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). |
| Molecular Weight | In fact, the molecular weight of lanthanum carbonate is 457.89 g/mol (anhydrous). However, the product Fosrenol includes a carbonate; the salt form is typically lanthanum carbonate hydrate. For consistency, report: 457.9 |
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 | No adequate studies in pregnant women; animal studies show no evidence of fetal harm at doses up to 27 times the human exposure; however, given its indication for chronic kidney disease, benefits may outweigh risks. |
| 2nd trimester | No adequate studies; animal reproduction studies not suggestive of risk; use only if clearly needed. |
| 3rd trimester | No adequate studies; theoretical risk of maternal calcium deficiency if used with restricted calcium intake; use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for FOSRENOL (FOSRENOL).
| Placental transfer | Not studied in humans; based on molecular weight (mostly >1000 Da), transfer is expected to be low. |
| Breastfeeding | Excretion in human milk unknown; given low oral bioavailability and large molecular size, systemic absorption in infant is likely minimal. Caution advised; consider alternative therapy. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to lanthanum carbonate or any componentBowel obstructionFecal impactionSevere gastrointestinal motility disorders
| 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 |
| Food/Dietary | Take Fosrenol with or immediately after meals to bind phosphorus from food. High-phosphorus foods (e.g., dairy, nuts, seeds, whole grains, cola drinks, processed foods) should be limited per dietary guidelines. The drug's efficacy depends on concurrent food intake; do not take on an empty stomach. |
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| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| 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. |
| Clinical Pearls | Fosrenol (lanthanum carbonate) is a non-calcium, non-aluminum phosphate binder used to control hyperphosphatemia in chronic kidney disease (CKD) patients on dialysis. It should be taken with or immediately after meals to bind dietary phosphate. Monitor serum phosphate levels regularly; target range is typically 3.5-5.5 mg/dL. Avoid co-administration with oral antibiotics (e.g., ciprofloxacin, tetracyclines) due to reduced absorption; separate by at least 2 hours. Chew tablets completely before swallowing; do not swallow whole. Lanthanum can accumulate in bone, but clinical significance is unknown. |
| Patient Advice | Take this medication with or right after meals as directed by your healthcare provider. · Chew the tablet completely before swallowing; do not swallow it whole. · Follow a low-phosphorus diet as recommended by your renal dietitian. · Take other medications (especially antibiotics) at least 2 hours before or after Fosrenol. · Common side effects include nausea, vomiting, diarrhea, or constipation; report severe or persistent symptoms. · Keep all appointments for blood tests to monitor phosphate levels. · Do not stop taking Fosrenol without consulting your doctor. · Store at room temperature away from moisture and heat. |