Sulfasalazine: bowel inflammation and rheumatoid arthritis

Sulfasalazine is an aminosalicylate, the same family as mesalazine, and it is prescribed for ulcerative colitis, Crohn's disease and other inflammatory bowel conditions as well as rheumatoid arthritis. It reduces redness and swelling and supports healing. In arthritis it acts like a slower-working disease-modifying medicine, reducing white blood cell activity in a way similar to immunosuppressants.

It is available only on prescription as tablets, a liquid to swallow, and suppositories. Different formulations work on different parts of the gut.

For inflammatory bowel disease the NHS describes starting doses of 2 to 4 tablets or 20 ml to 40 ml of liquid four times a day, or 1 to 2 suppositories twice a day. For rheumatoid arthritis it starts at 500 mg once daily and rises by one tablet a week until a daily 2 g or 3 g is reached, depending on response. Your prescriber sets the actual plan.

Space doses evenly across the day and night, with no more than 8 hours between the bedtime and morning doses. Tablets are swallowed whole with water, with or without food; the liquid is taken with food; suppositories are used morning and bedtime and take about 15 minutes to dissolve.

• Drink plenty of fluids to protect the kidneys.

• If you miss a dose, take it when you remember unless the next dose is due. Never double up.

• One extra dose is unlikely to cause problems; call NHS 111 if you took more than one extra or feel unwell.

• Do not stop it without speaking to your doctor, as symptoms may return.

Most adults and children aged 2 and over can take sulfasalazine. Tell your doctor if you have had an allergic reaction to it, to other sulfonamides, aspirin or salicylates, or to any medicine; if you have porphyria, kidney or liver problems, glucose-6-phosphate dehydrogenase deficiency, asthma, or frequent infections; or if you are pregnant, planning pregnancy or breastfeeding.

Common effects include indigestion, nausea, vomiting, diarrhoea, stomach pain, dizziness, headache, joint aches, cough, sore mouth, taste changes, trouble sleeping and tinnitus. Practical steps include adjusting meal timing, staying hydrated and keeping antacids at least 2 hours away. The orange urine is harmless, and the medicine can stain soft contact lenses.

Call NHS 111 for fever, joint pain, swollen glands and an itchy rash; for signs of infection such as sore throat, mouth sores or slow-healing wounds; for pallor, unusual bruising or extreme tiredness; for urinary changes; for an irregular heartbeat; for yellow skin or eyes with dark urine; or for back and stomach pain with fever and vomiting. Call 999 for chest pain, a severe blistering rash or a serious allergic reaction.

Suspected effects can be reported to the Yellow Card scheme.

There are no concerns that sulfasalazine in pregnancy harms the baby, but it affects folate levels. The NHS advises high-dose folic acid, 5 mg daily, for 3 months before conception and through the first 12 weeks, and it may be continued through pregnancy.

Healthy babies can be breastfed while the mother takes it, subject to a doctor's approval; small amounts reach milk, and rare diarrhoea has been reported, so watch for diarrhoea, vomiting, rash, sleep changes, irritability or jaundice.

There is no evidence it reduces fertility in women. In men it may reduce sperm count, which usually recovers within 2 to 3 months of stopping. Men whose partners have not conceived after 12 months can discuss stopping with their doctor.

Medicines the NHS names include digoxin, metformin, glibenclamide, methenamine, azathioprine, mercaptopurine and methotrexate. Folic acid may be less well absorbed, so a higher dose could be needed. Tell your doctor or pharmacist about all medicines and herbal products.

Kidney function is checked about every 3 months in the first year and then roughly yearly. Alcohol is allowed within 14 units a week but can irritate the gut. Sulfasalazine can make you dizzy, so avoid driving or using machinery if affected.