STI / STD Treatment — Evidence-Based Management Guide — Cost, Top Hospitals & Success Rates | MyMedicPlus

Sexually transmitted infections (STIs), previously termed sexually transmitted diseases (STDs), are caused by more than 30 bacteria, viruses, and parasites transmitted primarily through sexual contact. According to the World Health Organization, more than one million new STIs are acquired globally every day, making effective treatment and prevention a major public health priority.

STI management encompasses three overlapping goals: cure or suppression of the infection, prevention of onward transmission, and reduction of long-term sequelae such as pelvic inflammatory disease, infertility, neonatal infections, and cancer. Treatment strategies differ fundamentally depending on whether the causative agent is bacterial (curable with antibiotics), viral (manageable but rarely eradicated), or parasitic (treatable with antiparasitic agents).

Current treatment guidelines from the US Centers for Disease Control and Prevention (CDC), the European Centre for Disease Prevention and Control (ECDC), and the WHO provide evidence-graded recommendations that are regularly updated in response to emerging antimicrobial resistance (AMR) patterns. Gonorrhoea in particular has demonstrated progressive resistance to fluoroquinolones, azithromycin, and extended-spectrum cephalosporins, requiring stepwise escalation of first-line regimens.

Effective STI care integrates laboratory diagnosis, pathogen-appropriate pharmacotherapy, partner notification, condom counselling, vaccination where applicable, and screening for co-infections — particularly HIV in all patients presenting with an STI. Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) are now standard components of HIV prevention within sexual health services.

Modern sexual health clinics manage the full spectrum of STIs. The most clinically significant are summarised below.

• Chlamydia (Chlamydia trachomatis): The most reported bacterial STI globally. Often asymptomatic, it can cause urethritis, cervicitis, epididymo-orchitis, and pelvic inflammatory disease (PID) leading to infertility if untreated.
• Gonorrhoea (Neisseria gonorrhoeae): Second most common bacterial STI. Produces urethral discharge, dysuria, rectal and pharyngeal infection, and disseminated gonococcal infection in severe cases. Increasing AMR is the defining challenge of gonorrhoea management.
• Syphilis (Treponema pallidum): Staged infection (primary, secondary, latent, tertiary, congenital) with varied presentations from painless chancres to cardiovascular and neurosyphilis. Global rates have risen sharply since 2015.
• Genital Herpes (HSV-1 and HSV-2): Lifelong viral infection characterised by recurrent painful ulcers. HSV-2 seroprevalence is approximately 13% globally; HSV-1 is increasingly the cause of genital herpes in high-income countries.
• Human Immunodeficiency Virus (HIV): Without treatment, HIV destroys CD4+ T-cells leading to acquired immunodeficiency syndrome (AIDS). With modern antiretroviral therapy, life expectancy approaches that of the general population.
• Human Papillomavirus (HPV): The most common viral STI; persistent high-risk HPV strains (16, 18) cause approximately 99% of cervical cancers and also drive oropharyngeal, anal, vulval, vaginal, and penile cancers.
• Trichomonas vaginalis, Mycoplasma genitalium, pubic lice, scabies, hepatitis B and C are also managed within sexual health services.

STI treatment is indicated for any individual with a confirmed or clinically suspected sexually transmitted infection. The following groups warrant particular attention:

• Symptomatic individuals: Those presenting with genital ulcers, urethral or vaginal discharge, dysuria, pelvic pain, skin rashes consistent with secondary syphilis, or perianal symptoms.
• Asymptomatic contacts: Sexual partners of confirmed STI cases should receive contact tracing and syndromic or pathogen-directed treatment even in the absence of symptoms, as many bacterial STIs are asymptomatic.
• Pregnant women: Universal screening for syphilis, HIV, hepatitis B, chlamydia, and gonorrhoea in pregnancy is recommended by WHO to prevent congenital infections. Treatment dosing may differ from non-pregnant adults.
• People living with HIV: Immunocompromised individuals may experience atypical STI presentations, faster disease progression, and require careful drug-interaction assessment when adding STI treatments to existing antiretroviral regimens.
• Men who have sex with men (MSM) and transgender people: At increased risk for rectal chlamydia, gonorrhoea, syphilis, and HIV. Routine 3-site testing (genital, rectal, pharyngeal) is recommended every 3–6 months in sexually active MSM.
• Adolescents: Many jurisdictions permit minors to consent to STI testing and treatment without parental involvement to lower barriers to care.
• PrEP candidates: HIV-negative individuals at substantial ongoing risk of HIV acquisition (multiple partners, condomless sex, injecting drug use) should be offered PrEP as primary prevention.

