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Enrolling by invitationNCT07755618Updated Sep 17, 2026

Characterization of Doxycycline Pharmacokinetics and Adherence

A Phase 1 interventional study of Single-Dose PK Phase - DR Group and Single-Dose PK Phase - IR Group in Sexually Transmitted Infection, sponsored by HIV Prevention Trials Network. Enrolling by invitation at 1 site in United States. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-17.

Sponsored by HIV Prevention Trials Network · Phase 1, Interventional, and Basic science

Phase
Phase 1
Study type
Interventional
Enrollment
16
Allocation
Randomized
Ages
18 Years to 65 Years
Sex
All
01

Study summary

The purpose of this study is to evaluate the effect of body changes on doxycycline concentrations for different dosing schedules. This study will involve a single dose phase and a multiple dose phase. Healthy individuals who do not have a sexually transmitted infection (STI), including acute (e.g., gonorrhea or chlamydia) or chronic (e.g., HIV or HSV-2) infections will be enrolled in this study. Study participants will be randomized to a dosing schedule in each phase and come to the research clinic throughout their time on study for sample collection. Study participants that choose to enroll in this study will be enrolled for about 37 days.

Read the detailed description

Doxycycline is a Food and Drug Administration (FDA) approved broad-spectrum, second-generation tetracycline antibiotic that is generally well-tolerated and has been widely used as primary prophylaxis for bacterial and parasitic infections. While the pharmacokinetics (PK) of doxycycline in blood are well-described, knowledge gaps exist with intermittent dosing and establishing adherence thresholds for prophylactic use. Further, the multi-compartment distribution of the doxycycline has not been extensively characterized. The purpose of this study will be to characterize pharmacologic parameters for daily and non-daily doxycycline use and establish adherence cutoffs for daily and non-daily use.

02

Conditions studied

  • Sexually Transmitted Infection

Keywords

  • Doxycycline
  • Pharmacokinetics
  • PK Sampling
03

Who can participate

Ages eligible
18 Years to 65 Years
Sexes eligible
All
Accepts healthy volunteers
Yes

Inclusion criteria

  1. Aged 18 to 65 years of age at the time of screening
  2. Able and willing to follow study participation requirements and provide informed consent to take part in the study
  3. Has a non-reactive/negative HIV test results at screening per applicable algorithm
  4. Has and is able to maintain a caput (head) of hair, that has not been chemically treated (defined as hair that has been bleached, permed, relaxed or dyed/colored) and is greater than one centimeter in length for the duration of the study
  5. For females of reproductive potential: Has a negative urine pregnancy test at screening

  6. For females of reproductive potential: Using at least two effective methods of contraception for at least 30 days (inclusive) prior to enrollment and intending to use two effective methods of contraception for the duration of study participation. It is strongly recommended that at least one barrier method (e.g. condoms) in addition to a hormonal contraception method be used. Examples of acceptable and effective methods include:

    1. Hormonal methods (oral pills, vaginal ring, depo, transdermal or implant)
    2. Intrauterine device (IUD) inserted at least 30 days prior to enrollment
    3. Surgical sterilization (of participant or partner(s)) including bilateral tubal ligation or vasectomized male partners
    4. Barrier methods (condom with/without spermicide, sponge, cervical cap, diaphragm)
    5. Self-identifies as having same sex partners
    6. Self-reported sexually abstinent as defined by abstaining from penile-vaginal intercourse for 90 days prior to enrollment and intending to remain sexually abstinent for the duration of study participation
  7. Has access to a smartphone and/or laptop and is able and willing to participate in video-based communications with study staff for directly observed dosing requirements
  8. In good general health, in the opinion of the investigator of record (IoR) or designee and has no medical condition that would adversely impact the conduct of the study (inclusive of self-reported conditions and/or those found upon medical history and examination or in available medical records). This includes, but is not limited to, having an intact, healthy gastrointestinal tract (without damage or functional disruption) and the ability to swallow pills

Exclusion criteria

Exclusion Criteria:

  1. Per participant report, planned or active use of any anticonvulsants at screening and an unwillingness to restrict use of certain medications (iron, antacids, etc.) for the duration of the study
  2. For females of reproductive potential: Pregnant or currently breastfeeding, or intends to become pregnant and/or breastfeed during the study

