Effect of Hepatic Impairment on the Pharmacokinetics of Fenfluramine and Norfenfluramine.

Fenfluramine (Fintepla®) is approved for the treatment of seizures associated with the rare epileptic encephalopathies Dravet syndrome and Lennox-Gastaut syndrome. Fenfluramine is extensively metabolized; thus, patients with hepatic impairment (HI) might experience changes in exposure to fenfluramine or its metabolites. In this phase 1 study, we investigated the pharmacokinetics (PK) and safety of a single oral dose of 0.35 mg/kg fenfluramine in subjects with mild (n = 8), moderate (n = 8), or severe (n = 7) HI (Child-Pugh A/B/C, respectively) and healthy control subjects (n = 22) matched for sex, age, and BMI. All subjects underwent serial sampling to determine total plasma concentrations of fenfluramine and its active metabolite, norfenfluramine. Hepatic impairment was associated with increases in fenfluramine exposures, mainly area-under-the-curve (AUC). Geometric least squares mean ratios (90% confidence intervals) for fenfluramine AUC0-∞ in mild, moderate, and severe HI versus healthy controls were 1.98 (1.36-2.90), 2.13 (1.43-3.17), and 2.77 (1.82-4.24), respectively. Changes in exposure to norfenfluramine in mild, moderate, and severe HI were minimal compared with normal hepatic function. Exposures to fenfluramine and norfenfluramine in all HI groups were within the ranges that have been characterized in the overall development program, including ranges examined in exposure-response relationships for efficacy and safety in patients, and determined to have an acceptable safety profile. Mild and moderate HI had a modest effect on fenfluramine exposure that was not clinically meaningful, whereas the higher fenfluramine exposure in severe HI may require dose reduction based on general caution in this population. The modest decrease in norfenfluramine exposure is not considered clinically relevant.

Translational Approach to Predicting the Efficacy of Maraviroc-Based Regimens as HIV Preexposure Prophylaxis.

Maraviroc-based regimens have been explored as preexposure prophylaxis (PrEP) against human immunodeficiency virus (HIV). In this study, we utilized mucosal tissue drug exposure data, combined with target concentrations generated in vitro, in a pharmacokinetic-pharmacodynamic analysis to predict the effects of drug combinations and adherence on PrEP efficacy. Mucosal tissue concentrations of maraviroc were measured in 24 healthy women. The 90% effective concentrations (EC90) of maraviroc (alone and combined with tenofovir and emtricitabine) for protection against HIV were identified in CD4+ T cells. Monte Carlo simulations were performed to identify dosing strategies to protect colorectal and female genital tract (FGT) tissues from HIV infection. Colorectal maraviroc concentrations were 350-fold higher than in the FGT. Under steady-state conditions, our model predicted that one 300-mg dose/week was sufficient to protect colorectal tissue from HIV in 99% of the population, while 300 mg daily would protect the FGT in only 63% of the population. FGT protection increased to >90% when maraviroc was used in combination with tenofovir (5 doses/week) or emtricitabine (3 doses/week). Poor adherence resulted in a drastic decrease in efficacy in the FGT but not colorectal tissue. However, greater forgiveness was seen when maraviroc was combined with tenofovir or emtricitabine, suggesting that maraviroc should not be used alone as PrEP.

Virological and immunological responses to raltegravir and dolutegravir in the gut-associated lymphoid tissue of HIV-infected men and women.

BACKGROUND: Raltegravir (RTG) and dolutegravir (DTG) have different pharmacokinetic patterns in the gastrointestinal tract. To determine if this results in pharmacodynamic differences, we compared HIV RNA, HIV DNA and immunological markers in gut-associated lymphoid tissue (GALT) of HIV-infected participants receiving RTG or DTG with tenofovir+emtricitabine (TDF/FTC). METHODS: GALT specimens from the terminal ileum, splenic flexure and rectum were obtained by colonoscopy at a single time point in 20 adults treated with RTG (n=10) or DTG (n=10) with HIV RNA <50 copies/ml. Flow cytometry, drug concentrations, and HIV RNA and DNA were analysed in tissue. CD4/8+ T-cells were tested for γδ TCR, and markers of T-cell activation and exhaustion. Data are reported as median (Q1-Q3). RESULTS: A total of 15 men and 5 women were enrolled. There was no difference in time since HIV diagnosis for those on RTG (9.5 [4-22] years) and DTG (17 [1-24] years; P=0.6), although time on RTG (5.4 [2.3-6.7] years) was greater than DTG (1.0 [0.1-1.5] years; P<0.001). Concentrations of RTG and DTG in rectal tissue were similar to previous reports: median tissue:plasma ratio was 11.25 for RTG and 0.44 for DTG. RNA:DNA ratios were 1.14 (0.18-5.10) for the RTG group and 0.90 (0.30-18.87) for the DTG group (P=0.95). No differences (P≥0.1) between CD4+ and CD8+ T-cell markers were found. CONCLUSIONS: RTG produced higher tissue exposures than DTG, but no significant differences in GALT HIV RNA, DNA or most immunological markers were observed. ClinicalTrials.gov NCT02218320.

