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Background: Doxycycline postexposure prophylaxis (PEP) has been shown to prevent sexually transmitted infections (STIs) among cisgender men and transgender women, but data from trials involving cisgender women are lacking., Methods: We conducted a randomized, open-label trial comparing doxycycline PEP (doxycycline hyclate, 200 mg taken within 72 hours after condomless sex) with standard care among Kenyan women 18 to 30 years of age who were receiving preexposure prophylaxis against human immunodeficiency virus (HIV). The primary end point was any incident infection with Chlamydia trachomatis , Neisseria gonorrhoeae , or Treponema pallidum . Hair samples were collected quarterly for objective assessment of doxycycline use., Results: A total of 449 participants underwent randomization; 224 were assigned to the doxycycline-PEP group and 225 to the standard-care group. Participants were followed quarterly over 12 months. A total of 109 incident STIs occurred (50 in the doxycycline-PEP group [25.1 per 100 person-years] and 59 in the standard-care group [29.0 per 100 person-years]), with no significant between-group difference in incidence (relative risk, 0.88; 95% confidence interval [CI], 0.60 to 1.29; P = 0.51). Among the 109 incident STIs, chlamydia accounted for 85 (78.0%) (35 in the doxycycline-PEP group and 50 in the standard-care group; relative risk, 0.73; 95% CI, 0.47 to 1.13). No serious adverse events were considered by the trial investigators to be related to doxycycline, and there were no incident HIV infections. Among 50 randomly selected participants in the doxycycline-PEP group, doxycycline was detected in 58 of 200 hair samples (29.0%). All N. gonorrhoeae -positive isolates were resistant to doxycycline., Conclusions: Among cisgender women, the incidence of STIs was not significantly lower with doxycycline PEP than with standard care. According to hair-sample analysis, the use of doxycycline PEP among those assigned to receive it was low. (Funded by the National Institutes of Health; dPEP ClinicalTrials.gov number, NCT04050540.)., (Copyright © 2023 Massachusetts Medical Society.)

Background: Interventions to reduce sexually transmitted infections (STIs) among men who have sex with men (MSM) are needed., Methods: We conducted an open-label, randomized study involving MSM and transgender women who were taking preexposure prophylaxis (PrEP) against human immunodeficiency virus (HIV) infection (PrEP cohort) or living with HIV infection (persons living with HIV infection [PLWH] cohort) and who had had Neisseria gonorrhoeae (gonorrhea), Chlamydia trachomatis (chlamydia), or syphilis in the past year. Participants were randomly assigned in a 2:1 ratio to take 200 mg of doxycycline within 72 hours after condomless sex (doxycycline postexposure prophylaxis) or receive standard care without doxycycline. STI testing was performed quarterly. The primary end point was the incidence of at least one STI per follow-up quarter., Results: Of 501 participants (327 in the PrEP cohort and 174 in the PLWH cohort), 67% were White, 7% Black, 11% Asian or Pacific Islander, and 30% Hispanic or Latino. In the PrEP cohort, an STI was diagnosed in 61 of 570 quarterly visits (10.7%) in the doxycycline group and 82 of 257 quarterly visits (31.9%) in the standard-care group, for an absolute difference of -21.2 percentage points and a relative risk of 0.34 (95% confidence interval [CI], 0.24 to 0.46; P<0.001). In the PLWH cohort, an STI was diagnosed in 36 of 305 quarterly visits (11.8%) in the doxycycline group and 39 of 128 quarterly visits (30.5%) in the standard-care group, for an absolute difference of -18.7 percentage points and a relative risk of 0.38 (95% CI, 0.24 to 0.60; P<0.001). The incidences of the three evaluated STIs were lower with doxycycline than with standard care; in the PrEP cohort, the relative risks were 0.45 (95% CI, 0.32 to 0.65) for gonorrhea, 0.12 (95% CI, 0.05 to 0.25) for chlamydia, and 0.13 (95% CI, 0.03 to 0.59) for syphilis, and in the PLWH cohort, the relative risks were 0.43 (95% CI, 0.26 to 0.71), 0.26 (95% CI, 0.12 to 0.57), and 0.23 (95% CI, 0.04 to 1.29), respectively. Five grade 3 adverse events and no serious adverse events were attributed to doxycycline. Of the participants with gonorrhea culture available, tetracycline-resistant gonorrhea occurred in 5 of 13 in the doxycycline groups and 2 of 16 in the standard-care groups., Conclusions: The combined incidence of gonorrhea, chlamydia, and syphilis was lower by two thirds with doxycycline postexposure prophylaxis than with standard care, a finding that supports its use among MSM with recent bacterial STIs. (Funded by the National Institutes of Health; DoxyPEP ClinicalTrials.gov number, NCT03980223.)., (Copyright © 2023 Massachusetts Medical Society.)

