Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APOMORPHINE HYDROCHLORIDE vs TYLENOL W/ CODEINE NO. 4
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Non-ergoline dopamine agonist with high affinity for D2 and D3 receptors, moderate affinity for D4, D5, and adrenergic receptors; activates striatal dopamine receptors to improve motor function.
Codeine is a prodrug that undergoes O-demethylation by CYP2D6 to morphine, which acts as a μ-opioid receptor agonist, inhibiting adenylate cyclase and modulating neurotransmitter release in the CNS. Acetaminophen inhibits cyclooxygenase (COX) enzymes, primarily in the CNS, reducing prostaglandin synthesis and modulating pain perception.
FDA: Acute treatment of hypomobility episodes ('off' episodes) in Parkinson disease,Off-label: Refractory erectile dysfunction, treatment of levodopa-induced dyskinesias, depression
Management of mild to moderate pain where an opioid analgesic is needed
Subcutaneous injection: 0.2 m L (2 mg) test dose, then 0.2-0.6 m L (2-6 mg) as needed for acute hypomobility episodes; maximum single dose 0.6 m L (6 mg). Sublingual: 2-10 mg sublingually as needed, not more than every 2 hours, maximum 30 mg/day. Continuous subcutaneous infusion: 0.5-2.0 mg/hour via infusion pump.
One or 2 tablets (acetaminophen 300 mg-codeine 60 mg per tablet) orally every 4 hours as needed for pain; maximum 12 tablets per day.
Terminal elimination half-life is 40–60 minutes in adults with normal renal function; prolonged to 3–6 hours in end-stage renal disease.
Codeine: Terminal half-life of 2.5-3.5 hours; however, its active metabolite morphine has a half-life of 1.5-2 hours, and morphine-6-glucuronide (M6G) has a half-life of 2-4 hours. Acetaminophen: Terminal half-life of 2-3 hours in adults; prolonged in hepatic impairment (up to 4-5 hours) or overdose (4-12 hours). Clinically, duration of analgesic effect is approximately 4-6 hours.
Hepatic via CYP3A4, CYP2C9, and CYP2C19; main metabolite is apomorphine-8-O-sulfate; first-pass effect with rapid clearance.
Codeine: metabolized by CYP2D6 to morphine (active), CYP3A4 to norcodeine, and glucuronidation. Acetaminophen: extensively metabolized in the liver via conjugation (glucuronidation, sulfation) and minor oxidation by CYP2E1 to N-acetyl-p-benzoquinone imine (NAPQI), which is detoxified by glutathione.
Approximately 90% of an intravenous dose is excreted in urine within 24 hours, primarily as unchanged drug and sulfate conjugates. Biliary/fecal excretion is minimal (<5%).
Codeine and its metabolites (including morphine, morphine-6-glucuronide, and norcodeine) are primarily excreted renally. Approximately 90% of a codeine dose is excreted in urine within 24 hours, with 5-15% as free codeine, 5-13% as free morphine, 40-60% as codeine conjugates, and 5-10% as morphine conjugates. Fecal excretion accounts for less than 5%. Acetaminophen is primarily metabolized in the liver to glucuronide and sulfate conjugates; about 85% of a dose is excreted renally as conjugates within 24 hours, with 2-4% excreted unchanged. Minor biliary/fecal elimination occurs for both drugs.
Approximately 90–99% bound, primarily to albumin.
Codeine: Approximately 20-40% bound to plasma proteins (primarily albumin). Morphine: 20-35% bound. Acetaminophen: 10-25% bound to albumin. Binding is minimal and generally not clinically significant.
1.8–2.5 L/kg, indicating extensive tissue distribution.
Codeine: Vd approximately 3-4 L/kg (range 2.5-5 L/kg). Acetaminophen: Vd approximately 0.9 L/kg (range 0.7-1.0 L/kg). Codeine's larger Vd indicates extensive tissue distribution; acetaminophen distributes evenly throughout body fluids.
Subcutaneous: 100% (absolute); sublingual: 16–18%; oral: <1% due to extensive first-pass metabolism.
Oral: Codeine bioavailability is approximately 50-60% (first-pass metabolism). Acetaminophen bioavailability is 70-90% (absorbed rapidly from GI tract; first-pass metabolism minimal). Rectal bioavailability of acetaminophen is approximately 80-90% of oral.
