Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FLOLAN vs ACETAMINOPHEN AND CODEINE PHOSPHATE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Epoprostenol is a prostaglandin I2 (prostacyclin) analogue that directly vasodilates pulmonary and systemic arterial beds, inhibits platelet aggregation, and has antiproliferative effects on vascular smooth muscle.
Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.
Pulmonary arterial hypertension (PAH) (WHO Group I) in NYHA Class III-IV patients to improve exercise capacity and hemodynamics,Pulmonary arterial hypertension in patients who require chronic IV therapy,Off-label: Severe Raynaud's phenomenon, primary pulmonary hypertension in neonates, and as a bridge to lung transplantation
Mild to moderate pain,Pain accompanied by fever
Initial: 4 ng/kg/min via continuous IV infusion, then titrated in increments of 1-2 ng/kg/min at intervals of at least 15 minutes based on clinical response. Typical maintenance dose: 20-40 ng/kg/min; range: 10-80 ng/kg/min.
One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.
3–5 minutes (terminal elimination half-life; rapid inactivation necessitates continuous IV infusion).
Acetaminophen: 2–3 hours (prolonged in hepatic impairment). Codeine: 2.5–3.5 hours; metabolites: morphine 1.5–2.5 hours, codeine-6-glucuronide 3–4 hours. Clinical context: dosing interval every 4–6 hours.
Epoprostenol undergoes rapid hydrolysis at neutral p H and is also metabolized by enzymes including 15-hydroxyprostaglandin dehydrogenase to inactive metabolites (6-keto-PGF1alpha, 6,15-diketo-PGF1alpha, and 6,15-diketo-13,14-dihydro-PGF1alpha).
Acetaminophen: primarily glucuronidation and sulfation in liver; minor CYP450 (CYP2E1) to toxic NAPQI. Codeine: CYP2D6 to morphine; CYP3A4 to norcodeine; glucuronidation.
Renal: 70% (as inactive metabolites); biliary/fecal: negligible.
Acetaminophen: renal elimination of conjugated metabolites (glucuronide 60%, sulfate 30%, cysteine/mercapturate <5%), less than 5% unchanged. Codeine: renal elimination of codeine (5–15%), morphine (5–10%), norcodeine (10–20%), and conjugates; 90% excreted in urine within 24 hours.
Approximately 50% bound to albumin.
Acetaminophen: 10–25% (albumin). Codeine: 7–25% (primarily albumin).
0.03–0.1 L/kg; small Vd consistent with limited extravascular distribution.
Acetaminophen: 0.9 L/kg. Codeine: 3–6 L/kg (extensive tissue distribution).
Intravenous: 100% (only route of administration).
Oral: acetaminophen 88% (variable first-pass); codeine 50–60% (first-pass metabolism to morphine, norcodeine, and conjugates).
No specific dose adjustment required; monitor fluid and electrolyte balance due to potential hypotension.
GFR 30-50 m L/min: administer every 6 hours; GFR 10-29 m L/min: administer every 8 hours; GFR <10 m L/min: administer every 12 hours; hemodialysis: not recommended.
No specific dose adjustment required; consider reduced clearance in severe hepatic impairment (Child-Pugh class C) with cautious titration.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% and extend interval to every 8 hours; Child-Pugh C: contraindicated.
Initial: 2 ng/kg/min via continuous IV infusion, titrate by 1-2 ng/kg/min every 15 minutes as tolerated. Maximum dose not established; typical range 5-40 ng/kg/min.
For children ≥12 years: acetaminophen 10-15 mg/kg/dose and codeine 0.5-1 mg/kg/dose orally every 4-6 hours; maximum acetaminophen 75 mg/kg/day, codeine 6 mg/kg/day. For children <12 years: not recommended due to codeine safety concerns.
No specific dose adjustment; start at lower end of dosing range (4 ng/kg/min) and titrate cautiously due to increased sensitivity to hemodynamic effects.
Start with lowest effective dose; acetaminophen component maximum 3 g/day; consider reduced codeine dose (e.g., 15 mg) due to increased sensitivity and risk of respiratory depression; extend dosing interval to every 6-8 hours.
FLOLAN is a potent vasodilator and must be administered by continuous IV infusion through a permanent central venous catheter. Abrupt discontinuation or sudden large dose reductions may result in worsening pulmonary hypertension and death. Only clinicians experienced in PAH treatment should prescribe FLOLAN.
Risk of medication errors: confusion between milligram and milliliter doses, and between codeine and acetaminophen components. Contraindicated for postoperative pain management in children following tonsillectomy/adenoidectomy due to risk of respiratory depression and death.
Do not abruptly discontinue infusion (risk of rebound pulmonary hypertension), monitor for pulmonary edema (if suspect veno-occlusive disease), may cause bleeding complications (due to antiplatelet effects), monitor for sepsis/thrombosis from chronic IV catheter, use caution in patients with hepatic or renal impairment.
Hepatotoxicity (acetaminophen overdose); respiratory depression; drug dependence; ultra-rapid metabolizers of codeine (CYP2D6) leading to morphine toxicity; concomitant CNS depressants; use in pediatric patients; avoid alcohol.
