Intestinal anti-inflammatory (5-aminosalicylic acid derivative)
Mesalamine (5-aminosalicylic acid, 5-ASA) is a medicine used to treat ulcerative colitis, to induce and maintain remission in mild to moderate disease. It acts directly on the lining of the large intestine, reducing inflammation. It is generally well tolerated.
Also known as: Mesalamine, Asacol, Pentasa, mesalazine
Mesalazine may potentiate azathioprine myelosuppression (TPMT inhibition).
The mesalazine label documents the combination with "Azathioprine or 6-Mercaptopurine: increased risk of blood dyscrasias; monitor complete blood cell counts and platelet counts" (section 7.2). The mechanism is inhibition of thiopurine methyltransferase (TPMT) by aminosalicylates (mesalazine and sulfasalazine), which reduces the inactivating methylation of 6-mercaptopurine (the active metabolite of azathioprine) and shifts metabolism towards the more myelotoxic 6-thioguanine pathway. This interaction is well known in gastroenterology practice (inflammatory bowel disease), where azathioprine and mesalazine are often coadministered. Reduce the azathioprine dose by 25–50% and monitor blood counts weekly during the first month, then monthly; watch for leucopenia, thrombocytopenia and infectious symptoms.
Azathioprine + mesalazine: mesalazine inhibits TPMT and raises active 6-thioguanine levels — additive myelotoxicity. Monitor blood counts.
Mesalazine inhibits thiopurine methyltransferase (TPMT), raising active 6-thioguanine levels.
Periodic full blood count, especially in the first weeks.
Leucopenia, thrombocytopenia, serious infections.
Monitor the blood count regularly; watch for infection and bruising.
DailyMed (FDA) — approved Mesalazine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=47b5d1ee-b439-4ccb-9b01-c0875ccd748a ; approved Azathioprine label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5116b22b-1460-5535-e063-6394a90acbe5 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Taking mesalazine with food reduces gastrointestinal discomfort.
Take with food, as per the formulation.
EMC-UK (MHRA) — approved Mesalazine SmPC: https://www.medicines.org.uk/emc/product/6167/smpc
Mesalazine may affect liver function; monitor in patients with hepatic disease.
Use with caution and monitor transaminases.
EMC-UK (MHRA) — approved Mesalazine SmPC: https://www.medicines.org.uk/emc/product/6167/smpc
Mesalazine may cause or worsen nephrotoxicity (interstitial nephritis).
Assess renal function before and during treatment; adjust or stop if deterioration occurs.
EMC-UK (MHRA) — approved Mesalazine SmPC: https://www.medicines.org.uk/emc/product/6167/smpc
Mesalazine may be used in pregnancy to control inflammatory bowel disease; benefit usually outweighs risk.
Keep the minimum effective dose; do not stop treatment without medical advice.
Excreted into breast milk in small amounts; compatible with breastfeeding.
No specific additional contraception.
EMC-UK (MHRA) — approved Mesalazine SmPC: https://www.medicines.org.uk/emc/product/6167/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Intestinal anti-inflammatory (5-ASA) with local action in the colon (pH-sensitive delayed-release formulation); systemic absorption ~21-22% with most of the drug remaining in the colonic lumen.
Locally inhibits the COX and lipoxygenase pathways and prostaglandin/leukotriene synthesis, reduces neutrophil chemotaxis/degranulation and pro-inflammatory cytokine production in the colonic mucosa — topical anti-inflammatory effect.
Delayed release in the colon: the tablet passes intact through the upper GI tract; plasma concentrations detectable after ~2 h with a peak at 9-12 h; total systemic absorption ~21-22% (2.4-4.8 g/day); highly variable parameters between patients.
The absorbed fraction is N-acetylated (in the intestinal epithelium and liver) to N-acetyl-5-ASA (inactive); renal excretion of mesalamine and the metabolite; most of the dose is eliminated in faeces.
Apparent terminal half-life of mesalamine and its metabolite ~7-9 h with the delayed-release formulation (DailyMed label does not state a t½ — Lialda/FDA label value).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