Eligibility for specific antibiotic regimens must account for allergy history, renal and hepatic function, pregnancy status, and drug-drug interactions.

Treatment is pathogen-specific. Current evidence-based first-line regimens are summarised below.

• Chlamydia: Doxycycline 100 mg orally twice daily for 7 days is preferred per CDC 2021 and ECDC 2022 guidelines (superior efficacy to the previous azithromycin 1 g single-dose regimen in rectal infections). Azithromycin 1 g stat remains an option in pregnancy and where doxycycline compliance is uncertain. Levofloxacin 500 mg OD x 7 days is an alternative. Test-of-cure is not required unless pregnant or symptoms persist.
• Gonorrhoea: Ceftriaxone 500 mg IM single dose is the current first-line (CDC 2021; 1 g IM if weight >150 kg). Partner-notification and co-testing for chlamydia are essential. Oral cefixime 800 mg is a second-line option. Azithromycin combination is no longer recommended due to resistance. Pharyngeal gonorrhoea is harder to cure and requires the IM ceftriaxone dose.
• Syphilis: Benzathine benzylpenicillin G (BPG) remains the gold standard. Primary, secondary, and early latent syphilis: BPG 2.4 million units IM single dose. Late latent or unknown duration: BPG 2.4 MU IM weekly x 3 doses. Neurosyphilis: aqueous crystalline penicillin G 18–24 million units/day IV x 10–14 days (WHO 2020). Doxycycline 100 mg BD x 14–28 days is an alternative for penicillin-allergic patients (excluding pregnant women).
• Genital Herpes: Episodic therapy: aciclovir 400 mg TDS x 5 days or valaciclovir 500 mg BD x 3–5 days. Suppressive therapy (reduces recurrences by 70–80%): aciclovir 400 mg BD or valaciclovir 500 mg OD indefinitely. Suppressive therapy also reduces transmission risk by ~50%.
• HIV — Antiretroviral Therapy (ART): WHO-recommended first-line: TLD — tenofovir disoproxil fumarate 300 mg / lamivudine 300 mg / dolutegravir 50 mg once daily. The dolutegravir-based backbone offers a high genetic barrier to resistance and tolerability advantages over efavirenz. TDF/FTC/BIC and TDF/FTC/RPV are also first-line options in high-income settings. ART should be initiated as soon as possible after diagnosis, regardless of CD4 count.
• PrEP: TDF/FTC (Truvada or generic) once daily reduces HIV acquisition by >99% in adherent individuals. On-demand (2-1-1) regimen is effective in MSM. TAF/FTC (Descovy) is licensed in the US for non-receptive anal sex. Injectable cabotegravir monthly is an emerging long-acting PrEP option with superior efficacy.
• PEP: Three-drug ART (TDF/FTC + dolutegravir or raltegravir) started within 72 hours of potential exposure, continued for 28 days. PEP is most effective if started within 24 hours.
• HPV: No antiviral treatment exists for HPV infection itself. Genital warts are treated with topical imiquimod, podophyllotoxin, or cryotherapy. Cervical dysplasia is managed per colposcopy/LLETZ pathways. HPV vaccination (Gardasil-9; 9-valent) prevents 90% of cervical cancers and anogenital warts.

Timely and accurate STI treatment delivers substantial benefits at both individual and population levels.

