Impulsivity, Sexual Compulsivity, and Sexual Risk Behaviors among Hispanic Men Who Have Sex with Men in a US-Mexico Border City.

Hispanic men who have sex with men (HMSM) experience HIV risk-related and mental health disparities. The relationship of mental health (i.e., depressive symptoms and anxiety) on sexual risk behaviors of HMSM has been reported. However, little is known about the influence of impulsivity and compulsivity on sexual risk behaviors. A cross-sectional study explored these factors among 150 HMSM in the El Paso, Texas area utilizing standardized measures, in a cross-sectional study. Regression analysis determined the influence of sexual impulsivity and compulsivity, and demographic variables on sexual risk behaviors, indicating interventions should target these behaviors to mitigate sexual risk among HMSM.

Gender Differences in Methamphetamine Use Initiation and Trajectory of Use Among People Who Use Methamphetamine in a Mexico-U.S. Border City.

INTRODUCTION: Methamphetamine (meth) is a stimulant increasing in use and its prevalence has not yet been determined on the Mexico-U.S. border. Few studies highlight gender differences in meth use, trajectory, and initiation by gender. Ciudad Juárez, Mexico, across the border from El Paso, Texas, has an established stimulant using population and lies on drug trafficking route. This study assessed gender differences in drug and meth use patterns among people meth people use meth. MATERIAL AND METHODS: This cross-sectional study included 150 people with recent meth use, age 21 years or older, and living in Ciudad Juárez. Measures collected included sociodemographic characteristics, cross-border mobility, drug and meth use characteristics. Statistically (p-value<0.05) and marginally (p-value<0.10) significant gender differences were determined using appropriate bivariate tests. RESULTS: The sample included 45 cisgender women, five transgender women, and 100 cisgender men with a mean age of 30.9 years. Men had significantly higher rates of snorting meth by nose in powder or rock forms while trans/women more frequently using meth in pill form. Men had higher rates of crossing the border for work, with meth and to obtain meth. Trans/women reported higher rates of acquiring meth from main sexual partner and initiating meth use in Mexico. DISCUSSION: There are gender differences in patterns of meth use and initiation. CONCLUSIONS: Sample of people who use meth in general population can be achieved. These findings point to a need for evidence-based meth use reduction treatment programs that are culturally appropriate and tailored for gender.

Differences in Substance Use and Sexual Risk by Sexual Orientation and Gender Identity Among University and Community Young Adults in a U.S.-Mexico Border City.

Ethnic and sexual minority young adults in El Paso, Texas, are at high risk for substance use, human immunodeficiency virus (HIV), and hepatitis C virus (HCV). In 2014, a Hispanic-serving higher education institution partnered with two community-based organizations to implement integrated substance use interventions and HIV and HCV prevention among young adults on campus and in surrounding communities. Among the 95 young adults, aged 18-24 years, who responded to a needs assessment survey, 91.5% were Hispanic, 53.7% were female, and 27.4% were sexual or gender minorities (SGMs) as defined by behavior and identity. SGMs had significantly higher rates of current smoking, drinking when bored, and of being told they had a drinking problem. Compared with the other young adult survey respondents, SGMs had lower health risk perceptions for tobacco, alcohol, and marijuana use and reported similar or higher rates of lifetime drug use during sex and higher rates of HIV risk behaviors. Study findings have implications for including measures for sexual orientation and gender identity in substance use studies, examining regional and cultural norms that may intersect to shape substance use among SGMs, and incorporating unique risk contexts for SGMs in interventions for substance use.

Methamphetamine Use and Sexual Risk Behaviors among Men Who Have Sex With Men in a Mexico-US Border City.

