Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BONTRIL vs IBU
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Bontril (phendimetrazine) is a sympathomimetic amine that acts as an appetite suppressant. Its mechanism involves stimulating the hypothalamus to release norepinephrine and dopamine, which reduces hunger cues. It is a prodrug that is metabolized to the active agent phenmetrazine, which inhibits reuptake and increases release of norepinephrine and dopamine in the central nervous system.
Non-selective inhibitor of cyclooxygenase (COX-1 and COX-2), decreasing prostaglandin synthesis, thereby reducing inflammation, pain, and fever.
FDA-approved for management of obesity as a short-term adjunct (few weeks) in a regimen of weight reduction based on caloric restriction, exercise, and behavior modification. Off-label uses are not well documented due to limited evidence.
Rheumatoid arthritis,Osteoarthritis,Mild to moderate pain,Dysmenorrhea,Fever,Patent ductus arteriosus closure in neonates (off-label)
BONTRIL 50 mg orally once daily, with or without food.
200-800 mg orally every 6-8 hours as needed; maximum 3200 mg/day. For OTC use: 200-400 mg every 4-6 hours; max 1200 mg/day.
18-24 hours; prolonged in renal impairment (up to 40 hours) requiring dose adjustment.
Terminal elimination half-life: 2-4 hours in adults; prolonged in neonates (30 hours) and elderly (up to 6 hours). No accumulation with recommended dosing due to short t½.
Phendimetrazine is extensively metabolized in the liver, primarily via N-demethylation to its active metabolite phenmetrazine. Minor pathways include hydroxylation and conjugation. Cytochrome P450 enzymes are involved, though specific isoforms are not fully characterized.
Hepatic metabolism primarily via CYP2C9 to inactive metabolites; minor pathways include CYP2C8.
Primarily renal (60-70% unchanged) with minor biliary/fecal (10-15% as metabolites).
Renal (90% as conjugated metabolites, 10% unchanged), biliary/fecal (minor, <5%)
85-90% bound to albumin and alpha-1-acid glycoprotein.
99% bound primarily to albumin
3-5 L/kg; indicates extensive tissue distribution.
0.1-0.2 L/kg, indicating low tissue distribution; predominantly confined to plasma and extracellular fluid.
Oral: 70-80% (first-pass metabolism); IV: 100%.
Oral: 80-100% (immediate-release), 70-90% (extended-release); Topical: approximately 5-10% systemic absorption; Intravenous: 100%.
GFR >60 m L/min: no adjustment. GFR 30-60 m L/min: reduce dose to 25 mg once daily. GFR <30 m L/min: use is not recommended.
Cr Cl >30 m L/min: no adjustment. Cr Cl 10-30 m L/min: 200 mg every 12 hours; avoid if Cr Cl <10 m L/min.
Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose to 25 mg once daily. Child-Pugh Class C: use is contraindicated.
Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% or avoid. Child-Pugh C: contraindicated due to risk of hepatotoxicity.
Weight-based: 1 mg/kg orally once daily, with a maximum of 50 mg. Not recommended for children weighing less than 10 kg.
6 months to 12 years: 5-10 mg/kg/dose every 6-8 hours; max 40 mg/kg/day. For juvenile idiopathic arthritis: 30-40 mg/kg/day divided every 6-8 hours; max 50 mg/kg/day.
Start at 25 mg orally once daily; may increase to 50 mg after 2 weeks if tolerated and renal function is adequate (Cr Cl >60 m L/min).
Initiate at lowest effective dose; consider 200 mg every 8-12 hours; monitor renal function and GI bleeding risk.
None
NSAIDs cause an increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke, which can be fatal. Risk may increase with duration of use. Contraindicated for treatment of peri-operative pain in coronary artery bypass graft (CABG) surgery.
Risk of abuse, dependence, and tolerance; monitor for signs of addiction.,May cause serious cardiovascular events including pulmonary hypertension and valvular heart disease, especially with long-term use.,May impair ability to drive or operate machinery due to dizziness or blurred vision.,Use with caution in patients with hypertension, hyperthyroidism, glaucoma, or history of drug abuse.,Concomitant use with other sympathomimetics or MAO inhibitors can cause hypertensive crisis.,Not recommended for use in patients with a history of epilepsy or those taking other anorectic agents.
Cardiovascular thrombotic events,Gastrointestinal bleeding, ulceration, and perforation,Hypertension,Heart failure exacerbation,Renal toxicity,Anaphylactic reactions,Serious skin reactions (e.g., Stevens-Johnson syndrome),Hematologic effects (anemia, bleeding)
Known hypersensitivity to phendimetrazine or any component of the formulation.,History of cardiovascular disease including coronary artery disease, arrhythmias, or congestive heart failure.,Hypertension (moderate to severe).,Hyperthyroidism.,Glaucoma.,History of drug abuse or alcoholism.,Concurrent use of monoamine oxidase inhibitors or within 14 days of such use.,Pregnancy and breastfeeding.,Agitated states.,History of seizure disorders.
History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs,Peri-operative pain in CABG surgery,Active gastrointestinal bleeding,Advanced renal disease,Third trimester of pregnancy
Avoid high-fat meals as they may delay absorption of oral formulations. No specific food-drug interactions known; however, anticholinergic effects may be exacerbated by alcohol.
Ibuprofen can increase the risk of stomach bleeding when taken with alcohol. No specific food restrictions, but taking with food or milk can reduce GI irritation.
BONTRIL is classified as FDA Pregnancy Category X. First trimester: high risk of major congenital malformations including neural tube defects, cardiovascular anomalies, and cleft palate. Second and third trimesters: risk of fetal growth restriction, oligohydramnios, and neonatal respiratory depression if used near term.
