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Sunday, August 17, 2025

Mesalazine


Overview

Mesalazine (also known as mesalamine or 5-aminosalicylic acid, 5-ASA) is an anti-inflammatory agent widely used in the management of inflammatory bowel disease (IBD), particularly ulcerative colitis (UC) and, to a lesser extent, Crohn’s disease. It is a derivative of salicylic acid, structurally related to aspirin, but formulated to act locally on the intestinal mucosa.

Mesalazine exerts its effects by modulating local inflammatory processes in the colon rather than through systemic immunosuppression, which differentiates it from corticosteroids and immunomodulators. It is available in a range of oral and rectal formulations designed for targeted release to specific parts of the gastrointestinal tract.

Pharmacological Class and Formulations

  • Class: Anti-inflammatory drug (5-aminosalicylic acid derivative)

  • ATC Code: A07EC02

  • Formulations:

    • Oral tablets/capsules (delayed-release or extended-release, e.g., 400 mg, 500 mg, 800 mg)

    • Granules/sachets (1 g, 1.5 g, 3 g)

    • Rectal suppositories (250 mg, 500 mg, 1 g)

    • Rectal enemas (1 g, 2 g, 4 g per 60–100 mL)

    • Rectal foams (1 g per dose)

Mechanism of Action

Mesalazine acts locally on the intestinal mucosa. Its mechanisms include:

  • Inhibition of cyclooxygenase (COX) and lipoxygenase pathways → reduced prostaglandin and leukotriene synthesis.

  • Free radical scavenging and reduction of oxidative stress.

  • Modulation of cytokine production and nuclear factor-κB (NF-κB) activity.

  • Possible effects on immune cells (T lymphocytes, macrophages).

Unlike systemic immunosuppressants, mesalazine has minimal systemic absorption, which accounts for its favorable safety profile.

Pharmacokinetics

  • Absorption: Depends on formulation; delayed- and extended-release forms allow delivery to the colon.

  • Distribution: Minimal systemic absorption; acts locally in the bowel.

  • Metabolism: Rapid acetylation in intestinal mucosa and liver to N-acetyl-5-ASA (inactive).

  • Elimination: Mainly renal (in urine as acetylated metabolite).

  • Half-life: ~5–10 hours (systemic component).

Clinical Indications

  1. Ulcerative colitis (UC)

    • Induction of remission in mild to moderate disease.

    • Maintenance of remission (oral and/or rectal).

  2. Crohn’s disease

    • Limited role; may be used in mild disease affecting the colon.

  3. Other uses (less common)

    • Microscopic colitis (investigational/off-label).

    • Radiation-induced proctitis.

Contraindications

  • Hypersensitivity to mesalazine, salicylates, or any excipients.

  • Severe renal impairment (risk of nephrotoxicity).

  • Severe hepatic impairment.

  • History of salicylate-induced bronchospasm (caution in asthma).

Precautions

  • Renal toxicity: Risk of interstitial nephritis and renal impairment → monitor renal function before and during therapy.

  • Hepatic dysfunction: Use with caution; monitor liver function.

  • Blood dyscrasias: Rare but possible; monitor blood counts.

  • Gastrointestinal: Rare risk of pericarditis, myocarditis, and pancreatitis.

  • Pregnancy and breastfeeding: Generally considered safe; use lowest effective dose.

Adverse Effects

Common

  • Headache

  • Abdominal pain, nausea, diarrhea

  • Flatulence

Less Common

  • Rash, pruritus

  • Arthralgia, myalgia

  • Hair loss

Rare but Serious

  • Interstitial nephritis, renal failure

  • Hepatitis, pancreatitis

  • Pericarditis, myocarditis

  • Agranulocytosis, aplastic anemia

  • Hypersensitivity reactions (fever, rash, pneumonitis)

Drug Interactions

  • Azathioprine, 6-mercaptopurine, thioguanine: Increased risk of myelosuppression.

  • NSAIDs, nephrotoxic drugs: Increased risk of renal impairment.

  • Warfarin: Possible alteration of anticoagulant effect.

Dosage

Ulcerative Colitis (Adults)

Induction of remission

  • Oral:

    • 2.4–4.8 g/day in divided doses (immediate- or modified-release).

  • Rectal:

    • Suppositories: 1–1.5 g once daily (or in divided doses).

    • Enemas: 2–4 g once daily, usually at bedtime.

Maintenance of remission

  • Oral:

    • 1.2–2.4 g/day in divided doses (depending on formulation).

  • Rectal:

    • Suppositories: 500 mg–1 g once daily (or three times/week).

    • Enemas: 2–4 g once daily or less frequently depending on clinical stability.

Crohn’s Disease

  • Limited evidence; regimens similar to UC but less effective.

Pediatric Dosing (Ulcerative Colitis, ≥5 years)

  • Induction and maintenance: 30–50 mg/kg/day orally in divided doses (max 4 g/day).

  • Rectal: Age-appropriate adjustments, often 500 mg–1 g daily.

Monitoring

  • Baseline: Renal function, liver function, complete blood count.

  • During therapy:

    • Renal and liver function every 3–6 months.

    • Blood counts if symptoms suggest cytopenia.

  • Clinical: Monitor for relapse of symptoms and signs of intolerance (e.g., fever, rash, worsening colitis).

Patient Counseling Points

  • Take oral medication as prescribed; some forms must not be crushed or chewed.

  • Suppositories, foams, and enemas should be retained for as long as possible (preferably overnight).

  • Drink plenty of fluids to minimize kidney risk.

  • Report unexplained bruising, sore throat, rash, fever, chest pain, or shortness of breath.

  • Regular follow-up is essential for monitoring disease control and drug safety




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