How to use it
Choose the extent and whether the UC is active or in remission, answer the two safety questions, then pick an oral and/or a rectal product and dose. Each dose shows whether it is the Canadian monograph dose or outside the monograph but guideline-supported (for example once-daily Pentasa). The prescription text is built only from the chosen regimen, with the quantity for 30, 60 or 90 days.
Doses at a glance
| Situation | Guideline | Typical Canadian choices |
|---|---|---|
| Proctitis, active | Suppository 1 g/day (AGA strong; ACG; ECCO 2026 ≥1 g) | Salofalk, Pentasa, Mezera or ZDS 1 g at bedtime |
| Left-sided, active | Enema ≥1 g/day plus oral 2–4.8 g/day (ACG; ECCO 2026 Rec 4); enemas over rectal steroids (ECCO 2026 Rec 6) | Salofalk 4 g or Pentasa 1–4 g enema at bedtime, Mezera foam 2 g |
| Extensive, mild | Oral 2–3 g/day (AGA strong), ≥2 g (ACG, ECCO 2026, BSG 2025); add rectal (AGA conditional) | Mezavant 2.4–3.6 g once daily, Pentasa 2 g, Octasa 3.2 g |
| Moderate, or poor response | Oral over 3 g/day (usually 4.8 g) plus rectal (AGA conditional; BSG 2025: 3–4.8 g/day) | Mezavant 4.8 g, Octasa 4.8 g, Pentasa 4 g |
| Maintenance | Oral ≥1.5 g/day (ACG) or ≥2 g/day (ECCO 2026, BSG 2025); rectal for proctitis | Mezavant 2.4 g, Pentasa 2 g; suppository 1 g for proctitis |
If remission is not reached, escalate to steroids or advanced therapy rather than cycling between 5-ASA brands (ACG 2025); BSG 2025 starts oral steroids if there is no response within 2–4 weeks. For moderate to severe UC, 5-ASA is not the main therapy. Once a patient is in prolonged remission with mucosal healing on an advanced therapy or immunomodulator, 5-ASA can be stopped (BSG 2025 GPS 33).
Maintenance dose: guidelines differ. ACG 2025 accepts 1.5 g/day or more; ECCO 2026 and BSG 2025 use 2 g/day or more. In the EASI trial (Nordestgaard 2025), 178 people in remission were randomised to one 1.6 g tablet or three 800 mg tablets (2.4 g) once daily; relapses and adherence did not differ over a year. The tool keeps 2 g/day or more as its maintenance default, with the labelled Teva-5 ASA 1.6 g/day dose marked as such.
Once-daily dosing
AGA 2019 suggests once-daily over divided dosing (conditional, moderate certainty), and BSG 2025 and ECCO 2026 both note that once-daily dosing is as effective as divided dosing. In PODIUM (Dignass 2009), 362 patients with quiescent UC took prolonged-release mesalamine granules 2 g once daily or 1 g twice daily: remission at 1 year was 70.9% vs 58.9% (P = .024), so once daily was superior, with better self-reported adherence. The granules used in PODIUM are not sold in Canada. Mezavant and Octasa are labelled for once-daily use; Pentasa, Salofalk and Mezera tablets are labelled in divided doses.
Sulfasalazine
Start low and increase over the first few weeks; give doses evenly with no more than 8 hours overnight; 1 g three or four times daily for active disease and 1 g two or three times daily for maintenance. Monitoring (monograph): CBC with differential and liver tests before starting, every 2 weeks for 3 months, monthly for the next 3 months, then every 3 months; renal function and urinalysis at baseline and monthly for 3 months. Watch for hemolysis in G6PD deficiency. It impairs folate absorption: give folic acid 2 mg daily when planning pregnancy or pregnant (2025 Global Consensus). It can cause reversible oligospermia. The EN-tabs (enteric-coated) are better tolerated for people with GI side effects.
Pitfalls
- Monitoring. All Canadian mesalamine and sulfasalazine monographs list severe renal impairment (GFR below 30) as a contraindication, and interstitial nephritis is reported. BSG 2025 (GPS 85): CBC, renal and liver tests at baseline, at 3 months, then yearly, adjusted to the patient. Sulfasalazine needs more frequent tests (above).
- Brand switching. Delayed-release products differ in where they release mesalamine; the Octasa monograph advises a benefit–risk review before switching.
- Suppositories reach only the rectum. For left-sided colitis use an enema or foam.
- Asacol is no longer marketed in Canada.
- Olsalazine (Dipentum 250 mg capsules) is still marketed in Canada (monograph revised 2025): 500 mg four times daily for mild to moderate active UC, 500 mg twice daily for maintenance, built up over a week from 500 mg/day and taken with meals. About 15% get loose stools. It is not included in the prescription builder.
- Pregnancy. 5-ASA and sulfasalazine are continued in pregnancy; see the pregnancy tool.