• Cure of bacterial STIs: Chlamydia, gonorrhoea, and syphilis are curable with appropriate antibiotics, eliminating the infection entirely and preventing progression to chronic complications.
• Prevention of long-term sequelae: Treating chlamydia prevents PID, tubal-factor infertility, and ectopic pregnancy. Early syphilis treatment prevents cardiovascular syphilis and neurosyphilis. Gonorrhoea treatment prevents epididymo-orchitis and septic arthritis.
• Reduction of HIV transmission: The U=U (Undetectable = Untransmittable) principle, confirmed by the PARTNER and PARTNER2 studies (2016, 2019), demonstrates that people on effective ART with an undetectable viral load (HIV RNA <200 copies/mL) have a statistically zero risk of transmitting HIV sexually. ART initiation is therefore both a therapeutic and a public health intervention.
• Suppression of herpes recurrences: Suppressive antiviral therapy reduces outbreak frequency by approximately 70–80%, improves quality of life, and lowers partner transmission risk by 48% (Valaciclovir HSV Transmission Study, 2004).
• Cancer prevention through HPV vaccination: Gardasil-9 reduces the incidence of high-grade cervical, vulval, vaginal, and anal intraepithelial neoplasia by over 90% when administered prior to first exposure. Population-level data from Scotland and Australia demonstrate near-elimination of HPV-related cervical abnormalities in vaccinated cohorts.
• Interruption of transmission chains: Partner notification and empirical treatment of contacts rapidly reduces community prevalence and prevents reinfection of index cases.

While STI treatments are generally safe and well-tolerated, clinicians and patients should be aware of the following risks:

• Antibiotic side effects: Doxycycline commonly causes oesophageal irritation, photosensitivity, and gastrointestinal upset; patients should take it with a full glass of water and avoid prolonged sun exposure. Azithromycin can prolong the QT interval, particularly in patients on other QT-prolonging drugs. Ceftriaxone may cause anaphylaxis in patients with severe beta-lactam allergy (cross-reactivity with penicillin is less than 2%).
• Jarisch-Herxheimer reaction: Occurs in up to 50% of patients treated for syphilis within the first 24 hours — characterised by fever, chills, headache, and worsening of skin rashes. It is self-limiting but can precipitate preterm labour in pregnant women; patients should be warned and monitored.
• Antimicrobial resistance: Gonorrhoea demonstrates the most alarming resistance profile. Resistance to ciprofloxacin is now >90% in parts of Asia. Azithromycin resistance has reached clinically relevant levels globally. Emerging ceftriaxone-resistant strains (FC428 and related lineages) have been reported in Japan, the UK, and Australia, necessitating continued AMR surveillance and dual therapy research.
• ART side effects: Tenofovir disoproxil fumarate (TDF) is associated with renal tubular dysfunction and reduced bone mineral density with long-term use; TAF is renally safer. Dolutegravir is associated with modest weight gain and, in a minority, neuropsychiatric symptoms including insomnia and depression.
• Drug interactions: Dolutegravir is affected by antacids and rifampicin. PrEP with TDF should not be used in severe renal impairment (CrCl <30 mL/min). Many antiretrovirals interact with statins, antifungals, and rifampicins — always conduct a formal drug-interaction check.
• Reinfection risk: Treatment of the index patient without concurrent partner treatment leads to rapid reinfection. Expedited partner therapy (EPT), where legal, allows clinicians to prescribe antibiotics for partners without a clinic visit.

Post-treatment follow-up is essential for confirming cure, detecting reinfection, and monitoring for complications.

• Test of cure (TOC): Routinely recommended for gonorrhoea (NAAT at infected sites 2 weeks post-treatment), syphilis (RPR/VDRL at 3, 6, and 12 months — a 4-fold titre decline confirms treatment response), and in all pregnant women treated for any STI. TOC is not routinely required for uncomplicated chlamydia in non-pregnant adults unless symptoms persist.
• Partner notification (PN): Mandatory component of bacterial STI management. For chlamydia, partners from the past 6 months (or most recent partner if >6 months); gonorrhoea, past 3 months; syphilis, past 3 months for primary, 6 months for secondary, and 1 year for early latent. PN can be index-patient led (patient informs partners directly) or provider-led (health advisor contacts partners confidentially).
• HIV viral load monitoring: For people on ART, HIV viral load should be checked at baseline, at 3 months, and 6-monthly once undetectable. CD4 count monitoring is recommended in late presenters until CD4 exceeds 200 cells/mm³. All patients should undergo annual STI screening and assess whether PrEP or PEP has been used.
• Herpes recurrence review: Patients on suppressive therapy should be reviewed annually to reassess the need for continued treatment. Immunocompromised patients may require higher-dose or longer-duration antiviral therapy.
• HPV follow-up: Post-genital wart treatment review at 3–6 months. Cervical screening intervals depend on national programmes; HPV-vaccinated individuals may be eligible for less frequent screening according to emerging evidence.
• Routine retesting: Due to high reinfection rates, CDC recommends retesting for chlamydia and gonorrhoea 3 months after treatment (or at the next clinical encounter) in sexually active individuals.

