General Information

Canasa (mesalamine) is an aminosalicylate.

Canasa is specifically indicated for use in adults for the treatment of mildly to moderately active ulcerative proctitis.

Canasa is supplied as suppositories for rectal administration. The recommended adult dosage is 1000 mg administered rectally once daily at bedtime for 3 to 6 weeks. Safety and effectiveness beyond 6 weeks have not been established.

Mechanism of Action

The mechanism of action of mesalamine is not fully understood, but appears to be a topical anti-inflammatory effect on colonic epithelial cells. Mucosal production of arachidonic acid metabolites, both through the cyclooxygenase pathways, i.e., prostanoids, and through the lipoxygenase pathways, i.e., leukotrienes and hydroxyeicosatetraenoic acids, is increased in patients with ulcerative colitis, and it is possible that mesalamine diminishes inflammation by blocking cyclooxygenase and inhibiting prostaglandin production in the colon.

Side Effects

Adverse effects associated with the use of Canasa may include, but are not limited to, the following:

• dizziness
• rectal pain
• fever
• rash
• acne
• colitis

Clinical Trial Results

Two double-blind, placebo-controlled, multicenter trials of mesalamine suppositories were conducted in North America in adult patients with mildly to moderately active ulcerative proctitis. The regimen in Study 1 was a 500 mg mesalamine suppository administered rectally three times daily and in Study 2 was a 500 mg mesalamine suppository administered rectally twice daily. The primary measures of efficacy were clinical disease activity index (DAI) and histologic evaluations in both trials. Compared to placebo, mesalamine suppositories were statistically (p<0.01) superior to placebo in both trials with respect to improvement in stool frequency, rectal bleeding, mucosal appearance, disease severity, and overall disease activity after 3 and 6 weeks of treatment.

An additional multicenter, open-label, randomized, parallel group study in 99 patients diagnosed with mildly to moderately ulcerative proctitis compared 1000 mg Canasa administered rectally once daily at bedtime (N=35) to 500 mg mesalamine suppository administered rectally twice daily, in the morning and at bedtime (N=46), for 6 weeks. The primary measures of efficacy included the clinical disease activity index (DAI) and histologic evaluations. Patients were evaluated clinically and sigmoidoscopically at 3 and 6 weeks of treatment. The efficacy at 6 weeks was not different between the treatment groups. Both were effective in the treatment of ulcerative proctitis and resulted in a significant decrease at 6 weeks in DAI: in the mesalamine 500 mg twice daily group, the mean DAI value decreased from 6.6 to 1.6, and in the 1000 mg at bedtime group, the mean DAI value decreased from 6.2 to 1.3, which represents a decrease of greater than 75% in both groups. After 6 weeks of treatment, a DAI score of less than 3 was achieved in 78% of patients in the mesalamine 500 mg twice daily group and 86% of patients in the Canasa 1000 mg once daily group. The recommended dosage of Canasa is 1000 mg administered rectally once daily at bedtime.