Pentasa

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Pentasa on Prescriptsy

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Pentasa is a prolonged-release mesalazine (5-aminosalicylic acid, 5-ASA) preparation used to treat and maintain remission in ulcerative colitis and Crohn's disease.

It is one of the most widely prescribed mesalazine formulations in the United Kingdom and is available as prolonged-release tablets (500 mg and 1 g), prolonged-release granules (1 g, 2 g, and 4 g sachets), rectal suspension enemas (1 g per 100 mL), and suppositories (1 g).

Pentasa is a prescription-only medicine (POM) manufactured by Ferring Pharmaceuticals.

This page provides a detailed clinical guide to Pentasa, including how it works, dosage instructions, side effects, safety warnings, monitoring requirements, and how to obtain it in the United Kingdom.

Important safety information about Pentasa

Before reading further, please note these essential safety points.

• Pentasa is a prescription-only medicine. Do not stop or change your dose without medical advice, even if you feel well.
• Kidney function must be checked before starting Pentasa, at 3 months, and then annually during treatment.
• Mesalazine brands are not interchangeable. Your prescription should specify Pentasa by name.
• Report any unexplained bleeding, bruising, sore throat, fever, or malaise to your prescriber immediately.
• Seek urgent medical advice if you develop sudden severe abdominal pain, chest pain, breathlessness, or worsening bowel symptoms.

Understanding inflammatory bowel disease

Inflammatory bowel disease (IBD) encompasses two main conditions: ulcerative colitis and Crohn's disease.

Ulcerative colitis causes continuous inflammation of the mucosal lining of the colon and rectum, starting at the rectum and extending proximally to a variable extent.

Crohn's disease can affect any part of the gastrointestinal tract from mouth to anus, most commonly the terminal ileum and colon, and involves full-thickness (transmural) inflammation that may lead to strictures, fistulae, and abscesses.

Both conditions follow a relapsing and remitting course, with periods of active disease (flares) alternating with periods of remission.

In the UK, approximately 300,000 people live with IBD, with roughly equal numbers affected by ulcerative colitis and Crohn's disease.

The peak age of onset is between 15 and 30 years, although IBD can develop at any age.

The exact cause of IBD is not fully understood but involves a complex interplay between genetic susceptibility, environmental triggers (including diet, smoking, antibiotics, and infections), and an abnormal immune response to the gut microbiome.

The goals of IBD treatment are to induce remission during flares, maintain remission and prevent relapse, minimise treatment-related side effects, and improve quality of life.

How Pentasa works

Pentasa contains mesalazine, the active component responsible for the anti-inflammatory effects of the older drug sulfasalazine. Mesalazine acts topically on the inflamed intestinal mucosa through multiple mechanisms.

It inhibits the cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) enzyme pathways, reducing the synthesis of pro-inflammatory prostaglandins, thromboxanes, and leukotrienes.

It scavenges reactive oxygen species (free radicals) that contribute to tissue damage in inflamed mucosa.

It inhibits the activation of nuclear factor kappa-B (NF-kB), a transcription factor that drives the expression of inflammatory genes.

It also modulates local cytokine production and may have direct effects on intestinal epithelial cell function and mucosal healing.

The Pentasa formulation uses ethylcellulose-coated microgranules that are designed to release mesalazine gradually and continuously throughout the gastrointestinal tract, beginning in the duodenum and continuing through the jejunum, ileum, and colon.

This distribution pattern distinguishes Pentasa from other mesalazine preparations: Asacol and Octasa use pH-dependent coatings that release predominantly in the terminal ileum and colon (above pH 7), Salofalk releases at pH 6 and above (mainly in the ileum and colon), and Mezavant uses a multi-matrix (MMX) system designed for once-daily dosing with colonic release.

Because Pentasa delivers mesalazine throughout the entire intestinal tract, it is particularly useful for patients with small-bowel Crohn's disease as well as colonic disease.

Clinical evidence and UK prescribing guidance

Mesalazine is the cornerstone of treatment for mild-to-moderate ulcerative colitis.

NICE guideline NG130 (Ulcerative colitis: management, 2019) recommends high-dose mesalazine (at least 2.4 g daily, up to 4.8 g daily) as first-line induction therapy for mild-to-moderate flares.

For left-sided or extensive disease, a combination of oral and topical (rectal) mesalazine is more effective than either route alone.

For proctitis (disease limited to the rectum), topical mesalazine (suppositories or enemas) is recommended as first-line treatment.

For maintenance of remission in ulcerative colitis, NICE NG130 recommends mesalazine at a dose of at least 2 g daily.

Studies consistently demonstrate that adherent patients have significantly lower relapse rates.

