Aminosalicylates (5-ASA)

Aminosalicylates are anti‑inflammatory medicines used mainly for mild to moderate ulcerative colitis. The most common drug is mesalamine, with related options like sulfasalazine, balsalazide, and olsalazine. These medicines work in the gut lining, calm inflammation, and help maintain remission. They are not effective for Crohn’s disease. Oral and rectal forms can be used alone or together, depending on how far disease extends.

• Key takeaways

• 5‑ASA medicines are first‑line for mild to moderate ulcerative colitis.

• Rectal 5‑ASA treats rectal and left‑sided disease more directly than pills.

• Combining oral plus rectal mesalamine often works better than either alone.

• Safety is favorable, but kidney function should be checked regularly.

• 5‑ASA does not treat Crohn’s disease and should not delay needed escalation.

What are aminosalicylates?

• Aminosalicylates (5‑ASA) are anti‑inflammatory drugs that act on the colon lining.

• Examples: mesalamine (various delayed‑release or extended‑release forms), sulfasalazine (a sulfa‑linked prodrug), balsalazide, and olsalazine.

• They reduce inflammatory signals in the intestinal wall and help heal the mucosa.

When are they used?

• Best for mild to moderate ulcerative colitis (UC), including:

• Proctitis (rectum only).

• Left‑sided colitis.

• Extensive colitis, sometimes with combination therapy.

• Not effective for Crohn’s disease, either to induce or maintain remission.

• Used both to induce remission during a flare and to maintain remission afterward.

How they work and how fast

• 5‑ASA acts locally in the colon to block inflammatory pathways such as prostaglandins and leukotrienes.

• Symptom relief typically begins in 1 to 3 weeks, with continued improvement over 4 to 8 weeks.

• Rectal formulations can provide faster relief for rectal bleeding and urgency.

Formulations and dosing

Different products release medicine in different parts of the bowel. Many mesalamine formulations can be taken once daily, which supports adherence.

Oral 5‑ASA

• Mesalamine (delayed‑ or extended‑release): common induction dose is 2.4 to 4.8 g daily; maintenance often 1.6 to 2.4 g daily.

• Balsalazide: typical adult dose 6.75 g daily in divided or once‑daily dosing.

• Olsalazine: typical total daily dose 1 to 3 g; diarrhea is more frequent with this drug.

• Sulfasalazine: 2 to 6 g daily in divided doses; start low and increase as tolerated. Add folic acid 1 mg daily.

Rectal 5‑ASA

• Suppository (targets rectum): 1 g at bedtime for induction; some use 1 g three times per week for maintenance.

• Enema (reaches up to the splenic flexure): 2 to 4 g nightly for induction; maintenance can be 2 to 3 times weekly once controlled.

Quick comparison

Combining oral and rectal therapy

For left‑sided or extensive UC, using oral plus rectal mesalamine often induces remission faster and reduces bleeding more effectively than oral therapy alone. This approach is commonly used for flares, then tapered to the lowest regimen that maintains control.

Safety, side effects, and monitoring

5‑ASA medicines have a strong safety record. Most side effects are mild and improve with dose changes or switching formulations.

• Common effects: headache, nausea, gas, abdominal pain, and mild diarrhea.

• Less common: hair thinning, skin rash, photosensitivity.

• Rare but important:

• Kidney injury (interstitial nephritis). Check serum creatinine at baseline, again at about 3 months, then every 6 to 12 months.

• Pancreatitis or pericarditis/myocarditis. Stop the drug and seek urgent care if severe belly pain, chest pain, or shortness of breath occurs.

• Worsening colitis from hypersensitivity, with fever and cramping soon after starting.

• Sulfasalazine‑specific:

• More nausea and headache, possible low sperm count in males (reversible after stopping).

• Can lower folate levels, so supplement folic acid.

• Requires CBC and liver tests at baseline and during dose escalation, then periodically.

• Who should avoid or use caution:

• Known salicylate allergy.

• Significant kidney or liver disease.

• G6PD deficiency (sulfasalazine may increase hemolysis risk, discuss with the care team).

• Pregnancy and breastfeeding:

• Mesalamine and sulfasalazine are generally considered safe. Continue folic acid, especially with sulfasalazine. Always confirm choices with the obstetric and gastroenterology teams.

Practical use tips

• Take oral tablets or capsules as directed. Do not crush or chew delayed‑release forms.

• For enemas, warm the bottle to body temperature by holding it in the hand, lie on the left side, and try to retain the liquid overnight.

• For suppositories, insert after a bowel movement when possible.

• If a dose is missed, take it when remembered, but skip if near the next dose.

• Adherence matters. Once‑daily oral dosing and simplified rectal schedules often help.

When to move beyond 5‑ASA

Escalation is appropriate when any of the following occur:

• No meaningful improvement after about 2 to 4 weeks of adequate dosing and correct route.

• Frequent flares, need for systemic steroids, or persistent bleeding.

• Moderate to severe UC features, such as weight loss, anemia, high inflammatory markers, or more than six stools per day with blood.

• Options include budesonide MMX for mild to moderate colitis not responding to 5‑ASA, or advanced therapies such as biologics or small molecules for more active or steroid‑dependent disease. The goal is symptom control and mucosal healing, not just short‑term relief.

Special notes

• Possible chemoprevention: some studies suggest long‑term 5‑ASA may lower colorectal cancer risk in UC, but surveillance colonoscopy remains essential.

• Drug interactions: sulfasalazine can affect folate metabolism and may interact with certain anticoagulants and digoxin. Pharmacist review is recommended when starting new medicines.