Elder Sims dead just 3 hours after drinking ghost potion

So apparently, I let my elder dim drink a ghost potion and he of course turned into a ghost form. I thought that would only last for 3 hours. But after 3 hours, the grim reaper came and took him away. So basically he died from drinking the potion after 3 hours. So I tried the ghost potion on my adult Sims. She too turned into ghost form but after three hours, she went back to her human form. Is this some kind of glitch?