The study will determine tissue pharmacology of a single dose of doxycycline for sexually transmitted infection (STI) Post-exposure Prophylaxis (PEP).

To determine tissue pharmacology of a single dose of doxycycline for STI PEP, investigators at Emory University will collaborate with the Centers for Disease Control and Prevention (CDC) to conduct a clinical trial of up to 20 men who have sex with men (MSM) and women aged 18-59, with measurement of anti-retroviral drug and doxycycline concentrations in the rectum and vaginal regions.

Inclusion Criteria:

1. HIV negative person, who was assigned male or female at birth, who reports sex with another man in the last year and is in good general health
2. Aged 18-59 years
3. Not currently taking PrEP and no plans to initiate during study
4. Not currently taking PEP
5. Not currently taking doxycycline or other tetracycline-derived antibiotics and no plans to initiate during the study
6. Willing to use condoms consistently for the duration of the study
7. Able to provide informed consent in English
8. No plans for relocation in the next 4 months
9. Willing to undergo peripheral blood, urine, rectal or vaginal secretion collection, and a rectal or vaginal and cervical biopsy procedure
10. Willing to use study products as directed
11. Hepatitis B surface antigen (HBsAg) negative (screening lab test)
12. Creatinine clearance >60 ml/min

Exclusion Criteria:

1. Currently infected with hepatitis virus and/ or has liver disease

2. Current or chronic history of kidney disease or creatinine clearance (CrCl)<60 ml/min

3. Continued need for, or use during the 90 days prior to enrollment, of the following medications:

   1. Systemic immunomodulatory agents
   2. Supraphysiologic doses of steroids (short course steroids less than 7 days duration, allowable at the discretion of the investigators)
   3. Chemotherapy or radiation for treatment of malignancy
   4. Experimental medications, vaccines, or biologicals

4. Intent to use HIV antiretroviral pre/post-exposure prophylaxis (PrEP or PEP) during the study, outside of the study procedures

5. Intent to use doxycycline or other tetracycline-derived antibiotics during the course of the study, outside of the study procedures

6. Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study requirements

7. Not pregnant and no plans on getting pregnant throughout the duration of the study

8. Known allergic reaction to study drugs

Individual participant data that underlie the results published for this study (including text, tables, figures, and appendices), will be made available for sharing, after de-identification.

Data will be made available to researchers providing a methodologically sound proposal, beginning 9 months and ending 36 months following publication.

Proposals should be directed to colleen.kelley@emory.edu. To gain access, data requestors will need to sign a data access agreement.

Information on adverse events was collected beginning at the time of enrollment until the participants completed the study or withdrew from the study, up to 7 days.