BACKGROUND AND OBJECTIVES: Methamphetamine (meth) use and its related risk behaviors for HIV among men who have sex with men (MSM) are a public health concern across the Mexico-US border. This study aims to contribute to the limited literature of meth use and sexual risk behaviors among Latino MSM on the Mexico-US border. METHODS: Data were drawn from the Meth Pilot Study (2014-2015) among men who use meth (n = 100). Descriptive statistics and bivariate analysis comparing MSM to non-MSM were conducted using Pearson's χ2 test, Fisher's exact tests, and Mann-Whitney U test; all tests were conducted using SPSS v.25. RESULTS: Most participants obtained meth in El Paso, Texas (87.2%), used meth orally (65.2%) or smoked (78.3%), and the most common reason for initiation was curiosity. Significant differences (P < .05) in meth use behaviors and sexual risk behaviors between MSM and non-MSM who used meth included: median number of sex partners (7 vs 3), being penetrated anally by last sexual partner (31.6% vs 1.4%), and engaging in transactional sex ever (63.2% vs 9.6%) and past 12 months (52.6% vs 6.8%). Finally, rates of HIV positivity were higher among MSM than non-MSM (10.5% vs 1.4%). DISCUSSION AND CONCLUSIONS: Among men who use meth, MSM are engaging in higher HIV risk behaviors compared with non-MSM. Understanding these risks could help identify candidates for pre-exposure prophylaxis (PrEP) and evidence-based substance use disorder treatment options. SCIENTIFIC SIGNIFICANCE: This study reveals that Latino MSM who use meth is a high-risk group for HIV and a need for tailored interventions. (Am J Addict 2020;29:111-119).

Increasing Our Advocacy Capacity Through HIV Community Mobilization: Perspectives From Emerging and Mid-Career Professionals.

In this commentary, six public health practitioners and researchers discuss how their participation in the El Paso HIV Community Mobilization effort has contributed to their professional development and increased their collective capacity to advocate for practice and policy improvements that contribute to health equity in general and within the context of HIV prevention. Like previous commentaries in this department that have highlighted the value of the Certified Health Education Specialist credential ( http://www.nchec.org/health-education-credentialing ) and the importance of gaining experience in policy advocacy, this article is relevant for public health professionals in diverse work settings. The authors hope that their experience will encourage others to participate in community mobilization efforts, and they welcome communication and collaboration with anyone interested in learning more about the HIV Community Mobilization efforts discussed in this commentary.

A qualitative exploration of perceived gender differences in methamphetamine use among women who use methamphetamine on the Mexico-U.S. border.

The purpose of this study is to extend the research on contextual factors that influence the initiation and continued use of methamphetamine (meth) by women on the U.S.-Mexico border. At present, a minimal body of literature exists that explores meth use on the Mexico-U.S. border. A purposeful sample of 20 women who were active meth users aged ≥18 years was recruited by trained outreach workers from a variety of meth-user networks in Ciudad Juárez, Mexico, the city bordering El Paso, Texas. Respondents participated in in-depth, semi-structured interviews including questions on users' perceived familial, social, and environmental influences of meth use. Gender-based themes emerged from the analysis: (1) patterns of meth use; (2) places where drugs were used; (3) effects of relationship networks on meth use; (4) differential access to drugs; (5) trading sex for drugs; (6) perceived class differences; and (7) long-term drug use and its consequences. Respondents reported a preference for using meth as powder or pills as opposed to smoking or injecting the drug. They reported being introduced to meth by men they trust and relying on men for drug acquisition in spaces less accessible and more dangerous to women. They described how the drug changed their lifestyle and their behavior towards family members and friends, including instances of physical and psychological violence. Interventions for women on the Mexico-U.S. border should be developed based on users' social networks to target social processes to prevent initiation and to bring active meth users into treatment.

Understanding the Experiences of Latinx LGBTQ Texans at the Beginning of the COVID-19 Pandemic.

Marginalized communities have been disproportionately affected by COVID-19, including both racial/ethnic minority and sexual minority populations. To date, there has been little research examining the impact of the COVID-19 pandemic at the intersections of marginalized identities. Furthermore, available national data on COVID-19 outcomes may obscure our understanding of region-specific outcomes, particularly in the U.S. South. Using an intersectional approach, we explore differences in worries over COVID-19, preventative behaviors, and COVID-19 outcomes in the early months of the pandemic in a diverse sample of LGBTQ people (N = 1076) living in Texas. Our findings indicated that LGBTQ Latinx people in Texas reported more COVID-19 related worries and adverse outcomes than non-Latinx LGBTQ people. These findings are in line with previous research that found that the increased risk to Latinx and LGBTQ populations in public health crises is often overlooked and can be attributed to many factors such as socioeconomic status, occupational propensity, disparities in physical health, and barriers to healthcare access. Furthermore, our findings suggest the necessity of utilizing an intersectional approach when examining the disproportionate burden marginalized communities face in public health crises.

Healthcare and Social Services Providers Who Serve Sexual and Gender Minorities in a U.S.-Mexico Border City.

