title: Ciprofloxacin eye drops-induced subtherapeutic serum phenytoin levels resulting in breakthrough seizures.
abstract: An 81-year-old woman with a history of temporal lobe epilepsy-induced psychotic episodes was initially admitted to a general hospital where she was started on a course of oral antibiotics for community-acquired pneumonia, and ciprofloxacin eye drops to treat nasolacrimal duct obstruction. After one week, the patient was discharged back to a nursing home with these medications. However, she was admitted to our psychiatric ward two days later due to a relapse of psychosis. Another six days later, she developed breakthrough seizures associated with subtherapeutic serum phenytoin levels. Having explored all possible causes of reduced serum phenytoin levels, ciprofloxacin eye drops was discontinued in the patient, resulting in gradual return of phenytoin levels to the therapeutic range, with no further seizures observed in the patient.
authors.affiliation: Institute of Mental Health, 10 Buangkok View, Singapore 539747. Srinivasa_sastry_malladi@imh.com.sg.
authors.forename: Srinivasa Sastry
authors.initials: SS
authors.lastname: Malladi
authors.forename: Emily Kai Suen
authors.initials: EK
authors.lastname: Liew
authors.forename: Xiao Ting
authors.initials: XT
authors.lastname: Ng
authors.forename: Rita Kheng Siew
authors.initials: RK
authors.lastname: Tan
mesh_terms: D000284:Administration, Oral; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D002939:Ciprofloxacin / Q000008:administration & dosage / Q000009:adverse effects*; D004347:Drug Interactions; D004833:Epilepsy, Temporal Lobe / Q000188:drug therapy; D005260:Female; D006760:Hospitalization; D006801:Humans; D009883:Ophthalmic Solutions / Q000009:adverse effects*; D010672:Phenytoin / Q000097:blood*; D011618:Psychotic Disorders / Q000188:drug therapy; D012640:Seizures / Q000139:chemically induced*
chemical_list: D000900:Anti-Bacterial Agents; D009883:Ophthalmic Solutions; D002939:Ciprofloxacin; D010672:Phenytoin
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