1. Clinical Overview
Mesalazine, also known as 5-aminosalicylic acid (5-ASA), is a first-line anti-inflammatory drug used primarily for the treatment of mild to moderate ulcerative colitis. It acts topically on the colonic mucosa to reduce inflammation. In the Indian context, it is a cornerstone of therapy for inflammatory bowel disease (IBD), available in various oral and rectal formulations.
| Onset | Duration | Bioavailability |
|---|---|---|
| Therapeutic effect on symptoms (e.g., reduced stool frequency, rectal bleeding) is typically observed within 2-4 weeks of initiating therapy, though full mucosal healing may take longer. | Approximately 12-24 hours, necessitating multiple daily doses or a sustained-release formulation to maintain therapeutic mucosal concentrations. | Oral bioavailability is highly variable (20-30% for standard formulations) and formulation-dependent. It is designed for minimal systemic absorption, with the majority (70-80%) delivered topically to the colonic mucosa. |
2. Mechanism of Action
Mesalazine's exact mechanism is multifactorial and not fully elucidated. It acts locally on the colonic mucosa to inhibit key pathways in the inflammatory cascade of ulcerative colitis. It is not a systemic immunosuppressant.
3. Indications & Uses
- Induction and maintenance of remission in mild to moderate Ulcerative Colitis (distal, left-sided, and extensive)
- Treatment of mild to moderate active Crohn's disease affecting the colon (ileocolonic)
4. Dosage & Administration
Adult Dosage: Ulcerative Colitis (Induction): 2.4g to 4.8g per day in 2-3 divided doses. For 400mg tablets, this equals 6 to 12 tablets daily. Maintenance: 1.5g to 2.4g per day in divided doses. Always follow specific brand formulation instructions.
Administration: Oral tablets should be swallowed whole with a full glass of water; DO NOT crush, chew, or break the enteric-coated tablets. Take with or after food to reduce gastric upset. Doses should be evenly spaced. Do not take antacids or proton pump inhibitors (like omeprazole) within 2 hours of dosing as they may alter the pH-dependent release.
5. Side Effects
Common side effects may include:
- Headache
- Nausea, vomiting, dyspepsia
- Abdominal pain
- Diarrhea (may mimic disease flare)
- Flatulence
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin/Anticoagulants | Mesalazine may potentiate anticoagulant effect, increasing INR and bleeding risk. | Moderate |
| Azathioprine/6-Mercaptopurine | Concurrent use may increase risk of myelosuppression (leukopenia, pancytopenia). | Moderate |
| Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) | May increase risk of nephrotoxicity (additive renal effects). | Moderate |
| Lactulose | May lower colonic pH, potentially causing premature release of pH-dependent mesalazine in the small intestine. | Moderate |
| Proton Pump Inhibitors (e.g., Omeprazole) | May increase gastric pH, potentially affecting the release profile of pH-dependent formulations. | Low |
7. Patient Counselling
- DO swallow the tablet whole with plenty of water.
- DO take the medication regularly as prescribed, even if you feel better.
- DO inform all your doctors and dentists you are taking mesalazine.
- DO keep scheduled appointments for blood and urine tests to monitor kidney function.
- DON'T crush, chew, or break the tablet.
- DON'T take antacids or acid-reducing medicines close to the time you take this medicine without consulting your doctor.
- DON'T stop taking the medicine suddenly if you have a flare-up; contact your doctor.
8. Toxicology & Storage
Overdose: Nausea, vomiting, abdominal pain, diarrhea, tinnitus, vertigo, headache, hyperventilation, sweating, tachycardia. Severe overdose may lead to metabolic acidosis, hyperglycemia, hypokalemia, renal and liver impairment, bone marrow depression, and CNS effects (confusion, drowsiness).
Storage: Store below 30°C in a cool, dry place, protected from light and moisture. Keep the container tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.