What is the dosage of Minocycline I should ask my dad to prescribe me?

I have had little to none acne and good skin for most of my life but 8 months ago i had this terrible allergic reaction. It was a terrible reaction but i had recovered from it but it had left some marks. My forehead hasn't been clear within the last eight months. i can see the redness all over my face when i look in the mirror and my skin has worsened. My friend's dad prescribed him minocycline and it had seemed to work for him. Can this help me? How much and how long should i use it?