Translation of "taper off" into Spanish

Then, uh, a few weeks ago, they started to taper off, eventually to once or twice a week.

Luego, hace unas semanas, bajaron, una o dos veces por semana.

I understand that these things don't last a lifetime, but should not it taper off a bit?

Entiendo que esto no dure toda la vida, pero ¿no debería ir decayendo?

They're tapering off the phenobarb and they're getting the Dilantin up to a level where it'll work.

Están disminuyendo el fenobarb y subiendo el Dilantin hasta dar con la dosis que haga efecto.