FOSRENOL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FOSRENOL (FOSRENOL).
Lanthanum carbonate dissociates in the acidic environment of the stomach to release lanthanum ions, which bind to dietary phosphate to form insoluble lanthanum phosphate complexes, thereby reducing gastrointestinal phosphate absorption and lowering serum phosphate levels.
| Metabolism | Not metabolized; eliminated primarily unchanged in feces (via bile) and minimally in urine (<2%). |
| Excretion | Primarily fecal as unabsorbed drug (approximately 87-98% of the administered dose); negligible renal excretion (<0.1%). |
| Half-life | Terminal elimination half-life is not clinically relevant as the drug acts locally in the GI tract and is not absorbed; systemic exposure is negligible. |
| Protein binding | Not applicable; the drug is not absorbed systemically and does not bind to plasma proteins. |
| Volume of Distribution | Not applicable; the drug is not systemically absorbed, thus Vd is not defined. |
| Bioavailability | Oral bioavailability is negligible (<0.1%) due to lack of systemic absorption. |
| Onset of Action | Oral: Onset of phosphate binding occurs immediately upon contact with dietary phosphate in the GI tract, with clinical effects (reduced serum phosphate) typically observed within 1 week. |
| Duration of Action | Duration of action is dependent on continued oral administration; phosphate binding persists while the drug remains in the GI tract during transit (approximately 4-6 hours per dose). |
Initial dose: 800 mg orally three times daily; titrate to achieve target serum phosphorus levels, max 4000 mg per day.
| Dosage form | TABLET, CHEWABLE |
| Renal impairment | Not applicable; the drug is indicated only for patients with end-stage renal disease (ESRD) on dialysis. No dose adjustment for GFR as drug is not absorbed systemically. |
| Liver impairment | No specific dose adjustment recommended; hepatic impairment unlikely to affect drug as minimal systemic absorption. |
| Pediatric use | Safety and efficacy not established in pediatric patients. |
| Geriatric use | No specific dose adjustment; use with caution due to higher likelihood of comorbid conditions and polypharmacy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FOSRENOL (FOSRENOL).
| Breastfeeding | Lanthanum is not absorbed systemically, and excretion into breast milk is minimal. M/P ratio is not available due to negligible absorption. Considered compatible with breastfeeding if maternal serum phosphate levels are controlled; monitor infant for potential gastrointestinal effects. |
| Teratogenic Risk | Fosrenol (lanthanum carbonate) is not absorbed systemically in significant amounts; however, animal studies have shown no evidence of teratogenicity. In pregnant women, there are no adequate and well-controlled studies. First trimester: No known risk based on lack of systemic absorption. Second trimester: No known risk; monitor phosphate levels. Third trimester: No known risk; monitor maternal and fetal calcium and phosphate homeostasis. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to lanthanum carbonate or any component","Bowel obstruction, ileus, fecal impaction","Metabolic alkalosis (theoretical concern due to carbonate moiety)"]
| Precautions | ["Accumulation in tissues (bone, liver) with long-term use; monitor for potential toxicities","Risk of gastrointestinal obstruction, impaction, or perforation, especially in patients with underlying GI disorders","Severe nausea, vomiting, or abdominal pain may require discontinuation","May bind to oral medications; administer other drugs at least 2 hours before or after Fosrenol"] |
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| Fetal Monitoring | Monitor serum phosphate, calcium, and parathyroid hormone levels throughout pregnancy. Assess fetal growth and development via ultrasound as clinically indicated. Monitor for signs of maternal hypocalcemia or hypercalcemia. |
| Fertility Effects | Animal studies show no adverse effects on fertility at clinically relevant doses. Human data are lacking; no known impact on fertility. |