Can I stop zithromax after 3 days instead of 5?

Rather than simply stopping the Zithromax early, you are better off replacing it with a different antibiotic (erythromycin is one of the drugs of choice for this bacteria). Stopping antibiotics early favors the emergence of drug resistant bacteria that are more difficult to treat successfully. Another consideration is that if some of these bacteria are still hanging around in your throat after only 3 days a Zithro, you are a potential health threat to others you come in contact with. Pertussis is highly communicable, and can cause serious disease in adults, and death in infants and young kids. Don't fool around with this.