First and second trimester: Increased risk of miscarriage and congenital malformations (particularly cardiac defects) associated with NSAID use. Third trimester: Known risk of premature closure of ductus arteriosus, oligohydramnios, and neonatal renal impairment; contraindicated after 30 weeks gestation.
No data available on excretion into human breast milk. M/P ratio unknown. Due to potential for serious adverse effects in nursing infants, breastfeeding is contraindicated during BONTRIL therapy.
Ibuprofen is excreted into breast milk in low concentrations (M/P ratio approximately 0.01-0.03). Considered compatible with breastfeeding by the American Academy of Pediatrics; use lowest effective dose for shortest duration.
No dose adjustment required for pregnancy. However, due to teratogenicity, BONTRIL should be discontinued before conception or as soon as pregnancy is diagnosed.
Increased plasma volume and renal clearance in pregnancy may reduce drug levels; however, no standard dose adjustment recommended. Use lowest effective dose, avoid in third trimester.
BONTRIL (hyoscyamine) is an anticholinergic used for GI spasms; avoid in patients with glaucoma, myasthenia gravis, or obstructive uropathy. Onset of action is 2-3 minutes IV; monitor for heat stroke in high ambient temperatures due to decreased sweating.
Ibuprofen is a nonselective COX inhibitor with anti-inflammatory, analgesic, and antipyretic effects. Avoid in patients with aspirin allergy, active peptic ulcer, or severe renal impairment. Use lowest effective dose for shortest duration to minimize GI and cardiovascular risks. Not recommended in patients with advanced chronic kidney disease (e GFR <30 m L/min/1.73 m²). For acute pain, ibuprofen 200-400 mg every 6 hours PRN. Monitor for signs of GI bleeding, hypertension, and fluid retention.
Do not drive or operate machinery until you know how this medication affects you, as it may cause dizziness or blurred vision.,Avoid alcohol and other CNS depressants as they may increase sedation.,Report immediately if you experience eye pain, difficulty urinating, or rapid heartbeat.,Use caution in hot weather; this drug reduces sweating and increases risk of heat stroke.
Take with food or milk to reduce stomach upset.,Do not exceed 1200 mg per day unless directed by your doctor.,Avoid alcohol while taking this medication.,Stop use and seek medical help if you experience chest pain, weakness, slurred speech, or signs of stomach bleeding (black/tarry stools, vomit that looks like coffee grounds).,Do not take with other NSAIDs or aspirin without consulting your healthcare provider.
No interactions on record
"Concomitant use of Ibuprofen (a nonsteroidal anti-inflammatory drug, NSAID) and Methylprednisolone (a systemic corticosteroid) synergistically increases the risk of gastrointestinal (GI) ulceration, bleeding, and perforation due to additive inhibition of prostaglandin synthesis and mucosal protection. Additionally, Ibuprofen may potentiate the immunosuppressive effects of Methylprednisolone, elevating infection risk. This interaction can lead to serious clinical outcomes, including acute GI hemorrhage, perforation, and impaired wound healing."
"The combination of olopatadine, an antihistamine with sedative properties, and ibuprofen, a nonsteroidal anti-inflammatory drug (NSAID), may result in additive central nervous system (CNS) depression, leading to increased sedation, dizziness, and impaired psychomotor function. Ibuprofen can inhibit the metabolism of olopatadine via competition for hepatic CYP450 enzymes, potentially elevating olopatadine plasma concentrations and prolonging its systemic effects. Clinically, patients may experience exacerbated drowsiness, reduced alertness, and increased risk of falls or accidents, especially in the elderly or those with compromised hepatic function."
"Ibuprofen, a nonsteroidal anti-inflammatory drug (NSAID), can decrease the metabolism of pioglitazone, a thiazolidinedione antidiabetic agent, by inhibiting cytochrome P450 2C8 (CYP2C8) enzyme activity. This inhibition elevates plasma concentrations of pioglitazone, potentially enhancing its hypoglycemic effects and increasing the risk of adverse reactions such as edema, weight gain, and heart failure exacerbation. Clinically, concomitant use may lead to improved glycemic control but also raises concerns for dose-dependent toxicities, necessitating careful monitoring and possible dose adjustment of pioglitazone."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BONTRIL vs IBU, answered by our medical review team.
BONTRIL is a Sympathomimetic Anorectic that works by Bontril (phendimetrazine) is a sympathomimetic amine that acts as an appetite suppressant. Its mechanism involves stimulating the hypothalamus to release norepinephrine and dopamine, which reduces hunger cues. It is a prodrug that is metabolized to the active agent phenmetrazine, which inhibits reuptake and increases release of norepinephrine and dopamine in the central nervous system.. IBU is a Nonsteroidal Anti-inflammatory Drug (NSAID) that works by Non-selective inhibitor of cyclooxygenase (COX-1 and COX-2), decreasing prostaglandin synthesis, thereby reducing inflammation, pain, and fever.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BONTRIL and IBU 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 BONTRIL is: BONTRIL 50 mg orally once daily, with or without food.. The standard adult dose of IBU is: 200-800 mg orally every 6-8 hours as needed; maximum 3200 mg/day. For OTC use: 200-400 mg every 4-6 hours; max 1200 mg/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 BONTRIL and IBU 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. BONTRIL is classified as Category C. BONTRIL is classified as FDA Pregnancy Category X. First trimester: high risk of major congenital malformations including neural tube defects, cardiovascular anomalies, and cleft p. IBU is classified as Category C. First and second trimester: Increased risk of miscarriage and congenital malformations (particularly cardiac defects) associated with NSAID use. Third trimester: Known risk of prem. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.