Saw dr yesterday diagnosed I with strep. Gave me a 1.2 mill unit shot of penicillin. My throat still hurts and hacking up brown stuff in saliva now.
Sore throat. If your strep infection was confirmed by a throat culture, the bacteria should be killed by the penicillin which is bactericidal. Of course, you may have more than one infection at the same time. A viral infection could cause your cough, which may be irritating your throat and producing blood tinged sputum ((brown stuff). Penicillin won't affect a virus or some other types of bacteria.
Give it time. You probably just need to give it more time, especially if it was bicillin LA (benzathine penicillin). As long as you are not short of breath, fever increasing, or overall worsening, I'd wait a day or two to see how you do. You can always call the doctors office and ask them what else, if anything, needs to be done. Drs appreciate feedback...
Have you followup? You need to see your doctor again and they need to test you and check if the infection has cleared. There are resistant type of bacteria, that might not responded to the treatment.