STD Prevention Pill: Does It Work?

Most people are familiar with STD protection methods, such as the HPV vaccination, abstinence, or condom use. However, clinical evidence suggests that taking an STD prevention pill can also prevent the transmission of HIV and some bacterial STIs. 

In recent years, various clinical trials evaluated the effectiveness of prophylactic medication that could proactively protect against bacterial and viral STI infections. The results of the initial studies are promising and give rise to various advances in STI prevention. This article looks at the effectiveness of STD prevention drugs in preventing infections.

Drugs to Take to Prevent STDs

Antibiotics available for the prevention of STDs fall under the following categories: 

  • HIV pre-exposure prophylaxis (HIV PrEP)
  • HIV post-exposure prophylaxis (HIV PEP)
  • STI pre-exposure prophylaxis (STI PrEP)
  • STI post-exposure prophylaxis (STI PEP)


HIV PreP is a daily pill for people who are not HIV positive but have a high risk of contracting an infection. Taking this medication can prevent the virus from spreading in the body after exposure, impairing the function of immune cells and developing into acquired immunodeficiency syndrome (AIDS). The most common HIV PrEP medications, or antiretrovirals, are emtricitabine and tenofovir. 

A daily dose of an HIV PrEP in pill form can reduce your risk of HIV infection through sexual intercourse by around 90%. The prevention pill reduces the risk of infection through needle sharing by around 70%. Patients who take the combination drug orally also have a lower risk of contracting a genital herpes infection. 

Clinical evidence suggests that taking an HIV PrEP combination can be safe for a pregnant woman. According to the Centers for Disease Control and Prevention’s health department for HIV Prevention, HIV pre-exposure prophylaxis also has no interactions with the birth control pill.


Those suspecting HIV exposure should seek medical care within 72 hours after a possible contact. If you are HIV-negative or unsure of your HIV status, your healthcare provider might prescribe an HIV post-exposure prophylaxis (HIV PEP). You might have been exposed to HIV if: 

  • You are a healthcare worker who sustained a needle-stick injury
  • You were the victim of sexual assault
  • You had sexual intercourse with someone who might be HIV-positive
  • You shared needles or equipment for the preparation of illicit drugs 

HIV PEP medications include raltegravir, emtricitabine, and tenofovir. If your healthcare provider prescribes this STD prevention pill, you need to take it every day for at least 28 days. Your doctor will likely recommend an HIV screening test or rapid STD test at specific times to determine which treatments you need. 

An HIV PEP is only suitable as an emergency precaution, and you shouldn’t take it to mitigate the risks of frequent HIV exposure. If your sexual partner is HIV-positive, your doctor will likely recommend the HIV pre-exposure prophylaxis. 


STI pre-exposure prophylaxis is an approach to mitigate the risk of infection among individuals with an ongoing risk of exposure to bacterial STIs. 

Doxycycline is the drug under investigation for STI PrEP. This antibiotic prevents bacteria from reproducing and has proven effective in treating chlamydia and syphilis. However, around 50% of gonorrhea infections are resistant to doxycycline. 

Medical care providers are apprehensive about prescribing antibiotics prophylactically as it can cause the patient to develop antimicrobial resistance. In other words, syphilis or chlamydia infections can become harder to treat with doxycycline.


The STI post-exposure prophylaxis approach involves the administration of doxycycline to patients after possible exposure to a bacterial STI. As with HIV, you need to undergo same-day STD testing and medical treatment within 72 hours after potential exposure. 

Clinical evidence suggests that STI PEP might effectively prevent syphilis or chlamydia infection, though doctors prefer symptom-based treatments for these infections. However, infections causing long-term damage often don’t present symptoms, and regular screening is critical if you are frequently at risk for exposure.  

STI prophylaxis is not suitable for the prevention of HIV infections. Consult your doctor to determine which STD prevention pill is right for you.

Antibiotic for STD Prevention: Recommended Dosage and Intake


According to the CDC, the U.S. Food and Drug Administration (FDA) approved three drugs for use as HIV PrEP. Drug combinations in a single tablet that the patient needs to take daily include: 

  • 200 mg emtricitabine and 300 mg tenofovir disoproxil fumarate (Truvada®)
  • 200 mg emtricitabine and 25 mg tenofovir alafenamide (Descovy®) 

Doctors often recommend an injectable HIV PrEP to patients suffering from kidney disease who can’t take oral PrEP. The injectable PrEP dosage is 600 mg cabotegravir (Apretude®) once every two months.


The CDC recommends a 3-drug, 28-day course regimen as HIV PEP. Your doctor will formulate a regimen that minimizes adverse effects while ensuring PEP efficacy. 

If you are a healthy adolescent or adult, the recommended regimen is: 

One tablet containing 300 mg tenofovir fumarate and 200 mg emtricitabine once per day


One tablet containing 400 mg raltegravir twice per day


One tablet containing 50 mg dolutegravir once per day

STI Prophylaxis

The research on the safety and efficacy of bacterial STI prophylaxes is not conclusive. However, available clinical evidence suggests that patients with an ongoing risk of contracting a bacterial STO should take 100 mg of doxycycline every day. 

Those suspecting potential exposure to a bacterial STI should take a 200 mg preferably within 24 hours, but no later than 72 hours, after the encounter. 

If you maintain a high-risk lifestyle, don’t take doxycycline as STI PrEP, as this approach increases your antibiotics resistance. However, in the event of potential exposure, taking doxycycline as STI PEP will reduce your risk of infection, though this dosage will likely not affect you in terms of antibiotics resistance. 

