Dry Lips, Throat Infection. Prescribed Azithromycin, Black Lips, Getting Worse. Suggestions?

Hi,
First of all I had dry lips to begin with then I had a throat infection so my doctor prescribed azithromycin that whole week I used this medicine my lips especially the corners turned real black the rest of my lips look light black or probably really dark brown I feel that its getting worse day by day...I've tried lip balms and doesn't seems to make it get better..I don't know what to put on it all my lips are black and it makes me look very bad I can't even look at people when I talk sometimes..could it of been the medicine it was only a weeks prescription