Sexual and gender minorities, including lesbian, gay, bisexual, transgender, and queer (LGBTQ) individuals, experience barriers to healthcare as a result of stigma, discrimination, and poor cultural competence by healthcare and social services providers (HCSSP). The purpose of the study is to increase access to care and services for the LGBTQ community in a U.S.-Mexico border city by identifying LGBTQ-friendly HCSSP. A survey, developed based on concerns voiced in a predominantly Hispanic LGBTQ community, was administered to HCSSP and used to create a referral list, "The Purple Pages of El Paso" (PPoEP). Overall, 77 HCSSP have responded and 43 are included in the most recent version of the PPoEP. This model for developing a referral list of providers can be adapted in areas where LGBTQ communities face similar barriers to care and services. To be effective in reducing barriers to care, PPoEP must be updatable and sustainable.

Use of lead-glazed ceramic ware and lead-based folk remedies in a rural community of Baja California, Mexico.

BACKGROUND: Lead exposure from lead-glazed ceramics (LGCs) and traditional folk remedies have been identified as significant sources of elevated blood lead levels in Mexico and the United States. This study took place from 2005 to 2012 in a rural community in Baja California, Mexico. OBJECTIVES: 1) Investigate the knowledge, attitudes, and practices related to lead and lead exposures from LGCs and two lead-based folk remedies ( azarcon and greta); and 2) evaluate a pilot intervention to provide alternative lead-safe cookware. METHODS: A baseline household survey was conducted in 2005, followed by the pilot intervention in 2006, and follow-up surveys in 2007 and 2012. For the pilot intervention, families who reported using LGCs were given lead-safe alternative cookware to try and its acceptance was evaluated in the following year. RESULTS: The community was mostly of indigenous background from Oaxaca and a high proportion of households had young children. In 2006, all participants using traditional ceramic ware at the time ( n = 48) accepted lead-safe alternative cookware to try, and 97% reported that they were willing to exchange traditional ceramic ware for lead-safe alternatives. The use of ceramic cookware decreased from over 90% during respondents' childhood household use in Oaxaca to 47% in 2006 among households in Baja California, and further reduced to 16.8% in 2012. While empacho, a folk illness, was widely recognized as an intestinal disorder, there was almost universal unfamiliarity with the use and knowledge of azarcon and greta for its treatment. CONCLUSION: This pilot evaluation provides evidence 1) for an effective and innovative strategy to reduce lead exposure from LGCs and 2) of the feasibility of substituting lead-free alternative cookware for traditional ceramic ware in a rural indigenous community, when delivered in a culturally appropriate manner with health education. This strategy could complement other approaches to reduce exposure to lead from LGCs.

Developing Trans-Affirming Health Services in an Underserved Area: An Intersectional Approach.

Purpose: Gender-nonconforming patients are at higher risk for medical problems that require prompt medical and mental health intervention. Barriers to healthcare for transgender individuals have been well characterized in the literature, but not in low resource settings. The purpose of this paper is to present the barriers encountered when bringing healthcare to transgender children, adolescents, and adults in a medically underserved, predominantly Hispanic area of the United States. Methods: In this medically underserved area on the U.S.-Mexico border, there is a severe shortage of medical expertise for transgender individuals at both the primary- and specialty-care levels. Further, given the mainly Hispanic population, there is an additional culturally based barrier to obtaining medical care for transgender patients. Results: It is important for academic centers in these regions to collaborate to overcome these barriers through a multidisciplinary approach that includes providing education for medical students and physicians in training and identifying medical providers who are able and willing to provide transgender-competent care adapted to local culture and gender norms. Conclusion: In this manuscript, we will describe the efforts of various groups to address the needs of the transgender community in the region.

A randomized comparison of misoprostol to intrauterine instillation of hypertonic saline plus a prostaglandin F2alpha analogue for second-trimester induction termination in Uzbekistan.