Long-term use in patients with pulmonary veno-occlusive disease (PVOD), hypersensitivity to epoprostenol or structurally related drugs, or severe left ventricular systolic dysfunction (NYHA Class III-IV heart failure) due to risk of pulmonary edema.
Hypersensitivity to acetaminophen or codeine; severe respiratory depression; acute or severe asthma; paralytic ileus; post-operative pain management in children after tonsillectomy/adenoidectomy; breastfeeding (in ultra-rapid metabolizers); concomitant MAOIs.
No specific food interactions are reported for epoprostenol. Avoid excessive alcohol as it may worsen hypotension.
Avoid alcohol; high-fat meals may delay absorption but not clinically significant.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; however, no adequate and well-controlled studies in pregnant women. Epoprostenol is a potent vasodilator and inhibitor of platelet aggregation; theoretical risk of hemorrhage in the fetus. Use only if clearly needed.
Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respiratory depression and neonatal withdrawal if used near term; may cause neural tube defects and other malformations with first-trimester exposure, but data are conflicting. Use lowest effective dose for shortest duration.
Epoprostenol is not recommended during breastfeeding. No data on presence in human milk, effects on the breastfed infant, or milk production. Due to potential for serious adverse reactions (e.g., hypotension, bleeding), breastfeeding should be discontinued during treatment.
Acetaminophen is excreted into breast milk in low amounts (M/P ratio ~0.91-1.42) and is considered compatible with breastfeeding. Codeine is also excreted in breast milk; risk of infant opioid toxicity depends on maternal CYP2D6 phenotype. Ultra-rapid metabolizers may produce higher morphine levels. Use with caution, avoid in known CYP2D6 ultra-rapid metabolizers, and monitor infant for sedation and respiratory depression.
Pregnancy may alter pharmacokinetics; increase in plasma volume may require dose adjustments. No formal studies; titrate dose based on clinical response (e.g., symptoms of pulmonary arterial hypertension). Monitor for signs of overdose (hypotension, tachycardia) or underdose (worsening dyspnea).
No routine dose adjustment needed for acetaminophen. Codeine pharmacokinetics are altered in pregnancy: increased clearance and volume of distribution may require dose adjustment; however, due to variability in CYP2D6 metabolism, individualize dosing and monitor for efficacy and toxicity. Avoid codeine in pregnancy unless alternative analgesics are ineffective.
FLOLAN (epoprostenol) is a prostacyclin used for pulmonary arterial hypertension (PAH). It has a very short half-life (3-5 minutes) and must be administered via continuous IV infusion. Abrupt interruption can cause life-threatening rebound pulmonary hypertension. The drug is unstable at room temperature; requires ice packs during administration. Dose titration is done based on symptoms and side effects (e.g., jaw pain, flushing, headache, diarrhea).
For acute pain, limit codeine to 3 days; avoid in children under 12 due to CYP2D6 ultra-rapid metabolizer risk of fatal respiratory depression; monitor for constipation; assess liver function for acetaminophen hepatotoxicity; use with caution in renal impairment.
This medication is given continuously through an intravenous (IV) line using a portable infusion pump.,Never stop the infusion suddenly; sudden stoppage can cause severe worsening of your condition.,Keep the medication cold (with ice packs) during infusion; it degrades at room temperature.,Report any signs of infection at the IV site, such as redness, swelling, or pain.,Common side effects include headache, jaw pain, flushing, nausea, and diarrhea; these may improve over time.
Take exactly as prescribed; do not exceed 4000 mg acetaminophen per day.,Avoid alcohol while taking this medication.,Do not use with other acetaminophen-containing products.,May cause dizziness or drowsiness; avoid driving until you know how you react.,Common side effects include constipation, nausea, and drowsiness.,Seek emergency if signs of allergic reaction or difficulty breathing occur.
No interactions on record
"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 FLOLAN vs ACETAMINOPHEN AND CODEINE PHOSPHATE, answered by our medical review team.
FLOLAN is a Prostacyclin Vasodilator that works by Epoprostenol is a prostaglandin I2 (prostacyclin) analogue that directly vasodilates pulmonary and systemic arterial beds, inhibits platelet aggregation, and has antiproliferative effects on vascular smooth muscle.. ACETAMINOPHEN AND CODEINE PHOSPHATE is a Opioid Agonist that works by Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FLOLAN and ACETAMINOPHEN AND CODEINE PHOSPHATE 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 FLOLAN is: Initial: 4 ng/kg/min via continuous IV infusion, then titrated in increments of 1-2 ng/kg/min at intervals of at least 15 minutes based on clinical response. Typical maintenance dose: 20-40 ng/kg/min; range: 10-80 ng/kg/min.. The standard adult dose of ACETAMINOPHEN AND CODEINE PHOSPHATE is: One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.. 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 FLOLAN and ACETAMINOPHEN AND CODEINE PHOSPHATE 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. FLOLAN is classified as Category C. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; however, no adequate and well-controlled studies in pregnant women. Epoprostenol is a potent vasodilator . ACETAMINOPHEN AND CODEINE PHOSPHATE is classified as Category D/X. Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respirat. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.