A systematic review published in the Cochrane Library confirmed that oral mesalazine is superior to placebo for maintaining remission, with a number needed to treat of approximately 6.

In Crohn's disease, the role of mesalazine is more limited.

NICE guideline NG129 (Crohn's disease: management, 2019) recommends mesalazine as an option for maintaining remission after surgical resection, particularly in patients with ileocolonic disease.

For active Crohn's disease, corticosteroids, budesonide, exclusive enteral nutrition, or immunomodulators are generally preferred over mesalazine.

However, some clinicians still use mesalazine for mild ileal or ileocolonic Crohn's disease, especially in patients who prefer to avoid steroids or immunosuppressants.

The British Society of Gastroenterology (BSG) IBD guidelines (2019) reinforce the importance of mesalazine as first-line maintenance therapy in ulcerative colitis and emphasise the need for regular renal monitoring during treatment.

Pentasa compared with other mesalazine brands

Several mesalazine brands are available in the UK, each with a different release mechanism and site of drug delivery.

Pentasa releases mesalazine from the duodenum throughout the entire GI tract.

Asacol MR and Octasa MR use an Eudragit S coating that dissolves at pH 7 or above, releasing primarily in the terminal ileum and colon.

Salofalk uses an Eudragit L coating releasing at pH 6 and above, delivering drug slightly more proximally.

Mezavant XL uses a multi-matrix system for once-daily dosing with predominantly colonic release.

The BNF states that mesalazine preparations should be prescribed by brand name because the delivery characteristics differ and are not interchangeable.

Switching between brands without clinical supervision may result in the drug being released in the wrong part of the bowel, potentially leading to loss of disease control.

If a brand switch is necessary (for example, due to supply issues), it should be done under the guidance of the prescriber and the patient should be monitored closely for any change in symptoms.

Dosage and administration

For active ulcerative colitis, the usual adult dose is up to 4 g of Pentasa daily, taken in divided doses (for example, 1 g four times daily or 2 g twice daily).

Some prescribers use higher doses of up to 4.8 g daily for moderate flares. Pentasa prolonged-release tablets should be swallowed whole with water, not crushed or chewed.

Pentasa granules may be placed directly on the tongue and washed down with water or juice, or sprinkled onto soft food such as yoghurt and swallowed without chewing.

Crushing or chewing the granules would disrupt the prolonged-release mechanism.

For maintenance of remission, the usual dose is 2 g daily, which may be taken as a single daily dose or split into two doses.

Evidence from clinical trials supports once-daily dosing for maintenance, which may improve adherence.

For rectal disease, Pentasa enemas (1 g per 100 mL) are administered rectally at bedtime, retained overnight if possible. Pentasa suppositories (1 g) are used for proctitis.

Topical and oral mesalazine may be combined for greater efficacy in left-sided or extensive disease.

If you miss a dose, take it as soon as you remember unless it is nearly time for your next dose. Do not double up.

Consistent daily dosing is essential for maintaining remission. Poor adherence to mesalazine maintenance therapy is one of the most common causes of preventable relapse in ulcerative colitis.

Side effects of Pentasa

Common side effects

The most frequently reported side effects are gastrointestinal: nausea, vomiting, abdominal pain, diarrhoea, and flatulence. These symptoms may be difficult to distinguish from those of the underlying IBD.

Headache is also common. Most gastrointestinal side effects are mild and tend to improve with continued use.

Uncommon and rare side effects

Uncommon side effects include dizziness, skin rash, urticaria, and elevated liver transaminases.

Pancreatitis is a rare but important side effect that usually occurs within the first few weeks of starting treatment.

Symptoms include sudden severe upper abdominal pain radiating to the back, nausea, and vomiting. If this occurs, stop Pentasa and seek urgent medical advice.

Pancreatitis related to mesalazine usually resolves on drug withdrawal and is a contraindication to re-challenge.

Nephrotoxicity

Mesalazine can rarely cause renal impairment, most commonly interstitial nephritis.

This is an idiosyncratic reaction that may occur at any point during treatment but is most common in the first 12 months.

Symptoms may be insidious and include fatigue, reduced urine output, and ankle swelling. Regular monitoring of renal function (serum creatinine and eGFR) is essential.

The BNF recommends checking renal function before treatment, at 3 months, then annually. If renal function deteriorates, mesalazine should be stopped and the patient referred for nephrology assessment.

Blood disorders and cardiac reactions

Blood dyscrasias, including agranulocytosis, aplastic anaemia, neutropenia, and thrombocytopenia, are very rare. Patients should be advised to report unexplained bleeding, bruising, sore throat, fever, or malaise.

