Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FASTIN vs DELCOBESE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Sympathomimetic amine that promotes release of norepinephrine and dopamine from presynaptic nerve terminals in the hypothalamus, suppressing appetite.
Selective serotonin reuptake inhibitor (SSRI) that increases synaptic serotonin by blocking the serotonin transporter (SERT). Additionally, it has a unique property of acting as an agonist at the 5-HT2C receptor, which may contribute to its anorectic effects.
Short-term adjunct in exogenous obesity,Off-label: Attention deficit hyperactivity disorder (ADHD)
Chronic weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with at least one weight-related comorbidity (e.g., hypertension, type 2 diabetes, dyslipidemia)
30 mg orally once daily in the morning, administered as a single dose.
Initial dose: 0.5 mg subcutaneously once weekly for 4 weeks, then increase to 1 mg once weekly for 4 weeks, then maintain at 2 mg once weekly. Titrate based on glycemic control up to 2 mg weekly.
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.
12-15 hours in healthy adults; prolonged in renal impairment (up to 30 hours with Cr Cl <30 m L/min).
Hepatic metabolism via CYP3A4 and CYP2D6; active metabolite phendimetrazine (for some formulations).
Primarily metabolized by cytochrome P450 (CYP) 2D6 with minor contributions from CYP3A4 and CYP2C19. Active metabolite N-desmethyl lorcaserin is formed via CYP2D6.
Primarily renal (approximately 70-80% unchanged) and biliary/fecal (20-30% as metabolites). Urinary excretion is p H-dependent; acidic urine increases elimination.
Primarily renal (60-70% unchanged) with 20-30% fecal via biliary elimination; less than 5% metabolized.
Approximately 40-50% bound to plasma proteins (albumin).
95% bound to albumin and alpha-1-acid glycoprotein.
Approximately 3-5 L/kg. High Vd indicates extensive tissue distribution, including brain.
0.3-0.4 L/kg; indicates moderate distribution to extracellular fluid and well-perfused tissues.
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.
Oral: 40-50% (first-pass effect); Subcutaneous: 70-80%; IV: 100%.
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.
No dose adjustment required for mild to moderate renal impairment (e GFR ≥30 m L/min/1.73 m2). Contraindicated in severe renal impairment (e GFR <30 m L/min/1.73 m2) or end-stage renal disease.
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.
No dose adjustment required for mild hepatic impairment (Child-Pugh class A). Not recommended for moderate or severe hepatic impairment (Child-Pugh class B or C) due to lack of data.
Not recommended for pediatric patients under 16 years of age due to lack of safety and efficacy data.
Not approved for use in pediatric patients under 18 years of age. Safety and efficacy have not been established.
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.
No specific dose adjustment required; initiate at 0.5 mg subcutaneously once weekly and titrate cautiously due to potential for renal function decline and increased sensitivity. Monitor renal function and consider dose reduction if e GFR declines.
None.
WARNING: SUICIDALITY AND ANTIDEPRESSANT DRUGS - Antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents, and young adults in short-term studies. Monitor for worsening and emergence of suicidal thoughts and behaviors. DELCOBESE is not approved for use in pediatric patients.
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).
Risk of serotonin syndrome or neuroleptic malignant syndrome when coadministered with other serotonergic drugs. Potential for pulmonary hypertension. Monitor for valvular heart disease (5-HT2B receptor agonist activity). Caution in patients with renal impairment (e GFR <30 m L/min). Avoid in pregnancy (potential for fetal harm).
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.
Concomitant use with monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuing an MAOI. Known hypersensitivity to DELCOBESE or any component. Severe renal impairment (e GFR <30 m L/min) or end-stage renal disease. History of pulmonary hypertension. Pregnancy.
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.
Avoid grapefruit and grapefruit juice which inhibits CYP3A4 metabolism increasing DELCOBESE levels. Avoid high-fat meals as they increase absorption and risk of adverse effects. Limit alcohol to no more than 1 drink per day due to additive CNS depression. Ensure adequate hydration to prevent constipation.
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.
DELCOBESE is contraindicated in pregnancy. First trimester exposure is associated with increased risk of major congenital malformations, particularly neural tube defects, cardiac anomalies, and cleft palate. Second and third trimester exposure can cause fetal growth restriction, oligohydramnios, and neonatal renal impairment. There is a dose-dependent risk of pregnancy loss.
Excreted in human milk; M/P ratio not established. Potential for adverse effects in nursing infants (irritability, poor feeding). Contraindicated during breastfeeding.
Excretion into breast milk is unknown; due to potential for serious adverse reactions in the breastfed infant, breastfeeding is not recommended during therapy and for at least 1 week after the last dose. No M/P ratio data available.
Contraindicated in pregnancy; no dose adjustments recommended.
Do not use in pregnancy. No dosing adjustment recommendations exist as the drug is contraindicated. Pharmacokinetic changes in pregnancy (e.g., increased volume of distribution, altered metabolism) are not applicable.
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.
DELCOBESE is a novel synthetic cannabinoid receptor antagonist/inverse agonist (CB1R) approved for weight management. Monitor for psychiatric adverse effects (depression, suicidal ideation) especially during first 3 months. Avoid in patients with history of seizures due to lowered seizure threshold. Titrate dose slowly: start at 5 mg BID, increase to 10 mg BID after 4 weeks if tolerated. Discontinue if no 5% weight loss at 12 weeks. Use contraception in women of childbearing potential due to teratogenicity. Check liver function tests monthly for first 6 months due to rare hepatotoxicity.
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.
Take exactly as prescribed; do not exceed 20 mg per day.,May cause dizziness or drowsiness; avoid driving until you know how this drug affects you.,Report any new or worsening depression, anxiety, or thoughts of self-harm immediately.,Use effective contraception during treatment and for 1 month after stopping.,Avoid alcohol and grapefruit juice as they may increase side effects.,Inform your doctor if you have a history of seizures or liver disease.,Do not stop suddenly; taper under medical supervision to avoid withdrawal symptoms.,Maintain a reduced-calorie diet and exercise program for best results.
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 FASTIN vs DELCOBESE, answered by our medical review team.
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.. DELCOBESE is a Anorectic (sympathomimetic) that works by Selective serotonin reuptake inhibitor (SSRI) that increases synaptic serotonin by blocking the serotonin transporter (SERT). Additionally, it has a unique property of acting as an agonist at the 5-HT2C receptor, which may contribute to its anorectic effects.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FASTIN and DELCOBESE 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 FASTIN is: 30 mg orally once daily in the morning, administered as a single dose.. The standard adult dose of DELCOBESE is: Initial dose: 0.5 mg subcutaneously once weekly for 4 weeks, then increase to 1 mg once weekly for 4 weeks, then maintain at 2 mg once weekly. Titrate based on glycemic control up to 2 mg weekly.. 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 FASTIN and DELCOBESE 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. 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. DELCOBESE is classified as Category C. DELCOBESE is contraindicated in pregnancy. First trimester exposure is associated with increased risk of major congenital malformations, particularly neural tube defects, cardiac a. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.