Educating yourself on the myths about STDs, undergoing regular testing, and taking the necessary safety precautions will go a long way towards protecting you against bacterial infection. If you believe that you might contract a bacterial STI, schedule an appointment with your doctor to ensure that you receive the correct STI prophylaxis dose.

Who Should Take These Anti-STD Drugs?


HIV PrEP is a viable precautionary measure for people with a high and ongoing risk of an HIV infection due to their sexual lifestyle, illicit drug use, or other factors. 

Consider taking HIV PrEP if you are a gay or bisexual man who: 

  • Has a partner who is HIV-positive
  • Has a partner who is unsure of their HIV status
  • Has a partner who has multiple sexual partners
  • Has multiple sexual partners
  • Regularly has unprotected anal sex
  • Has been diagnosed with an STI during the past six months 

Consider taking HIV PrEP if you are a heterosexual man or woman who: 

  • Has a partner who is HIV positive
  • Has a partner who is unsure of their HIV status
  • Has a partner who has multiple sexual partners
  • Has multiple sexual partners
  • Regularly has unprotected sex with someone who injects drugs
  • Regularly has unprotected sex with a bisexual man who is unsure of their HIV status 

You should also consider taking HIV PrEP if you inject drugs and share needles or drug preparation equipment. 

If you are a woman with an HIV-positive partner and want to get pregnant, taking HIV PrEP can protect you and your baby against HIV infection. Consult with your doctor to learn more about your options.


You should consider taking HIV PEP if you: 

  • Are HIV negative or unsure of your HIV status
  • Used an injection drug and shared needles or preparation equipment
  • Suffered a needle-stick injury in a healthcare facility
  • Are the victim of sexual assault
  • Had unprotected sex with someone who is HIV-positive or unsure of their HIV status 

Generally speaking, HIV can enter your body through your mouth, penis, rectum, vulva, or vaginal lining during sexual contact. Contact with infected blood can also result in an infection, though the risk of contracting HIV through a blood transfusion is low. 

Any person who suspects exposure to HIV should consider getting HIV PEP.


Individuals who have a high and ongoing risk of contracting a bacterial STI should consult with their doctor to determine if the STD prevention pill is the right option.


Catching an STD from a one-night stand is possible. Individuals who recently had unprotected sex with someone who is not their monogamous partner can consider taking STD PEP, ideally within 24 hours after the potential exposure.

Positive and Negative Effects of a Pill to Prevent STDs


Generally speaking, HIV PrEP and PEP are highly effective in preventing infections, provided that patients follow the recommended regimen and take their medications consistently. Most health insurance plans cover HIV PrEP and PEP, while other programs offer these free medications for free. 

The side effects from both HIV PrEP and PEP are generally not severe or debilitating, and you can expect them to get better over time. Most people report mild effects such as nausea while taking these prophylaxes. 

Another benefit of HIV prophylaxes is that they might be safe for pregnant women to take. However, if you are pregnant, planning to get pregnant, or breastfeeding, consult with your doctor to ensure that taking these STD prevention pills is safe for you and your baby. 

The benefits of STI PrEP and PEP are not as clear-cut as those of HIV PrEP and PEP. Clinicians are apprehensive about prescribing doxycycline, though these medications can benefit some individuals. For example, if you have contracted genital sores several times, STI PrEP might be a viable treatment to prevent this condition in the future.


Antibiotic Resistance

The most significant concern with STD prophylaxis is the increasing risk of antibiotic resistance. A patient becomes antibiotic-resistant when the targeted bacteria mutate, rendering the antibiotic ineffective.

Generally speaking, the more antibiotics a patient takes, the higher the risk that the bacteria will develop a drug-resistant strain. The patient can also pass this strain to others, posing a public health threat. 

While there is uncertainty about the risks of STI prophylaxis, evidence suggests that a broad rollout of these medications can cause antibiotic-resistant strains of syphilis and chlamydia to become more common. Other bacterial infections that are not STIs can also become more resistant to doxycycline.

Side Effects

Unlike HIV prophylaxis, taking STD prophylaxis can cause adverse effects, especially with prolonged use, which is another reason why clinicians are skeptical about prescribing STI PrEP. Most people tolerate the STD prevention pill well in the short term. However, some experience effects such as skin issues and gastrointestinal disturbances.

Latest Trends

The introduction of STD prevention pills to the market resulted in significant changes in sexual behaviors within some communities. For example, as antiretroviral medications enhanced patients’ quality of life and sexual health, infection rates among people with men who had sex with men (MSM) increased significantly. 

Most clinicians recognize doxycycline’s potential benefits as STI PrEP and PEP. However, antibiotic resistance remains a concern, and doctors will likely remain hesitant about prescribing these medications to their patients. 

If you are concerned about STIs, consult your doctor to learn more about the HIV prophylaxes and educate yourself about STIs such as gonorrhea, chlamydia, and syphilis. Condoms remain one of the most effective ways to protect yourself against STIs. Consider using polyurethane condoms if you are allergic to latex. 

Regular testing is also critical to protect your health, especially if you frequently have unprotected sex. If you are a man who regularly engages in sexual activity with multiple men, you should undergo testing for STIs every three months.


After reading this guide on the effectiveness of the STD prevention pill, we hope that you have all the information you need to make informed decisions about your health. At Rapid STD Testing, we offer testing solutions for all STIs. You can also order a 10-panel STD test to detect the presence of certain substances. Call our 24-hour line at (866) 872-1888 if you have questions.