Fampradine is 4-AP and available from a compounding Pharmacy (they make it in tab. form )and 4-AP does have a shelf life and older 4-AP may be less strong so try to go with recommended pharmacy. Although not yet FDA approved, it is available with a doctor's prescription. I have tried it (live in Maryland, got from recommened pharmacy in AZ from a Pharmacist friend knows.) I am in a chair, PPMS - did not help me but I knew it probably would not (my sit.- going in.) Was inexpensive as it is now generic , Can possibly have side effects (like everything!) and worth investigating. Talk to your neuro. Like Interferons and other CRABS it has@@@@33% success rate I think. May be right for you. Never know until ypu try. Have heard yes and nopes about it, like everything. Internet has info - use generic name to look up.