BACKGROUND: The study was conducted to compare the efficacy and acceptability of second-trimester induction termination using vaginal misoprostol to hypertonic saline and d-cloprostenol, a prostaglandin F(2alpha) (PGF) analogue, in Tashkent, Uzbekistan. STUDY DESIGN: Eleven clinics providing second-trimester induction terminations were randomized to provide one of two regimens for second-trimester induction termination: vaginal misoprostol 400 mcg every 3 h or hypertonic 10% saline intrauterine instillation plus an intravenous PGF analogue, d-cloprostenol, 2.5 mg/h. Demographic information, and obstetric and medical history data were collected, and interviewers administered questionnaires to measure procedural pain and satisfaction. Differences in procedure time and complication rate, the primary outcomes, were analyzed with survival analysis and chi(2) tests. RESULTS: Of 228 participants, 120 received misoprostol and 108 received hypertonic saline and d-cloprostenol; the groups did not significantly differ by age, parity or gestational age. Both misoprostol and saline procedures were effective, with 99.2% and 100% successful abortion rates, respectively. Median procedure time (13.1 vs. 29.2 h, p<.001), and number of women with retained placenta (2 vs. 70, p<.001) or hemorrhage (3 vs. 19, p=.001) were lower for the misoprostol group. Both provider (p<.001) and patient (p<.001) procedural satisfaction scores were higher for the misoprostol group. CONCLUSION: While equally effective, vaginal misoprostol had a shorter time to abortion, was more acceptable to providers and patients and had fewer complications than saline instillation plus intravenous administration of a PGF analogue in Tashkent. This evidence supports change of the existing standard of care for second-trimester induction termination in Uzbekistan.

Substance Use by Immigrant Generation in a U.S.-Mexico Border City.

Immigrant generation status has an impact on substance use, with lower use rates for recent immigrants. Substance use surveillance data are reported at the national and state levels; however, no systematic collection of data exists at the city level for the general population. In particular, rates of substance use have not been published for El Paso, Texas. The aims of this study are to estimate the prevalence of substance use among Hispanics in El Paso and to determine the association between substance use and immigrant generation. Hispanic residents of El Paso (N = 837) were interviewed. Demographic, immigration, and substance use data were collected. Bivariate analysis indicated that substance use increased as immigrant generation increased, while perceived problems with substance use decreased. In comparison to Texas and national data, our data showed that the rates of tobacco, marijuana, and illicit drug use were lower among young adults in El Paso.

Navigator Approach to Improve Quality of Care for Vulnerable Populations in Mexico.

For nearly 30 years, Programa Compañeros Inc (Compañeros) has worked in Ciudad Juarez, Chihuahua, Mexico, to ensure that vulnerable populations can exercise their rights to receive HIV and substance abuse prevention and treatment services. Compañeros staff has worked to ameliorate the negative results that limit access to care to the most vulnerable individuals: those who are poor, homeless, sex workers, addicted, and others whose life context put them at greater risk for being infected with HIV. With support from the MAC AIDS Foundation, Compañeros has expanded its capacity to deliver services to persons living with HIV/AIDS (PLWHA) and to HIV-vulnerable populations. This short communication describes findings from an internal evaluation conducted to investigate the effectiveness of the MAC AIDS-funded navigator-based program implemented at Compañeros.

Correlates of early versus later initiation into sex work in two Mexico-U.S. border cities.

PURPOSE: To examine correlates of early initiation into sex work in two Mexico-U.S. border cities. METHODS: Female sex workers (FSWs) >/=18 years without known HIV infection living in Tijuana and Ciudad Juarez who had recent unprotected sex with clients underwent baseline interviews. Correlates of initiation into sex work before age 18 were identified with logistic regression. RESULTS: Of 920 FSWs interviewed in Tijuana (N=474) and Ciudad Juarez (N=446), 9.8% (N=90) were early initiators (<18 years) into sex work. Median age of entry into sex work was 26 years (range: 6-58). After adjusting for age, compared to older initiators, early initiators were more likely to use inhalants (21.1% vs. 9.6%, p=.002), initiate sex work to pay for alcohol (36.7% vs. 18.4%, p < .001), report abuse as a child (42.2% vs. 18.7%, p<.0001), and they were less likely to be migrants (47.8% vs. 62.3%, p=.02). Factors independently associated with early initiation included inhalant use (adjOR=2.39), initiating sex work to pay for alcohol (adjOR=1.88) and history of child abuse (adjOR=2.92). Factors associated with later initiation included less education (adjOR=0.43 per 5-year increase), migration (adjOR=0.47), and initiating sex work for better pay (adjOR=0.44) or to support children (adjOR=0.03). CONCLUSIONS: Different pathways for entering sex work are apparent among younger versus older females in the Mexico-U.S. border region. Among girls, interventions are needed to prevent inhalant use and child abuse and to offer coping skills; among older initiators, income-generating strategies, childcare, and services for migrants may help to delay or prevent entry into sex work.

Drug-related behaviors independently associated with syphilis infection among female sex workers in two Mexico-US border cities.

