Giant cell arteritis treatment failure resulting from probable steroid/antiepileptic drug-drug interaction.

Case report An 83-year-old man with previous cerebral abscess (surgically resected 55 years prior) and postoperative seizure disorder presented with headache, scalp tenderness and reduced left eye visual acuity. His medications were: phenytoin 400mg daily, cilazapril 1.5mg daily, omeprazole 40mg daily, melatonin 3mg nightly, bendrofl uazide 2.5mg daily and primidone 500mg daily. Examination revealed visual acuity of 4/5 in the right eye, and hand movements only in the left eye. Fundoscopy showed left sided ischaemic optic neuropathy. Physical examination was otherwise normal. Bloods are shown in Table 1. Left temporal artery biopsy was diagnostic of giant cell arteritis.