Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
MECLOFENAMATE SODIUM vs ALFENTA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Meclofenamate sodium is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2), thereby reducing prostaglandin synthesis, which mediates inflammation, pain, and fever.
μ-opioid receptor agonist that activates G-protein coupled receptors to inhibit adenylate cyclase, decreasing c AMP production, leading to reduced neuronal excitability and pain transmission.
Relief of mild to moderate acute pain,Treatment of primary dysmenorrhea,Management of osteoarthritis,Management of rheumatoid arthritis
Induction and maintenance of anesthesia,Analgesic supplement during surgical procedures,Intravenous use for monitored anesthesia care (MAC)
50 mg or 100 mg orally three times daily; maximum 400 mg/day.
Intravenous: Initial dose 8-20 mcg/kg (0.5-1 min) then 0.5-3 mcg/kg/min or 3-5 mcg/kg q5-20min. For short procedures: 8-20 mcg/kg. For longer procedures: 50-75 mcg/kg followed by 0.5-3 mcg/kg/min.
2-4 hours (terminal half-life; may be prolonged in hepatic impairment or elderly)
Terminal elimination half-life: 90–111 minutes (1.5–1.85 hours); prolonged in hepatic impairment.
Primarily hepatic via cytochrome P450 enzymes, including CYP2C9 and CYP3A4.
Hepatic via CYP3A4 to inactive metabolites; major metabolite is desmethylalfentanil (inactive).
Renal (60-70% as metabolites and conjugates), biliary/fecal (20-30%)
Primarily renal (urinary) elimination as metabolites; approximately 80% recovered in urine, 20% in feces.
>99% (primarily to albumin)
Approximately 92% bound, primarily to alpha-1 acid glycoprotein and albumin.
0.5-1.0 L/kg (indicates extensive tissue distribution)
0.5–1.0 L/kg; reflects moderate tissue distribution; higher Vd in neonates and elderly.
100% (oral, well absorbed)
Intravenous: 100%; intramuscular: approximately 90%; intrathecal: approximately 10% (due to systemic absorption following spinal administration).
e GFR 30-59 m L/min: use with caution, reduce dose by 50%; e GFR <30 m L/min: contraindicated.
No specific dose adjustment is recommended for renal impairment; however, alfentanil is primarily metabolized in the liver and its pharmacokinetics are not significantly altered in renal failure.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated.
In hepatic impairment (Child-Pugh class A, B, C): Reduce dose by 50% and titrate carefully due to prolonged elimination half-life. Consider lower initial doses and extended dosing intervals.
Not recommended for children under 14 years; for adolescents ≥14 years, same as adult dosing.
Children (1-12 years): Induction of anesthesia: 10-20 mcg/kg IV; maintenance: 5-10 mcg/kg IV or infusion 0.5-1 mcg/kg/min. For neonates and infants: Dose individualization required; titrate to effect.
Initiate at lowest effective dose (50 mg twice daily); monitor renal function and GI bleeding risk.
Elderly patients (>65 years): Reduce initial dose by 30-50% and administer slowly. Due to decreased clearance and increased sensitivity, lower infusion rates (e.g., 0.3-0.5 mcg/kg/min) may be needed.
NSAIDs cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may increase with duration of use. Patients with cardiovascular disease or risk factors may be at greater risk. Meclofenamate is contraindicated for treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
Risk of respiratory depression, particularly in elderly or debilitated patients. Concomitant use with benzodiazepines or other CNS depressants may cause profound sedation, respiratory depression, coma, and death.
Cardiovascular thrombotic events,Gastrointestinal bleeding, ulceration, and perforation,Hypertension and edema,Renal toxicity,Anaphylactoid reactions,Exacerbation of asthma,Hematologic toxicity including anemia,Hepatic enzyme elevations
Respiratory depression; abuse potential; hypotension; bradycardia; muscle rigidity; serotonin syndrome with concurrent serotonergic drugs; adrenal insufficiency; risk of withdrawal with prolonged use.