Myocarditis and pericarditis are very rare hypersensitivity reactions that usually occur within the first few weeks of treatment and present with chest pain, breathlessness, palpitations, and fever.

These require immediate discontinuation and hospital assessment.

When to seek medical advice

Stop Pentasa and seek urgent medical advice if you develop sudden severe abdominal pain, chest pain, breathlessness, signs of severe allergic reaction (facial swelling, difficulty breathing), unexplained bruising or bleeding, worsening diarrhoea with blood, or high fever.

Call 999 in an emergency. Report suspected adverse reactions to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk .

Warnings and precautions

Contraindications

Pentasa is contraindicated in patients with known hypersensitivity to mesalazine, any other salicylate, or any excipient in the formulation. It must not be used in patients with severe renal impairment (eGFR below 20 mL/min/1.73 m2) or severe hepatic impairment.

Renal monitoring

All patients taking mesalazine require regular renal function monitoring. Check serum creatinine and eGFR before starting treatment, at 3 months, and then at least annually.

More frequent monitoring is recommended for patients with pre-existing renal impairment, concurrent use of nephrotoxic drugs (including NSAIDs), or other risk factors.

If renal function declines, consider stopping mesalazine and referring for specialist assessment.

Brand prescribing

Mesalazine brands are not interchangeable. The BNF states that the brand should be specified on the prescription.

Pentasa has a distinct prolonged-release ethylcellulose-coated microgranule formulation that delivers mesalazine throughout the gastrointestinal tract. Switching brands without clinical supervision may alter drug delivery and lead to relapse.

Salicylate sensitivity

Patients with a history of aspirin or salicylate hypersensitivity should use mesalazine with caution. Cross-reactivity is uncommon but possible.

Patients who had an allergic reaction to sulfasalazine due to the sulfonamide component can usually tolerate mesalazine.

Those whose reaction was attributable to the 5-ASA moiety should avoid mesalazine.

Pregnancy and breastfeeding

Mesalazine is generally considered safe during pregnancy and breastfeeding.

The BSG, NICE, and the BNF recommend continuing mesalazine during pregnancy to maintain IBD remission, as active disease poses a greater risk to the mother and baby than the medicine.

Small amounts of mesalazine pass into breast milk, and diarrhoea has been reported rarely in breastfed infants.

Discuss your treatment with your IBD team if you are pregnant or planning a pregnancy.

Drug interactions

Mesalazine may enhance the anticoagulant effect of warfarin. It inhibits thiopurine methyltransferase (TPMT) in vitro, which may increase the risk of myelosuppression when co-prescribed with azathioprine or mercaptopurine.

Full blood count monitoring is essential during concurrent use.

Avoid regular use of NSAIDs (such as ibuprofen or naproxen) without medical advice, as these may worsen IBD symptoms and increase the risk of nephrotoxicity.

Living with IBD and supporting your treatment

Adherence to mesalazine maintenance therapy is one of the most important factors in preventing relapse.

Taking your medication consistently every day, even when you feel well, significantly reduces the risk of flares.

Simplifying your regimen (for example, using once-daily dosing where appropriate) may help. Keeping a regular supply, using pill organisers, and setting reminders can all support adherence.

A balanced diet, regular exercise, stress management, and adequate sleep all contribute to overall wellbeing for people living with IBD.

While no specific diet has been proven to prevent IBD flares, some patients find that avoiding certain trigger foods (such as very spicy or high-fibre foods during active disease) helps manage symptoms.

Smoking is strongly associated with worse outcomes in Crohn's disease; stopping smoking is one of the most effective interventions for reducing relapse risk in Crohn's disease.

For ulcerative colitis, oddly, ex-smokers have a slightly higher risk of developing the condition, but smoking is not recommended as a treatment due to its overwhelming cardiovascular and cancer risks.

Support organisations such as Crohn's and Colitis UK provide valuable information, peer support, and advocacy for people living with IBD. Your IBD team, including gastroenterologists, IBD specialist nurses, and dietitians, are your key points of contact for managing your condition.

How to get Pentasa in the UK

Pentasa is available on NHS prescription from your GP, gastroenterologist, or IBD specialist team.

The standard NHS prescription charge in England is 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.

If you take multiple prescription items, a prepayment certificate may save money.

People with certain medical conditions may be eligible for a medical exemption certificate that provides free prescriptions.

Sources

• Pentasa Slow Release Tablets, Summary of Product Characteristics (EMC)
• Mesalazine, British National Formulary (BNF)
• NICE NG130: Ulcerative colitis, management
• NICE NG129: Crohn's disease, management
• Inflammatory bowel disease, NHS
• British Society of Gastroenterology
• MHRA Yellow Card Scheme