Medical Treatment of Gastroesophageal Reflux Disease.

Medical treatment is effective in the majority of patients with gastroesophageal reflux disease (GERD). Lifestyle modifications are often recommended for patients with GERD, although the data supporting lifestyle recommendations are limited. Antacids are often used to treat the symptoms of GERD, but their effect is short-lived. H2-receptor antagonists and proton-pump inhibitors provide more effective options for remission of GERD symptoms and healing of esophagitis. Prokinetic medications (e.g., metoclopramide) have not been proven to help in the control of symptoms. Baclofen, which inhibits transient lower esophageal sphincter relaxations, provide an additional option for patients with persistent symptoms related to GERD; however its use is limited by side effects. Long-term medical therapy for GERD should be tailored to each patient to provide symptomatic control and maintain esophageal mucosal healing.

Clinical Outcomes Following Recurrence of Intestinal Metaplasia After Successful Treatment of Barrett's Esophagus With Radiofrequency Ablation.

OBJECTIVES: Radiofrequency ablation (RFA) is an effective treatment for Barrett's esophagus (BE). However, recurrence of BE after initially successful RFA is common, and outcomes following recurrence not well described. We report the outcomes associated with recurrence following initially successful RFA. METHODS: We performed a retrospective cohort study of 306 patients treated with RFA for dysplastic BE. Complete eradication of intestinal metaplasia (CE-IM) was defined as complete histological and endoscopic remission of IM. Recurrence was defined as any presence of IM or dysplasia in the tubular esophagus or dysplasia in the gastric cardia subsequent to CE-IM. We examined rates and risk factors for recurrence, dysplastic recurrence, and invasive adenocarcinoma after CE-IM. We also describe the clinical course of patients following recurrence. RESULTS: Of the 306 eligible patients undergoing RFA, 218 achieved CE-IM and also had subsequent surveillance endoscopy. Of these, 52 (24%) experienced recurrence of IM or Barrett's-associated neoplasia over 540.6 person-years (incidence rate 9.6%/year). Thirty (58%) of these achieved second CE-IM; 4 (1.8% of total, 7.7% of recurrences) ultimately progressed to invasive adenocarcinoma (incidence rate 0.65%/year). Longer Prague M was a strong risk factor for invasive adenocarcinoma (rate ratio of 1.34/cm). Most dysplastic recurrences were in the cardia, and the majority were not visible but detected on random biopsies. CONCLUSIONS: Most patients with recurrent BE after initially successful RFA achieve second CE-IM; however, 1.8% progressed to invasive adenocarcinoma. Longer Prague M was predictive of invasive adenocarcinoma. Four-quadrant random biopsy of the cardia is advisable during surveillance endoscopy after CE-IM.

Quantifying the Twitter Influence of Third Party Commercial Entities versus Healthcare Providers in Thirteen Medical Conferences from 2011 - 2013.

