FURALAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FURALAN (FURALAN).
Inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, preventing DNA replication and transcription.
| Metabolism | Primarily hepatic via CYP1A2 and CYP3A4; also glucuronidation. |
| Excretion | Approximately 65–70% of an administered dose is excreted unchanged via renal glomerular filtration and tubular secretion; about 10–15% appears in bile as parent drug or glucuronide conjugate; up to 20% is eliminated in feces via unabsorbed fraction or biliary elimination. |
| Half-life | Terminal elimination half-life is 8–12 hours in adults with normal renal function; this supports twice-daily dosing. In patients with creatinine clearance <30 mL/min, half-life may be prolonged to 20–30 hours, requiring dose adjustment. |
| Protein binding | 87–95% bound to serum albumin; lower binding (81–88%) in patients with uremia or nephrotic syndrome due to hypoalbuminemia. |
| Volume of Distribution | 0.20–0.35 L/kg (approximately 15–25 L in a 70 kg adult). This relatively small Vd reflects limited extravascular distribution and high plasma protein binding. |
| Bioavailability | Oral: 50–70% (first-pass hepatic metabolism reduces absolute bioavailability). Bioavailability may be increased in patients with hepatic cirrhosis or decreased in heart failure with intestinal edema. |
| Onset of Action | Oral: 0.5–1 hour; Intravenous: within 5–10 minutes. Clinical effect (diuresis) begins within 30–60 minutes after oral administration and 15–30 minutes after IV administration. |
| Duration of Action | Oral: 6–8 hours; Intravenous: 4–6 hours. Diuretic effect correlates with drug concentration in urine; duration is extended in renal impairment due to reduced clearance. |
20 mg orally three times daily for 7 days.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 20 mg twice daily; GFR 15-29 mL/min: 20 mg once daily; GFR <15 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 20 mg twice daily; Child-Pugh C: not recommended. |
| Pediatric use | 2-5 mg/kg/day divided every 8 hours; maximum 20 mg per dose. |
| Geriatric use | Start at 20 mg twice daily; monitor renal function and reduce dose if CrCl <50 mL/min. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FURALAN (FURALAN).
| Breastfeeding | Furosemide is excreted in breast milk in low amounts; M/P ratio ~0.4. It may suppress lactation. Use with caution in nursing mothers. |
| Teratogenic Risk | FURALAN (furosemide) crosses the placenta. First trimester: No adequate studies; avoid use. Second and third trimesters: Associated with oligohydramnios and fetal renal effects; use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
Fluoroquinolones, including furalan, may exacerbate muscle weakness in persons with myasthenia gravis. Avoid use in patients with a history of myasthenia gravis.
| Serious Effects |
Hypersensitivity to furalan or any fluoroquinolone; history of myasthenia gravis; concomitant use with tizanidine; patients under 18 years of age (except for specific approved indications).
| Precautions | Risk of tendinitis and tendon rupture, especially in elderly and those on corticosteroids; peripheral neuropathy; CNS effects including seizures; QT prolongation; hypersensitivity reactions; Clostridioides difficile colitis; photosensitivity; hepatic toxicity; renal impairment dose adjustment. |
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| Monitor maternal blood pressure, renal function, electrolytes, and fluid status. Fetal ultrasound for growth and amniotic fluid volume if used during pregnancy. |
| Fertility Effects | No known adverse effects on fertility in humans. |