Doxycycline hydrochloride tablets can be taken for syphilis. The drug’s instructions clearly state that it can treat syphilis, so syphilis patients can take doxycycline hydrochloride tablets. This product is a broad-spectrum bacteriostatic agent, with bactericidal effect at high concentration. Its mechanism of action is that the drug can specifically bind to the A position of the 30S subunit of the bacterial ribosome, inhibiting the growth of peptide chains and affecting the synthesis of bacterial proteins. Clinically, the drug is used not only for the treatment of rickettsial diseases, Mycoplasma spp. infections, Chlamydia spp. infections, cholera, but also for the treatment of tetanus in patients with penicillin allergy, gas gangrene, yaws, syphilis, gonorrhea and leptospirosis, as well as for the adjuvant treatment of patients with moderate and severe acne. Adverse reactions such as headache, nausea, vomiting, abdominal pain, maculopapular rash and erythema have been observed after administration. It is contraindicated in persons with a history of tetracycline allergy and in children under 8 years of age. In the treatment of venereal disease, if there is a suspicion of syphilis spirochete infection at the same time, dark-field microscopy and serologic examination should be performed before the use of the drug; long-term use of the drug should be checked regularly for blood and liver function; pregnant women and lactating women should be cautious of use. Patients with syphilis should go to a specialized hospital for examination in time to avoid delaying their condition.