  3. Has any of the following laboratory abnormalities:

    1. An estimated calculated creatinine clearance (CrCl) less than 60 mL/min by the Cockcroft-Gault formula at screening
    2. Positive for hepatitis B surface antigen (HBsAg) at screening
    3. Has a Grade 2 or higher clinically significant laboratory abnormality as defined by The Division of AIDS Table for Grading the Severity of Adult and Pediatric Adverse Events, Corrected Version 2.1 - July 2017 (exception: a CrCl ≥ 60 mL/min at enrollment is permissible for enrollment)
  4. Per participant reported symptoms or clinical and/or laboratory diagnosis of an active pharyngeal, anorectal, or reproductive tract infection (RTI) requiring treatment at screening and enrollment per current US Centers for Disease Control and Prevention (CDC) guidelines (https://www.cdc.gov/std/treatment-guidelines/default.htm). Infections requiring treatment include Neisseria gonorrhoeae (GC), Chlamydia trachomatis (CT), syphilis, active herpes simplex virus (HSV) lesions, or symptomatic genital warts, chancroid, pelvic inflammatory disease (PID), bacterial vaginosis (BV), symptomatic vaginal candidiasis, and trichomoniasis
  5. Participation in research studies involving drugs, products, or vaccines within 30 days of the enrollment and for the duration of the study
  6. Has donated blood within 8 weeks of enrollment of approximately 1 pint (550 mL)
  7. Has a known allergy (adverse reaction) to any of the components of the study product, including known hypersensitivity to tetracycline-class antibiotics
  8. Prior use of doxycycline or any other tetracycline-class antibiotic within 30 days prior to enrollment
  9. Has an active infection that may be responsive to treatment with doxycycline or another tetracycline antibiotic
  10. Has evidence or history of any other condition (e.g., gastrectomy, seizure disorder), that, in the opinion of the IoR or designee, would make study participation unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving study objectives
04

Study design

Phase
Phase 1
Primary purpose
Basic science
Allocation
Randomized
Intervention model
Parallel assignment
Masking
None (open label)
Enrollment
16 participants (estimated)

Study arms

  • Experimental
    Single-Dose PK Phase- 200mg delayed release (DR) doxycycline tablet

    Participants in this arm will take one 200 mg delayed release (DR) doxycycline hyclate tablet

    Drug: Single-Dose PK Phase - DR Group

  • Experimental
    Multi-Dose PK Phase- daily dosing (every 24 hours)

    Participants randomized to this arm will receive one 200mg doxycycline hyclate delayed release (DR) tablet daily (every 24 hours) for 10 days.

    Drug: Multi-Dose PK Phase - Daily Group

  • Experimental
    Single Dose PK Phase- Two 100mg immediate release (IR) doxycycline tablets

    Participants in this arm will take two 100mg immediate release (IR) doxycycline hyclate tablets

    Drug: Single-Dose PK Phase - IR Group

  • Experimental
    Multi-dose PK Phase- Intermittent (every 72 hours) dosing

    Participants randomized to this arm will receive one 200mg doxycycline hyclate delayed release (DR) tablet intermittently (every 72 hours) for 10 days.

    Drug: Multi-Dose PK Phase - Intermittent Group

Interventions

  • DrugSingle-Dose PK Phase - DR Group

    One 200 mg doxycycline hyclate delayed release (DR) tablet

  • DrugSingle-Dose PK Phase - IR Group

    Two 100 mg doxycycline hyclate immediate-release (IR) tablets

  • DrugMulti-Dose PK Phase - Daily Group

    One 200 mg doxycycline hyclate delayed release (DR) tablet every 24 hours

  • DrugMulti-Dose PK Phase - Intermittent Group

    One 200 mg doxycycline hyclate delayed release (DR) tablet every 72 hours

05

What researchers measure

Primary outcomes

  1. Maximum observed plasma concentration (Cmax) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) plasma doxycycline hyclate Cmax (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  2. Minimum observed plasma concentration (Cmin) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) plasma doxycycline hyclate Cmin (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  3. Time to reach maximum plasma concentration (Tmax) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) plasma doxycycline hyclate Tmax (hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  4. Plasma half-life (T1/2) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) plasma doxycycline hyclate half-life (T1/2, hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  5. Area Under the Concentration-Time Curve in plasma From One to 336 Hours After Dosing (AUC0-24) of 200mg doxycycline hyclate.

