TOPAMAX 25 TABLET 25mg FOR ORAL USE

Product Information

Registration Status: Active

TOPAMAX 25 TABLET 25mg is approved to be sold in Singapore with effective from 1998-03-24. It is marketed by JOHNSON & JOHNSON PTE LTD, with the registration number of SIN09688P.

This product contains Topiramate 25mg in the form of TABLET, FILM-COATED. It is approved for ORAL use.

This product is manufactured by CILAG AG in SWITZERLAND.

It is a Prescription Only Medicine that can only be obtained from a doctor or a dentist, or a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Description

Topiramate (brand name Topamax) is an anticonvulsant drug produced by Ortho-McNeil Neurologics, a division of Johnson & Johnson. It is used to treat epilepsy in both children and adults. In children it is also indicated for treatment of Lennox-Gastaut syndrome (a disorder that causes seizures and developmental delays). It is also Food and Drug Administration (FDA) approved for, and now most frequently prescribed for, the prevention of migraines.. A combination product containing phentermine and topiramate extended-release called QSYMIA® is indicated for the management of obesity. On August 2013, an extended released formulation, marketed as Trokendi XR has been approved for the management of partial onset, tonic-clonic, and Lennox-Gastaut Syndrome seizures.

Indication

Used for the treatment and control of partial seizures and severe tonic-clonic (grand mal) seizures and also for the prevention of migraine headaches. In children it is also used for treatment of Lennox-Gastaut syndrome. Qsymia® is indicated for the treatment and management of obesity.

Mechanism of Action

The precise mechanism of action of topiramate is not known. However, studies have shown that topiramate blocks the action potentials elicited repetitively by a sustained depolarization of the neurons in a time-dependent manner, suggesting a state-dependent sodium channel blocking action. Topiramate also augments the activity of the neurotransmitter gamma-aminobutyrate (GABA) at some subtypes of the GABA_A receptor (controls an integral chloride channel), indicating a possible mechanism through potentiation of the activity of GABA. Topiramate also demonstrates antagonism of the AMPA/kainate subtype of the glutamate excitatory amino acid receptor. It also inhibits carbonic anhydrase (particularly isozymes II and IV), but this action is weak and unlikely to be related to its anticonvulsant actions.

Pharmacokinetics

Absorption: Rapid with pleak plasma concentrations occurring after 2 hours and a bioavailability of 80%. The pharmacokinetic profile of the extended release formulation is non linear at 25 mg due to binding of topiramate to carbonic anhydrase in red blood cells. The peak plasma concentration was 24 hours after a single 200 mg oral dose of the extended release formulation. It is also bioequivalent to immediate-release tablet that has been administered twice-daily. Fluctuation of topiramate plasma concentrations at steady-state for Trokendi XR™ administered once-daily was approximately 26% and 42% in healthy subjects and in epileptic patients, respectively, compared to approximately 40% and 51%, respectively, for immediate-release topiramate. When topiramate is given to elderly and young adults, the maximum plasma concentration was achieved in 1 to 2 hours.
Distribution
Metabolism: Not extensively metabolized, 70% of the dose is eliminated unchanged in the urine. The other 30% is metabolized hepatically to six metabolites (formed by hydroxylation, hydrolysis, and glucuronidation), none of which constitute more than 5% of an administered dose. There is evidence of renal tubular reabsorption of topiramate.
Elimination

Clearance

* Plasma clearance (CL/F) =20-30 mL/min [in humans following oral administration] Clearance in adults was not affected by gender or race. Pediatric patients on adjunctive treatment exhibited a higher oral clearance compared to those on monotherapy. This may be because of concomitant administration with enzyme-inducing antiepileptic drugs.

Toxicity

Symptoms of overdose include abdominal pain, agitation, blurred vision, convulsions, depression, dizziness, double vision, drowsiness, impaired coordination, impaired mental activity, low blood pressure, reduced consciousness, severe diarrhea, sluggishness, and speech problems.

Active Ingredient/Synonyms

Source of information: Drugbank (External Link). Last updated on: 3^rd July 18. *Trade Name used in the content below may not be the same as the HSA-registered product.