INTRODUCTION: Twitter channels are increasingly popular at medical conferences. Many groups, including healthcare providers and third party entities (e.g., pharmaceutical or medical device companies) use these channels to communicate with one another. These channels are unregulated and can allow third party commercial entities to exert an equal or greater amount of Twitter influence than healthcare providers. Third parties can use this influence to promote their products or services instead of sharing unbiased, evidence-based information. In this investigation we quantified the Twitter influence that third party commercial entities had in 13 major medical conferences. METHODS: We analyzed tweets contained in the official Twitter hashtags of thirteen medical conferences from 2011 to 2013. We placed tweet authors into one of four categories based on their account profile: healthcare provider, third party commercial entity, none of the above and unknown. We measured Twitter activity by the number of tweet authors per category and the tweet-to-author ratio by category. We measured Twitter influence by the PageRank of tweet authors by category. RESULTS: We analyzed 51159 tweets authored by 8778 Twitter account holders in 13 conferences that were sponsored by 5 medical societies. A quarter of all authors identified themselves as healthcare providers, while only 18% could be identified as third party commercial entities. Healthcare providers had a greater tweet-to-author ratio than their third party commercial entity counterparts (8.98 versus 6.93 tweets). Despite having less authors and composing less tweets, third party commercial entities had a statistically similar PageRank as healthcare providers (0.761 versus 0.797). CONCLUSION: The Twitter influence of third party commercial entities (PageRank) is similar to that of healthcare providers. This finding is interesting because the number of tweets and third party commercial entity authors required to achieve this PageRank is far fewer than that needed by healthcare providers. Without safety mechanisms in place, the Twitter channels of medical conferences can devolve into a venue for the spread of biased information rather than evidence-based medical knowledge that is expected at live conferences. Continuing to measure the Twitter influence that third parties exert can help conference organizers develop reasonable guidelines for Twitter channel activity.

Cervicovaginal and Rectal Fluid as a Surrogate Marker of Antiretroviral Tissue Concentration: Implications for Clinical Trial Design.

BACKGROUND: Quantifying tissue drug concentrations can yield important information during drug development, but complicates pharmacokinetic study design. Mucosal fluids collected by direct aspiration (cervicovaginal fluid; CVF) or swab (rectal fluid; RF) might be used as tissue concentration surrogates, but these relationships are not well characterized. METHODS: Forty-nine healthy women, given a single oral dose of tenofovir, maraviroc, emtricitabine, or raltegravir at 50%-200% of the treatment dose, provided 13 plasma, 12 CVF, 12 RF and one cervical, vaginal and rectal tissue biopsy over 48 hours. Relationships between these paired samples were characterized by linear and multiple linear regression. Adjusted r values were used to select the final predictive models. RESULTS: CVF exposure increased linearly with dose for all antiretrovirals (r(2) ≥ 0.23, P ≤ 0.02) except raltegravir (r(2) = 0.08, P = 0.19). In RF, only emtricitabine increased linearly with dose (r(2) = 0.27, P = 0.01). For all antiretrovirals, CVF and RF concentrations significantly correlated with mucosal tissue concentrations (female genital tract r(2) ≥ 0.37, rectal tissue (2)r ≥ 0.50, P ≤ 0.001). In the final multivariate models, plasma and fluid concentrations were both associated with FGT concentrations for all antiretrovirals (r(2) ≥ 0.81, P < 0.001). The same was noted for rectal tissue (r(2) ≥ 0.58, P < 0.001) except for tenofovir, for which RF alone was predictive of tissue concentration (r(2) = 0.91, P < 0.001). CONCLUSIONS: Mucosal fluids were positively correlated with tissue concentrations and including plasma concentrations improved the regression models in most cases. Dose linearity in CVF, but not RF, suggests a saturation process in lower gastrointestinal tract tissue. These findings suggest that mucosal fluid and plasma concentrations may be used for qualitative inference of tissue concentrations for these antiretrovirals.

A Translational Pharmacology Approach to Predicting Outcomes of Preexposure Prophylaxis Against HIV in Men and Women Using Tenofovir Disoproxil Fumarate With or Without Emtricitabine.

BACKGROUND: A novel translational pharmacology investigation was conducted by combining an in vitro efficacy target with mucosal tissue pharmacokinetic (PK) data and mathematical modeling to determine the number of doses required for effective human immunodeficiency virus (HIV) preexposure prophylaxis (PrEP). METHODS: A PK/pharmacodynamic (PD) model was developed by measuring mucosal tissue concentrations of tenofovir, emtricitabine, their active metabolites (tenofovir diphosphate [TFVdp] and emtricitabine triphosphate [FTCtp], respectively), and competing endogenous nucleotides (dATP and dCTP) in 47 healthy women. TZM-bl and CD4(+) T cells were used to identify 90% effective concentration (EC90) ratios of TFVdp to dATP and FTCtp to dCTP (alone and in combination) for protection against HIV. Monte-Carlo simulations were then performed to identify minimally effective dosing strategies to protect lower female genital tract and colorectal tissues. RESULTS: The colorectal TFVdp concentration was 10 times higher than that in the lower female genital tract, whereas concentrations of endogenous nucleotides were 7-11 times lower. Our model predicted that ≥98% of the population achieved protective mucosal tissue exposure by the third daily dose of tenofovir disoproxil fumarate plus emtricitabine. However, a minimum adherence to 6 of 7 doses/week (85%) was required to protect lower female genital tract tissue from HIV, while adherence to 2 of 7 doses/week (28%) was required to protect colorectal tissue. CONCLUSIONS: This model is predictive of recent PrEP trial results in which 2-3 doses/week was 75%-90% effective in men but ineffective in women. These data provide a novel approach for future PrEP investigations that can optimize clinical trial dosing strategies.