Hypersensitivity to meclofenamate or any other NSAID,History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs,Perioperative pain in setting of CABG surgery,Active peptic ulcer disease or gastrointestinal bleeding
Hypersensitivity to alfentanil or any component; significant respiratory insufficiency; severe asthma; paralytic ileus; concurrent use of MAOIs (or within 14 days); acute or postoperative pain management in children (except for procedural sedation).
Avoid high-fat meals as they may delay absorption. Limit salt intake to reduce fluid retention. Do not consume alcohol as it increases the risk of GI bleeding. Meclofenamate may decrease the effectiveness of diuretics and antihypertensive medications when taken with potassium-rich foods; monitor potassium levels.
No known interactions with food. However, grapefruit juice may increase alfentanil serum concentrations due to CYP3A4 inhibition; avoid concurrent consumption.
Avoid in 1st and 2nd trimester; contraindicated in 3rd trimester due to risk of premature closure of ductus arteriosus, oligohydramnios, and neonatal renal impairment. Associated with cardiovascular malformations if used in 1st trimester.
Alfentanil, a short-acting opioid analgesic, is classified as FDA Pregnancy Category C. No well-controlled studies in pregnant women exist. In animal studies, no teratogenic effects were observed at clinically relevant doses; however, high doses caused embryotoxicity and increased fetal mortality. Trimester-specific risks: First trimester - potential for minor malformations based on limited human data; second trimester - possible risk if used chronically; third trimester - prolonged use may lead to neonatal respiratory depression, withdrawal syndrome, or opioid dependence. Use only if benefits outweigh risks.
Excreted into breast milk in small amounts; M/P ratio not established. Use caution due to potential adverse effects in neonates (e.g., gastrointestinal bleeding, platelet dysfunction).
Alfentanil is excreted into human breast milk in low concentrations. The milk-to-plasma (M/P) ratio is approximately 0.3. Estimated infant dose is <1% of maternal weight-adjusted dose, which is considered clinically insignificant. However, due to potential for neonatal opioid effects, caution is advised; monitor infant for drowsiness, respiratory depression, and feeding difficulties. Consider alternative analgesics with established safety profiles, such as acetaminophen or ibuprofen, for lactation.
Increased plasma volume may require dose adjustments in 2nd and 3rd trimesters, but specific studies lacking; generally avoid use. If necessary, use lowest effective dose for shortest duration.
Pregnancy can alter pharmacokinetics of alfentanil. Increased plasma volume and distribution may require higher doses to achieve same effect, while decreased plasma protein binding may increase free fraction, potentiating effects. Alpha-1-acid glycoprotein levels change in pregnancy, affecting binding. In third trimester, clearance may be increased by up to 50% due to enhanced hepatic metabolism. Therefore, dose adjustments may be needed: consider starting at low dose and titrating to effect, with close monitoring. For intravenous administration, typical adult doses (5-20 μg/kg) may need adjustments; no standard pregnancy-specific dosing exists. Use the lowest effective dose for the shortest duration. In labor, avoid high doses prior to delivery due to risk of neonatal respiratory depression.
Meclofenamate sodium is a nonsteroidal anti-inflammatory drug (NSAID) used for mild to moderate pain, dysmenorrhea, and inflammatory arthropathies. It has a higher incidence of gastrointestinal (GI) side effects, especially diarrhea, which can be dose-limiting. Monitor renal function and blood pressure, as it may cause fluid retention and worsening of hypertension. Use with caution in patients with a history of peptic ulcer disease or bleeding disorders. It is contraindicated in perioperative pain in coronary artery bypass graft (CABG) surgery.
Alfentanil is a potent, rapid-onset, short-acting opioid analgesic used primarily for induction and maintenance of anesthesia. Due to its high protein binding (90%) and rapid redistribution, it has a shorter duration of action than fentanyl, making it suitable for brief, painful procedures. It undergoes hepatic metabolism via CYP3A4, so concomitant use with CYP3A4 inhibitors like ketoconazole or erythromycin can prolong its effects. Use caution in elderly or hypovolemic patients due to increased risk of hypotension. Naloxone reverses respiratory depression. Alfentanil is 5-10 times less potent than fentanyl.
