Sexually transmitted infections (STIs) are not all treated in the same way. Some are caused by bacteria and can usually be cured with antibiotics. Others are caused by viruses, meaning treatment may control the infection without completely removing it from the body. Parasitic infections require antiparasitic medicine, while conditions such as pubic lice and scabies are treated with medicines that kill insects or mites.
More than 30 bacteria, viruses and parasites can be transmitted through sexual contact. The correct treatment depends on the specific organism, the part of the body affected, pregnancy status, medication allergies, previous treatments and local patterns of antimicrobial resistance. For this reason, it is important to test before taking medicine whenever possible.
Healthcare professionals follow evidence-based resources such as the CDC STI Treatment Guidelines when selecting the appropriate medicine and treatment duration.
This guide provides general educational information about commonly used treatments. It should not be used to choose or start medication without an assessment by a qualified healthcare professional.
Why Identifying the Type of STI Matters
Bacterial STIs are generally treated with antibiotics. Examples include chlamydia, gonorrhoea and syphilis. When the correct antibiotic is used for the appropriate length of time, these infections can usually be cured.
Viral STIs require a different approach. Antiviral medicines can suppress viruses such as herpes, HIV and hepatitis B, but they do not necessarily remove the virus completely. Hepatitis C is an important exception because modern direct acting antiviral combinations can cure most infections.
Trichomoniasis is caused by a protozoan parasite and is treated with antiprotozoal medication. Pubic lice and scabies are external parasite infestations and require topical or oral medicines designed to kill the lice or mites.
Taking the wrong type of medicine will not treat the infection. For example, antibiotics will not cure herpes, HIV or HPV, and penicillin will not treat Mycoplasma genitalium because this organism does not have the cell wall that penicillin normally targets.
Chlamydia: Antibiotic Treatment
Chlamydia is caused by the bacterium Chlamydia trachomatis. It can affect the cervix, urethra, rectum, throat and, in some cases, the eyes.
Doxycycline is commonly recommended as the first-choice antibiotic for uncomplicated chlamydia in nonpregnant adults. It is generally more reliable than single dose azithromycin, particularly for rectal infections. Azithromycin or another appropriate antibiotic may still be selected when doxycycline is unsuitable, including in certain pregnancy or adherence situations.
The treatment decision should consider the site of infection. A medicine that performs reasonably well for genital chlamydia may not be equally effective for rectal infection. Patients should also avoid sexual contact until treatment has been completed, the recommended waiting period has passed and their partners have been treated.
Gonorrhoea: A Cephalosporin Antibiotic
Gonorrhoea is caused by Neisseria gonorrhoeae. It may infect the genitals, rectum, throat or eyes.
The main recommended treatment for uncomplicated gonorrhoea is an injection of ceftriaxone, which belongs to the cephalosporin family of antibiotics. Gonorrhoea has developed resistance to several medicines that were previously effective, including older penicillins, fluoroquinolones and, in many areas, azithromycin. This is why patients should not attempt to treat gonorrhoea using leftover antibiotics.
Older guidelines commonly recommended ceftriaxone together with azithromycin for every gonorrhoea infection. Routine dual treatment is no longer recommended in current CDC guidance. However, an additional antibiotic for chlamydia may be prescribed when chlamydia has not been ruled out.
Throat gonorrhoea can be particularly difficult to eliminate. A follow up test may therefore be required after treatment of a throat infection. Persistent symptoms or a positive follow up test require clinical review and may require culture and antibiotic-susceptibility testing.
Syphilis: Penicillin Treatment
Syphilis is caused by the bacterium Treponema pallidum. Treatment depends on the stage of infection and whether the brain, eyes, ears or nervous system may be involved.
Penicillin G is the preferred treatment for every stage of syphilis. Early syphilis is usually treated with an appropriate form of injectable penicillin, while late or unknown duration syphilis requires a longer treatment course. Neurosyphilis, ocular syphilis and otosyphilis require a different penicillin preparation that can reach the nervous system effectively.
Not all penicillin products are interchangeable. Using the wrong formulation may fail to treat the infection adequately. Penicillin is also the only treatment with established effectiveness for syphilis during pregnancy. A pregnant patient who reports a penicillin allergy may need allergy assessment or desensitisation before receiving treatment.
Blood tests must be repeated after treatment to confirm that the infection is responding appropriately. A person may remain antibody-positive after successful treatment, so clinicians assess changes in specific test levels rather than expecting every syphilis test to become negative.
