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Included as part of the PRECAUTIONS section.


Gastrointestinal Adverse Effects

There have been reports of serious cases of gastrointestinal obstruction, ileus, and fecal impaction reported in association with lanthanum, some requiring surgery or hospitalization.

Risk factors for gastrointestinal obstruction identified from post-marketing reports in patients taking FOSRENOL Chewable Tablets include altered gastrointestinal anatomy (e.g., history of gastrointestinal surgery, colon cancer), hypomotility disorders (e.g., constipation, ileus, diabetes) and concomitant medications (e.g., calcium channel blockers). Some cases were reported in patients with no history of gastrointestinal disease.

Advise patients who are prescribed FOSRENOL Chewable Tablets to chew the tablet completely to reduce the risk of serious adverse gastrointestinal events such as those described above.

Patients with acute peptic ulcer, ulcerative colitis, Crohn's disease or bowel obstruction were not included in FOSRENOL clinical studies [see CONTRAINDICATIONS].

Diagnostic Tests

FOSRENOL has radio-opaque properties and therefore may give the appearance typical of an imaging agent during abdominal X-ray procedures.

Patient Counseling Information

Advise the patient to read the FDA-approved patient labelling (Medication Guide). Advise patients to take FOSRENOL with or immediately after meals [see DOSAGE AND ADMINISTRATION].

Instruct patients on concomitant medications that should be dosed apart from FOSRENOL [see DRUG INTERACTIONS]

Instruct patients who are prescribed FOSRENOL Chewable Tablets to chew or crush tablets completely before swallowing. Emphasize that FOSRENOL Chewable Tablets should not be swallowed intact. Consider crushing FOSRENOL Chewable Tablets completely or prescribing the oral powder formulation for patients with poor dentition [see DOSAGE AND ADMINISTRATION].

Instruct patients who are prescribed FOSRENOL Oral Powder to sprinkle powder on a small quantity of applesauce or other similar food. Patients should be instructed to consume the entire dose immediately. FOSRENOL Oral Powder is insoluble so no attempt should be made to dissolve the powder in liquid for administration [see DOSAGE AND ADMINISTRATION].

Advise patients who are taking an oral medication where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy to separate the dosing of FOSRENOL from the dosing of the affected drug by several hours [see DRUG INTERACTIONS].

Advise patients to notify their physician that they are taking FOSRENOL prior to an abdominal x-ray [see WARNINGS AND PRECAUTIONS].

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Oral administration of lanthanum carbonate to rats for up to 104 weeks, at doses up to 1500 mg of the salt per kg/day [2.5 times the MRHD of 5725 mg, on a mg/m² basis, assuming a 60-kg patient] revealed no evidence of carcinogenic potential. In the mouse, oral administration of lanthanum carbonate for up to 99 weeks, at a dose of 1500 mg/kg/day (1.3 times the MRHD) was associated with an increased incidence of glandular stomach adenomas in male mice.

Lanthanum carbonate tested negative for mutagenic activity in an in vitro Ames assay using Salmonella typhimurium and Escherichia coli strains and in vitro HGPRT gene mutation and chromosomal aberration assays in Chinese hamster ovary cells. Lanthanum carbonate also tested negative in an oral mouse micronucleus assay at doses up to 2000 mg/kg (1.7 times the MRHD), and in micronucleus and unscheduled DNA synthesis assays in rats given IV lanthanum chloride at doses up to 0.1 mg/kg, a dose that produced plasma lanthanum concentrations > 2000 times the peak human plasma concentration. Lanthanum carbonate, at doses up to 2000 mg/kg/day (3.4 times the MRHD), did not affect fertility or mating performance of male or female rats.

Use In Specific Populations


Pregnancy Category C. No adequate and well-controlled studies have been conducted in pregnant women. The effect of FOSRENOL on the absorption of vitamins and other nutrients has not been studied in pregnant women. FOSRENOL is not recommended for use during pregnancy.

Studies in pregnant rabbits showed that oral administration of lanthanum carbonate at 1500 mg/kg/day (5 times the maximum recommended daily human dose (MRHD) of 5725 mg, on a mg/m² basis, assuming a 60 kg patient) was associated with increased post-implantation loss, reduced fetal weights, and delayed fetal ossification [see Nonclinical Toxicology].

Labor And Delivery

No FOSRENOL treatment-related effects on labor and delivery were seen in animal studies. The effects of FOSRENOL on labor and delivery in humans is unknown.

Nursing Mothers

It is not known whether lanthanum carbonate is excreted in human milk. As many drugs are excreted in human milk, consider the possibility of infant exposure when FOSRENOL is administered to a nursing woman.

Pediatric Use

The safety and efficacy of FOSRENOL in pediatric patients have not been established. While growth abnormalities were not identified in long-term animal studies, lanthanum was deposited into developing bone including growth plate. The consequences of such deposition in developing bone in pediatric patients are unknown. Therefore, the use of FOSRENOL in this population is not recommended.

Geriatric Use

Of the total number of patients in clinical studies of FOSRENOL, 32% (538) were ≥ 65, while 9.3% (159) were ≥ 75. No overall differences in safety or effectiveness were observed between patients ≥ 65 years of age and younger patients.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 3/7/2016


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