Asacol ® (mesalamine) Delayed-Release Tablets

Inactive Ingredients: Each tablet contains colloidal silicon dioxide, dibutyl phthalate, edible black ink, iron oxide red, iron oxide yellow, lactose, magnesium stearate, methacrylic acid copolymer B (Eudragit S), polyethylene glycol, povidone, sodium starch glycolate, and talc.

Pharmacokinetics: Asacol tablets are coated with an acrylic-based resin that delays release of mesalamine until it reaches the terminal ileum and beyond. This has been demonstrated in human studies conducted with radiological and serum markers. Approximately 28% of the mesalamine in Asacol tablets is absorbed after oral ingestion, leaving the remainder available for topical action and excretion in the feces. Absorption of mesalamine is similar in fasted and fed subjects. The absorbed mesalamine is rapidly acetylated in the gut mucosal wall and by the liver. It is excreted mainly by the kidney as N-acetyl-5-aminosalicylic acid.

Mesalamine from orally administered Asacol tablets appears to be more extensively absorbed than the mesalamine released from sulfasalazine. Maximum plasma levels of mesalamine and N-acetyl-5-aminosalicylic acid following multiple Asacol doses are about 1.5 to 2 times higher than those following an equivalent dose of mesalamine in the form of sulfasalazine. Combined mesalamine and N-acetyl-5-aminosalicylic acid AUC's and urine drug dose recoveries following multiple doses of Asacol tablets are about 1.3 to 1.5 times higher than those following an equivalent dose of mesalamine in the form of sulfasalazine.

The t_max for mesalamine and its metabolite, N-acetyl-5-aminosalicylic acid, is usually delayed, reflecting the delayed release, and ranges from 4 to 12 hours. The half-lives of elimination (t1/2_elm) for mesalamine and N-acetyl-5-aminosalicylic acid are usually about 12 hours, but are variable, ranging from 2 to 15 hours. There is a large intersubject variability in the plasma concentrations of mesalamine and N-acetyl-5-aminosalicylic acid and in their elimination half-lives following administration of Asacol tablets.

Mildly to moderately active ulcerative colitis: Two placebo-controlled studies have demonstrated the efficacy of Asacol tablets in patients with mildly to moderately active ulcerative colitis. In one randomized, double-blind, multi-center trial of 158 patients, Asacol doses of 1.6 g/day and 2.4 g/day were compared to placebo. At the dose of 2.4 g/day, Asacol tablets reduced the disease activity, with 21 of 43 (49%) Asacol patients showing improvement in sigmoidoscopic appearance of the bowel compared to 12 of 44 (27%) placebo patients (p = 0.048). In addition, significantly more patients in the Asacol 2.4 g/day group showed improvement in rectal bleeding and stool frequency. The 1.6 g/day dose did not produce consistent evidence of effectiveness.

In a second randomized, double-blind, placebo-controlled clinical trial of 6 weeks duration in 87 ulcerative colitis patients, Asacol tablets, at a dose of 4.8 g/day, gave sigmoidoscopic improvement in 28 of 38 (74%) patients compared to 10 of 38 (26%) placebo patients (p < 0.001). Also, more patients in the Asacol 4.8 g/day group showed improvement in overall symptoms.

Maintenance of remission of ulcerative colitis: A 6-month, randomized, double-blind, placebo-controlled, multi-center study involved 264 patients treated with Asacol 0.8 g/day (n = 90), 1.6 g/day (n = 87), or placebo (n = 87). The proportion of patients treated with 0.8 g/day who maintained endoscopic remission was not statistically significant compared to placebo. In the intention to treat (ITT) analysis of all 174 patients treated with Asacol 1.6 g/day or placebo, Asacol maintained endoscopic remission of ulcerative colitis in 61 of 87 (70.1%) of patients, compared to 42 of 87 (48.3%) of placebo recipients (p = 0.005).

A pooled efficacy analysis of 4 maintenance trials compared Asacol, at doses of 0.8 g/day to 2.8 g/day, with sulfasalazine, at doses of 2 g/day to 4 g/day (n = 200). Treatment success was 59 of 98 (59%) for Asacol and 70 of 102 (69%) for sulfasalazine, a non-significant difference.

Study to assess the effect on male fertility: The effect of Asacol (mesalamine) on sulfasalazine-induced impairment of male fertility was examined in an open-label study. Nine patients (age < 40 years) with chronic ulcerative colitis in clinical remission on sulfasalazine 2 g/day to 3 g/day were crossed over to an equivalent Asacol dose (0.8 g/day to 1.2 g/day) for 3 months. Improvement in sperm count (p < 0.02) and morphology (p < 0.02) occurred in all cases. Improvement in sperm motility (p < 0.001) occurred in 8 of the 9 patients.

General: Patients with pyloric stenosis may have prolonged gastric retention of Asacol tablets which could delay release of mesalamine in the colon.

