How long do the side effects of Fortaz last after you stop taking it? ## Hi Mary - I did not find specific information as far as how long you could be experiencing side effects after stopping the drug. I know from my own experience that it can be weeks in the case of other antibiotics. You might consider calling the manufacturer Teligent Pharma at 856-697-1441. DailyMed also has a pretty detailed list of possible adverse effects. May I ask what you are experiencing?