Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE vs FASTIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
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.
Sympathomimetic amine that promotes release of norepinephrine and dopamine from presynaptic nerve terminals in the hypothalamus, suppressing appetite.
Symptomatic relief of upper respiratory symptoms associated with allergic rhinitis, common cold, or sinusitis including nasal congestion, rhinorrhea, sneezing, and cough.
Short-term adjunct in exogenous obesity,Off-label: Attention deficit hyperactivity disorder (ADHD)
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.
30 mg orally once daily in the morning, administered as a single dose.
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).
Terminal elimination half-life is approximately 16-20 hours for the immediate-release formulation. With sustained-release forms, effective half-life may extend to 24-34 hours due to prolonged absorption. Clinical context: time to reach steady state is about 3-5 days.
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.
Hepatic metabolism via CYP3A4 and CYP2D6; active metabolite phendimetrazine (for some formulations).
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.
Primarily renal (approximately 70-80% unchanged) and biliary/fecal (20-30% as metabolites). Urinary excretion is p H-dependent; acidic urine increases elimination.
Brompheniramine: 60-80% (primarily albumin, alpha-1-acid glycoprotein). Pseudoephedrine: <10% (negligible). Dextromethorphan: 50-60% (possibly to albumin).
Approximately 40-50% bound to plasma proteins (albumin).
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).
Approximately 3-5 L/kg. High Vd indicates extensive tissue distribution, including brain.
Brompheniramine: ~70% (oral). Pseudoephedrine: 90-100% (oral). Dextromethorphan: ~10-30% (oral, due to extensive first-pass metabolism; in poor metabolizers, bioavailability higher).
Oral immediate-release: ~90% (high first-pass metabolism; absolute bioavailability is lower, but systemic exposure is adequate). Oral sustained-release: similar extent but with prolonged absorption.
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).
Contraindicated in severe renal impairment (e GFR <30 m L/min/1.73 m²). For moderate impairment (e GFR 30-59 m L/min/1.73 m²), reduce dose to 15 mg once daily.
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).
Contraindicated in Child-Pugh class C cirrhosis. In Child-Pugh class A or B, initiate at 15 mg once daily and titrate cautiously to maximum 30 mg once daily.
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).
Not recommended for pediatric patients under 16 years of age due to lack of safety and efficacy data.
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.
Initiating at 15 mg once daily is recommended due to increased sensitivity and potential for central nervous system adverse effects; maximum dose 30 mg once daily.
None.
None.
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).
Cardiovascular events (hypertension, tachycardia, stroke), psychiatric adverse effects (psychosis, dependence), primary pulmonary hypertension, valvular heart disease, tolerance, withdrawal symptoms, glaucoma, hyperthyroidism, seizure disorder, diabetes (dose adjustment required), elderly patients (higher sensitivity).
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)
Cardiovascular disease (e.g., coronary artery disease, arrhythmias, hypertension), hyperthyroidism, glaucoma, agitated states, history of drug abuse, MAOIs (concurrent or within 14 days), hypersensitivity to sympathomimetics.
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.
Avoid excessive caffeine intake (e.g., coffee, tea, cola, energy drinks) as it may potentiate CNS and cardiovascular effects. Grapefruit juice may alter drug metabolism; avoid concurrent consumption. Maintain a balanced, reduced-calorie diet as part of the weight loss plan. Alcohol should be avoided due to potential additive CNS effects.
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.
FDA Pregnancy Category X. First trimester: Increased risk of oral clefts and cardiac malformations with amphetamine use. Second and third trimesters: Risk of premature delivery, low birth weight, and neonatal withdrawal syndrome. Avoid use in pregnancy.
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.
Excreted in human milk; M/P ratio not established. Potential for adverse effects in nursing infants (irritability, poor feeding). Contraindicated during breastfeeding.
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.
Contraindicated in pregnancy; no dose adjustments recommended.
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.
Fastin (phentermine) is a sympathomimetic amine indicated for short-term (up to 12 weeks) monotherapy for obesity. It should be used in conjunction with a reduced-calorie diet and exercise. Avoid co-administration with MAOIs or within 14 days of MAOI use due to hypertensive crisis risk. Use with caution in patients with hypertension, diabetes, or history of drug abuse. Monitor blood pressure and heart rate regularly. Tachyphylaxis may develop; discontinue if tolerance occurs. Do not use in patients with advanced arteriosclerosis, hyperthyroidism, glaucoma, or agitated states.
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.
Take Fastin exactly as prescribed, usually once daily in the morning to avoid insomnia.,Do not crush or chew the extended-release capsule; swallow whole.,Avoid taking late in the day to prevent difficulty sleeping.,Report any chest pain, palpitations, shortness of breath, or dizziness immediately.,Do not increase dose or take more frequently than prescribed; risk of dependence and side effects.,Fastin is for short-term use only (up to 12 weeks) and should be combined with a reduced-calorie diet and exercise.,Do not use if you have taken an MAO inhibitor in the last 14 days.,Avoid alcohol and other CNS stimulants (e.g., caffeine in large amounts) as they may increase side effects.,Do not stop abruptly; follow your doctor's instructions for tapering off.,Keep out of reach of children; misuse can cause severe cardiac toxicity.
"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."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE vs FASTIN, answered by our medical review team.
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.. FASTIN is a Sympathomimetic Anorectic that works by Sympathomimetic amine that promotes release of norepinephrine and dopamine from presynaptic nerve terminals in the hypothalamus, suppressing appetite.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE and FASTIN 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 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.. The standard adult dose of FASTIN is: 30 mg orally once daily in the morning, administered as a single dose.. 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 BROMPHENIRAMINE MALEATE, PSEUDOEPHEDRINE HYDROCHLORIDE AND DEXTROMETHORPHAN HYDROBROMIDE and FASTIN 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. 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. FASTIN is classified as Category C. FDA Pregnancy Category X. First trimester: Increased risk of oral clefts and cardiac malformations with amphetamine use. Second and third trimesters: Risk of premature delivery, lo. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.