Background: The appropriate antibiotic treatment for severe scrub typhus, a neglected but widespread reemerging zoonotic infection, is unclear., Methods: In this multicenter, double-blind, randomized, controlled trial, we compared the efficacy of intravenous doxycycline, azithromycin, or a combination of both in treating severe scrub typhus. Patients who were 15 years of age or older with severe scrub typhus with at least one organ involvement were enrolled. The patients were assigned to receive a 7-day course of intravenous doxycycline, azithromycin, or both (combination therapy). The primary outcome was a composite of death from any cause at day 28, persistent complications at day 7, and persistent fever at day 5., Results: Among 794 patients (median age, 48 years) who were included in the modified intention-to-treat analysis, complications included those that were respiratory (in 62%), hepatic (in 54%), cardiovascular (in 42%), renal (in 30%), and neurologic (in 20%). The use of combination therapy resulted in a lower incidence of the composite primary outcome than the use of doxycycline (33% and 47%, respectively), for a risk difference of -13.3 percentage points (95% confidence interval [CI], -21.6 to -5.1; P = 0.002). The incidence with combination therapy was also lower than that with azithromycin (48%), for a risk difference of -14.8 percentage points (95% CI, -23.1 to -6.5; P<0.001). No significant difference was seen between the azithromycin and doxycycline groups (risk difference, 1.5 percentage points; 95% CI, -7.0 to 10.0; P = 0.73). The results in the per-protocol analysis were similar to those in the primary analysis. Adverse events and 28-day mortality were similar in the three groups., Conclusions: Combination therapy with intravenous doxycycline and azithromycin was a better therapeutic option for the treatment of severe scrub typhus than monotherapy with either drug alone. (Funded by the India Alliance and Wellcome Trust; INTREST Clinical Trials Registry-India number, CTRI/2018/08/015159.)., (Copyright © 2023 Massachusetts Medical Society.)

Background: Rectal chlamydia is a common bacterial sexually transmissible infection among men who have sex with men. Data from randomized, controlled trials are needed to guide treatment., Methods: In this double-blind trial conducted at five sexual health clinics in Australia, we randomly assigned men who have sex with men and who had asymptomatic rectal chlamydia to receive doxycycline (100 mg twice daily for 7 days) or azithromycin (1-g single dose). Asymptomatic chlamydia was selected as the trial focus because more than 85% of men with rectal chlamydia infection are asymptomatic, and clinical guidelines recommend a longer treatment course for symptomatic infection. The primary outcome was a negative nucleic acid amplification test for rectal chlamydia (microbiologic cure) at 4 weeks., Results: From August 2016 through August 2019, we enrolled 625 men (314 in the doxycycline group and 311 in the azithromycin group). Primary outcome data were available for 290 men (92.4%) in the doxycycline group and 297 (95.5%) in the azithromycin group. In the modified intention-to-treat population, a microbiologic cure occurred in 281 of 290 men (96.9%; 95% confidence interval [CI], 94.9 to 98.9) in the doxycycline group and in 227 of 297 (76.4%; 95% CI, 73.8 to 79.1) in the azithromycin group, for an adjusted risk difference of 19.9 percentage points (95% CI, 14.6 to 25.3; P<0.001). Adverse events that included nausea, diarrhea, and vomiting were reported in 98 men (33.8%) in the doxycycline group and in 134 (45.1%) in the azithromycin group (risk difference, -11.3 percentage points; 95% CI, -19.5 to -3.2)., Conclusions: A 7-day course of doxycycline was superior to single-dose azithromycin in the treatment of rectal chlamydia infection among men who have sex with men. (Funded by the National Health and Medical Research Council; RTS Australian New Zealand Clinical Trials Registry number, ACTRN12614001125617.)., (Copyright © 2021 Massachusetts Medical Society.)

