BITARTRATE
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
Acetaminophen: analgesic and antipyretic effects via inhibition of cyclooxygenase (COX) and activation of descending serotonergic pathways; central action. Hydrocodone: mu-opioid receptor agonist; activates G-protein coupled receptors to modulate pain perception and emotional response.
| Metabolism | Acetaminophen: primarily via glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation; minor CYP2E1 oxidation to NAPQI (toxic metabolite). Hydrocodone: CYP3A4 and CYP2D6; N-demethylation to norhydrocodone; O-demethylation to hydromorphone (CYP2D6). |
| Excretion | Acetaminophen: primarily renal excretion of conjugated metabolites (glucuronide and sulfate) with approximately 5% excreted unchanged. Hydrocodone: renal excretion as unchanged drug and metabolites (O-demethylated and N-demethylated); total renal excretion accounts for about 60-70% of dose (parent and metabolites). Biliary/fecal elimination is minimal. |
| Half-life | Acetaminophen: 2-3 hours in adults; prolonged in hepatic impairment (up to 5 hours). Hydrocodone: 3.8-4.5 hours (range 3-5 hours) in healthy adults; prolonged in elderly or hepatic/renal impairment. Clinical context: repeated dosing may require extended intervals in renal impairment. |
| Protein binding | Acetaminophen: 10-25% bound, nonspecific binding to albumin. Hydrocodone: 25-50% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Acetaminophen: 0.8-1.0 L/kg, indicating distribution into total body water; clinically relevant for loading dose calculations. Hydrocodone: 3.0-4.0 L/kg, suggesting extensive tissue distribution; higher Vd may require higher loading doses but has no clinical target. |
| Bioavailability | Acetaminophen: oral bioavailability 85-95% (first-pass metabolism minimal). Hydrocodone: oral bioavailability about 25-45% due to first-pass hepatic metabolism; significant interindividual variability. |
| Onset of Action | Oral: 10-30 minutes for analgesic effect; peak effect at 30-60 minutes. |
| Duration of Action | Oral: 4-6 hours for analgesia. Clinical notes: duration may be shorter with repeated use due to tolerance; extended-release formulations available but immediate-release product typically lasts 4-6 hours. |
| Molecular Weight | Acetaminophen: 151.16 Da; Hydrocodone: 299.36 Da |
1-2 tablets (containing 5-10 mg hydrocodone and 300-325 mg acetaminophen) orally every 4-6 hours as needed for pain; maximum 8 tablets per day.
| Dosage form | CAPSULE |
| Renal impairment | GFR 10-50 mL/min: administer every 6 hours; GFR <10 mL/min: administer every 8 hours; avoid in severe impairment due to acetaminophen metabolite accumulation. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% or extend interval; Child-Pugh C: use with caution, avoid if possible, consider alternative therapy. |
| Pediatric use | Dosing based on hydrocodone component: 0.1-0.2 mg/kg/dose every 4-6 hours; maximum daily acetaminophen limit: 75 mg/kg/day; not recommended for children <2 years. |
| Geriatric use | Initiate at lowest effective dose, typically 1 tablet (2.5-5 mg hydrocodone) every 6 hours; monitor for respiratory depression and acetaminophen toxicity; avoid in frail elderly with hepatic impairment. |
| 1st trimester | Use during first trimester is associated with risk of congenital malformations, particularly respiratory and cardiac defects. Hydrocodone is a category C drug; acetaminophen is category B. Avoid unless benefits outweigh risks. |
| 2nd trimester | Use during second trimester is associated with risk of fetal growth restriction and preterm labor. Hydrocodone may cause fetal dependence. Avoid prolonged use. |
| 3rd trimester | Use during third trimester may cause neonatal withdrawal syndrome, respiratory depression, and neonatal abstinence syndrome. Acetaminophen is safe at therapeutic doses; hydrocodone should be avoided near term. |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur.
| FDA category | Positive |
| Placental transfer | Both drugs cross the placenta. Acetaminophen crosses readily; hydrocodone crosses with fetal concentrations approximately 80% of maternal levels. Transfer is higher in third trimester. |
■ FDA Black Box Warning
Addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion of acetaminophen; neonatal opioid withdrawal syndrome; interaction with alcohol; risk of medication errors.
