Mesalazine (5-ASA) — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Mesalazine (5-ASA)?
Mesalazine (5-aminosalicylic acid, 5-ASA) is an anti-inflammatory medicine used to treat and maintain remission in inflammatory bowel disease. This medication is funded by Pharmac for ulcerative colitis.
What is Mesalazine (5-ASA) Used For?
Mesalazine is used for the treatment of mild-to-moderate ulcerative colitis (UC) — inducing and maintaining remission. It may also reduce the risk of colorectal cancer in patients with long-standing UC. Role in Crohn’s disease is less established.
How Does Mesalazine (5-ASA) Work?
Mesalazine acts locally in the colonic mucosa to reduce inflammation by inhibiting the production of prostaglandins, leukotrienes, and reactive oxygen species. It also activates PPAR-gamma receptors in the colon — reducing inflammatory cytokine production. Its exact mechanism is not fully understood.
How to Take Mesalazine (5-ASA)
Oral formulations: tablets (Asacol®, Pentasa®) or granules, taken 2–4 g/day in divided doses (acute) or 1.5–2 g/day for maintenance. Topical formulations: mesalazine enemas (Salofalk® 2 g/60 mL) for left-sided colitis, or suppositories (500 mg or 1 g) for proctitis. Oral and topical combination is more effective than either alone.
Common Side Effects of Mesalazine (5-ASA)
- Headache
- Nausea and abdominal pain
- Diarrhoea (paradoxically can occur)
- Rash
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Nephrotoxicity (rare but serious — renal function should be monitored annually)
- Mesalazine-induced colitis (rare — paradoxical worsening)
- Pancreatitis (rare)
- Severe allergic reactions including pericarditis (mesalazine hypersensitivity)
Drug Interactions
Mesalazine (5-ASA) may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Azathioprine and 6-mercaptopurine (mesalazine increases levels — enhanced bone marrow suppression risk)
- Warfarin (decreased anticoagulant effect reported)
New Zealand Prescribing Information
Mesalazine (Asacol® MR tablets 400 mg, 800 mg; Pentasa® prolonged-release granules 1 g; Salofalk® 2 g enema; Salofalk® 500 mg, 1 g suppositories) are funded by Pharmac for ulcerative colitis. Annual renal function monitoring (creatinine, eGFR) is recommended for all patients on long-term mesalazine. Adherence to maintenance mesalazine reduces the risk of UC flare and colorectal cancer.
Frequently Asked Questions
How long do I need to take mesalazine?
Mesalazine for ulcerative colitis is usually a lifelong maintenance treatment — studies show it significantly reduces the risk of relapse and colorectal cancer. Stopping maintenance mesalazine when in remission greatly increases the risk of relapse.
Can I use mesalazine enemas and tablets at the same time?
Yes — combination of oral and topical mesalazine is more effective than either alone for active left-sided or extensive ulcerative colitis. Enemas or suppositories provide concentrated drug to the distal colon and rectum where inflammation is often most active.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: