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Mesalazine

AEMPS

Locally acting intestinal aminosalicylate

ATC code: A07EC02

Brand names: Asacol, Salofalk, Mezavant, Claversal

Updated · Methodology

Indications

A

Ulcerative colitis

First line

First-line for mild-to-moderate ulcerative colitis to induce and maintain remission per 2022 and the Spanish GETECCU 2023. Induction 2.4–4.8 g daily in 2–3 doses; maintenance 1.5–2.4 g daily. In distal colitis and proctitis, add enemas 4 g once daily or suppositories 1 g once daily. The 2020 Cochrane meta-analysis showed remission induction in 50–60% and 2–3-fold reduction in relapse risk.

Sources

  1. AEMPS: Ficha técnica de Mesalazina (2024)
  2. Cochrane Database Syst Rev: Oral 5-aminosalicylic acid for induction of remission in ulcerative colitis. (2020)
  3. Cochrane Database Syst Rev: Oral 5-aminosalicylic acid for maintenance of remission in ulcerative colitis. (2020)
  4. ECCO: ECCO Guidelines on Therapeutics in Ulcerative Colitis: Medical Treatment (2022)

ICD-10: K51 · ICD-11: DD71

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

F

“Gut dysbiosis” as a standalone clinical diagnosis

Not recommended

Mesalazine (5-aminosalicylic acid, 5-ASA) is an anti-inflammatory drug for inflammatory bowel disease. It is prescribed for ulcerative colitis and Crohn's disease with colonic involvement ( 2024, 2024). For intestinal dysbiosis, mesalazine is not indicated: dysbiosis is not recognized as an independent diagnosis in immunocompetent people in international medicine, with no agreed diagnostic criteria. The drug has specific risks: nephrotoxicity (requires renal function monitoring), hepatotoxicity, myocarditis and pericarditis (rare), pancreatitis, and severe skin reactions. If mesalazine was prescribed for dysbiosis outside ulcerative colitis or Crohn's disease, consider seeking a second opinion.

Sources

  1. AEMPS: Ficha técnica de Mesalazina (2024)
  2. AEG: Posición AEG sobre la microbiota intestinal y suplementos probióticos (2022)
How to read tiers A–F
  • AStrong evidence – first or second line in international guidelines
  • BRecommended in selected cases
  • CStudy data contradict each other
  • DBenefit not proven, no documented harm
  • FDocumented harm, or risk without benefit

Mechanism of action

Pure 5-aminosalicylic acid (5-ASA). Acts locally on colonic mucosa: inhibits prostaglandin and leukotriene synthesis, neutrophil migration to inflammation sites, and NF-κB. Compared with sulfasalazine, no sulfapyridine component – fewer systemic side effects. Various formulations target specific bowel segments: granules and tablets with pH-dependent release (Asacol, Pentasa), time-dependent (Salofalk), enemas and suppositories for distal colitis and proctitis.

Safety

Contraindications

  • Mesalazine or salicylate hypersensitivity
  • Severe hepatic or renal impairment
  • Active peptic ulcer
  • Age under 6

Serious adverse effects

  • Acute interstitial nephritis
  • Paradoxical colitis flare («mesalazine intolerance»)
  • Pericarditis and myocarditis (rare)
  • Hepatotoxicity
  • Pancreatitis
  • Severe cutaneous reactions (Stevens–Johnson, DRESS, rare)

Common adverse effects

  • Headache
  • Nausea, diarrhea
  • Abdominal pain
  • Skin rash
  • Fatigue

Pregnancy: can you take Mesalazine?

AEMPS summary of product characteristics (section 4.6): mesalazine is not used in pregnancy unless, in the specialist's opinion, the potential benefit outweighs the risk, and inflammatory bowel disease itself may increase the risk of an adverse pregnancy outcome. Mesalazine crosses the placenta, with lower concentrations in umbilical cord plasma than in maternal plasma, and oral mesalazine showed no harmful effects on pregnancy or fetal development in animal studies. There are no adequate controlled studies in pregnant women; limited published human data show no rise in the overall rate of congenital malformations, and some data show more preterm births, fetal deaths and low birth weight, outcomes that are also linked to active inflammatory bowel disease. Leukopenia, thrombocytopenia and anaemia have been reported in newborns of treated mothers, and neonatal renal failure in one isolated case of long-term high-dose use (2–4 g orally).

Breastfeeding: can you take Mesalazine?

