FASTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FASTIN (FASTIN).
Sympathomimetic amine that promotes release of norepinephrine and dopamine from presynaptic nerve terminals in the hypothalamus, suppressing appetite.
| Metabolism | Hepatic metabolism via CYP3A4 and CYP2D6; active metabolite phendimetrazine (for some formulations). |
| Excretion | Primarily renal (approximately 70-80% unchanged) and biliary/fecal (20-30% as metabolites). Urinary excretion is pH-dependent; acidic urine increases elimination. |
| Half-life | 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. |
| Protein binding | Approximately 40-50% bound to plasma proteins (albumin). |
| Volume of Distribution | Approximately 3-5 L/kg. High Vd indicates extensive tissue distribution, including brain. |
| Bioavailability | 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. |
| Onset of Action | Oral immediate-release: 1-2 hours; sustained-release: 2-4 hours. Time to peak appetite suppression. |
| Duration of Action | Immediate-release: 4-6 hours; sustained-release: 8-12 hours. Note: For sustained-release, clinical effect may persist up to 12-16 hours depending on individual metabolism. |
30 mg orally once daily in the morning, administered as a single dose.
| Dosage form | CAPSULE |
| Renal impairment | Contraindicated in severe renal impairment (eGFR <30 mL/min/1.73 m²). For moderate impairment (eGFR 30-59 mL/min/1.73 m²), reduce dose to 15 mg once daily. |
| Liver impairment | 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. |
| Pediatric use | Not recommended for pediatric patients under 16 years of age due to lack of safety and efficacy data. |
| Geriatric use | 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. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FASTIN (FASTIN).
| Breastfeeding | Excreted in human milk; M/P ratio not established. Potential for adverse effects in nursing infants (irritability, poor feeding). Contraindicated during breastfeeding. |
| Teratogenic Risk | 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. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
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.
| Precautions | 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). |
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| Monitor maternal blood pressure, heart rate, and weight. Assess for signs of abuse or dependence. Fetal ultrasound for growth and anomalies if exposed. |
| Fertility Effects | May impair fertility in females due to altered hormone levels or weight loss; no direct evidence of male fertility impairment. |