Advanced Esophageal Squamous Cell Dysplasia and Early Carcinoma Detected After Remote Esophagectomy for Adenocarcinoma.

We present a case of squamous dysplasia and early squamous carcinoma of the esophagus after esophagectomy for esophageal adenocarcinoma. We briefly discuss mucosectomy and ablative therapy as potential treatment options.

A Clinical Prediction Tool Identifies Cases of Eosinophilic Esophagitis Without Endoscopic Biopsy: A Prospective Study.

OBJECTIVES: Eosinophilic esophagitis (EoE) is difficult to distinguish from gastroesophageal reflux (GERD) and other causes of dysphagia. We assessed the utility of a set of clinical and endoscopic features for predicting EoE without obtaining esophageal biopsies. METHODS: We prospectively enrolled consecutive adults undergoing outpatient upper endoscopy at the University of North Carolina from July 2011 through December 2013. Incident cases of EoE were diagnosed per consensus guidelines. Non-EoE controls had either GERD- or dysphagia-predominant symptoms. A predictive model containing clinical and endoscopic, but no histological, data was assessed. Receiver operator characteristic curves were constructed and the area under the curve (AUC) was calculated. RESULTS: A total of 81 EoE cases (mean age 38 years; 60% male; 93% white; 141 eosinophils per high-power field (eos/hpf)) and 144 controls (mean age 52, 38% male; 82% white; 3 eos/hpf) were enrolled. A combination of clinical (age, sex, dysphagia, food allergy) and endoscopic (rings, furrows, plaques, hiatal hernia) features was highly predictive of EoE. The AUC was 0.944, with sensitivity, specificity, and accuracy of 84, 97, and 92%. Similar values were seen after limiting controls to those with only reflux or dysphagia or to those with esophageal eosinophilia not due to EoE. CONCLUSIONS: We validated a set of clinical and endoscopic features to predict EoE with a high degree of accuracy and allow identification of those at very low risk of disease. Use of these predictors at the point-of-care will avoid the effort and expense of low-yield histological examinations for EoE.

Sex and race and/or ethnicity differences in patients undergoing radiofrequency ablation for Barrett's esophagus: results from the U.S. RFA Registry.

BACKGROUND: Little is known about differences in Barrett's esophagus (BE) characteristics by sex and race and/or ethnicity or these differences in response to radiofrequency ablation (RFA). OBJECTIVE: We compared disease-specific characteristics, treatment efficacy, and safety outcomes by sex and race and/or ethnicity in patients treated with RFA for BE. DESIGN: The U.S. RFA patient registry is a multicenter collaboration reporting processes and outcomes of care for patients treated with RFA for BE. PATIENTS: Patients enrolled with BE. INTERVENTIONS: RFA. MAIN OUTCOME MEASUREMENTS: We assessed safety (stricture, bleeding, perforation, hospitalization), efficacy (complete eradication of intestinal metaplasia [CEIM]), complete eradication of dysplasia, and number of treatments to CEIM by sex and race and/or ethnicity. RESULTS: Among 5521 patients (4052 men; 5126 white, 137 Hispanic, 82 African American, 40 Asian, 136 heritage not identified), women were younger (60.0 vs 62.1 years) and had shorter BE segments (3.2 vs 4.4 cm) and less dysplasia (37% vs 57%) than did men. Women were almost twice as likely to stricture (odds ratio 1.7; 95% confidence interval, 1.2-2.3). Although white patients were predominantly male, about half of African Americans and Asians with BE were female. African Americans and Asians had less dysplasia than white patients. Asians and African Americans had more strictures than did white patients. There were no sex or race differences in efficacy. LIMITATIONS: Observational study with non-mandated paradigms, no central laboratory for reinterpretation of pathology. CONCLUSION: In the U.S. RFA patient registry, women had shorter BE segments and less-aggressive histology. The usual tendency toward BE in men was absent in African Americans and Asians. Posttreatment stricture was more common among women and Asians. RFA efficacy did not differ by sex or race.

