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�Doxy-PEP for STI Prevention

Resident lectures 07/11/2024

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What is Doxy-PEP?

  • An approach to decrease acquisition and transmission of bacterial sexually transmitted infections (STIs) in cisgender men who have sex with men (MSM) and transgender women who have sex with men

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  • Used to decrease risk of chlamydia, gonorrhea, and syphilis

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Background

  • Incidence of chlamydia, gonorrhea, and syphilis is increasing in the United States
  • Doxycycline (doxy) has been used as both PrEP and PEP for malaria and lyme disease
  • Doxy is well absorbed and tolerated, with a half-life of 12 hours
  • Doxy is used as first line treatment for chlamydia, as an alternative treatment for syphilis in non-pregnant individuals who have a penicillin allergy or when penicillin is unavailable, and has been effective as treatment for gonorrhea, although there is elevated antimicrobial resistance
  • A 2015 randomized controlled study of MSM on HIV PrEP taking daily doxy hyclate 100mg showed a 73% reduction in rates of chlamydia and gonorrhea

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Background

  • Since then, 3 large randomized controlled trials among MSM and transgender women who have sex with men taking doxy 200mg after sex have shown significant reductions in STI acquisition
  • The New England Journal of Medicine DoxyPEP study found a 65% overall reduction in new STIs among those who took doxy 200mg within 24-72 hours after condomless sex

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  • The French IPERGAY study as well as the ANRS DOXYVAC study both showed similar results

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Cisgender Women and Transgender Men

  • The only trial conducted among cisgender women was an open-label 1:1 randomized controlled trial of doxy 200mg within 72h of sex vs standard of care conducted between 2020 and 2022 in 449 cisgender women in Kenya
  • No significant reduction was found in chlamydia or gonorrhea
  • Efficacy against syphilis could not be evaluated due to only 2 cases of early syphilis during the trial
  • Analysis done on hair samples of the women studied showed that non-adherence may have been an issues, but no further studies on cisgender women or transgender men have yet been published
  • Thus, doxy-PEP is not currently recommended for use in cisgender women or transgender men, nor in gender diverse/nonbinary people assigned female at birth

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Potential Harms

  • Side effects – Most patients have little or no side effects
    • Photosensitivity
    • Abdominal pain
    • Diarrhea
    • Pain/discomfort in throat or chest after swallowing meds
  • Weight Gain
    • Some studies show that long-term use of doxycycline for other conditions may result in abnormal weight gain, although this was not seen in the doxy-PEP study

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Potential Harms

  • Antibiotic Resistance
    • Doxy-PEP could lead to increased antibiotic resistance in the future, both at the individual and population levels
    • This includes risk of increased resistance to the bacteria that cause gonorrhea, staph infections, pneumonia, Mycoplasma genitalium, as well as microorganisms in intestinal flora
    • There is no or low known risk of increased resistance for the bacteria that cause chlamydia and syphilis
    • Thus far, we have not seen resistance with patients taking long term doxy for malaria or acne

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Potential Harms

  • Microbiome Changes
    • Doxy-PEP may result in changes in the microbiome—microbes, such as bacteria, fungi, viruses that naturally live on our bodies and inside us— some of which are important for general health
    • Some studies unrelated to doxy-PEP have linked changes in the microbiome to chronic illnesses, such as diabetes and inflammatory bowel disease
    • We do not know whether doxy-PEP may change microbiomes or the health impact of these potential changes.

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Potential benefits

  • Using doxy-PEP can be empowering, allowing patients to take charge of their sexual health and reduce feelings of anxiety and stigma about STIs
  • Doxy-PEP might decrease how much STIs there are in the population as a whole, though this will depend on how many people use doxy-PEP

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  • The CDC issued clinical guidelines for Doxy-PEP in 06/2024:

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Who Should Consider Doxy-PEP?

  • People with a penis (cisgender men and transgender women) who have sex with men AND
    • History of a bacterial STI in the past year
    • Condomless oral or anal intercourse with more than 1 partner with a penis in the past year
  • Generally offered in conjunction with PrEP for HIV
  • Can be offered with shared decision making in cisgender men who engage in sex with multiple partners assigned female at birth and have had a bacterial STI in the past year

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Recommendations

  • Take a comprehensive sexual history as part of routine care for all patients
  • Provide doxy-PEP based on shared decision making with the patient, providing information on effectiveness, potential risks and benefits, as well as other options to prevent STIs
  • Consider prescribing doxy-PEP on an episodic basis for patients who anticipate periods when their STI risk may be higher (eg attendance at group sex parties)

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Dosing

  • Single dose of doxy (hyclate or monohydrate immediate release) 200mg as soon as possible and no later than 72 hours after condomless sex (oral, anal, or vaginal)
  • Can be taken as often as daily depending on sexual activity, but no more than 200mg per 24 hour period
  • Should be taken with a full glass of water and avoid laying down for 30 minutes after ingestion to avoid esophagitis
  • Separate taking doxy by two hours from taking calcium, antacids, iron, magnesium, sodium bicarbonate, and dairy products
  • There is no standard number of pills to prescribe, the number given should be decided based on usual sexual activity through shared decision making

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Monitoring/Follow up

  • STI screening (HIV, RPR, up to 3 site testing for GC/CT) at initial visit and at 3-6 month follow up visits
  • No routine lab monitoring needed
  • If diagnosed with an STI while on doxy-PEP, treat according to CDC STI treatment guidelines
  • If not already taking it, offer HIV PrEP!
  • Use ICD 10 code Z20.2 (contact with and (suspected) exposure to infections with a predominately sexual mode of transmission

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Key Points for Patient Education

  • Doxy-PEP is not 100% effective and is not effective against all STIs
  • For cisgender men and transgender women at risk of STIs who are engaged in routine sexual healthcare, Doxy-PEP reduced the likelihood of STI diagnosis by >50%
  • Evaluation by a clinician after a possible STI exposure is necessary to determine if treatment is needed
  • Review adverse effects
  • Discuss STI screening every 3-6 months
  • Discuss HIV PrEP

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Patient Education Handout

   

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