SEVELAMER CARBONATE

The active ingredient in sevelamer carbonate tablets is sevelamer carbonate, a polymeric amine that binds phosphate and is meant for oral administration. It was developed as a pharmaceutical alternative to sevelamer hydrochloride (Renagel ®) . Sevelamer carbonate is an anion exchange resin, with the same polymeric structure as sevelamer hydrochloride, in which carbonate replaces chloride as the counterion. While the counterions differ for the two salts, the polymer itself, the active moiety involved in phosphate binding, is the same. Sevelamer carbonate is known chemically as poly(allylamine-co-N,N’-diallyl-1,3-diamino-2-hydroxypropane) carbonate salt. Sevelamer carbonate is hygroscopic, but insoluble in water. The structure is represented in Figure 1. Figure 1. Chemical Structure of Sevelamer Carbonate a, b = number of primary amine groups a + b = 9 c = number of crosslinking groups c = 1 m = large number to indicate extended polymer network Sevelamer Carbonate Tablets: Each film-coated tablet contains 800 mg of sevelamer carbonate on an anhydrous basis. The inactive ingredients are microcrystalline cellulose, silicified microcrystalline cellulose, crospovidone, hydroxy propyl cellulose, talc, colloidal silicon dioxide, sodium stearyl fumarate, hydroxy propyl methyl cellulose and diacetylated monoglycerides. Chemical Structure/Figure 1

Sevelamer carbonate is indicated for the control of serum phosphorus in adults with chronic kidney disease (CKD) on dialysis Pediatric use information is approved for Genzyme Corporation’s Renvela (sevelamer carbonate) tablets. However, due to Genzyme Corporation’s marketing exclusivity rights, this drug product is not labeled with that pediatric information Sevelamer carbonate is a phosphate binder indicated for the control of serum phosphorus in adults with chronic kidney disease on dialysis. ( 1 )

Starting dose of sevelamer carbonate is 0.8 or 1.6 grams administered orally three times per day with meals based on serum phosphorus levels for adult patients ( 2.1 ) Titrate by 0.8 g per meal in two week intervals for adult patients as needed to obtain serum phosphorus target ( 2.1 ) 2.1 General Dosing Information Starting Dose for Adult Patients Not Taking a Phosphate Binder. The recommended starting dose of sevelamer carbonate is 0.8 to 1.6 g taken orally with meals based on serum phosphorus level. Table 1 provides recommended starting doses of sevelamer carbonate for adult patients not taking a phosphate binder. Table 1. Starting Dose for Adult Dialysis Patients Not Taking a Phosphate Binder Serum Phosphorus Sevelamer Carbonate 800 mg Tablet > 5.5 and < 7.5 mg/dL 0.8 g three times daily with meals ≥ 7.5 mg/dL 1.6 g three times daily with meals Dose Titration for Adult Patients Taking Sevelamer Carbonate Tablets. Titrate the sevelamer carbonate dose by 0.8 g three times per day with meals at two-week intervals as necessary to achieve target serum phosphorus levels. Based on clinical studies, the average prescribed adult daily dose of sevelamer carbonate is approximately 7.2 g per day. The highest daily adult dose of sevelamer carbonate studied was 14 grams in CKD patients on dialysis. Switching from Sevelamer Hydrochloride Tablets. For adult patients switching from sevelamer hydrochloride tablets to sevelamer carbonate tablets or powder, use the same dose in grams. Switching between Sevelamer Carbonate Tablets and Powder. Use the same dose in grams. Switching from Calcium Acetate .Table 3 gives recommended starting doses of sevelamer carbonate based on a patient's current calcium acetate dose. Table 3. Starting Dose for Dialysis Patients Switching From Calcium Acetate to Sevelamer carbonate Calcium Acetate 667 mg (Tablets per meal) Sevelamer Carbonate Tablet 1 tablet 0.8 g 2 tablets 1.6 g 3 tablets 2.4 g Pediatric use information is approved for Genzyme Corporation’s Renvela (sevelamer carbonate) tablets. However, due to Genzyme Corporation’s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Sevelamer carbonate is contraindicated in patients with bowel obstruction. Sevelamer carbonate is contraindicated in patients with known hypersensitivity to sevelamer carbonate, sevelamer hydrochloride, or to any of the excipients. Bowel obstruction. ( 4 ) Known hypersensitivity to sevelamer carbonate, sevelamer hydrochloride, or to any of the excipients. ( 4 )