    Median (IQR) plasma doxycycline hyclate area under the concentration time curve (AUC)0-inf (ng\*hr/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  6. Plasma concentrations at 24 hours (C24) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) plasma concentration at 24 hours post last dose (ng/mL units)

    Time frame: 24 hours post last dose of the multiple dose phase.

  7. Plasma concentrations at 48 hours (C48) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) plasma concentration at 48 hours post last dose (ng/mL units)

    Time frame: 48 hours post last dose of the multiple dose phase.

  8. Plasma concentrations at 72 hours (C72) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) plasma concentration at 72 hours post last dose (ng/mL units)

    Time frame: 72 hours post last doseof the multiple dose phase.

Secondary outcomes

  1. Number of gastrointestinal (GI)-related adverse events reported after doxycycline hyclate dosing during the multiple dose phase.

    Number of GI-related adverse events during 10 days of daily or intermittent doxycycline dosing

    Time frame: Study visit days 14-23

  2. Number of gastrointestinal (GI)-related adverse events reported after doxycycline hyclate dosing after the multiple dose phase.

    Number of GI-related adverse events for 14 days following final daily or intermittent dose (through the Final/Day 37 visit)

    Time frame: Up to 14 days post last dose.

  3. Maximum observed dried blood spot (DBS) concentration (Cmax) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) DBS doxycycline hyclate Cmax (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  4. Minimum observed dried blood spot (DBS) concentration (Cmin) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) DBS doxycycline hyclate Cmin (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  5. Time to reach maximum dried blood spot (DBS) concentration (Tmax) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) DBS doxycycline hyclate Tmax (hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  6. Dried blood spot (DBS) half-life (T1/2) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) DBS doxycycline hyclate half-life (T1/2, hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  7. Area Under the Concentration-Time Curve in dried blood spots (DBS) From One to 336 Hours After Dosing (AUC0-24) of 200mg doxycycline hyclate.

    Median (IQR) DBS doxycycline hyclate area under the concentration time curve (AUC)0-inf (ng\*hr/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  8. Maximum observed anorectal fluid concentration (Cmax) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) anorectal doxycycline hyclate Cmax (ng/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  9. Minimum observed anorectal fluid concentration (Cmin) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) anorectal doxycycline hyclate Cmin (ng/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  10. Time to reach maximum anorectal fluid concentration (Tmax) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) anorectal doxycycline hyclate Tmax (hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  11. Anorectal fluid half-life (T1/2) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) anorectal doxycycline hyclate half-life (T1/2, hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  12. Area Under the Concentration-Time Curve in anorectal fluid From One to 336 Hours After Dosing (AUC0-24) of 200mg doxycycline hyclate.

    Median (IQR) anorectal doxycycline hyclate area under the concentration time curve (AUC)0-inf (ng\*hr/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  13. Maximum observed vaginal fluid concentration (Cmax) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) vaginal doxycycline hyclate Cmax (ng/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  14. Minimum observed vaginal fluid concentration (Cmin) for 200mg doxycycline hyclate after a single dose.

    Median (IQR) vaginal doxycycline hyclate Cmin (ng/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  15. Time to reach maximum vaginal fluid concentration (Tmax) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) vaginal doxycycline hyclate Tmax (hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  16. Vaginal fluid half-life (T1/2) of 200mg doxycycline hyclate after a single dose.

    Median (IQR) vaginal doxycycline hyclate half-life (T1/2, hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  17. Area Under the Concentration-Time Curve in vaginal fluid From One to 336 Hours After Dosing (AUC0-24) of 200mg doxycycline hyclate.

    Median (IQR) vaginal doxycycline hyclate area under the concentration time curve (AUC)0-inf (ng\*hr/swab units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  18. Maximum observed pooled urine concentration (Cmax) for 200mg doxycycline hyclate after a single dose.

    Mean (95% CI) urine doxycycline hyclate Cmax (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  19. Minimum observed pooled urine concentration (Cmin) for 200mg doxycycline hyclate after a single dose.

    Mean (95% CI) urine doxycycline hyclate Cmin (ng/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  20. Time to reach maximum pooled urine concentration (Tmax) of 200mg doxycycline hyclate after a single dose.