Background: The treatment of persistent symptoms attributed to Lyme disease remains controversial. We assessed whether longer-term antibiotic treatment of persistent symptoms attributed to Lyme disease leads to better outcomes than does shorter-term treatment., Methods: In a randomized, double-blind, placebo-controlled trial conducted in Europe, we assigned patients with persistent symptoms attributed to Lyme disease--either related temporally to proven Lyme disease or accompanied by a positive IgG or IgM immunoblot assay for Borrelia burgdorferi--to receive a 12-week oral course of doxycycline, clarithromycin plus hydroxychloroquine, or placebo. All study groups received open-label intravenous ceftriaxone for 2 weeks before initiating the randomized regimen. The primary outcome measure was health-related quality of life, as assessed by the physical-component summary score of the RAND-36 Health Status Inventory (RAND SF-36) (range, 15 to 61, with higher scores indicating better quality of life), at the end of the treatment period at week 14, after the 2-week course of ceftriaxone and the 12-week course of the randomized study drug or placebo had been completed., Results: Of the 281 patients who underwent randomization, 280 were included in the modified intention-to-treat analysis (86 patients in the doxycycline group, 96 in the clarithromycin-hydroxychloroquine group, and 98 in the placebo group). The SF-36 physical-component summary score did not differ significantly among the three study groups at the end of the treatment period, with mean scores of 35.0 (95% confidence interval [CI], 33.5 to 36.5) in the doxycycline group, 35.6 (95% CI, 34.2 to 37.1) in the clarithromycin-hydroxychloroquine group, and 34.8 (95% CI, 33.4 to 36.2) in the placebo group (P=0.69; a difference of 0.2 [95% CI, -2.4 to 2.8] in the doxycycline group vs. the placebo group and a difference of 0.9 [95% CI, -1.6 to 3.3] in the clarithromycin-hydroxychloroquine group vs. the placebo group); the score also did not differ significantly among the groups at subsequent study visits (P=0.35). In all study groups, the SF-36 physical-component summary score increased significantly from baseline to the end of the treatment period (P<0.001). The rates of adverse events were similar among the study groups. Four serious adverse events thought to be related to drug use occurred during the 2-week open-label ceftriaxone phase, and no serious drug-related adverse event occurred during the 12-week randomized phase., Conclusions: In patients with persistent symptoms attributed to Lyme disease, longer-term antibiotic treatment did not have additional beneficial effects on health-related quality of life beyond those with shorter-term treatment. (Funded by the Netherlands Organization for Health Research and Development ZonMw; PLEASE ClinicalTrials.gov number, NCT01207739.).

Background: Mansonella perstans infection is common in areas of Africa where Wuchereria bancrofti, a causative agent of lymphatic filariasis, is endemic. M. perstans is refractory to standard antifilarial therapies. The recent discovery of bacterial endosymbionts (e.g., wolbachia) in most filarial species, including M. perstans, provides new therapeutic options for reducing microfilaremia., Methods: In an open-label, randomized trial, we recruited subjects with M. perstans microfilaremia, with or without concomitant W. bancrofti infection, from four villages in Mali and randomly assigned them to receive doxycycline, at a dose of 200 mg daily for 6 weeks (106 subjects), or no treatment (110). At 6 months, subjects who were coinfected with W. bancrofti underwent a second random assignment, to treatment with a single dose of albendazole (400 mg) and ivermectin (150 microg per kilogram of body weight) or no treatment. Subjects were monitored daily during the first 6-week study period for adverse events. M. perstans and W. bancrofti microfilarial levels were assessed at 6, 12, and 36 months., Results: At 12 months, 67 of 69 subjects who had received treatment with doxycycline only (97%) had no detectable M. perstans microfilariae per 60 microl of blood, as compared with 10 of 63 subjects who had received no treatment (16%) (relative risk, 6.18; 95% confidence interval, 3.63 to 11.89; P<0.001). At 36 months, M. perstans microfilaremia remained suppressed in 48 of 64 subjects who had received treatment with doxycycline only (75%), a finding that was consistent with a macrofilaricidal effect of doxycycline. Vomiting was more frequent in the doxycycline-treated group than in the untreated group (17% vs. 4%)., Conclusions: These results are consistent with previous findings that M. perstans harbors the intracellular endosymbiont, wolbachia, and suggest that doxycycline is an effective therapy for M. perstans infection. (ClinicalTrials.gov number, NCT00340691.), (2009 Massachusetts Medical Society)

