It is pregabalin

The short version: pregabalin at 600 mg/day is a high dose, the weight gain and brain fog are documented side effects, and you need a slow taper to avoid withdrawal seizures or psychiatric symptoms.

You are on the maximum approved dose for most indications. The long-term safety study of pregabalin for anxiety disorders found that 24.4% of patients reported weight gain over one year [4]. That is about 1 in 4 people. Brain fog is not tracked as a formal endpoint in these studies, but dizziness (12.5%) and somnolence (7.6%) are common [4], and disturbance in attention was reported in a smaller trial [3]. These are the drug's mechanism at work: pregabalin calms overactive neurons by binding calcium channels, and that same calming produces cognitive slowing.

The withdrawal risk is real and documented. A 2026 case report describes a 24-year-old man who had a generalized tonic-clonic seizure three days after abruptly stopping pregabalin at a very high dose (4200 mg/day) [2]. A 2024 commentary warns that psychiatric symptoms can appear after sudden withdrawal even at standard doses [1]. The seizure case is extreme in dose but the mechanism applies at lower doses: the brain adapts to the drug's presence, and removing it too fast can trigger rebound excitation.

The evidence that would tell you exactly how fast to taper from 600 mg/day does not exist in this retrieval. No head-to-head trial compares a 10% per week taper to a faster one for this drug at this dose. What the evidence does show is that abrupt discontinuation is dangerous [1, 2] and that a gradual taper resolved withdrawal symptoms in the case report [2].

My call is to reduce by no more than 50 to 75 mg every one to two weeks, and to expect the brain fog to lift gradually as the dose drops while the weight may take longer to reverse. Work with a clinician who will let you go at your pace and who understands that these side effects are real reasons to come off the drug. Confidence is moderate for the general rule of slow tapering, low for any specific schedule because the optimal taper rate for your dose has not been studied.