AIMS: To identify correlates of active syphilis infection among female sex workers (FSWs) in Tijuana and Ciudad Juarez. DESIGN: Cross-sectional analyses of baseline interview data. Correlates of active syphilis (antibody titers >1 : 8) were identified by logistic regression. Setting Tijuana and Ciudad Juarez, two Mexican cities on the US border that are situated on major drug trafficking routes and where prostitution is quasi-legal. PARTICIPANTS: A total of 914 FSWs aged > or =18 years without known human immunodeficiency virus (HIV) infection who had had recent unprotected sex with clients. MEASUREMENTS: Baseline interviews and testing for syphilis antibody using Treponema pallidum particle agglutination (TPPA) and rapid plasma reagin (RPR) tests. FINDINGS: Median age and duration in sex work were 32 and 4 years, respectively. Overall, 18.0% had ever injected drugs, 14.2% often or always used illegal drugs before or during sex in the past month, 31.4% had clients in the last 6 months who injected drugs, and 68.6% reported having clients from the United States. Prevalence of HIV and active syphilis were 5.9% and 10.3%, respectively. Factors independently associated with active syphilis included injecting drugs (AOR: 2.39; 95% CI: 1.40, 4.08), using illegal drugs before or during sex (AOR: 2.06; 95% CI: 1.16, 3.65) and having any US clients (AOR: 2.85; 95% CI: 1.43, 5.70). CONCLUSIONS: Among female sex workers in Tijuana and Ciudad Juarez, drug-using behaviors were associated more closely with active syphilis than were sexual behaviors, suggesting the possibility of parenteral transmission of T. pallidum. Syphilis eradication programs should consider distributing sterile syringes to drug injectors and assisting FSWs with safer-sex negotiation in the context of drug use.

Cross-border paid plasma donation among injection drug users in two Mexico-U.S. border cities.

OBJECTIVE: Paid plasma donation has contributed to HIV epidemics in many countries. Eleven million liters of plasma are fractionated annually in the U.S., mainly from paid donors. Deferral of high-risk donors such as injection drug users (IDUs) is required for paid donations. We studied circumstances surrounding paid plasma donation among IDUs in two Mexico-U.S. border cities. METHODS: In 2005, IDUs > or = 18 years old in Tijuana (N=222) and Cd. Juarez (N=206) who injected in the last month were recruited through respondent-driven sampling. Subjects underwent antibody testing for HIV and HCV and an interviewer-administered survey including questions on donating and selling whole blood and plasma. RESULTS: Of 428 IDUs, HIV and HCV prevalence were 3% and 96%, respectively; 75 (17.5%) reported ever having donated/sold their blood or plasma, of whom 28 (37%) had sold their plasma for an average of $16 USD. The majority of IDUs selling plasma were residents of Ciudad Juarez (82%); 93% had sold their plasma only in the U.S. The last time they sold their plasma, 65% of IDUs had been asked if they injected drugs. Although the median time since last selling plasma was 13 years ago, 3 had done so within the prior 2 years, one within the prior 6 months; of these 3 IDUs, 2 were from Cd. Juarez, one from Tijuana; all 3 had only sold their plasma in the U.S. CONCLUSIONS: Although selling plasma appears uncommon among IDUs in these two Mexican border cities, the majority sold plasma in the U.S. and only one-third were deferred as high-risk donors. Paying donors for plasma should be a matter of public inquiry to encourage strict compliance with regulations. Plasma clinics should defer donors not only on behavioral risks, but should specifically inspect for injection stigmata.

Individual, social, and environmental influences associated with HIV infection among injection drug users in Tijuana, Mexico.

OBJECTIVE: We examined correlates of HIV infection among injection drug users (IDUs) in Tijuana, Mexico, a city bordering the United States, which is situated on major migration and drug trafficking routes. METHODS: IDUs aged > or =18 years were recruited using respondent-driven sampling. Participants underwent antibody testing for HIV and syphilis and structured interviews. Weighted logistic regression identified correlates of HIV infection. RESULTS: Of 1056 IDUs, the median age was 37 years, 86% were male, and 76% were migrants. HIV prevalence was higher in female participants than in male participants (8% vs. 3%; P = 0.01). Most IDUs testing HIV-positive were previously unaware of their serostatus (93%). IDUs reported injecting with a median of 2 people in the prior 6 months and had been arrested for having injection stigmata (ie, "track-marks") a median of 3 times. Factors independently associated with HIV infection were being female, syphilis titers consistent with active infection, larger numbers of recent injection partners, living in Tijuana for a shorter duration, and being arrested for having track-marks. CONCLUSIONS: Individual, social, and environmental factors were independently associated with HIV infection among IDUs in Tijuana. These findings suggest the need to intervene not solely on individual risk behaviors but on social processes that drive these behaviors, including problematic policing practices.

