Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PROMETH VC PLAIN vs ACETAMINOPHEN AND HYDROCODONE BITARTRATE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Promethazine is a phenothiazine derivative that acts as a potent histamine H1 receptor antagonist, blocking allergic reactions; it also has anticholinergic, antiemetic, sedative, and local anesthetic effects.
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.
FDA: Allergic conditions (rhinitis, urticaria, pruritus), motion sickness, nausea/vomiting, preoperative sedation, postoperative pain control (adjunct),Off-label: Nausea in pregnancy (morning sickness), vertigo, sedation in pediatric procedures
Moderate to moderately severe pain,Cough suppression (hydrocodone; off-label)
Adults: 1-2 tablets (each containing Promethazine 6.25 mg and Phenylephrine 5 mg) orally every 4-6 hours; maximum 12 tablets per day.
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.
Promethazine: terminal half-life 9-16 hours (mean 12 hours) in adults; longer in elderly (13.5-18 hours) and in hepatic impairment. Phenylephrine: half-life 2-3 hours.
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.
Primarily hepatic metabolism via CYP2D6 and other pathways; metabolites include promethazine sulfoxide and N-demethylated derivatives.
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).
Primarily renal; promethazine is excreted in urine as unchanged drug (approximately 6%) and as metabolites (promethazine sulfoxide and N-demethylpromethazine); less than 1% excreted in feces. Phenylephrine is primarily metabolized by MAO and COMT; renal excretion of metabolites and unchanged drug (about 16%).
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.
Promethazine: approximately 93% bound to plasma proteins (mainly albumin). Phenylephrine: approximately 95% bound to plasma proteins (mainly albumin).
Acetaminophen: 10-25% bound, nonspecific binding to albumin. Hydrocodone: 25-50% bound, primarily to albumin and alpha-1-acid glycoprotein.
Promethazine: Vd 5-17 L/kg (mean ~12 L/kg), indicating extensive tissue distribution. Phenylephrine: Vd 4-5 L/kg, also widely distributed.
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.
Oral promethazine: approximately 25% due to extensive first-pass metabolism. Intramuscular: nearly 100%. Rectal: approximately 70% of oral. Phenylephrine: oral bioavailability is low (about 38%) due to first-pass metabolism by MAO in gut and liver.
Acetaminophen: oral bioavailability 85-95% (first-pass metabolism minimal). Hydrocodone: oral bioavailability about 25-45% due to first-pass hepatic metabolism; significant interindividual variability.
No specific guidelines; use with caution in renal impairment (Cr Cl <30 m L/min) due to potential accumulation of promethazine; consider dose reduction or extended intervals.
GFR 10-50 m L/min: administer every 6 hours; GFR <10 m L/min: administer every 8 hours; avoid in severe impairment due to acetaminophen metabolite accumulation.
Child-Pugh Class A-C: Use with caution; reduce dose or avoid in severe hepatic impairment (Child-Pugh Class C) due to decreased metabolism of promethazine.
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.
Children aged 6-12 years: 1 tablet orally every 4-6 hours; maximum 6 tablets per day. Not recommended for children under 6 years due to risk of respiratory depression.
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.
Elderly patients: Initiate at lower doses (e.g., 1 tablet orally every 6-8 hours) and titrate carefully; monitor for anticholinergic effects, sedation, and orthostatic hypotension.
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.
Promethazine should not be used in children younger than 2 years due to risk of respiratory depression, including fatalities. Use in children aged 2+ with caution. Not for intra-arterial or subcutaneous injection (risk of severe tissue injury).
Addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion of acetaminophen; neonatal opioid withdrawal syndrome; interaction with alcohol; risk of medication errors.
Risk of respiratory depression (especially in children, elderly, or with CNS depressants); use caution in asthma, sleep apnea, respiratory insufficiency. May impair cognitive/motor function; avoid alcohol. Extrapyramidal symptoms (rare). Caution in glaucoma, prostatic hyperplasia, urinary retention. Use in pregnancy (only if clearly needed).
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.
Hypersensitivity to promethazine or phenothiazines; children <2 years; comatose patients; CNS depression (e.g., alcohol, barbiturates); Reye's syndrome (avoid in children with viral illness due to risk of Reye's? – actually contraindicated in patients with suspected Reye's). Also contraindicated for intra-arterial or subcutaneous injection.
Hypersensitivity to acetaminophen or hydrocodone; significant respiratory depression; acute or severe bronchial asthma; upper airway obstruction; known or suspected gastrointestinal obstruction; paralytic ileus; concomitant use of monoamine oxidase inhibitors (MAOIs) or within 14 days; severe hepatic impairment (acetaminophen toxicity risk); acute alcoholism.