Trichomoniasis: Antiprotozoal Medicine
Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis. Because it is not a bacterium or virus, it requires medication with antiprotozoal activity.
Metronidazole is the most commonly used treatment. Tinidazole is an alternative in some circumstances. The recommended treatment schedule may differ between men and women, and a longer course may be more effective for women than a single large dose.
Sexual partners usually require treatment at the same time, even when they do not have symptoms. Otherwise, the infection may pass back and forth between partners. Persistent infection may be caused by reinfection, incomplete treatment or, less commonly, resistance to the medicine.
Mycoplasma Genitalium: Sequential or Resistance-Guided Antibiotics
Mycoplasma genitalium, often shortened to Mgen or MG, can cause urethritis, cervicitis and pelvic inflammatory disease. It is one of the more complicated bacterial STIs to treat because antibiotic resistance is common.
This bacterium has no cell wall, so penicillins and cephalosporins do not work against it. A single dose of azithromycin is also no longer recommended because it can fail and contribute to further macrolide resistance.
Treatment commonly uses a two stage approach. Doxycycline is given first to reduce the amount of bacteria. It is then followed by another antibiotic chosen according to resistance results. A macrolide sensitive infection may be treated with an extended azithromycin course, while a macrolide resistant infection is commonly treated with moxifloxacin.
This is an example of sequential combination treatment: the medicines are taken one after the other rather than necessarily at the same time. Follow up testing may be required, especially when resistance guided treatment is unavailable or symptoms continue.
Lymphogranuloma Venereum: A Longer Chlamydia Treatment
Lymphogranuloma venereum, or LGV, is caused by specific types of Chlamydia trachomatis. It can cause genital ulcers, swollen lymph nodes or severe rectal inflammation.
Although ordinary chlamydia and LGV are caused by related bacteria, LGV normally requires a longer course of doxycycline. Severe swelling or abscess like lymph nodes may also require drainage in addition to antibiotics.
Patients treated for LGV should be tested for other STIs, including HIV, gonorrhoea and syphilis, and should be retested for chlamydia after treatment.
Chancroid: Antibiotic Treatment for Haemophilus Ducreyi
Chancroid is a genital ulcer infection caused by Haemophilus ducreyi. It is uncommon in many countries but may still be included in comprehensive sexual health PCR panels.
Several antibiotics can treat chancroid, including selected macrolides, cephalosporins or other appropriate antibacterial medicines. The precise choice depends on availability, pregnancy status, allergies and local resistance.
A person with a suspected chancroid ulcer should also be tested for herpes, syphilis and HIV because these conditions may cause similar symptoms or occur at the same time. The patient should be reassessed when ulcers do not begin improving after treatment.
Granuloma Inguinale: Extended Antibiotic Treatment
Granuloma inguinale, also known as donovanosis, is a rare genital ulcer infection caused by Klebsiella granulomatis.
Treatment usually involves an extended course of an antibiotic such as azithromycin or doxycycline. Treatment continues for several weeks and until the lesions have completely healed. Severe or slow-responding infections may require an additional antibiotic or specialist assessment.
Genital Herpes: Antiviral Medicine
Genital herpes is caused by herpes simplex virus type 1 or type 2. Antibiotics do not work because herpes is a viral infection.
Acyclovir, valacyclovir and famciclovir are commonly used antiviral medicines. These medicines do not remove herpes from the body, but they can reduce the severity and duration of an outbreak.
Episodic treatment is taken when symptoms begin. It is most effective when started during the early tingling or burning stage or within the first day after sores appear. Suppressive treatment is taken regularly to reduce the frequency of outbreaks and lower the risk of passing genital HSV-2 to a partner.
A first recognised genital herpes outbreak is normally treated even when symptoms appear mild because initial episodes can last longer or become more uncomfortable without treatment.
HIV: Combination Antiretroviral Therapy
HIV is treated with antiretroviral therapy, commonly known as ART. Unlike treatment for a simple bacterial STI, HIV treatment uses a combination of medicines that act on different stages of the virus’s life cycle.
Modern treatment may combine two or three active medicines in a single daily tablet. Using multiple active medicines prevents the virus from reproducing effectively and reduces the chance of drug resistance.
ART is recommended for everyone diagnosed with HIV and should begin as soon as possible. Treatment can reduce the amount of virus in the blood to an undetectable level, protect the immune system and prevent sexual transmission when viral suppression is maintained.
