Dear , This is Dr. S. Tomar from healthcaremagic.com s medical team and I ll be your medical advisor for this question. First of all thank you for sharing your concern with us and showing trust on us. Throat ulcers are mainly caused by viral infections , bacterial infections , fungal infections , wrong eating habits , trauma and rarely cancer. Such ulcers can persists weeks to months and can relapse also as the treatment is stopped . Penicillins can be prescribed for extended period of time in special cases like recurrent streptococcal infections , chronic tonsillitis , strep throat . If the cultures were positive for such bacteria then extended use is indicated otherwise not. Cancer issue should be ruled out first with histopathological studies if ulcer does not responds to antibiotic therapy . I would recommend to consult the issue further with ENT specialist . This is my initial response and discussion is open untill you have any query or need further clarification. I wish you good health . Thank you for your question and feel free to contact further for any question . sincerely, Dr. Shardendu Tomar