Maybe just make your own thing up instead of strength drain, like
Weakened: while weakened you have disadvantage on attacks and ability score checks. You remain weakened until you are brought up to full hit points.
Then since it is basicly just poisoned value it the same as poison.
The only reason to make it not poison is to give it a different feel and let it circumvent poison resistance and immunity, but it is easier to get rid of then the poison condition for the most part.
I guess I never liked strength drain as it only effects one type of character the strength based warriors, dexterity rogues and archers still function at full effect, as do spellcasters. Things like poisoned or weakness that give disadvantage effect most everyone.