ART controls HIV but does not currently remove it from the body. Treatment therefore needs to be continued as prescribed, with regular viral-load monitoring.
HPV: Treatment for Warts or Abnormal Cells, Not the Virus
Human papillomavirus, or HPV, is a viral infection. There is no antibiotic or antiviral tablet that eliminates HPV itself. In many people, the immune system eventually makes the infection undetectable without specific treatment.
Medical treatment is directed at conditions caused by HPV. External genital warts may be treated with prescription creams, freezing, chemical application, electrosurgery, laser treatment or surgical removal. The most appropriate method depends on the number, size and location of the warts.
High-risk HPV types may cause abnormal or precancerous cells. These are managed through cervical or other appropriate screening and procedures that remove or destroy abnormal tissue.
HPV vaccination prevents many infections and HPV-related cancers, but it does not treat an HPV infection that is already present.
Hepatitis B: Monitoring and Antiviral Treatment When Needed
Hepatitis B is a viral infection affecting the liver. It can be transmitted through sex, blood exposure or from a pregnant person to their baby.
Most adults with acute hepatitis B recover without antiviral medicine and receive supportive care and monitoring. Chronic hepatitis B is different. Some people require long-term antiviral treatment, while others may initially need regular blood tests, viral-load testing, liver assessment and liver-cancer surveillance.
Tenofovir and entecavir are among the main oral antiviral medicines used for chronic hepatitis B. These medicines suppress viral replication and reduce the risk of liver damage, but they do not usually eliminate the virus completely. Not every person with chronic hepatitis B needs immediate medication, so treatment decisions depend on viral activity, liver inflammation, fibrosis, other medical conditions and pregnancy considerations.
Vaccination is the most effective way to prevent hepatitis B.
Hepatitis C: Curative Direct-Acting Antiviral Combinations
Hepatitis C is mainly transmitted through blood, although sexual transmission can occur, particularly when sexual activity involves blood exposure or when HIV or another STI is present.
Hepatitis C is treated with combinations of oral direct-acting antivirals, commonly shortened to DAAs. These medicines target different proteins that the virus needs to reproduce.
Unlike herpes, HIV and hepatitis B treatment, modern hepatitis C therapy can cure the infection. Current oral combinations cure more than 95% of people, often within approximately eight to twelve weeks.
The particular combination depends on factors including previous treatment, liver condition, kidney function, other medicines and whether hepatitis B or HIV is also present.
Hepatitis A: Supportive Care Rather Than Antiviral Medicine
Hepatitis A is mainly spread through the faecal–oral route, but it can also spread during sexual activity, particularly oral–anal contact.
There is no specific antiviral medicine for hepatitis A. Treatment focuses on rest, hydration, nutrition and medical monitoring. People should avoid unnecessary medicines or substances that could place additional stress on the liver.
Hepatitis A does not normally become a chronic infection. Vaccination is the most effective form of prevention and may also be recommended after certain recent exposures.
Pubic Lice: Medicines That Kill Lice
Pubic lice are insects that attach to coarse body hair and are commonly transmitted through close physical or sexual contact.
They are treated with lice-killing products containing medicines such as permethrin or pyrethrins with piperonyl butoxide. Alternative treatments may be considered when the initial product fails or local resistance is suspected.
Shaving the affected hair does not reliably eliminate pubic lice. Clothing, towels and bedding also need to be handled appropriately, and recent close contacts or sexual partners may require treatment.
Scabies: Topical or Oral Antiparasitic Treatment
Scabies is caused by mites that burrow into the skin. It can spread through prolonged skin contact, including sexual contact, although it is not exclusively sexually transmitted.
Permethrin cream is a common first-line treatment. Oral ivermectin may be used in certain patients or outbreaks, while severe crusted scabies may require both topical and oral therapy.
Close household and sexual contacts are often treated at the same time because symptoms may not begin until several weeks after the infestation was acquired. Itching can continue temporarily after successful treatment and does not always mean that the mites remain present.
Conditions Found on STI Panels That Are Not Always STIs
Comprehensive PCR panels sometimes detect organisms that can be present without causing disease. A positive result does not automatically mean that the person has a sexually transmitted infection or needs medication.
Bacterial Vaginosis and Gardnerella
Bacterial vaginosis is an imbalance in vaginal bacteria and may involve Gardnerella vaginalis together with several other organisms. It is associated with sexual activity but is not considered a simple infection caught from one specific partner.
