Brief Answer:
Sometimes just stopping medications is enough.

Detailed Answer:
Hello dear, welcome to 'Ask A Doctor' service.
I read your query and here is my advice.

I think it would be better if you show me a photo of the acne you are having and specify what drug are you taking. You can simply upload/attach it to the 'Reports section' of this web page.

If you have finished the treatment and are better now just discontinuing it can help the acne go away.

Some medications can't be discontinued and you may need to treat the acne to a dermatologist.
You may need to use Isotretinoin and antibiotics

Hope I have answered the question.
Let me know if I can assist you further.

---

Brief Answer:
Visiting a dermatologist is necessary.

Detailed Answer:
Hello dear and thank you for asking again.

I don't think that prochlorperazine can cause acne directly as a side effect.
It may increase sweating especially at night and it may have favored acne creation.
The prochlorperazine doesn't need to get discontinued.

I see the picture you attached and your back looks to have acne almost all over.

I think you should get treated by a dermatologist using Isotretinoin and antibiotics such as Minocycline.

---