| Common Effects | Cough |
| Serious Effects |
Hypersensitivity to acetaminophen or hydrocodoneSevere respiratory depressionAcute or severe bronchial asthmaParalytic ileusConcurrent MAO inhibitor use (or within 14 days)Significant respiratory compromiseAcetaminophen overdose history
| Precautions | Hepatotoxicity from acetaminophen overdose; respiratory depression; increased intracranial pressure; CNS depression; elderly/debilitated patients; renal impairment; opioid-induced hyperalgesia; serotonin syndrome; interaction with CNS depressants; risk of adrenal insufficiency; severe hypotension; use in patients with gastrointestinal obstruction; convulsion risk; severe hepatic impairment; urinary retention; acute abdominal conditions; hypothyroidism; prostatic hypertrophy; adrenocortical insufficiency; pregnancy/lactation; pediatric use; geriatric use; renal impairment; hepatic impairment. |
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| Breastfeeding | Both acetaminophen and hydrocodone are excreted into breast milk. Hydrocodone concentrations in milk are low, but there is risk of infant sedation and respiratory depression, especially in poor metabolizers. The American Academy of Pediatrics considers hydrocodone compatible with breastfeeding when used short-term at low doses, but advise caution and monitoring for infant drowsiness. |
| Lactation Rating | L3 - Moderately Safe |
| Teratogenic Risk | First trimester: Acetaminophen considered low risk; hydrocodone is a pregnancy category C drug. Data from retrospective studies suggest a small increased risk of certain congenital malformations (e.g., neural tube defects, cleft palate) with first trimester opioid use, but absolute risk is low. Second trimester: Low risk as above. Third trimester: Prolonged use of hydrocodone can cause neonatal opioid withdrawal syndrome (NOWS); acetaminophen is safe. Use only if benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal vital signs, respiratory rate, pain control, and signs of opioid misuse. Fetal monitoring: In third trimester, assess fetal movement and consider nonstress test or biophysical profile if prolonged opioid exposure. Neonatal monitoring: Observe for signs of NOWS (irritability, poor feeding, respiratory distress) for at least 48 hours after birth if maternal use near term. |
| Fertility Effects | Acetaminophen: No known significant effect on fertility. Hydrocodone: Chronic opioid use can cause hypothalamic-pituitary-gonadal axis suppression, leading to menstrual cycle irregularities, anovulation, and reduced fertility. Effects are reversible after discontinuation. |
| Food/Dietary | Avoid alcohol consumption during therapy; ethanol increases acetaminophen hepatotoxicity risk and enhances CNS depression. Grapefruit juice may inhibit CYP2D6 (minor effect) but no significant clinical interaction. No other specific food restrictions. |
| Clinical Pearls | Acetaminophen-hydrocodone is contraindicated in severe respiratory depression, acute or severe bronchial asthma, and known hypersensitivity. Monitor for respiratory depression, especially in elderly or debilitated patients. Avoid use with other acetaminophen-containing products to prevent hepatotoxicity. Hydrocodone is a prodrug metabolized by CYP2D6 to hydromorphone; CYP2D6 ultrarapid metabolizers may experience toxicity. Use with caution in patients with head injury, increased intracranial pressure, or severe hepatic impairment. Naloxone is the reversal agent for opioid effects; acetylcysteine for acetaminophen overdose. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Avoid alcohol and other CNS depressants (e.g., benzodiazepines, sedatives) as they increase risk of severe drowsiness and respiratory depression. · Do not exceed 4000 mg of acetaminophen per day from all sources; check labels of other medications. · This medication may cause dizziness or drowsiness; avoid driving or operating heavy machinery until you know how it affects you. · Store securely out of reach of others, especially children, as misuse can cause overdose and death. · Do not stop abruptly; withdrawal may occur. Taper under medical supervision. · Contact emergency if you experience trouble breathing, extreme drowsiness, or signs of allergic reaction. · Report any history of substance abuse, as this medication has abuse potential. |