What is the standard dose and number of pills given for Doxycycline (Doxycycline) post-exposure prophylaxis for Sexually Transmitted Infections (STI)?

From the Guidelines

The standard dose for doxycycline post-exposure prophylaxis (PEP) for sexually transmitted infections (STIs) is 200 mg taken as a single dose within 72 hours after sexual contact, as recommended by the CDC 1. This typically involves taking two 100 mg pills at once. Doxycycline PEP is primarily effective against bacterial STIs including chlamydia, syphilis, and some strains of gonorrhea, though it's essential to note that it doesn't protect against viral STIs like HIV, herpes, or HPV. The medication works by inhibiting bacterial protein synthesis, preventing bacteria from reproducing. For optimal effectiveness, the dose should be taken as soon as possible after exposure, ideally within 24 hours, though benefits may still occur up to 72 hours post-exposure. Some key points to consider when prescribing doxycycline PEP include:

• Counseling on the benefits and potential harms of doxycycline PEP, including known side effects such as photosensitivity, esophagitis, and gastrointestinal intolerance 1.
• Guidance on actions to take to mitigate potential side effects, including taking doxycycline on a full stomach with a full glass of liquid and avoiding lying down for 1 hour after taking doxycycline to prevent esophagitis 1.
• The need to take doxycycline exactly as individually prescribed and only for its intended purpose, with a maximum dose of 200 mg per 24 hours 1.
• Potential drug interactions, including the importance of separating the doxycycline dose by at least 2 hours from dairy products, antacids, and supplements that contain calcium, iron, magnesium, or sodium bicarbonate 1. Recent studies have shown that doxycycline PEP can reduce the incidence of chlamydia by 70% to 88% and early syphilis by 73% to 87% 1. However, effects on gonorrhea are less consistent, presumably due to high rates of tetracycline resistance. Dosing may be taken as frequently as daily, and this intervention should be considered as part of a comprehensive sexual health approach, including risk reduction counseling, STI screening and treatment, recommended vaccination, and linkage to HIV PrEP, HIV care, or other services as appropriate 1.

From the FDA Drug Label

Adults: The usual dose of oral doxycycline is 200 mg on the first day of treatment (administered 100 mg every 12 hours) followed by a maintenance dose of 100 mg/day Inhalational anthrax (post-exposure): ADULTS: 100 mg of doxycycline, by mouth, twice a day for 60 days.

The standard dose for doxycycline post-exposure prophylaxis is 100 mg, twice a day. However, the provided text does not explicitly mention the use of doxycycline for STI post-exposure prophylaxis. For STIs, the text mentions various doses for different infections, such as:

• Uncomplicated gonococcal infections: 100 mg, twice a day for 7 days
• Uncomplicated urethral, endocervical, or rectal infection caused by Chlamydia trachomatis: 100 mg, twice a day for 7 days
• Nongonococcal urethritis (NGU) caused by C. trachomatis or U. urealyticum: 100 mg, twice a day for 7 days 2

From the Research

Doxycycline Post-Exposure Prophylaxis for STI

• The standard dose of doxycycline for post-exposure prophylaxis is 200 mg taken within 72 hours after condomless sex 3.
• However, it is noted that some individuals have used a dosage other than the 200-mg dose shown to be effective 4.
• The number of pills given for doxycycline post-exposure prophylaxis is not explicitly stated in the provided studies, but it can be inferred that a single dose of 200 mg is typically used.

Effectiveness and Usage

• Doxycycline post-exposure prophylaxis has been shown to be effective in preventing bacterial sexually transmitted infections (STIs) among men who have sex with men and transgender women 5, 6.
• The effectiveness of doxycycline post-exposure prophylaxis in preventing STIs among cisgender women is still unclear, with one study showing no significant difference in incidence compared to standard care 3.
• The use of doxycycline post-exposure prophylaxis is highly variable, and its effectiveness can depend on factors such as adherence to the prescribed dosage and timing 6, 4.

Resistance and Safety

• There is concern about the potential risk of promoting antimicrobial resistance (AMR) with the use of doxycycline post-exposure prophylaxis 7.
• However, studies have shown that doxycycline post-exposure prophylaxis has little or no risk of promoting the spread of AMR 5, 6.
• No serious adverse events have been reported to be related to doxycycline use in the context of post-exposure prophylaxis 3.