DOXY-PEP

The medication should be taken quickly after unprotected sex, ideally within 24 hours, and no later than 72 hours (3 days).   

One dose of doxycycline is two 100 mg tablets, for a total of 200 mg of doxycycline.   

Only one dose (two tablets) should be taken per 24-hour period. If you have unprotected sex within 24 hours of taking the dose of doxycycline, you must take another dose 24 hours after the last dose.  

If you have sex for 2-3 days, you can take one dose on the last day of your sexual activity: there is no need to take one dose per day.  

The effectiveness of doxy-PEP is well documented, particularly through three major studies conducted among gay and bisexual men, men who have sex with men, and transgender women.    

These studies have shown that doxy-PEP reduces the incidence of chlamydia by 70 to 89% and syphilis by 73 to 87%.  
 

As for gonorrhoea, the reduction ranges from 17% to 57%, depending on the resistance of different strains of gonorrhoea to tetracyclines (a large class of antibiotics that includes doxy-PEP). This resistance means that doxy-PEP is mainly recommended to reduce the risk of contracting chlamydia and syphilis, and not for gonorrhoea.   

This resistance is monitored worldwide and in Quebec, and recommendations are updated as studies are conducted.  

At present, in Quebec, the interim advisory from the Ministère de la Santé states that:  

• Doxy-PEP is recommended for gay and bisexual men and men who have sex with men, as well as transgender women 

• Doxy-PEP is not yet recommended for cisgender women and transgender men

• • Its effectiveness for these two populations has not yet been officially demonstrated. Further studies will need to be published before an official recommendation can be issued.  

• Doxy-PEP is mainly recommended for people who:  

• • have had a bacterial STI (syphilis, chlamydia, gonorrhoea) in the last year or are at higher risk of contracting one 

• • are already taking PrEP for HIV   

• • do not always use condoms  

Note: Doxy-PrEP, i.e. doxycycline taken pre-exposure rather than post-exposure, is not yet officially recommended. This is because the studies on the subject had too few participants, making it impossible to generalize the results to a larger population. Further studies are needed.    

Although it is generally well tolerated, doxy-PEP can cause side effects:  

• Digestive system problems: diarrhea, nausea, vomiting, stomach pain, irritation of the esophagus 

• Photosensitivity, meaning your skin may react more strongly to sunlight.   

To avoid side effects, it is recommended that you:     

• Take doxy-PEP while sitting or standing with a large glass of water and wait 30 minutes before lying down.  

• Wait 24 hours after taking doxy-PEP before going out in the sun or to a tanning salon. If you do go out in the sun, apply sunscreen to protect your skin, which will be more sensitive than usual.  

Doxycycline is an antibiotic, so resistance to the drug may develop. Doxycycline is used to treat other health conditions such as acne or malaria. To date, studies have not reported any cases of resistance to doxycycline for syphilis or chlamydia. 

Usually, since doxy-PEP is prescribed to people who are at higher risk of contracting an STI, your doctor should test you for HIV and STIs. He or she should also talk to you about HIV PrEP to assess whether it might be right for you if you are not already taking it. After that, follow-ups and screenings should be every three months. 

Doxycycline is usually prescribed in packs of 30 tablets, which is enough for 15 doses, renewable twice. 

If you think doxy-PEP is right for you, you can get it by obtaining a prescription from any doctor who agrees to prescribe it. You can also talk to your family doctor, if you have one, or go to a sexual health clinic.   

If you don’t know where to turn, you can consult your local HIV or sexual health community organization for support and referrals. To find the organization closest to you, use the postal code search tool.  

Since doxy-PEP is a new prevention tool, your doctor may not be familiar with this strategy. You can use the guide created by the Community Research Centre (CBRC) to prepare for your appointment with a doctor who may not be familiar with doxy-PEP. 

Recent changes now allow pharmacists to prescribe doxy-PEP. Negotiations are still ongoing. If you are having difficulty obtaining doxy-PEP in your area, you can contact the Proxim pharmacy in the Village (Montreal), which offers remote consultations and deliveries throughout Quebec. 

Doxy-PEP is covered by RAMQ and most private insurance plans. If you don’t have drug insurance, the tablets cost about $15 for 15 uses (30 tablets). The pharmacy will add administrative fees to the bill. Consult your pharmacy for more information on costs and your insurance contract for more information on your coverage.  

Doxy-PEP: a medication to prevent syphilis, chlamydia, and gonorrhea (Community Research Centre (CBRC), March 2025)  

Interim advisory on post-exposure chemoprophylaxis for sexually transmitted bacterial infections with doxycycline (French) (MSSS, March 2025)