    Mean (95% CI) urine doxycycline hyclate Tmax (hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  21. Pooled urine half-life (T1/2) of 200mg doxycycline hyclate after a single dose.

    Mean (95% CI) urine doxycycline hyclate half-life (T1/2, hours units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  22. Area Under the Concentration-Time Curve in urine From One to 336 Hours After Dosing (AUC0-24) of 200mg doxycycline hyclate.

    Mean (95% CI) urine doxycycline hyclate area under the concentration time curve (AUC)0-inf (ng\*hr/mL units)

    Time frame: 1, 2, 3, 4, 6, 8, 24, 72, 96, 168, 240, and 336 hours post dose.

  23. Dried blood spot (DBS) concentrations at 24 hours (C24) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) DBS concentration at 24 hours post last dose (ng/mL units)

    Time frame: 24 hours post last dose of the multiple dose phase.

  24. Dried blood spot (DBS) concentrations at 48 hours (C48) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) DBS concentration at 48 hours post last dose (ng/mL units)

    Time frame: 48 hours post last dose of the multiple dose phase.

  25. Dried blood spot (DBS) concentrations at 72 hours (C72) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) DBS concentration at 72 hours post last dose (ng/mL units)

    Time frame: 72 hours post last dose of the multiple dose phase.

  26. Urine concentrations at 24 hours (C24) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) urine concentration at 24 hours post last dose (ng/mL units)

    Time frame: 24 hours post last dose of the multiple dose phase.

  27. Urine concentrations at 48 hours (C48) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) urine concentration at 48 hours post last dose (ng/mL units)

    Time frame: 48 hours post last dose of the multiple dose phase.

  28. Urine concentrations at 72 hours (C72) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) urine concentration at 72 hours post last dose (ng/mL units)

    Time frame: 72 hours post last dose of the multiple dose phase.

  29. Anorectal fluid concentrations at 24 hours (C24) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) anorectal concentration at 24 hours post last dose (ng/swab units)

    Time frame: 24 hours post last dose of the multiple dose phase.

  30. Anorectal fluid concentrations at 48 hours (C48) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) anorectal concentration at 48 hours post last dose (ng/swab units)

    Time frame: 48 hours post last dose of the multiple dose phase.

  31. Anorectal fluid concentrations at 72 hours (C72) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) anorectal concentration at 72 hours post last dose (ng/swab units)

    Time frame: 72 hours post last dose of the multiple dose phase.

  32. Vaginal fluid concentrations at 24 hours (C24) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) vaginal concentration at 24 hours post last dose (ng/swab units)

    Time frame: 24 hours post last dose of the multiple dose phase.

  33. Vaginal fluid concentrations at 48 hours (C48) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) vaginal concentration at 48 hours post last dose (ng/swab units)

    Time frame: 48 hours post last dose of the multiple dose phase.

  34. Vaginal fluid concentrations at 72 hours (C72) post last dose of doxycycline following 10 days of daily or intermittent dosing.

    Median (IQR) vaginal concentration at 72 hours post last dose (ng/swab units)

    Time frame: 72 hours post last dose of the multiple dose phase.

06

Study locations

1 site
  • University of North Carolina at Chapel Hill
    Chapel Hill, North Carolina 27599, United States
07

References and documents

Study documents

  • Protocol and informed consent form · Jan 7, 2026

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: Yes — For studies within two years of primary objective(s) publication, de-identified individual participant data that underlie results in a publication, will be provided upon request. For studies more than two years from the primary objective(s) publication, de-identified datasets will be available upon request (Public Use Datasets).

Supporting information: Study protocol, Sap

08

Registry details

Key details

Study ID
NCT07755618
Lead sponsor
HIV Prevention Trials Network
Collaborators
National Institute of Allergy and Infectious Diseases (NIAID)
Responsible party
Sponsor
First posted
Aug 10, 2026
Start date
Aug 27, 2026
Primary completion
Jul 1, 2027 (estimated)
Completion
Jul 1, 2027 (estimated)
Last update
Sep 17, 2026

Study contacts

Mackenzie Cottrell, PharmD, MS
study chair · University of North Carolina, Chapel Hill
Mark Marzinke, PhD
study chair · Johns Hopkins University

Oversight

Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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