No dose adjustment for mild to moderate impairment. Severe impairment (GFR <15 m L/min): avoid use as apomorphine is renally eliminated and accumulation may occur; use with caution and reduce dose if necessary at GFR 15-29 m L/min.
e GFR 30-50 m L/min: use with caution, reduce dose by 25%. e GFR <30 m L/min: not recommended due to risk of accumulation and respiratory depression.
Child-Pugh A and B: no dose adjustment necessary. Child-Pugh C: pharmacokinetics not studied; use with caution and monitor closely.
Child-Pugh class A: caution, maximum 2 tablets per dose; class B or C: contraindicated.
Safety and efficacy not established; no pediatric dosing recommendations.
Not recommended for children under 12 years. For ages 12-18: weight-based codeine dosing 0.5-1 mg/kg/dose every 4-6 hours (max 60 mg/dose); acetaminophen 15 mg/kg/dose every 4-6 hours (max 75 mg/kg/day). Use lowest effective dose.
Elderly patients may be more sensitive to neuropsychiatric effects; initiate at low end of dosing range (e.g., 1-2 mg subcutaneously) and titrate slowly; monitor for hypotension and falls.
Initiate at half the adult dose (1 tablet) every 4 hours due to increased sensitivity to opioids and acetaminophen hepatotoxicity; maximum 8 tablets per day. Monitor renal and hepatic function closely.
None.
WARNING: ADDICTION, ABUSE, AND MISUSE; LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; ULTRA-RAPID METABOLISM OF CODEINE AND OTHER RISK FACTORS FOR LIFE-THREATENING RESPIRATORY DEPRESSION IN CHILDREN; NEONATAL OPIOID WITHDRAWAL SYNDROME; HEPATOTOXICITY; INTERACTION WITH ALCOHOL; RISKS FROM CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; RISK OF MEDICATION ERRORS.
Risk of hypotension, syncope, and orthostatic hypotension,Severe nausea and vomiting (pretreat with antiemetic),Potential for hallucination, dyskinesia, and impulse control disorders,Do not mix with serotonin 5-HT3 antagonists (e.g., ondansetron) due to severe hypotension,Use caution in patients with cardiovascular disease, hypotension, or renal impairment
Risk of addiction, abuse, and misuse,Life-threatening respiratory depression, especially in patients with compromised respiratory function,Accidental ingestion of even one dose, especially by children, can be fatal,Ultra-rapid metabolism of codeine to morphine due to CYP2D6 polymorphism leading to toxicity,Neonatal opioid withdrawal syndrome with prolonged use during pregnancy,Hepatotoxicity due to acetaminophen, especially with doses >4000 mg/day or with concurrent alcohol use,Interaction with alcohol and other CNS depressants,Concomitant use with MAOIs or within 14 days is contraindicated,Avoid use in children <12 years of age and in children <18 years after tonsillectomy/adenoidectomy
Concurrent use with serotonin 5-HT3 antagonists (e.g., ondansetron),Hypersensitivity to apomorphine or sulfite-containing products,Severe asthma or sulfite allergy
Hypersensitivity to codeine, acetaminophen, or any component,Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment,Known or suspected gastrointestinal obstruction, including paralytic ileus,Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days,Children <12 years of age,Children <18 years of age after tonsillectomy/adenoidectomy
Avoid alcohol: may increase drowsiness and hypotension. Grapefruit juice: may increase risk of QT prolongation. No specific food interactions; maintain normal diet but monitor for changes in blood pressure.
Avoid alcohol and foods containing alcohol (e.g., desserts, sauces) due to increased risk of hepatotoxicity and CNS depression. No specific food restrictions otherwise.
Apomorphine hydrochloride is a dopamine agonist indicated for Parkinson's disease. Limited human pregnancy data; animal studies show fetotoxicity and teratogenicity at doses near maternal toxic doses. FDA Pregnancy Category C. First trimester: Avoid use unless benefit outweighs risk. Second/third trimester: No established safety; potential fetal effects include altered dopamine receptor development. Postnatal: Risk of neonatal withdrawal if used near term.