Background: It is unclear whether antimicrobial treatment after an Ixodes scapularis tick bite will prevent Lyme disease., Methods: In an area of New York where Lyme disease is hyperendemic we conducted a randomized, double-blind, placebo-controlled trial of treatment with a single 200-mg dose of doxycycline in 482 subjects who had removed attached I. scapularis ticks from their bodies within the previous 72 hours. At base line, three weeks, and six weeks, subjects were interviewed and examined, and serum antibody tests were performed, along with blood cultures for Borrelia burgdorferi. Entomologists confirmed the species of the ticks and classified them according to sex, stage, and degree of engorgement., Results: Erythema migrans developed at the site of the tick bite in a significantly smaller proportion of the subjects in the doxycycline group than of those in the placebo group (1 of 235 subjects [0.4 percent] vs. 8 of 247 subjects [3.2 percent], P<0.04). The efficacy of treatment was 87 percent (95 percent confidence interval, 25 to 98 percent). Objective extracutaneous signs of Lyme disease did not develop in any subject, and there were no asymptomatic seroconversions. Treatment with doxycycline was associated with more frequent adverse effects (in 30.1 percent of subjects, as compared with 11.1 percent of those assigned to placebo; P<0.001), primarily nausea (15.4 percent vs. 2.6 percent) and vomiting (5.8 percent vs. 1.3 percent). Erythema migrans developed more frequently after untreated bites from nymphal ticks than after bites from adult female ticks (8 of 142 bites [5.6 percent] vs. 0 of 97 bites [0 percent], P=0.02) and particularly after bites from nymphal ticks that were at least partially engorged with blood (8 of 81 bites [9.9 percent], as compared with 0 of 59 bites from unfed, or flat, nymphal ticks [0 percent]; P=0.02)., Conclusions: A single 200-mg dose of doxycycline given within 72 hours after an I. scapularis tick bite can prevent the development of Lyme disease.

Background: It is controversial whether prolonged antibiotic treatment is effective for patients in whom symptoms persist after the recommended antibiotic treatment for acute Lyme disease., Methods: We conducted two randomized trials: one in 78 patients who were seropositive for IgG antibodies to Borrelia burgdorferi at the time of enrollment and the other in 51 patients who were seronegative. The patients received either intravenous ceftriaxone, 2 g daily for 30 days, followed by oral doxycycline, 200 mg daily for 60 days, or matching intravenous and oral placebos. Each patient had well-documented, previously treated Lyme disease but had persistent musculoskeletal pain, neurocognitive symptoms, or dysesthesia, often associated with fatigue. The primary outcome measures were improvement on the physical- and mental-health-component summary scales of the Medical Outcomes Study 36-item Short-Form General Health Survey (SF-36)--a scale measuring the health-related quality of life--on day 180 of the study., Results: After a planned interim analysis, the data and safety monitoring board recommended that the studies be discontinued because data from the first 107 patients indicated that it was highly unlikely that a significant difference in treatment efficacy between the groups would be observed with the planned full enrollment of 260 patients. Base-line assessments documented severe impairment in the patients' health-related quality of life. In intention-to-treat analyses, there were no significant differences in the outcomes with prolonged antibiotic treatment as compared with placebo. Among the seropositive patients who were treated with antibiotics, there was improvement in the score on the physical-component summary scale of the SF-36, the mental-component summary scale, or both in 37 percent, no change in 29 percent, and worsening in 34 percent; among seropositive patients receiving placebo, there was improvement in 40 percent, no change in 26 percent, and worsening in 34 percent (P=0.96 for the comparison between treatment groups). The results were similar for the seronegative patients., Conclusions: There is considerable impairment of health-related quality of life among patients with persistent symptoms despite previous antibiotic treatment for acute Lyme disease. However, in these two trials, treatment with intravenous and oral antibiotics for 90 days did not improve symptoms more than placebo.

