ODE45 speed up and for loops

ODE45 speed up and for loops

I have a coupled first order ODE to solve of the form
dy = f(t,x) dx = d(f,x)
which depend on a common parameter which I have to solve for over some
range. I can solve the system using ODE45 and a for loops which increments
the parameter of interest at each loop, however, this is very slow!!! Can
I avoid solving this problem in loops? Or what is best practice with
problems of this type.