Memory loss and other cognitive adverse effects are well known to occur with gabapentin (brand name Neurontin) and they appear to be dose related, meaning higher doses result in a higher incidence rate.
In your situation, your dose far exceeds the maximum recommended daily dose, which is 3,600mg (given as divided doses throughout the day). Even then, dosages of 3600 mg/day have only been studied in a limited number of patients for a relatively short duration of time.
While you state your doctor has prescribed you 4,600mg a day (which is higher than the maximum recommended dose, but they may be trying alternative dosing for your specific situation), you are taking more than two to three times this dose day. This is dangerous and should not be done. Possible side effects from overdose include:
- Loss of full control of bodily movements
- Labored breathing
- Drooping eyelids
- Double vision
- Slurred speech
- Gastrointestinal problems
- Impaired cognition (e.g. amnesia, memory impairment, confusion)
The memory issues you are experiencing may be very well due to the extremely high dose of gabapentin you are taking. Fortunately, memory loss and other side effects associated with gabapentin are not considered permanent and should resolve upon discontinuation of therapy or with a dose decrease.
Please reach out to your doctor regarding the side effects you are experiencing and the high doses you are taking, which are far beyond your prescribed therapy and medical guidelines.