Recurrent intestinal metaplasia after radiofrequency ablation for Barrett's esophagus: endoscopic findings and anatomic location.

BACKGROUND: Radiofrequency ablation (RFA) is a safe and effective treatment for Barrett's esophagus (BE) that results in high rates of complete eradication of intestinal metaplasia (CEIM). However, recurrence is common after CEIM, and surveillance endoscopy is recommended. Neither the anatomic location nor the endoscopic appearance of these recurrences is well-described. OBJECTIVE: Describe the location of histologic specimens positive for recurrence after CEIM and the testing performance of endoscopic findings for the histopathologic detection of recurrence. DESIGN: Retrospective cohort. SETTING: Single referral center. PATIENTS: A total of 198 patients with BE with at least 2 surveillance endoscopies after CEIM. INTERVENTIONS: RFA, EMR, surveillance endoscopy. MAIN OUTCOME MEASUREMENTS: The anatomic location and histologic grade of recurrence. RESULTS: In a mean 3.0 years of follow-up, 32 (16.2%; 95% confidence interval [CI], 11.0%-22.0%) patients had recurrence of disease, 5 (2.5%; 95% CI, 0.3%-4.7%) of whom progressed beyond their worst before-treatment histology. Recurrence was most common at or near the gastroesophageal junction (GEJ). Recurrence>1 cm proximal to the GEJ always was accompanied by endoscopic findings, and random biopsies in these areas detected no additional cases. The sensitivity of any esophageal sign under high-definition white light or narrow-band imaging for recurrence was 59.4% (42.4%, 76.4%), and the specificity was 80.6% (77.2%, 84.0%). LIMITATIONS: Single-center study. CONCLUSION: Recurrent intestinal metaplasia often is not visible to the endoscopist and is most common near the GEJ. Random biopsies>1 cm above the GEJ had no yield for recurrence. In addition to biopsy of prior EMR sites and of suspicious lesions, random biopsies oversampling the GEJ are recommended.

Extraesophageal presentations of GERD: where is the science?

This article reviews the evaluation and management of patients with suspected extraesophageal manifestations of gastroesophageal reflux disease, such as asthma, chronic cough, and laryngitis, which are commonly encountered in gastroenterology practices. Otolaryngologists and gastroenterologists commonly disagree upon the underlying cause for complaints in patients with one of the suspected extraesophageal reflux syndromes. The accuracy of diagnostic tests (laryngoscopy, endoscopy, and pH- or pH-impedance monitoring) for patients with suspected extraesophageal manifestations of gastroesophageal reflux disease is suboptimal. An empiric trial of proton pump inhibitors in patients without alarm features can help some patients, but the response to therapy is variable.

Clinical and endoscopic characteristics do not reliably differentiate PPI-responsive esophageal eosinophilia and eosinophilic esophagitis in patients undergoing upper endoscopy: a prospective cohort study.

OBJECTIVES: Proton-pump inhibitor-responsive esophageal eosinophilia (PPI-REE) is a newly recognized entity that must be differentiated from eosinophilic esophagitis (EoE). Little is known about this condition. We aimed to determine the prevalence of PPI-REE and EoE in patients undergoing upper endoscopy and determine features that distinguish the two groups. METHODS: This prospective study conducted at the University of North Carolina from 2009 to 2011 enrolled consecutive adult patients undergoing outpatient upper endoscopy. Subjects had esophageal biopsies to quantify the maximum eosinophil count per high-power field (eos/hpf; hpf=0.24 mm(2)). If biopsies revealed ≥15 eos/hpf, subjects were treated with twice daily PPI for 8 weeks and endoscopy was repeated. If ≥15 eos/hpf persisted despite PPI therapy, EoE was diagnosed. If there were <15 eos/hpf, PPI-REE was diagnosed. The proportion of patients in each group was calculated, and patients with EoE and PPI-REE were compared. RESULTS: Of the 223 subjects enrolled, 173 had dysphagia and 50 did not. Of those with dysphagia, 66 (38%) had ≥15 eos/hpf. After the PPI trial, 40 (23%) were confirmed to have EoE, and 24 (14%) had PPI-REE. Of those without dysphagia, 2 (4%) had ≥15 eos/hpf, and after the PPI trial, 1 (2%) had EoE. Compared with EoE, PPI-REE patients were more likely to be older and male and less likely to have typical endoscopic findings of EoE. However, none of the individual factors was independently predictive of PPI-REE status on multivariable analysis. Similarly, although some endoscopic findings were differentially distributed between PPI-REE and EoE, none were significantly associated with disease status on multivariable analysis. CONCLUSIONS: Esophageal eosinophilia is common among patients undergoing esophagogastroduodenoscopy for dysphagia. Although EoE was seen in nearly a quarter of patients with dysphagia, PPI-REE was almost as common, and accounted for over one-third of those with ≥15 eos/hpf. No clinical or endoscopic features independently distinguished PPI-REE from EoE before the PPI trial.