Compatible with breastfeeding. Low systemic bioavailability, minimal milk concentrations. Transient infant diarrhea is possible.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Practical notes

Timing and administration

Take with or without food, with water. Enteric-coated tablets not broken; granules and powders dispersed in water. Before start and every 3 months monitor renal function – rare but documented interstitial nephritis. In patients with sulfonamide hypersensitivity, mesalazine is preferred over sulfasalazine. In Crohn's disease, efficacy is limited – does not recommend mesalazine in Crohn's (unlike UC).
Label mentions7 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

  • ModerateAINEclass named in the label
    «Insuficiencia renal: No se recomienda el uso del fármaco en pacientes con la función renal deteriorada, y en pacientes con diátesis hemorrágica. Se debe monitorizar la función renal a intervalos…»

    AEMPS, section 4.4 · Open on CIMA

  • ModerateAzathioprine
    «Insuficiencia renal: No se recomienda el uso del fármaco en pacientes con la función renal deteriorada, y en pacientes con diátesis hemorrágica. Se debe monitorizar la función renal a intervalos…»

    AEMPS, section 4.4 · Open on CIMA

  • anticoagulantesclass named in the label
    «Existe poca evidencia de que la mesalazina pueda disminuir el efecto anticoagulante de la warfarina.»

    AEMPS, section 4.5 · Open on CIMA

  • Warfarin
    «Existe poca evidencia de que la mesalazina pueda disminuir el efecto anticoagulante de la warfarina.»

    AEMPS, section 4.5 · Open on CIMA

From other drugs’ labels

  • ModerateAzathioprine
    «Existe evidencia in vitro e in vivo de que los derivados de aminosalicilatos (por ejemplo, olsalazina, mesalazina o sulfasalazina) inhiben la enzima TPMT. Por consiguiente, puede ser necesario…»

    AEMPS, section 4.5 · Open on CIMA

  • ModerateAzathioprine
    «DRUG INTERACTIONS: Use with Aminosalicylates: There is in vitro evidence that aminosalicylate derivatives (e.g., sulphasalazine, mesalazine, or olsalazine) inhibit the TPMT enzyme. Concomitant use of…»

    FDA, section 7 · Open on DailyMed

  • Sulfasalazine
    «Medicamentos hepatotóxicos: En pacientes expuestos a la sulfasalazina y/o a su metabolito, la mesalamina o mesalazina, se han observado varios casos de posible interferencia con las mediciones…»

    AEMPS, section 4.5 · Open on CIMA

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Frequently asked

What is Mesalazine used for?

Mesalazine is evaluated for the following indications with varying evidence strength: Ulcerative colitis (evidence tier A), “Gut dysbiosis” as a standalone clinical diagnosis (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Mesalazine?

Common side effects of Mesalazine (≥ 1 in 100): Headache, Nausea, diarrhea, Abdominal pain, Skin rash, Fatigue. See the Safety section for uncommon and serious reactions.

Is Mesalazine safe during pregnancy?

AEMPS summary of product characteristics (section 4.6): mesalazine is not used in pregnancy unless, in the specialist's opinion, the potential benefit outweighs the risk, and inflammatory bowel disease itself may increase the risk of an adverse pregnancy outcome. Mesalazine crosses the placenta, with lower concentrations in umbilical cord plasma than in maternal plasma, and oral mesalazine showed no harmful effects on pregnancy or fetal development in animal studies. There are no adequate controlled studies in pregnant women; limited published human data show no rise in the overall rate of congenital malformations, and some data show more preterm births, fetal deaths and low birth weight, outcomes that are also linked to active inflammatory bowel disease. Leukopenia, thrombocytopenia and anaemia have been reported in newborns of treated mothers, and neonatal renal failure in one isolated case of long-term high-dose use (2–4 g orally).

Is Mesalazine compatible with breastfeeding?

Compatible with breastfeeding. Low systemic bioavailability, minimal milk concentrations. Transient infant diarrhea is possible.

Who should not take Mesalazine?

Mesalazine is contraindicated in: Mesalazine or salicylate hypersensitivity; Severe hepatic or renal impairment; Active peptic ulcer; Age under 6. Full list in the Safety section.

Official sources

Direct links to regulator labels. Open in a new tab.

Other drugs in this group

Nifuroxazide, Nystatin, Probiotics (Lactobacillus spp., Bifidobacterium spp., Saccharomyces boulardii), Saccharomyces boulardii CNCM I-745, Bifidobacterium longum, Diosmectite, Sulfasalazine, Berberine