Minocycline treats inflammatory acne while you are on it by suppressing the growth of acne bacteria and decreasing the inflammation. Once your inflammatory acne subsides, recurrence of acne is reduced by maintenance topical therapy, usually with topical retinoids (tretinoin, adapalene).
Oral antibiotics can take up to eight weeks to start seeing improvement; therefore you will not be able to see the results right away. It takes awhile to see a change as over time, bacteria do become resistant to antibiotics. Despite that, you should only be taking minocycline as adviced by your doctor.
If maintenance topical therapy after minocycline is not adhered to, then a recurrence of acne may occur.