Background: Currently, there is no single-dose therapy that is effective in the treatment of urethral or endocervical infections with Chlamydia trachomatis. Azithromycin is a new azalide antibiotic that has substantial activity against C. trachomatis, is concentrated intracellularly, and has a long half-life in serum and tissue., Methods: We conducted a trial in which 299 female patients and 158 male patients with uncomplicated genital infection and a positive C. trachomatis antigen test were randomly assigned to receive either azithromycin (1 g once orally) or doxycycline (100 mg orally twice daily for seven days). Only patients subsequently determined to have a culture positive for C. trachomatis at base line were included in the evaluation of efficacy., Results: Among the patients who could be evaluated, 5 of the 141 patients (4 percent) treated with azithromycin did not respond to treatment, as compared with 3 of the 125 patients (2 percent) treated with doxycycline (difference between groups, 2 percent; 95 percent confidence interval, 0 to 6 percent). Of the patients evaluated 21 to 35 days after treatment, none of 112 treated with azithromycin and 1 of 102 treated with doxycycline had a positive culture. The rates of bacteriologic cure were similar for the 98 female patients (97 percent) and the 43 male patients (95 percent) treated with azithromycin. Seventeen percent of the patients who received azithromycin and 20 percent of those treated with doxycycline had mild-to-moderate drug-related side effects, mainly gastrointestinal symptoms., Conclusions: A single 1-g dose of azithromycin is as effective for the treatment of uncomplicated genital chlamydial infections as a standard seven-day course of doxycycline.

Background: In areas of endemic disease, the probability of Lyme disease after a tick bite ranges from about 0.012 to 0.05. Early treatment with oral antibiotics prevents most complications of Lyme disease, but antibiotics are generally not prescribed until rash or other symptoms develop., Methods: We used decision analysis to evaluate the outcomes, costs, and cost effectiveness of three alternative strategies to treat patients bitten by ixodes ticks in areas of endemic Lyme disease: empirically treat all patients with two weeks of doxycycline, treat only patients in whom erythema migrans develops, and treat only patients with erythema migrans or a positive serologic test for Lyme disease one month after exposure., Results: Empirical treatment is the least expensive strategy and results in the fewest cases of Lyme disease and the fewest complications when the probability of Borrelia burgdorferi infection after a tick bite is 0.036 or higher. For probabilities of infection below 0.036, empirical therapy prevents most major complications, sequelae, and adverse events, but it incurs additional minor complications, especially as the probability of infection falls below 0.01., Conclusions: Empirical treatment of patients with tick bites is indicated when the probability of B. burgdorferi infection after a bite is 0.036 or higher, and this treatment may be preferred when the probability of infection ranges from 0.01 to 0.035. When the probability of infection after a tick bite is less than 0.01, empirical therapy is not warranted.

To assess the cause of nonspecific vaginitis, we performed a prospective case-control study of vaginal flora and a randomized unblinded trial of different therapies. Haemophilus vaginalis was isolated from 17 to 18 women with signs of vaginitis but only one of 18 normal matched controls (P less than 0.002). The concentration of anaerobic bacteria in vaginal washings also was increased in patients. Clinical improvement and eradication of H. vaginalis occurred in one of seven patients given sulfonamide vaginal cream, two of 15 given oral doxycycline, nine of 27 given oral ampicillin, and 80 of 81 given oral metronidazole. On the seventh day of therapy signs of nonspecific vaginitis persisted in 31 of 31 with, and in two of 92 without, persistent H. vaginalis infection (P less than 0.001). These data suggest the causal role of H. vaginalis in nonspecific vaginitis, possibly in concert with vaginal anaerobes. The widespread use of sulfonamide creams is inappropriate. Metronidazole is effective, but its efficacy must be weighed against its possible toxicity.

Because leptospirosis has been an important cause of morbidity in U.S. soldiers training in the Republic of Panama, we conducted a randomized, double-blind, placebo-controlled field trial during the fall of 1982 to determine whether doxycycline was an effective chemoprophylactic agent against this infection. Doxycycline (200 mg) or placebo was administered orally on a weekly basis and at the completion of training to 940 volunteers from two U.S. Army units deployed in Panama for approximately three weeks of jungle training. Twenty cases of leptospirosis occurred in the placebo group (an attack rate of 4.2 per cent), as compared with only one case in the doxycycline group (attack rate, 0.2 per cent, P less than 0.001), yielding an efficacy of 95.0 per cent. This study demonstrated the value of doxycycline as a prophylactic drug against leptospirosis.