Topvex 25/Topvex 50/Topvex 100 Special Precautions

A syndrome consisting of acute myopia associated with secondary angle closure glaucoma has been reported in patients receiving Topiramate. Symptoms include acute onset of decreased visual acuity and/or ocular pain. Ophthalmic findings can include myopia, anterior chamber shallowing, ocular hyperemia (redness) and increased intraocular pressure. Mydriasis may or may not occur. This syndrome may be associated with supraciliary effusion resulting in anterior displacement of the lens and iris, with secondary angle closure glaucoma. Symptoms typically occur within one month of initiating Topiramate therapy. Secondary angle closure glaucoma associated with Topiramate has been reported in paediatric patients as well as adult patients. Treatment includes discontinuation of Topiramate, as rapidly as possible and appropriate measures to reduce intraocular pressure.
Metabolic Acidosis: Hyperchloremic, non-anion gap, metabolic acidosis (i.e. decreased serum bicarbonate below the normal reference range in the absence of respiratory alkalosis) is associated with topiramate treatment. This decrease in serum bicarbonate is due to the inhibitory effect of topiramate on renal carbonic anhydrase and consequent renal bicarbonate wasting. These decreases are usually mild to moderate (average decrease of 4 mmol/L at doses of 100 mg/day or above in adults and at approximately 6 mg/kg/day in paediatric patients). However, patients have experienced decreases to values below 10 mmol/L. Conditions or therapies that predispose to acidosis (such as renal disease, severe respiratory disorders, status epilepticus, diarrhoea, surgery, ketogenic or certain drugs) may be addictive to bicarbonate lowering effects of topiramate. Chronic metabolic acidosis in paediatric patients can reduce growth rate. Chronic metabolic acidosis can lead to nephrolithiasis and increased risk of fractures. Evaluation of bicarbonate levels is recommended with topiramate therapy. If metabolic acidosis develops and persists, consideration should be given to reducing the dose or discontinuing topiramate.