Hello, Doxycycline and Flagyl (metronidazole) are antibiotics commonly used to treat bacterial infections. In your husband s case, the doctor has prescribed these medications to treat a possible infection in the semen. Like any medication, doxycycline and Flagyl can have side effects. Common side effects of doxycycline include nausea, vomiting, diarrhea, and sensitivity to sunlight. Flagyl can cause nausea, vomiting, diarrhea, abdominal cramps, and metallic taste in the mouth. In rare cases, these medications can cause more severe side effects such as allergic reactions or liver problems. It s important to take the medications as prescribed and to complete the full course of treatment to ensure the infection is fully treated. If your husband experiences any severe or persistent side effects, he should contact his doctor right away. It s also important to note that these medications can interact with other medications, so your husband should inform his doctor of any other medications or supplements he is taking. Overall, it s best to follow your doctor s advice and to take the prescribed medications as directed to effectively treat any possible infection and reduce the risk of complications. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Shah Hussain, General & Family Physician