mesalazine and intracranial hypertension

Idiopathic intracranial hypertension (IIH) has been very rarely reported in patients treated with mesalazine (1):

• a European review of safety data for mesalazine identified an association between mesalazine and idiopathic intracranial hypertension following very rare reports of this event
• the number of reports of intracranial hypertension and mesalazine received in the UK and identified through the European review are very low
  • MHRA has received 6 UK Yellow Card reports of increased intracranial pressure disorders associated with mesalazine
  • total prescribing for mesalazine averages approximately 1.5 million items per year across all regional teams in NHS England

Possible presenting features of IIH include (1):

• a headache that is progressively more severe and frequent; the type of headache can be highly variable
• transient visual obscurations (unilateral or bilateral darkening of the vision typically lasting seconds)
• pulsatile tinnitus
• back pain
• dizziness
• neck pain
• visual blurring
• cognitive disturbances
• radicular pain
• typically horizontal diplopia

A case report of intracranial hypertension occurring after introduction of mesalazine therapy concluded that (2):

• periodic ocular fundus examination should be undertaken for patients undergoing long-term therapy with mesalazine, especially if decreased vision, headaches, or neck stiffness are present, to avoid potentially severe complications of intracranial hypertension

Diagnosis

• may be achieved through blood pressure monitoring and ophthalmology examination
  • if diagnostic uncertainty remains, then seek expert advice and further investigations such as brain imaging and/or lumbar puncture be indicated

Advice for Healthcare Professionals (1):

• idiopathic intracranial hypertension (IIH) has been very rarely reported in patients receiving mesalazine
• the number of reports in the UK is very low
• patients using any form of mesalazine should be warned to look for signs and symptoms of IIH including severe or recurrent headache, visual disturbances or tinnitus
• remain vigilant of signs and symptoms of IIH in patients taking mesalazine and act promptly with a multidisciplinary approach, involving clinicians managing the patient’s mesalazine as well as neurology, neurosurgery and ophthalmology teams as appropriate
• if symptoms of IIH occurs, discontinuation of mesalazine should be considered and management of the symptoms should begin immediately
• caution is advised when prescribing for patients who have previously diagnosed or suspected IIH

Notes:

• background incidence of IIH has been reported as between 1.8 and 7.8 per 100,000 population per year across Scotland, England and Wales
• intracranial hypertension can be associated with inflammatory bowel disease (IBD), or triggered by medications used in the management of such disorders, for example, sulfasalazine, mesalazine, or withdrawal of corticosteroid therapy (3)
• in specific cases linked to IBD, treating the underlying inflammation with mesalazine has paradoxically led to the resolution (cure) of pre-existing IIH, suggesting mesalazine can either trigger or improve it depending on the underlying mechanism (3)

Reference:

1. MHRA Drug Safety Update volume 19, issue 5: December 2025: 1.
2. Rosa N, Giamundo A, Jura A, Iaccarino G, Romano A. Mesalazine-associated benign intracranial hypertension in a patient with ulcerative colitis. Am J Ophthalmol. 2003 Jul;136(1):212-3.
3. Khanna RK, Hage R, Hage A, Polin V, Sené T, Vignal-Clermont C. Mesalazine treatment causing resolution of intracranial hypertension secondary to ulcerative colitis: A case report. Medicine (Baltimore). 2018 Dec;97(49):e13365.