Pregnancy Category C prior to 2015; current data insufficient for definitive risk. Acetaminophen: no consistent evidence of major malformations; codeine: opioid use in first trimester associated with small increased risk of neural tube defects (OR 1.1-1.3); third trimester use may cause neonatal opioid withdrawal syndrome (NOWS) and respiratory depression at delivery.
No data on apomorphine excretion in human milk. M/P ratio unknown. Due to potential for serious adverse reactions in breastfeeding infants (e.g., somnolence, hypotension, dyskinesia), breastfeeding is not recommended during therapy.
Acetaminophen is compatible (low levels in milk). Codeine is present in milk; M/P ratio approximately 2:1 (morphine). Caution: ultra-rapid CYP2D6 metabolizers may produce high morphine levels leading to infant toxicity. Use lowest effective dose for shortest duration; monitor infant for drowsiness, difficulty breathing.
Pregnancy can alter apomorphine pharmacokinetics due to increased plasma volume, renal blood flow, and hepatic metabolism. No specific dose adjustment guidelines exist. Use lowest effective dose with careful titration. Monitor for reduced efficacy or increased adverse effects (e.g., hypotension, nausea).
No specific dose adjustment recommended for acetaminophen; codeine pharmacokinetics altered in pregnancy (increased clearance, decreased half-life). Avoid codeine in pregnancy if possible; if used, lowest effective dose for shortest duration. Consider alternative analgesics (e.g., acetaminophen alone). Postpartum: resume standard dosing.
Administer subcutaneously; avoid intravenous use due to risk of hemolytic anemia and hypotension. Onset is rapid (5-15 minutes) with short duration (1 hour). Use an antiemetic (e.g., domperidone or trimethobenzamide) for 3 days before starting to prevent nausea. Do not use with 5-HT3 antagonists (e.g., ondansetron) due to profound hypotension. Monitor for dyskinesia, orthostatic hypotension, and QT prolongation. Avoid in patients with dementia, psychosis, or severe respiratory depression; caution in hepatic/renal impairment. Test dose (0.2-0.5 m L) is required before first prescription.
Each tablet contains acetaminophen 300 mg and codeine phosphate 60 mg. Maximum acetaminophen dose: 4 g/day; avoid other acetaminophen-containing products. Codeine is a prodrug; CYP2D6 poor metabolizers may have reduced efficacy, while ultra-rapid metabolizers risk toxicity. Monitor for respiratory depression, especially in opioid-naive patients. Use with caution in patients with liver impairment or G6PD deficiency.
Take this medication exactly as prescribed; it is for on-demand treatment of 'off' episodes.,Inject under the skin (subcutaneous) as directed; do not inject into a vein or muscle.,You may feel dizzy or lightheaded when standing up; rise slowly from sitting or lying down.,Nausea is common; your doctor may prescribe an anti-nausea medicine to take before each dose.,Report any chest pain, fainting, or severe dizziness immediately.,Avoid alcohol and grapefruit juice while using this medication.,Do not change your dose or frequency without consulting your doctor.,Keep this medication away from children and pets.
Do not exceed 12 tablets in 24 hours due to acetaminophen content.,Avoid alcohol while taking this medication.,This drug may cause drowsiness; do not drive or operate machinery until you know how it affects you.,Contact your doctor if you experience signs of allergic reaction (rash, difficulty breathing) or liver injury (yellowing of skin/eyes, dark urine).,Do not take with other products containing acetaminophen (e.g., Tylenol, cold medicines).,Codeine can be habit-forming; use only as prescribed.,Women who are breastfeeding should consult their doctor; codeine can pass into breast milk.
"Coadministration of morphine with palbociclib may increase plasma concentrations of palbociclib due to morphine-induced inhibition of intestinal P-glycoprotein (P-gp) efflux transporter and potential competition for CYP3A4 metabolism. This elevation can heighten the risk of palbociclib-related toxicities, including myelosuppression (neutropenia, leukopenia, anemia), hepatotoxicity, and gastrointestinal adverse effects (e.g., diarrhea, nausea). Patients should be monitored for signs of excessive palbociclib exposure and dose reductions considered if toxicity occurs."
