Volume of distribution (L/kg)       : 0.55–0.8
half-life – normal/ESRD (hrs)      : 20–30/48–60 (12–15 hours if used with another enzyme-inducing anti-epileptic drug)
DOSE IN RENAL IMPAIRMENT
GFR (mL/MIN)
20 to 50     : Migraine/epilepsy: Dose as in normal renal function
10 to 20     : Migraine: Dose as in normal renal function Epilepsy: 50% of normal dose and increase according to response
<10           : Migraine: Dose as in normal renal function Epilepsy: 25–50% of normal dose and increase according to response
DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
CAPD                : Unknown dialysability. Dose as for GFR <10 mL/min
HD                     : Dialysed. Dose as for GFR <10 mL/min
HDF/high flux   : Dialysed. Dose as for GFR <10 mL/min
CAV/VVHD      : Unknown dialysability. Dose as for GFR 10 to 20 mL/min
IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugs
Antidepressants: antagonism of anticonvulsant effect
Anti-epileptics: concentration reduced by phenytoin and carbamazepine; increases phenytoin concentration
Antimalarials: mefloquine antagonises anticonvulsant effect; chloroquine and hydroxychloroquine occasionally reduces convulsive threshold Oestrogens and progestogens: reduced contraceptive effect
ADMINISTRATION
Reconstition
–
Route
Oral
Rate of Administration
–
Comments
–
OTHER INFORMATION
Patients with moderate to severe renal impairment may take 10–15 days to reach steady state, compared to 4–8 days in patients with normal renal function A higher frequency of renal stones has been noted in topiramate treated patients, although the risk is not related to dose or duration of therapy. Adequate hydration is recommended to reduce this risk .