Can finasteride stop working?

[Caswall]

My hair started thinning at the forehead and crown about a year ago. I started taking finasteride and after about three months I started to get some re-growth in the affected areas. But a couple of weeks ago I noticed that the hair at the front had started to thin out again.

I recently missed a day of treatment because the tablets I ordered online took longer than expected to arrive. I also started taking fexofenadine (for hayfever) around the time the thinning started, although I’ve stopped now. I don’t know if either of these could be the reason for the thinning? I’m really hoping the finasteride hasn’t stopped working!

Any advice would be appreciated. Thanks.