Sir,

Trimethoprim is the most commonly used drug in the treatment of urinary tract infection in women. Common side effects associated with its use include skin rash, itching, gastrointestinal upset, anaemia, and swelling of the tongue. We report a rare case of trimethoprim-induced bilateral acute anterior uveitis.

Case report

A 41-year-old woman, who had been taking oral trimethoprim 200 mg twice daily for 2 days, was referred by her general practitioner with a 8-h history of bilateral painful red eyes. She had also developed sudden-onset chills, itching, arthralgia, and myalgia. The examination revealed bilateral acute anterior nongranulomatous uveitis with raised intraocular pressures. Her fundi were normal.

Her past ocular history was unremarkable. She had been treated with trimethoprim on two previous occasions without any adverse effects.

The uveitis was treated with topical steroids and mydriatics, with complete recovery within a few days of discontinuing trimethoprim. Routine blood tests including acute phase reactants were all normal. Her chest radiograph was negative, as were toxoplasmosis antibodies, antistreptolysin-O and antinuclear antibodies. No bacteria were detected in her urine. HLA-B27 was negative.

With the patient's informed consent, she was re-challenged with a single oral dose of 200 mg of trimethoprim. Approximately 45 min after taking the drug she became ill, with visual disturbance, headache, arthralgia, and myalgia. There was bilateral acute anterior uveitis. Topical treatment was instituted and recovery was again rapid and complete.

Comment

Trimethoprim is a widely used antibiotic, either alone or in combination with sulpha drugs. Serious side effects are rare, although there have been occasional case reports of aseptic meningitis and Stevens–Johnson syndrome.1, 2 Acute uveitis has been described only twice previously.1, 2 Retinal haemorrhages have been reported.3 In the past uveitis has been attributed to the systemic use of sulphonamide derivatives.4 Sulphonamides are frequently administered in combination with trimethoprim, and it is possible that some of the reported cases of sulphonamide-induced uveitis may in fact have been due to trimethoprim.

Trimethoprim is widely distributed in body fluids, including aqueous and vitreous humour. Interestingly, our patient had no side effects on the first and second occasions she was given trimethoprim. On the third occasion, she developed symptoms after three doses, and there was an even more rapid recurrence of uveitis with rechallenge. This strongly suggests the possibility of an immunologically mediated process. A similar chain of events was noted in the case report by Gilroy et al.2 It appears, therefore, that a patient who has shown no side effects with trimethoprim in the past can develop uveitis on repeated exposure.

The association of bilateral anterior uveitis with systemic use of drugs has rarely been reported, and physicians, general practitioners, and ophthalmologists should be aware of potential complication and include side effects of systemic drugs in the differential diagnosis of uveitis.