"Morphine, a potent opioid analgesic, can inhibit the metabolism of sulfisoxazole, a sulfonamide antibiotic, by competing for hepatic glucuronidation pathways. This pharmacokinetic interaction leads to increased plasma concentrations of sulfisoxazole, potentially elevating the risk of dose-dependent adverse effects such as crystalluria, hypersensitivity reactions, and bone marrow suppression. Co-administration requires careful monitoring for sulfonamide toxicity, especially in patients with renal impairment or those receiving high-dose morphine."
"Morphine is a potent opioid analgesic that can inhibit the metabolism of isavuconazonium (prodrug of isavuconazole) via competitive inhibition of CYP3A4, the primary enzyme responsible for its activation. This leads to reduced conversion to the active antifungal isavuconazole, potentially decreasing its efficacy against invasive fungal infections. Conversely, isavuconazonium may also inhibit morphine metabolism, increasing opioid side effects such as respiratory depression, sedation, and constipation."
"Pirenzepine, a selective M1 muscarinic antagonist, reduces gastrointestinal motility and secretions, while codeine, an opioid agonist, also decreases gastrointestinal motility via mu-opioid receptors. Concurrent use leads to additive anticholinergic and opioid effects, resulting in enhanced risk of severe constipation, paralytic ileus, and central nervous system depression. Clinically, patients may experience exacerbated sedation, respiratory depression, and urinary retention."
"Ropinirole, a non-ergoline dopamine agonist used in Parkinson's disease and restless legs syndrome, may reduce the analgesic efficacy of codeine. This is likely due to pharmacodynamic antagonism at central dopamine and opioid receptors, as well as potential pharmacokinetic interactions that decrease the conversion of codeine to its active metabolite morphine via CYP2D6 inhibition by ropinirole. The resultant blunted opioid response can lead to inadequate pain control, necessitating dose adjustment or alternative therapy."
"Vemurafenib induces CYP3A4, significantly reducing the plasma concentrations of codeine, which is metabolized via CYP3A4 to its active metabolite morphine. This may diminish codeine's analgesic efficacy, potentially leading to inadequate pain control. Additionally, reduced formation of morphine may lower the risk of opioid-related adverse effects."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about APOMORPHINE HYDROCHLORIDE vs TYLENOL W/ CODEINE NO. 4, answered by our medical review team.
APOMORPHINE HYDROCHLORIDE is a Opioid Agonist that works by Non-ergoline dopamine agonist with high affinity for D2 and D3 receptors, moderate affinity for D4, D5, and adrenergic receptors; activates striatal dopamine receptors to improve motor function.. TYLENOL W/ CODEINE NO. 4 is a Opioid Agonist that works by Codeine is a prodrug that undergoes O-demethylation by CYP2D6 to morphine, which acts as a μ-opioid receptor agonist, inhibiting adenylate cyclase and modulating neurotransmitter release in the CNS. Acetaminophen inhibits cyclooxygenase (COX) enzymes, primarily in the CNS, reducing prostaglandin synthesis and modulating pain perception.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between APOMORPHINE HYDROCHLORIDE and TYLENOL W/ CODEINE NO. 4 depend on the specific clinical indication. These are both Opioid Agonist agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of APOMORPHINE HYDROCHLORIDE is: Subcutaneous injection: 0.2 m L (2 mg) test dose, then 0.2-0.6 m L (2-6 mg) as needed for acute hypomobility episodes; maximum single dose 0.6 m L (6 mg). Sublingual: 2-10 mg sublingually as needed, not more than every 2 hours, maximum 30 mg/day. Continuous subcutaneous infusion: 0.5-2.0 mg/hour via infusion pump.. The standard adult dose of TYLENOL W/ CODEINE NO. 4 is: One or 2 tablets (acetaminophen 300 mg-codeine 60 mg per tablet) orally every 4 hours as needed for pain; maximum 12 tablets per day.. 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 APOMORPHINE HYDROCHLORIDE and TYLENOL W/ CODEINE NO. 4 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. APOMORPHINE HYDROCHLORIDE is classified as Category D/X. Apomorphine hydrochloride is a dopamine agonist indicated for Parkinson's disease. Limited human pregnancy data; animal studies show fetotoxicity and teratogenicity at doses near m. TYLENOL W/ CODEINE NO. 4 is classified as Category D/X. Pregnancy Category C prior to 2015; current data insufficient for definitive risk. Acetaminophen: no consistent evidence of major malformations; codeine: opioid use in first trimes. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.