Exacerbation of the symptoms of colitis has been reported in 3% of Asacol-treated patients in controlled clinical trials. This acute reaction, characterized by cramping, abdominal pain, bloody diarrhea, and occasionally by fever, headache, malaise, pruritus, rash, and conjunctivitis, has been reported after the initiation of Asacol tablets as well as other mesalamine products. Symptoms usually abate when Asacol tablets are discontinued.

Some patients who have experienced a hypersensitivity reaction to sulfasalazine may have a similar reaction to Asacol tablets or to other compounds which contain or are converted to mesalamine.

Renal: Renal impairment, including minimal change nephropathy, acute and chronic interstitial nephritis, and, rarely, renal failure has been reported in patients taking Asacol tablets as well as other compounds which contain or are converted to mesalamine. In animal studies (rats, dogs), the kidney is the principal target organ for toxicity. At doses of approximately 750 mg/kg to 1000 mg/kg [15 to 20 times the administered recommended human dose (based on a 50 kg person) on a mg/kg basis and 3 to 4 times on a mg/m² basis], mesalamine causes renal papillary necrosis. Therefore, caution should be exercised when using Asacol (or other compounds which contain or are converted to mesalamine or its metabolites) in patients with known renal dysfunction or history of renal disease. It is recommended that all patients have an evaluation of renal function prior to initiation of Asacol tablets and periodically while on Asacol therapy.

Use in Hepatic Impairment: There have been reports of hepatic failure in patients with pre-existing liver disease who have been administered mesalamine. Caution should be exercised when administering Asacol to patients with liver disease.

Information for Patients: Patients should be instructed to swallow the Asacol tablets whole, taking care not to break cut, or chew the tablets, because the coating is an important part of the delayed-release formulation. In 2% to 3% of patients in clinical studies, intact or partially intact tablets have been reported in the stool. If this occurs repeatedly, patients should contact their physician.

Patients with ulcerative colitis should be made aware that ulcerative colitis rarely remits completely, and that the risk of relapse can be substantially reduced by continued administration of Asacol at a maintenance dosage.

Drug Interactions: There are no known drug interactions.

Carcinogenesis, Mutagenesis, Impairment of Fertility: Dietary mesalamine was not carcinogenic in rats at doses as high as 480 mg/kg/day, or in mice at 2000 mg/kg/day. These doses are 2.4 and 5.1 times the maximum recommended human maintenance dose of Asacol of 1.6 g/day (32 mg/kg/day if 50 kg body weight assumed or 1184 mg/m²), respectively, based on body surface area. Mesalamine was negative in the Ames assay for mutagenesis, negative for induction of sister chromatid exchanges (SCE) and chromosomal aberrations in Chinese hamster ovary cells in vitro, and negative for induction of micronuclei (MN) in mouse bone marrow polychromatic erythrocytes. Mesalamine, at oral doses up to 480 mg/kg/day (about 1.6 times the recommended human treatment dose on a body surface area basis), was found to have no effect on fertility or reproductive performance of male and female rats.

Pregnancy: Teratogenic Effects: Pregnancy Category B: Reproduction studies have been performed in rats at oral doses up to 480 mg/kg/day (about 1.6 times the recommended human treatment dose on a body surface area basis) and rabbits at oral doses up to 480 mg/kg/day (about 3.2 times the recommended human treatment dose on a body surface area basis) and have revealed no evidence of impaired fertility or harm to the fetus due to mesalamine. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers: Low concentrations of mesalamine and higher concentrations of its N-acetyl metabolite have been detected in human breast milk. While the clinical significance of this has not been determined, caution should be exercised when mesalamine is administered to a nursing woman.

Pediatric Use: Safety and effectiveness of Asacol tablets in pediatric patients have not been established.

Geriatric Use: Clinical studies of Asacol did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy in elderly patients should be considered when prescribing Asacol. Reports from uncontrolled clinical studies and post-marketing reporting systems suggest a higher incidence of blood dyscrasias, i.e., agranulocytosis, neutropenia, pancytopenia, in subjects receiving Asacol who are 65 years or older. Caution should be taken to closely monitor blood cell counts during drug therapy.

This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken when prescribing this drug therapy. As stated in the PRECAUTIONS section, it is recommended that all patients have an evaluation of renal function prior to initiation of Asacol tablets and periodically while on Asacol therapy.

Abuse: None reported.

Dependency: Drug dependence has not been reported with chronic administration of mesalamine.

For the treatment of mildly to moderately active ulcerative colitis: The usual dosage in adults is two 400-mg tablets to be taken three times a day for a total daily dose of 2.4 grams for a duration of 6 weeks.

For the maintenance of remission of ulcerative colitis: The recommended dosage in adults is 1.6 grams daily, in divided doses. Treatment duration in the prospective, well-controlled trial was 6 months.

Two Asacol 400 mg tablets have not been shown to be bioequivalent to one Asacol HD 800 mg tablet.