Symptomatic bacterial vaginosis is commonly treated with metronidazole or clindamycin. However, detecting Gardnerella alone does not necessarily confirm bacterial vaginosis, and routine treatment of male partners is not generally recommended.
Candida
Candida causes vaginal thrush or vulvovaginal candidiasis. It is a fungal condition rather than a typical STI and is not usually acquired through sexual intercourse.
Symptomatic Candida infections are treated with antifungal medicines, commonly from the azole family. These may be used as topical creams or vaginal preparations, while oral fluconazole may be suitable for some nonpregnant patients.
Finding Candida in a person without symptoms is not normally an indication for treatment because Candida may be present naturally. Oral fluconazole is also not routinely recommended during pregnancy.
Ureaplasma and Mycoplasma Hominis
Ureaplasma parvum, Ureaplasma urealyticum and Mycoplasma hominis may be present in healthy people without causing symptoms. European STI experts have advised against routine testing and treatment of asymptomatic or symptomatic adults for these organisms because colonisation is common and unnecessary antibiotic use can contribute to resistance.
This is different from Mycoplasma genitalium, which is a recognised STI requiring specific treatment. A positive Ureaplasma or M. hominis result should therefore be interpreted together with symptoms, examination findings and other test results rather than treated automatically.
Group B Streptococcus
Group B streptococcus, or GBS, may naturally colonise the vagina or rectum. It is not generally classified as an STI. Its greatest clinical importance is during pregnancy because it can be passed to a baby during delivery.
A positive vaginal result outside pregnancy does not always require antibiotics. Treatment is normally based on pregnancy guidance or evidence that GBS is causing a genuine clinical infection.
When Is Combination Therapy Needed?
Combination therapy may be required when one medicine cannot adequately cover every likely organism.
A person with confirmed gonorrhoea may receive ceftriaxone plus treatment for chlamydia when chlamydia has not been excluded. Mycoplasma genitalium commonly requires sequential antibiotics because the first medicine reduces the bacterial load and the second clears the remaining infection.
Pelvic inflammatory disease is often treated with several antibiotics because it may involve gonorrhoea, chlamydia, anaerobic bacteria and other organisms simultaneously. Common regimens therefore combine a cephalosporin with doxycycline and metronidazole.
HIV is treated with combination antiretroviral therapy to block the virus at more than one stage and prevent resistance. Hepatitis C is similarly treated with direct-acting antiviral combinations that target different viral proteins.
When two separate STIs are found, each infection may need its own appropriate medicine. There is no single antibiotic that reliably treats every STI.
Why You Should Not Treat an STI Without Testing
Burning, discharge, itching, ulcers and pelvic discomfort can have many possible causes. Chlamydia, gonorrhoea, trichomoniasis, herpes, candidiasis, bacterial vaginosis and noninfectious irritation may produce overlapping symptoms.
Taking antibiotics before testing can produce temporary improvement without curing the real infection. It may also affect test results, cause side effects and encourage antimicrobial resistance.
Testing should use the correct sample for the site of exposure. A urine test may detect a genital infection but miss an infection in the throat or rectum. Fresh ulcers may require a swab, while HIV, syphilis and viral hepatitis are usually assessed with blood tests.
Do Sexual Partners Need Treatment?
Partner management depends on the infection. Partners of people with chlamydia, gonorrhoea, syphilis or trichomoniasis commonly need evaluation and treatment to prevent reinfection.
For herpes, HIV, HPV and hepatitis, partners may need testing, vaccination, preventative medication or counselling rather than the same medicine as the diagnosed person.
Sex should normally be avoided until the recommended treatment and waiting period have been completed, symptoms have resolved where applicable and partners have been appropriately managed.
The Bottom Line
The medicine used for an STI depends on what causes it. Bacterial infections such as chlamydia, gonorrhoea and syphilis require specific antibiotics. Trichomoniasis requires antiprotozoal medicine. Herpes, HIV and hepatitis B are controlled with antivirals, while hepatitis C can usually be cured with direct-acting antiviral combinations.
HPV treatment targets warts or abnormal cells rather than the virus itself. Pubic lice and scabies require medicines that kill external parasites. Other organisms found on sexual health panels, including Candida, Gardnerella, Ureaplasma and Group B streptococcus, do not always represent an STI or require treatment.
Accurate testing, correct medication selection, treatment of relevant partners and appropriate follow-up are all important. Anyone with STI symptoms, a positive test result or a recent exposure should speak with a healthcare professional rather than using leftover or unprescribed medication.