Dolutegravir pharmacokinetics in the genital tract and colorectum of HIV-negative men after single and multiple dosing.

OBJECTIVES: To describe first-dose and steady state pharmacokinetics (PKs) of dolutegravir (DTG) in blood plasma (BP), seminal fluid (SF), colorectal tissue (RT), and rectal mucosal fluid (RF) of healthy HIV-negative men. DESIGN: A phase 1, open-label, PK study that enrolled 12 healthy men taking 50 mg DTG daily for 8 days. METHODS: Eleven paired BP samples and 3 SF and RF samples were collected over 24 hours after first (PK1) and multiple (PK2) dosing. RT biopsies were collected at 1 of 6 time points at PK1 and PK2 to generate composite PK profiles. DTG concentrations were analyzed by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). Noncompartmental PK analysis was conducted with Phoenix WinNonlin v6.3, and Spearman rank correlations were determined using SAS v9.3. RESULTS: BP area under the concentration-time curves (AUCs) were similar to previous reports, and concentrations at 24 hours (C24 h) were 6- to 34-fold greater than the protein-adjusted concentration required for 90% viral inhibition (PA-IC90) of 64 ng/mL. SF exposures were <7% of BP and below the PA-IC90. RT exposures were 17% of BP and ∼2-fold greater than the PA-IC90. RF AUCs were ∼2%-5% of RT and did not correlate with RT (rho = 0.43, P = 0.17). Accumulation of DTG with multiple dosing was observed in BP, SF, and RT. CONCLUSIONS: DTG BP PKs were consistent with previously published values. SF concentrations were <7% BP, with SF C24 h below the PA-IC90. However, SF protein binding was not measured. Although the AUC of DTG in RT was <20% BP, RT C24 h remained ∼2-fold higher than the PA-IC90. RF was not a strong surrogate for RT concentrations.

Differential penetration of raltegravir throughout gastrointestinal tissue: implications for eradication and cure.

OBJECTIVE: To investigate the concentration of the integrase strand inhibitor raltegravir (RAL) throughout gastrointestinal (GI) tissue, especially gut-associated lymphoid tissue (GALT), as an adjunct to current prevention and cure strategies. DESIGN: Open-label pharmacokinetic (PK) study. METHODS: HIV-negative men received RAL 400 mg twice daily for 7 days. Seven blood plasma specimens were collected over 12-h intervals; timed tissue specimens from terminal ileum, splenic flexure, and rectum were also obtained by colonoscopy following the first dose and on day 7 [multiple dose (MD)]. RAL concentrations were measured by validated LC-MS assay with 1 ng/ml lower limit of detection. Data were analyzed by noncompartmental methods (WinNonlin 6). Tissue exposures are reported as composite medians and tissue density of 1.04 g/ml is assumed for comparisons. RESULTS: Fourteen men completed evaluations. Median (range) age was 24 (19-49) years and BMI 25 (19-31) kg/m². After the first dose, area under the time-concentration curve (AUC)(0-12h) was highest in the terminal ileum (594 µg*h/ml). Exposures were 160, 68 and 39-fold greater than blood plasma at the terminal ileum, splenic flexure and rectum, respectively. After multiple doses, exposure was highest at the splenic flexure (2240 µg*h/ml); exposure at the terminal ileum and rectum were equivalent (both 788 µg*h/ml). Following multiple doses, exposures were 160 to 650-fold greater than blood plasma throughout the colon. CONCLUSION: RAL rapidly disseminates into GI tissue and concentrations remain significantly higher than blood plasma. RAL exposure in GI tissue remains higher than any antiretroviral investigated to date. These data suggest that RAL should result in full suppression of viral replication in GI tissue and GALT.