No clinically significant food interactions. However, taking with food may reduce gastrointestinal upset. Avoid grapefruit juice as it may theoretically increase sedation.
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.
First trimester: Avoid. Inadequate studies; animal studies not sufficient. Second/third trimester: Use only if clearly needed; may cause neonatal respiratory depression, irritability, and tremors if used near term.
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.
Promethazine is excreted into breast milk in small amounts; M/P ratio unknown. Caution suggested; avoid in infants with apnea, respiratory issues, or in mothers of preterm infants.
Acetaminophen excretion in breast milk is low (M/P ratio ~0.9). Hydrocodone is excreted in small amounts (M/P ratio ~2.1). The relative infant dose is estimated to be 2.5-3.5% of maternal weight-adjusted dose for hydrocodone. Monitor infant for sedation and respiratory depression. Consider benefit to mother and potential neonatal opioid withdrawal if used chronically.
No standard dose adjustment required during pregnancy. Use lowest effective dose; monitor for increased sedation and anticholinergic effects due to physiological changes.
During pregnancy, increased plasma volume and enhanced hepatic clearance may reduce serum concentrations of both drugs. However, dosing adjustments are not routinely recommended due to risk of undertreatment. Use the lowest effective dose of hydrocodone for the shortest duration. For acetaminophen, maximum daily dose should not exceed 3000 mg to avoid hepatotoxicity.
Promethazine is a phenothiazine derivative with antihistamine, antiemetic, sedative, and anticholinergic properties. Administer deep IM if parenteral route required; avoid intra-arterial or subcutaneous injection due to risk of severe tissue damage. Monitor for extrapyramidal symptoms in children and elderly. Use with caution in patients with asthma, COPD, or sleep apnea due to respiratory depression risk. Do not use in children <2 years due to risk of fatal respiratory depression.
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.
Do not drive or operate heavy machinery until you know how this medication affects you, as it can cause drowsiness and dizziness.,Avoid alcohol and other central nervous system depressants while taking this medication.,Take exactly as prescribed; do not exceed recommended dose or duration.,Contact your healthcare provider if you experience difficulty breathing, involuntary muscle movements, or signs of jaundice (yellowing of skin/eyes).
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.
No interactions on record
"Hydrocodone, an opioid agonist, and scopolamine, an anticholinergic agent, both exhibit central nervous system (CNS) depressant effects. When co-administered, their combined activity can lead to additive CNS depression, resulting in enhanced sedation, respiratory depression, and cognitive impairment. This interaction may also increase the risk of constipation and urinary retention due to additive anticholinergic effects from both drugs."
"Pargyline, a monoamine oxidase inhibitor (MAOI), irreversibly inhibits the metabolism of amines, leading to increased intraneuronal stores of norepinephrine. Hydrocodone, a semisynthetic opioid, can release these stored catecholamines, potentially causing a hypertensive crisis, serotonin syndrome, or CNS excitation. Coadministration may also result in excessive sedation and respiratory depression due to additive CNS depressant effects, requiring immediate clinical attention."
"Hydrocodone, an opioid agonist, and oxprenolol, a non-selective beta-adrenoceptor antagonist, are both central nervous system (CNS) depressants. Their combined use can lead to additive CNS depression, resulting in excessive sedation, respiratory depression, hypotension, and bradycardia. This interaction is particularly dangerous in patients with compromised cardiac or respiratory function, potentially leading to coma or death."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PROMETH VC PLAIN vs ACETAMINOPHEN AND HYDROCODONE BITARTRATE, answered by our medical review team.
PROMETH VC PLAIN is a Antihistamine-decongestant combination that works by Promethazine is a phenothiazine derivative that acts as a potent histamine H1 receptor antagonist, blocking allergic reactions; it also has anticholinergic, antiemetic, sedative, and local anesthetic effects.. ACETAMINOPHEN AND HYDROCODONE BITARTRATE is a Opioid Agonist that works by 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PROMETH VC PLAIN and ACETAMINOPHEN AND HYDROCODONE BITARTRATE 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 PROMETH VC PLAIN is: Adults: 1-2 tablets (each containing Promethazine 6.25 mg and Phenylephrine 5 mg) orally every 4-6 hours; maximum 12 tablets per day.. The standard adult dose of ACETAMINOPHEN AND HYDROCODONE BITARTRATE is: 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.. 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 PROMETH VC PLAIN and ACETAMINOPHEN AND HYDROCODONE BITARTRATE 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. PROMETH VC PLAIN is classified as Category C. First trimester: Avoid. Inadequate studies; animal studies not sufficient. Second/third trimester: Use only if clearly needed; may cause neonatal respiratory depression, irritabili. ACETAMINOPHEN AND HYDROCODONE BITARTRATE is classified as Category D/X. 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. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.