Take with food or milk to reduce stomach upset.,Avoid alcohol and aspirin while taking this medication.,Report signs of GI bleeding (black, tarry stools; blood in vomit) immediately.,May cause diarrhea; notify your doctor if it becomes severe or persistent.,Do not take with other NSAIDs without consulting your doctor.,Stay hydrated, but avoid excessive salt intake to prevent fluid retention.,Inform your doctor if you have kidney disease, high blood pressure, or a history of stomach ulcers.,Do not use during pregnancy, especially in the third trimester.
This medication is given only by a healthcare professional in a hospital or surgical setting.,You may feel drowsy, dizzy, or nauseated after receiving this drug.,Report any difficulty breathing or slow heart rate to your healthcare provider immediately.,Avoid alcohol and sedatives for 24 hours after administration, as they can increase side effects.,Do not drive or operate machinery until the effects have fully worn off.
No interactions on record
"Propantheline, an anticholinergic agent, can competitively antagonize muscarinic acetylcholine receptors, potentially reducing gastrointestinal motility and secretion. Alfentanil, a mu-opioid receptor agonist, also decreases gastrointestinal motility through central and peripheral opioid receptors. Concomitant use may synergistically inhibit peristalsis, leading to severe constipation, paralytic ileus, or delayed gastric emptying, which can increase the risk of aspiration and complicate anesthesia recovery."
"Alfentanil, a potent opioid analgesic, can cause significant hypotension and respiratory depression. When combined with furosemide, a loop diuretic that reduces blood volume and vascular resistance, there is a synergistic decrease in blood pressure, which may precipitate cardiovascular collapse, especially in patients with compromised circulatory reserves. Additionally, furosemide may enhance the sedative and respiratory depressant effects of alfentanil, leading to increased risk of respiratory acidosis and altered mental status."
"Alfentanil, a potent mu-opioid receptor agonist, can enhance the bradycardic effects of nebivolol, a beta-1 selective blocker with additional nitric oxide-mediated vasodilation. The combination may lead to excessive slowing of heart rate, reduced cardiac output, and potential hemodynamic instability, particularly in patients with underlying cardiac conduction abnormalities or hypovolemia."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about MECLOFENAMATE SODIUM vs ALFENTA, answered by our medical review team.
MECLOFENAMATE SODIUM is a NSAID that works by Meclofenamate sodium is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2), thereby reducing prostaglandin synthesis, which mediates inflammation, pain, and fever.. ALFENTA is a Opioid Analgesic that works by μ-opioid receptor agonist that activates G-protein coupled receptors to inhibit adenylate cyclase, decreasing c AMP production, leading to reduced neuronal excitability and pain transmission.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between MECLOFENAMATE SODIUM and ALFENTA 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 MECLOFENAMATE SODIUM is: 50 mg or 100 mg orally three times daily; maximum 400 mg/day.. The standard adult dose of ALFENTA is: Intravenous: Initial dose 8-20 mcg/kg (0.5-1 min) then 0.5-3 mcg/kg/min or 3-5 mcg/kg q5-20min. For short procedures: 8-20 mcg/kg. For longer procedures: 50-75 mcg/kg followed by 0.5-3 mcg/kg/min.. 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 MECLOFENAMATE SODIUM and ALFENTA 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. MECLOFENAMATE SODIUM is classified as Category C. Avoid in 1st and 2nd trimester; contraindicated in 3rd trimester due to risk of premature closure of ductus arteriosus, oligohydramnios, and neonatal renal impairment. Associated w. ALFENTA is classified as Category C. Alfentanil, a short-acting opioid analgesic, is classified as FDA Pregnancy Category C. No well-controlled studies in pregnant women exist. In animal studies, no teratogenic effect. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.