High-risk sexual and drug using behaviors among male injection drug users who have sex with men in 2 Mexico-US border cities.

OBJECTIVES: The population of Latino men who have sex with men (MSM) and who are also injection drug users (IDUs) is understudied. We explored risk behaviors of MSM/IDUs compared with other male IDUs in 2 Mexican border cities. STUDY DESIGN: In 2005, IDUs who had injected within the previous 30 days were recruited using respondent-driven sampling (RDS) in Tijuana and Ciudad Juárez. They underwent antibody testing for HIV, HCV, and syphilis and interviewer-administered surveys. Men were categorized as MSM if they reported > or =1 lifetime male partners. Logistic regression was used to compare MSM/IDUs with non-MSM/IDUs. RESULTS: A third (31%) of 377 male IDUs were categorized as MSM (47% in Tijuana and 13% in Ciudad Juárez, P <0.01). Combined RDS-adjusted prevalence of HIV and Hepatitis C was 3% (95% CI: 1, 5) and 96%, (95% CI: 94, 99) respectively, while 17% (95% CI: 2, 36) of MSM and 8% (95% CI: 3, 12) of non-MSM tested positive for syphilis antibody. In multivariate logistic regression adjusted for site, MSM/IDUs were more likely than non-MSM/IDUs to have ever used inhalants (OR: 3.4; 95% CI: 1.8, 6.2) or oral tranquilizers (OR: 2.4; 95% CI: 1.3, 4.6), received treatment for a drug problem (OR:1.9; 95% CI: 1.1, 3.2) shared needles in the last six months (OR: 2.1; 95% CI: 1.0, 4.2) and also had higher numbers of lifetime female partners (log-transformed continuous variable, OR: 1.6; 95% CI: 1.2, 2.1). CONCLUSIONS: In these Mexican cities, the proportion of MSM among male IDUs was high. Compared with other male IDUs, MSM/IDUs were more likely to engage in behaviors placing them at risk of acquiring HIV/STIs. Culturally appropriate interventions targeting Latino MSM/IDUs are warranted.

Diffusion of cancer education information through a Latino community health advisor program.

OBJECTIVE: To examine diffusion of breast and cervical cancer screening information through a community health advisor program targeting Latino women of low socioeconomic level and low level of acculturation in San Diego, California. METHOD: Seventeen community health advisors ("consejeras") were recruited and trained to conduct educational group sessions. Each consejera recruited peers from the community to participate in the 12 sequential weekly sessions (i.e., primary participants). In addition, each of the primary participants identified up to two friends and/or family members (i.e., "learning partners") with whom they intended to share the cancer education information received. Pretest and posttest telephone surveys were conducted between 1996 and 1997. A total of 311 primary participants completed the pretest and 285 the posttest. Among the learning partners, 269 completed the pretest and 222 the posttest. RESULTS: Knowledge about breast and cervical cancer and self-reported use of screening tests increased among primary participants and learning partners. However, the increase was not statistically significant in mammography screening among participants 40 years old or older. Overall, increases in knowledge were more pronounced among primary participants when compared to learning partners. CONCLUSION: The utilization of the learning partner model represents a promising diffusion tool to enhance cancer early detection programs relying on community health advisors.

Embolization itself stimulates thrombus propagation in pulmonary embolism.

The role of active thrombosis in the pathophysiology of pulmonary embolism is unclear. We tested the hypothesis that venous thrombi significantly increase their thrombotic activity once they embolize into the high-flow circulation of the pulmonary arteries. Thrombotic activity was measured using an immunoassay that measures both fibrinopeptide B (FPB) as well as its most abundant metabolite des-arginine FPB. Thrombi were formed in the femoral veins of adult dogs. In one group, the thrombi were embolized without anticoagulation. In the second group, heparin (300 U/kg bolus, then 90 U x kg(-1) x h(-1) infusion) was administered before embolization to prevent subsequent thrombotic activity. Plasma FPB concentrations were significantly suppressed in the heparinized group relative to the nonheparinized group for 1 h postembolization (P = 0.038). We conclude that pulmonary embolization itself causes preexisting venous thrombi to greatly intensify their thrombotic activity and that embolization-associated thrombus propagation can be prevented by heparin.