Is Canasa a Mesalamine Enema?
No, Canasa is not a mesalamine enema—it is a mesalamine suppository formulation specifically designed for ulcerative proctitis, not an enema for proctosigmoiditis or left-sided colitis. 1
Key Distinctions Between Formulations
Suppositories vs. Enemas
- Mesalamine suppositories (like Canasa) are designed to treat ulcerative proctitis, defined as disease extending less than 15-20 cm from the anal verge 1
- Mesalamine enemas are formulated for ulcerative proctosigmoiditis and left-sided colitis, extending up to the splenic flexure or approximately 50 cm from the anal verge 1
- Suppositories deliver medication directly to the rectum and are better retained than enemas for proctitis 1, 2
Distribution Patterns
- A 60-mL mesalamine enema routinely spreads retrograde to the sigmoid colon in all patients and reaches the splenic flexure in 92% of cases, but rarely extends beyond this point 3
- Mesalamine foam enemas spread to the descending colon in 90% of patients with an average of 23% of the dose present in the descending colon at 4 hours 4
- Suppositories remain localized to the rectal area and do not achieve the proximal distribution of enemas 1
Clinical Implications for Treatment Selection
For Ulcerative Proctitis
- Mesalamine suppositories 1 gram once daily are the preferred initial treatment, with moderate quality evidence supporting superiority over placebo for both induction (RR 0.44) and maintenance (RR 0.50) of remission 1, 2
- Suppositories are more appropriate than enemas because they better target the site of inflammation and are better tolerated 2
For Ulcerative Proctosigmoiditis or Left-Sided Colitis
- Mesalamine enemas 2-4 grams once daily at night are the appropriate formulation, with moderate to high quality evidence (RR 0.50 vs. placebo) 1, 5
- Rectal mesalamine enemas are superior to rectal corticosteroids for inducing clinical remission (RR 0.74) 1, 5
Common Pitfall to Avoid
Do not use suppositories for disease extending beyond the rectum—they will not achieve adequate drug delivery to inflamed mucosa in the sigmoid or descending colon, leading to treatment failure 1, 2. Conversely, enemas are unnecessary and less well-tolerated for isolated proctitis where suppositories suffice 2.