Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BONTRIL vs SUPRENZA
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.
Partial agonist at mu-opioid receptors; also a weak antagonist at kappa-opioid receptors. Provides analgesic effects with reduced respiratory depression compared to full agonists.
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.
Management of moderate to severe chronic pain,Off-label: Treatment of opioid use disorder (as a maintenance therapy similar to buprenorphine)
BONTRIL 50 mg orally once daily, with or without food.
Adults: 200 mg orally twice daily with meals.
18-24 hours; prolonged in renal impairment (up to 40 hours) requiring dose adjustment.
Terminal elimination half-life is approximately 12-15 hours in patients with normal renal function, allowing for twice-daily dosing.
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.
Primarily hepatic via CYP3A4 and CYP3A5 to norbuprenorphine (active metabolite); also undergoes glucuronidation.
Primarily renal (60-70% unchanged) with minor biliary/fecal (10-15% as metabolites).
Approximately 60-80% of a dose is excreted renally as unchanged drug, with 20-40% eliminated via biliary/fecal routes.
85-90% bound to albumin and alpha-1-acid glycoprotein.
Approximately 95-98% bound to plasma proteins, primarily albumin.
3-5 L/kg; indicates extensive tissue distribution.
Volume of distribution is approximately 2-3 L/kg, indicating extensive tissue distribution beyond plasma volume.
Oral: 70-80% (first-pass metabolism); IV: 100%.
Oral bioavailability is approximately 70-80%.
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.
e GFR <45 m L/min/1.73m²: contraindicated. e GFR ≥45: no adjustment.
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 Class A: no adjustment; Class B: reduce to 200 mg once daily; Class C: contraindicated.
Weight-based: 1 mg/kg orally once daily, with a maximum of 50 mg. Not recommended for children weighing less than 10 kg.
Not recommended for patients under 18 years; safety and efficacy not established.
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).
No specific dose adjustment; monitor renal function and use caution due to increased risk of adverse effects.
None
Risk of respiratory depression, especially in non-opioid-tolerant patients. Risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy. Risk of serious injury or death due to accidental exposure in children.
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.
Respiratory depression, particularly in the first 24-72 hours of treatment; caution in patients with pulmonary disease. Risk of QT prolongation. Adrenal insufficiency. Severe hypotension. Risk of misuse, abuse, and addiction. Tolerance and physical dependence.
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.
Hypersensitivity to buprenorphine or any component of the formulation. Severe respiratory insufficiency. Acute or severe bronchial asthma. Gastrointestinal obstruction, including paralytic ileus.
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.
No significant food interactions. Grapefruit juice may increase buprenorphine levels; avoid large quantities.
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.
Supr ENza (testosterone) is contraindicated in pregnancy due to virilization of female fetus. First trimester: high risk of clitoromegaly, labial fusion, and urogenital sinus abnormalities. Second and third trimesters: risk of continued virilization, including phallic enlargement and ambiguous genitalia. Fetal growth restriction may occur.
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.
Testosterone is present in breast milk; M/P ratio not reported. Avoid breastfeeding due to potential for androgenization of the infant. Use only if clearly needed and no safer alternative.
No dose adjustment required for pregnancy. However, due to teratogenicity, BONTRIL should be discontinued before conception or as soon as pregnancy is diagnosed.
Not applicable; Supr ENza is contraindicated in pregnancy. No dose adjustments are recommended as use is avoided entirely.
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.
SUPRENZA (buprenorphine/naloxone) sublingual film is used for opioid dependence. Monitor for respiratory depression especially when combined with benzodiazepines or alcohol. The naloxone component is poorly absorbed sublingually but precipitates withdrawal if injected. Administer only after clear signs of withdrawal to avoid precipitated withdrawal. Adjust dose in hepatic impairment as buprenorphine is hepatically metabolized.
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 exactly as prescribed; do not increase dose or frequency without consulting your doctor.,Place film under the tongue until fully dissolved; do not chew or swallow.,Avoid alcohol and benzodiazepines as they can cause severe respiratory depression.,Keep out of reach of children; accidental exposure can be fatal.,Do not abruptly stop; withdrawal symptoms may occur.,Store at room temperature away from moisture and heat.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BONTRIL vs SUPRENZA, 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.. SUPRENZA is a Sympathomimetic Anorectic that works by Partial agonist at mu-opioid receptors; also a weak antagonist at kappa-opioid receptors. Provides analgesic effects with reduced respiratory depression compared to full agonists.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BONTRIL and SUPRENZA depend on the specific clinical indication. These are both Sympathomimetic Anorectic agents 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 SUPRENZA is: Adults: 200 mg orally twice daily with meals.. 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 SUPRENZA 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. SUPRENZA is classified as Category C. SuprENza (testosterone) is contraindicated in pregnancy due to virilization of female fetus. First trimester: high risk of clitoromegaly, labial fusion, and urogenital sinus abnorm. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.