Most of the safety experience is with sevelamer tablets and sevelamer hydrochloride. In long-term studies with sevelamer hydrochloride, which contains the same active moiety as sevelamer carbonate, the most common adverse events included: vomiting (22%), nausea (20%), diarrhea (19%), dyspepsia (16%), abdominal pain (9%), flatulence (8%) and constipation (8%). ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Exelan Pharmaceuticals, Inc., at 1-855-295-7455 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. There are limited clinical trial data on the safety of sevelamer carbonate. However, because it contains the same active ingredient as the hydrochloride salt, the adverse event profiles of the two salts are expected to be similar. In a cross-over study in hemodialysis patients with treatment durations of eight weeks each and no washout, and another cross-over study in hemodialysis patients, with treatment durations of four weeks each and no washout between treatment periods, the adverse reactions on sevelamer carbonate powder were similar to those reported for sevelamer hydrochloride. In a parallel design study of sevelamer hydrochloride with treatment duration of 52 weeks, adverse reactions reported for sevelamer hydrochloride (n=99) were similar to those reported for the active-comparator group (n=101). Overall adverse reactions among those treated with sevelamer hydrochloride occurring in > 5% of patients included: vomiting (22%), nausea (20%), diarrhea (19%), dyspepsia (16%), abdominal pain (9%), flatulence (8%) and constipation (8%). A total of 27 patients treated with sevelamer and 10 patients treated with comparator withdrew from the study due to adverse reactions. Based on studies of 8 to 52 weeks, the most common reason for withdrawal from sevelamer hydrochloride was gastrointestinal adverse reactions (3 to 16%). In 143 peritoneal dialysis patients studied for 12 weeks using sevelamer hydrochloride, most common adverse reactions were similar to adverse reactions observed in hemodialysis patients. The most frequently occurring treatment emergent serious adverse reaction was peritonitis (8 reactions in 8 patients [8%] in the sevelamer group and 2 reactions in 2 patients [4%] on active-control). Thirteen patients (14%) in the sevelamer group and 9 patients (20%) in the active-control group discontinued, mostly for gastrointestinal adverse reactions. 6.2 Postmarketing Experience Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or to establish a causal relationship to drug exposure. The following adverse reactions have been identified during post-approval use of sevelamer hydrochloride or sevelamer carbonate: hypersensitivity, pruritus, rash, abdominal pain, fecal impaction, and uncommon cases of ileus, intestinal obstruction, and intestinal perforation. Appropriate medical management should be given to patients who develop constipation or have worsening of existing constipation to avoid severe complications.

There are no empirical data on avoiding drug interactions between sevelamer carbonate and most concomitant oral drugs. For oral medication where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy (e.g., cyclosporine, tacrolimus, levothyroxine), consider separation of the timing of the administration of the two drugs [see Clinical Pharmacology (12.3) ] . The duration of separation depends upon the absorption characteristics of the medication concomitantly administered, such as the time to reach peak systemic levels and whether the drug is an immediate release or an extended release product. Where possible consider monitoring clinical responses and/or blood levels of concomitant drugs that have a narrow therapeutic range. Table 5. Sevelamer Drug Interactions Oral drugs for which sevelamer did not alter the pharmacokinetics when administered concomitantly Digoxin Enalapril Iron Metoprolol Warfarin Oral drugs that have demonstrated interaction with sevelamer and are to be dosed separately from sevelamer carbonate Dosing Recommendations Ciprofloxacin Mycophenolate mofetil Take at least 2 hours before or 6 hours after sevelamer Take at least 2 hours before sevelamer For oral medication where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy consider separation of the timing of administration and/or monitor clinical responses or blood levels of the concomitant medication. ( 7 ) Sevelamer did not alter the pharmacokinetics of digoxin, enalapril, iron, metoprolol and warfarin. ( 7 ) Sevelamer has demonstrated interaction with ciprofloxacin, mycophenolate mofetil, and therefore these drugs should be dosed separately from sevelamer carbonate. ( 7 ) Pediatric use information is approved for Genzyme Corporation’s Renvela (sevelamer carbonate) tablets. However, due to Genzyme Corporation’s marketing exclusivity rights, this drug product is not labeled with that pediatric information.