FERNDEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FERNDEX (FERNDEX).
Ferndex is a selective serotonin reuptake inhibitor (SSRI) that potentiates serotonergic activity in the central nervous system by inhibiting the reuptake of serotonin at the synaptic cleft.
| Metabolism | Primarily metabolized by CYP2D6 and CYP3A4; active metabolite N-desmethylferndex formed via CYP3A4. |
| Excretion | Primarily renal excretion as unchanged drug (60-70%) and glucuronide conjugates (15-20%); biliary/fecal elimination accounts for <10%. |
| Half-life | Terminal elimination half-life is 12-15 hours in adults with normal renal function; may be prolonged to 24-30 hours in elderly or patients with renal impairment (CrCl <30 mL/min). |
| Protein binding | 99% bound to albumin and alpha-1-acid glycoprotein; reduces free fraction in hypoalbuminemia or renal failure. |
| Volume of Distribution | 0.12-0.15 L/kg; indicates distribution primarily into extracellular fluid and highly perfused tissues; low Vd reflects high protein binding. |
| Bioavailability | Oral: 85-90% (first-pass metabolism minimal); Rectal: 50-70%; Intramuscular: 100% (absolute). |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 5-10 minutes; Intramuscular: 15-30 minutes. |
| Duration of Action | Analgesic effect lasts 4-6 hours; antipyretic effect lasts 6-8 hours; anti-inflammatory effect requires 1-2 weeks for maximal effect (dosing interval: 6-8 hours). |
Adults: 100 mg orally three times daily.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 100 mg twice daily; GFR <30 mL/min: 100 mg once daily; hemodialysis: 100 mg after dialysis. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 100 mg twice daily; Child-Pugh C: 100 mg once daily. |
| Pediatric use | Children >2 years: 2 mg/kg orally three times daily; maximum 100 mg per dose. |
| Geriatric use | Age >65 years: start at 100 mg twice daily; monitor renal function and adjust accordingly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FERNDEX (FERNDEX).
| Breastfeeding | FERNDEX is excreted in human breast milk. M/P ratio unknown. Potential for infant adrenal suppression; use during breastfeeding only if clearly needed and monitor infant for signs of adrenal insufficiency. |
| Teratogenic Risk | FERNDEX is contraindicated in pregnancy. First trimester exposure is associated with increased risk of orofacial clefts and neural tube defects. Second and third trimester use may cause fetal adrenal suppression, intrauterine growth restriction, and premature closure of ductus arteriosus. |
■ FDA Black Box Warning
WARNING: SUICIDALITY AND ANTIDEPRESSANT DRUGS - Ferndex increases the risk of suicidal thinking and behavior in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders. Closely monitor for clinical worsening, suicidality, or unusual changes in behavior.
| Serious Effects |
Concurrent use with MAOIs (including linezolid and IV methylene blue), known hypersensitivity to ferndex or any excipient, concurrent use with pimozide or thioridazine.
| Precautions | Serotonin syndrome, discontinuation syndrome, activation of mania/hypomania, seizures, angle-closure glaucoma, hyponatremia, increased bleeding risk, QT prolongation, sexual dysfunction. |
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| Fetal Monitoring |
| Monitor maternal serum cortisol, blood glucose, and blood pressure. Assess fetal growth via ultrasound due to risk of intrauterine growth restriction. Perform fetal echocardiography if used in first trimester. |
| Fertility Effects | FERNDEX may impair fertility in women by disrupting ovulatory cycles via suppression of hypothalamic-pituitary-adrenal axis. Reversible upon discontinuation. |