Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BONTRIL vs BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE
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.
Brompheniramine is a first-generation antihistamine that competitively inhibits histamine at H1 receptors, reducing allergic symptoms. Pseudoephedrine is a sympathomimetic amine that directly stimulates alpha-adrenergic receptors, causing vasoconstriction and nasal decongestion. Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist that suppresses the cough reflex in the medulla oblongata.
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.
Symptomatic relief of upper respiratory symptoms associated with allergic rhinitis, common cold, or sinusitis including nasal congestion, rhinorrhea, sneezing, and cough.
BONTRIL 50 mg orally once daily, with or without food.
Adults and children ≥12 years: 1 tablet (brompheniramine maleate 4 mg, pseudoephedrine HCl 60 mg, dextromethorphan HBr 15 mg) orally every 4 hours, not to exceed 4 tablets in 24 hours, or 2 tablets (extended-release) every 12 hours, not to exceed 4 tablets in 24 hours.
18-24 hours; prolonged in renal impairment (up to 40 hours) requiring dose adjustment.
Brompheniramine: 12-34 hours (mean ~24 h), prolonged in hepatic impairment. Pseudoephedrine: 5-8 hours (p H-dependent urinary excretion; alkaline urine prolongs half-life). Dextromethorphan: 3-4 hours (extensive metabolizers) or 18-24 hours (poor metabolizers of CYP2D6).
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.
Brompheniramine: extensively metabolized via hepatic CYP450 (CYP2D6, CYP3A4) to desmethylbrompheniramine and other metabolites. Pseudoephedrine: partially metabolized via N-demethylation (CYP450) to norgseudoephedrine; 43-96% excreted unchanged. Dextromethorphan: primarily metabolized via CYP2D6 to dextrorphan (active), also via CYP3A4/5 to 3-methoxymorphinan.
Primarily renal (60-70% unchanged) with minor biliary/fecal (10-15% as metabolites).
Brompheniramine: Renal (approx. 80% as metabolites, <1% unchanged). Pseudoephedrine: Renal (70-90% unchanged, rest as metabolites). Dextromethorphan: Renal (primarily as metabolites, <1% unchanged). Biliary/fecal: Minor for all three.
85-90% bound to albumin and alpha-1-acid glycoprotein.
Brompheniramine: 60-80% (primarily albumin, alpha-1-acid glycoprotein). Pseudoephedrine: <10% (negligible). Dextromethorphan: 50-60% (possibly to albumin).
3-5 L/kg; indicates extensive tissue distribution.
Brompheniramine: 7-10 L/kg (large, due to extensive tissue distribution). Pseudoephedrine: 2.5-3.5 L/kg (moderate, distributes into body water). Dextromethorphan: 3-5 L/kg (moderate, distributed to tissues including brain).
Oral: 70-80% (first-pass metabolism); IV: 100%.
Brompheniramine: ~70% (oral). Pseudoephedrine: 90-100% (oral). Dextromethorphan: ~10-30% (oral, due to extensive first-pass metabolism; in poor metabolizers, bioavailability higher).
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.
GFR ≥30 m L/min: No adjustment. GFR 10-29 m L/min: Administer every 6 hours; monitor for CNS effects. GFR <10 m L/min: Avoid use (risk of toxicity from pseudoephedrine and dextromethorphan accumulation).
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 frequency (e.g., every 6 hours) and monitor for CNS depression. Child-Pugh C: Avoid use (dextromethorphan metabolism reduced; brompheniramine may accumulate).
Weight-based: 1 mg/kg orally once daily, with a maximum of 50 mg. Not recommended for children weighing less than 10 kg.
Children 6-11 years: 1/2 tablet (brompheniramine maleate 2 mg, pseudoephedrine HCl 30 mg, dextromethorphan HBr 7.5 mg) orally every 4 hours, not to exceed 4 doses in 24 hours. Children 2-5 years: Not recommended (safety and efficacy not established). Children <2 years: Contraindicated (risk of respiratory depression).
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).
Elderly >65 years: Initiate at lowest effective dose (e.g., 1/2 tablet) every 6-8 hours due to increased anticholinergic effects, hypotension, and CNS excitation. Maximum: 2 tablets in 24 hours. Monitor for confusion, urinary retention, and elevated blood pressure.
None
None.
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 effects: hypertension, palpitations, tachycardia, arrhythmias, especially in patients with pre-existing heart disease or hyperthyroidism.,CNS depression: avoid concurrent use with alcohol or other sedatives; may impair mental/physical abilities.,Serotonin syndrome: risk with concomitant serotonergic drugs including MAOIs, SSRIs, SNRIs, triptans, linezolid, methylene blue.,QT prolongation: caution with drugs that prolong QT interval or predisposing conditions (e.g., electrolyte abnormalities, bradycardia).,Anticholinergic effects: caution in patients with glaucoma, prostatic hypertrophy, urinary retention, or asthma.,Inhibition of CYP2D6: dextromethorphan may increase levels of CYP2D6 substrates (e.g., TCAs, antipsychotics).
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 any component,Concurrent use or within 14 days of MAO inhibitors (hypertensive crisis),Severe hypertension or coronary artery disease,Narrow-angle glaucoma,Urinary retention,During or immediately after treatment with serotonergic drugs (risk of serotonin syndrome)
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.
