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Malladi SS, Liew E, Ng XT, Tan KS
Correspondence: Dr Srinivasa Sastry Malladi, Srinivasa_sastry_malladi@imh.com.sg
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.
Keywords: ciprofloxacin, phenytoin, seizures
Singapore Med J 2014; 55(7): e114-e115; http://dx.doi.org/10.11622/smedj.2014095
|1. CILOXAN® (Ciprofloxacin HCI ophthalmic solution). In: Alcon [online]. Available at: http://ecatalog.alcon.com/PI/CiloxanSol_us_en.pdf.|
|2. Dillard ML, Fink RM, Parkerson R. Ciprofloxacin-phenytoin interaction. Ann Pharmacother 1992; 26:263.
|3. Brouwers PJ, de Boer LE, Guchelaar HJ. Ciprofloxacin-phenytoin interaction. Ann Pharmacother 1997; 31:498.
|4. Otero MJ, Moran D, Valverde MP. Interaction between phenytoin and ciprofloxacin. Ann Pharmacother 1999; 33:251-2.
|5. McLeod R, Trinkle R. Comment: unexpectedly low phenytoin concentration in a patient receiving ciprofloxacin. Ann Pharmacother 1998; 32:1110-1.
|6. Pollak PT, Slayter KL. Comment: ciprofloxacin-phenytoin interaction. Ann Pharmacother 1997; 31:1549-50.
|7. Hull RL. Possible phenytoin-ciprofloxacin interaction. Ann Pharmacother 1993; 27:1283.
|8. Job ML, Arn SK, Strom JG, Jacobs NF, D'Souza MJ. Effect of ciprofloxacin on the pharmacokinetics of multiple-dose phenytoin serum concentrations. Ther Drug Monit 1994; 16:427-31.
|9. Schroeder D, Frye J, Alldredge B, Messing R, Flaherty J Jr. Effect of ciprofloxacin on serum phenytoin concentrations in epileptic patients. Pharmacotherapy 1991; 11:275.|