The cost of STI treatment varies considerably depending on the infection, the setting, and the healthcare system.

• Bacterial STI antibiotics: In the public sector (NHS, US Title X clinics, WHO essential medicines), first-line antibiotics for chlamydia and gonorrhoea cost less than USD 10–30 per course when procured generically. Private sector pricing may be 5–10 times higher. Doxycycline generics are extremely low cost globally; ceftriaxone IM requires a clinical visit, adding facility charges.
• Syphilis treatment: Benzathine penicillin G (BPG) is inexpensive but has experienced periodic global shortages. In high-income settings, a complete syphilis treatment course may cost USD 50–200 including clinic attendance. Neurosyphilis requires inpatient IV penicillin, significantly increasing costs.
• HIV antiretrovirals: Branded TDF/3TC/DTG (Triumeq or Dovato) can cost USD 15,000–25,000 per year in high-income countries without insurance. Generic TLD produced under voluntary licensing for low- and middle-income countries costs under USD 75 per patient per year. In countries with universal health coverage, ART is often provided free at the point of care.
• PrEP costs: Generic TDF/FTC is available in many countries for under USD 100/year. In the US, branded Truvada previously cost USD 2,000/month; Gilead Sciences now provides generic access and patient assistance programmes. The injectable cabotegravir PrEP option (Apretude) costs significantly more but offers superior adherence.
• HPV vaccination: Gardasil-9 costs approximately USD 150–250 per dose (3-dose series for adults; 2-dose series for adolescents under 15) in private markets. Many national immunisation programmes provide it free to target age groups.
• Testing and diagnosis: NAAT testing for chlamydia/gonorrhoea costs USD 30–150 per test in private labs. STI panel testing (4–6 infections) can cost USD 200–500 privately. Free or low-cost testing is available at sexual health clinics, community health centres, and through self-sampling postal services in many countries.

Treatment of established infection is only one component of comprehensive STI management. Prevention strategies are equally critical and should be discussed at every clinical encounter.

• Condom use: Consistent and correct use of male latex or polyurethane condoms reduces the risk of chlamydia, gonorrhoea, and HIV transmission by 80–95%. Female condoms are equally effective when used correctly. Condoms offer partial but not complete protection against skin-to-skin transmitted infections (herpes, HPV, syphilis).
• Pre-exposure prophylaxis (PrEP): Daily oral TDF/FTC reduces HIV acquisition by over 99% in high-adherence populations (iPrEx trial, Partners PrEP, TDF2). PrEP should be offered to all individuals at substantial HIV risk, including MSM, transgender women, serodiscordant couples, sex workers, and people who inject drugs.
• Post-exposure prophylaxis (PEP): Three-drug ART initiated within 72 hours of potential HIV exposure and continued for 28 days provides approximately 80% risk reduction. PEP services should be available 24/7 through emergency departments or sexual health services.
• Vaccination: HPV vaccination (Gardasil-9) prevents 9 HPV types responsible for 90% of anogenital cancers and warts. Hepatitis B vaccination (3-dose series) prevents sexual transmission of HBV. HAV vaccination is recommended for MSM and people with chronic liver disease. Mpox vaccination (MVA-BN/JYNNEOS) is recommended for individuals at risk of mpox through sexual networks.
• Behavioural interventions: Sexual health counselling, mutual monogamy, reduction in number of concurrent partners, and regular STI screening for sexually active individuals at risk contribute significantly to population-level STI control.
• Doxycycline post-exposure prophylaxis (Doxy-PEP): Doxycycline 200 mg taken within 72 hours of unprotected sexual exposure has demonstrated 65–88% reduction in bacterial STIs (chlamydia, gonorrhoea, syphilis) in MSM and transgender women in the DOXYVAC and DoxyPEP trials (2022–2023). CDC issued interim guidance supporting Doxy-PEP in 2023 for adults who have had at least one bacterial STI in the past year.