Topiramate
Topiramate is an antiseizure drug with several actions at once: it blocks sodium channels, enhances GABA signalling, dampens glutamate activity and weakly inhibits carbonic anhydrase. That last property explains much of its side-effect profile. It is used for epilepsy and for preventing migraine attacks.
It can be taken with or without food, but a generous fluid intake through the day matters, because carbonic anhydrase inhibition acidifies the blood, alkalinises the urine and makes kidney stones more likely; creatinine and potassium are monitored for the same reason. Cognitive dulling is the other familiar effect — slowed word-finding, poorer concentration and mental fog — usually most noticeable early or after an increase. Topiramate can reduce the effectiveness of combined ethinylestradiol-and-progestin contraception, so an alternative or additional method is worth discussing before starting. Abrupt discontinuation risks seizures even when the drug is being taken for migraine.
Flank or back pain, blood in the urine or pain on passing urine suggest a stone and need medical assessment. Sudden blurred vision or eye pain, persistent confusion, unusual tingling with rapid breathing, or a fever without sweating are also reasons to see a doctor.
Reference information, not medical advice. Discuss any change with your doctor.