Abstracts

Objective: At the conclusion of this presentaion, participants should be aware of the safety of continued use of Zonisamide following the development of renal calculi.
Rationale: The incidence of development of renal calculi with Zonisamide (ZNS) is approximately 4%. Most often these are assymptomatic but they may be symptomatic in approximately 1.2% of patients. Zonisamide is often discontinued after the development of renal calculi. There is no information available about the safety of the continued use of ZNS in patients.
METHODS: A retrospective chart review was performed at two academic epilepsy centers (Baylor College of Medicine Comprehensive Epilepsy Center in Houston, Texas and Rush Epilepsy Center in Chicago, Illinois). Patients with epilepsy who developed renal calculi following ZNS and continued to use it following their development were included.
RESULTS: Three patients who met the above mentioned criteria were identified. All three were diagnosed with medically intractable partial seizures. Please refer to table for patient demographics.
Patient MD developed severe flank pain and the ZNS was discontinued after a diagnosis of renal calculi was made. Seizures became very frequent after discontinuing ZNS. ZNS was restarted after attempts at controlling seizures with other medications were unsuccessful. A renal ultrasound was performed after 4 months which demonstrated no renal calculi.
Patient MS also elected to continue treatment with ZNS due to significant reduction in seizure frequency. A renal ultrasound was performed after 4 months which demonstrated no renal calculi.
Patient AD had previously developed renal calculi with Topiramate and also had a positive family history. He elected to continue treatment with ZNS due to a greater than 90% reduction in seizure frequency with ZNS.
CONCLUSIONS: ZNS is indicated for adjunctive therapy for partial seizures in adult epilepsy patients. The development of renal calculi often results in discontinuation of the medication. We present three patients who elected to continue treatment with ZNS despite development of symptomatic renal calculi and who have since remained assymptomatic despite continued treatment. All three patients elected to continue treatment because of a signicant reduction in seizure frequency with ZNS. Renal ultrasounds were performed in two patients 4 months after the development of calculi and both demonstrated no recurrence. This indicates that development of renal calculi should not be considered a contraindication to continued use of ZNS and that continued use may be safe in some patients. This also supports the effectiveness of ZNS in patients with medically intractable epilepsy.[table1]
(Disclosure: Consulting - Elan Pharmaceuticals, Honoraria - Elan Pharmaceuticals)