Avoid alcohol, which may potentiate CNS depression. Limit caffeine intake (coffee, tea, cola) as pseudoephedrine may increase stimulant effects. High-tyramine foods (e.g., aged cheese, cured meats, fermented products) may cause hypertensive crisis if combined with MAOIs, but this combination is contraindicated. No other significant food interactions.
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.
Brompheniramine: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Pseudoephedrine: Case-control studies suggest small increased risk of gastroschisis and hemifacial microsomia with first-trimester use; vasoconstriction may reduce uteroplacental blood flow in third trimester. Dextromethorphan: No human teratogenicity data; animal studies show no fetal harm at therapeutic doses. Overall, combination is not recommended in first trimester; avoid in third trimester due to pseudoephedrine effects.
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.
Brompheniramine: excreted in breast milk in small amounts; may cause infant irritability or drowsiness. Pseudoephedrine: concentrated in breast milk (M/P ratio ~3.0); may reduce milk production. Dextromethorphan: likely excreted in breast milk but no data on infant levels. Avoid during breastfeeding due to potential infant CNS effects and reduced milk supply.
No dose adjustment required for pregnancy. However, due to teratogenicity, BONTRIL should be discontinued before conception or as soon as pregnancy is diagnosed.
No specific dose adjustments studied for combination in pregnancy. Due to increased plasma volume and clearance, standard adult doses may be less effective; however, avoid use in pregnancy due to risks. No PK studies available.
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.
Do not use in children under 6 years due to risk of respiratory depression from dextromethorphan. Avoid in patients with hypertension or coronary artery disease due to pseudoephedrine. Brompheniramine has pronounced anticholinergic effects; use cautiously in elderly or those with glaucoma, urinary retention, or BPH. For severe cough, dextromethorphan efficacy is limited; consider if nonproductive cough is disruptive. Maximum duration of treatment is 7 days; prolonged use may lead to rebound congestion and dependence.
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.
Do not take more than 6 doses in 24 hours. Do not exceed 7 days of use without consulting a doctor.,Avoid alcohol and other CNS depressants (e.g., sedatives, tranquilizers) as they may increase drowsiness.,Do not use if you have taken a monoamine oxidase inhibitor (MAOI) within the last 14 days.,Stop use and ask a doctor if symptoms do not improve within 7 days, are accompanied by fever, or if cough persists with headache, rash, or persistent headache.,Take with a full glass of water. May cause drowsiness; avoid driving or operating heavy machinery until you know how this medication affects you.,For the decongestant effect, take the last dose of the day several hours before bedtime to minimize insomnia.,Shake suspension well before use. Use only the dosing device provided.
No interactions on record
"Brompheniramine, a first-generation antihistamine, may inhibit the hepatic metabolism of sulfamethoxazole, a sulfonamide antibiotic, via competitive inhibition of cytochrome P450 enzymes, particularly CYP2C9. This results in elevated plasma concentrations of sulfamethoxazole, potentially increasing the risk of dose-dependent adverse effects such as hypersensitivity reactions, crystalluria, and hematologic toxicity (e.g., agranulocytosis). Clinically, patients may present with prolonged or intensified drug effects, including increased bone marrow suppression and renal impairment, especially in those with pre-existing hepatic or renal dysfunction."
"Dextropropoxyphene, an opioid analgesic, and brompheniramine, a first-generation antihistamine with anticholinergic properties, can synergistically depress the central nervous system (CNS) and respiratory centers. This interaction increases the risk of profound sedation, respiratory depression, coma, and death, particularly in elderly patients or those with pre-existing respiratory or hepatic impairment. Concurrent use also amplifies anticholinergic adverse effects such as urinary retention, constipation, and cognitive dysfunction."
"Brompheniramine, a first-generation antihistamine with significant central nervous system (CNS) depressant properties, can potentiate the CNS depressant effects of brimonidine, an alpha-2 adrenergic agonist used for ocular hypertension and glaucoma. This interaction leads to additive sedation, drowsiness, and dizziness, which may impair cognitive and motor function, increasing the risk of falls and accidents. Severe cases could result in excessive CNS depression, including somnolence and respiratory depression, particularly in elderly patients or those with compromised hepatic function."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BONTRIL vs BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE, 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.. BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE is a Sympathomimetic that works by Brompheniramine is a first-generation antihistamine that competitively inhibits histamine at H1 receptors, reducing allergic symptoms. Pseudoephedrine is a sympathomimetic amine that directly stimulates alpha-adrenergic receptors, causing vasoconstriction and nasal decongestion. Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist that suppresses the cough reflex in the medulla oblongata.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BONTRIL and BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE 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 BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE is: Adults and children ≥12 years: 1 tablet (brompheniramine maleate 4 mg, pseudoephedrine HCl 60 mg, dextromethorphan HBr 15 mg) orally every 4 hours, not to exceed 4 tablets in 24 hours, or 2 tablets (extended-release) every 12 hours, not to exceed 4 tablets in 24 hours.. 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 BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE 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. BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE is classified as Category A/B. Brompheniramine: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Pseudoephedrine: Case-control studies suggest small increased risk of gastr. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.