Mesalamine: uses, dosing, side effects & brands

Canasa (Mesalamine) is an aminosalicylate used to treat Ulcerative Colitis, Proctitis, Sigmoid Diseases.

The FDA classifies mesalamine as an aminosalicylate. Aminosalicylates (5-ASA drugs like mesalamine) act directly on the inflamed lining of the colon, where they are thought to calm the local inflammatory response by blocking several inflammation-driving chemicals and mopping up tissue-damaging free radicals, which helps the gut heal in ulcerative colitis. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The elimination half-life of mesalamine is about 7 to 9 hours (apparent terminal half-life) — that is how long the body takes to clear half of a dose. This is the apparent TERMINAL (elimination) half-life of mesalamine (5-ASA) itself, from the delayed-release tablet label after 2.4 g and 4.8 g doses; the per-dose table gives terminal-phase means of 8.56 h (1.2 g), 7.05 h (2.4 g) and 7.25 h (4.8 g), with very large between-person variability (standard deviations of 5-8 hours). Metabolite: the label reports the apparent terminal half-life of the major metabolite, N-acetyl-5-aminosalicylic acid (N-Ac-5-ASA), as 8 to 12 hours — longer than the parent. Mesalamine suppository labels describe N-Ac-5-ASA as "the active metabolite," so the active material can persist somewhat longer than the parent figure alone suggests. Timing caveat: these are delayed-release oral products designed to release drug in the terminal ileum and colon, so absorption is slow and highly variable (median Tmax ~9-24 h depending on product, longer with a high-fat meal) — plasma drug can still be rising many hours after the dose, and the half-life alone does not describe how long drug is present. Older adults: increased age slows apparent elimination — terminal half-life averaged 5.68 h in subjects 18-35 vs 9.68 h at 65-75 and 8.67 h at 75+, with roughly 2-fold higher Cmax. Kidney impairment: the label states systemic exposure is inversely correlated with renal function (lower creatinine clearance, higher exposure); mesalamine is cleared mainly by the kidney as N-Ac-5-ASA. Liver impairment: this label does not state a hepatic-impairment half-life. Mesalamine is not a prodrug (it is the active moiety; sulfasalazine and balsalazide are prodrugs of it). Not a drug-test detection window and not dosing guidance. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run mesalamine against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

We track 10 mesalamine-containing products in the U.S.: Asacol Hd, Canasa, Delzicol, Rowasa, Apriso, Asacol, Lialda and Mesalamine, and 2 more. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Across the brands we track, mesalamine is currently marketed as tablet, delayed release, suppository, capsule, delayed release, suspension, capsule, extended release, enema, kit and capsule, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Yes. Our catalog lists 1 generic mesalamine product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

The FDA's Enforcement database lists 2 recall records whose product description mentions mesalamine. The most recent: Mesalamine Extended-Release Capsules (Feb 5, 2024). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

For oral delayed-release mesalamine in adults, the side effects reported in at least 2% of patients are headache, gas, abnormal liver function tests, abdominal pain, and diarrhea. In the two 8-week induction trials, headache occurred in 6% on 2.4 g daily versus under 1% on placebo, gas in 4% versus 3% on placebo, abnormal liver tests in 2% on 4.8 g versus 1% on placebo, and hair loss and itching in about 1% each. Pancreatitis occurred in under 1% of patients and led to stopping the drug in everyone who had it. In children, the reactions at 5% or more were abdominal pain, upper respiratory infection, vomiting, anemia, headache, and viral infection.

No. Oral mesalamine has no FDA boxed warning. It does carry several serious labeled risks you should know: kidney damage ranging from minimal change disease to interstitial nephritis and rarely kidney failure; an acute intolerance syndrome; hypersensitivity reactions that can attack the heart lining, kidneys, liver, or lungs; liver failure; severe skin reactions; photosensitivity; and mesalamine kidney stones that standard X-ray and CT cannot see. Your doctor should check kidney function before you start and periodically during treatment, and stop the drug if kidney function worsens.

Do not take it if you have a known or suspected hypersensitivity to salicylates, to aminosalicylates, or to any ingredient in the product — that is the only outright contraindication on the label. Two more situations call for avoiding it rather than a flat ban: the label says to avoid oral delayed-release mesalamine if you have pyloric stenosis or any other organic or functional blockage of the upper digestive tract, because the tablet can sit in your stomach and delay drug release into the colon. Tell your doctor if you have known kidney impairment, a history of kidney disease, existing liver impairment, or take other drugs that are hard on the kidneys, since the risk-benefit calculation changes.

It might be. Mesalamine causes an acute intolerance syndrome that is genuinely hard to tell apart from a colitis flare — it occurred in 3% of patients in controlled trials of mesalamine or sulfasalazine. The symptoms are cramping, acute abdominal pain, and bloody diarrhea, sometimes with fever, headache, and rash. Do not simply assume worsening symptoms mean your colitis is flaring and the dose should go up. Contact your prescriber; if acute intolerance syndrome is suspected, the label says to stop the drug promptly.

Yes. Kidney stones have been reported with mesalamine, and the important detail is that mesalamine-containing stones are undetectable by standard X-ray or CT — a normal scan does not rule them out. Staying well hydrated during treatment is the label's specific advice. Separately, mesalamine can interfere with a lab test: it can produce falsely elevated urinary normetanephrine results when measured by liquid chromatography with electrochemical detection, which matters if you are ever worked up for pheochromocytoma. Tell the lab you take it.