Pharmacokinetics, Safety, and Tolerability of Once-Daily Darunavir With Cobicistat and Weekly Isoniazid/Rifapentine.

BACKGROUND: Once-weekly isoniazid with rifapentine (HP) for 3 months is a recommended treatment for latent tuberculosis infection in persons with HIV. HP reduces exposures of certain antiretroviral medications, resulting in limited options for the concomitant use of these therapies. Here, we examined the pharmacokinetics (PK), safety, and tolerability of darunavir/cobicistat with HP. METHODS: This was an open-label, fixed sequence, two-period crossover study in persons without HIV. Participants received darunavir 800 mg/cobicistat 150 mg once-daily alone for 4 days, then continued darunavir/cobicistat once-daily for days 5-19 with HP coadministration on days 5, 12, and 19. Intensive PK assessments were performed on days 4, 14, and 19. PK parameters were determined using noncompartmental methods. Geometric mean ratios with 90% confidence intervals (CIs) were calculated and compared between phases using mixed-effects models. RESULTS: Thirteen participants were enrolled. Two withdrew after day 4, and one withdrew after day 14. Of the 3 withdrawals, 2 were attributed to drug-related adverse events. Darunavir area under the concentration-time curve, maximum concentrations (Cmax), and concentrations at 24 hours postdose (C24h) were reduced by 71%, 41%, and 96% ∼48-72 hours after HP administration (day 14), respectively, and 36%, 17%, and 89% with simultaneous HP administration (day 19), respectively. On day 14, 45% of the predose and 73% of C24h concentrations were below the darunavir EC50 (0.055 µg/mL). CONCLUSIONS: Darunavir exposures were significantly decreased with HP coadministration. Temporal relationships between HP coadministration and the extent of induction or mixed inhibition/induction of darunavir metabolism were apparent. Coadministration of darunavir/cobicistat with 3HP should be avoided.

Quantitative Benefit-Risk Assessment of P-gp-Mediated Drug-Drug Interactions of Dabigatran Coadministered With Pharmacokinetic Enhancers in Patients With Renal Impairment.

Drug-drug interactions (DDIs) between dabigatran and ritonavir/cobicistat are of major concern in people living with HIV, particularly in those with impaired renal function, because they can result in increased dabigatran exposure and thus an increased risk of major bleeding events. However, the extent of this interaction and subsequent need for dose adjustment in subjects with varying degrees of renal function is currently not yet fully understood. To close this knowledge gap, we conducted an integrated population physiologically-based pharmacokinetic/pharmacodynamic analysis linking changes in dabigatran exposure due to DDIs and varying degrees of renal function to the probability of experiencing an ischemic stroke or major bleeding event within 1 year. The results of our analysis suggest that coadministration of dabigatran etexilate (dabigatran prodrug) and ritonavir/cobicistat should be avoided in subjects with severe renal impairment. A 2-hour dose separation or dabigatran etexilate dose reduction to 110 mg b.i.d. (twice daily) should be considered in subjects with moderate renal impairment when coadministered with ritonavir, while the dabigatran etexilate dose should be further reduced to 75 mg b.i.d. when coadministered with cobicistat. No dabigatran etexilate dose adjustment is needed in subjects with normal renal function receiving ritonavir, but dabigatran etexilate dose reduction to 110 mg b.i.d. should be considered when coadministered with cobicistat.

The Effect of GS-548351 on the Pharmacokinetics of Midazolam Following Multiple Doses of ANS-6637 in Healthy Adults.

ANS-6637, a pro-drug of GS-548351, is a selective, reversible inhibitor of aldehyde dehydrogenase isoform 2 under development as an anticraving agent for the treatment of substance use disorders. In vitro testing indicates that GS-548351 is an inhibitor and inducer of cytochrome P450 family 3, subfamily A (CYP3A). In this phase 1 single-center, open-label, fixed-sequence drug-drug interaction study we assessed the impact of steady-state GS-548351 on single-dose pharmacokinetics of midazolam, an index substrate for CYP3A. Twelve healthy volunteers received 600 mg of ANS-6637 by mouth daily from study days 3 to 8 and a single 5-mg oral dose of midazolam on days 1 and 8. Pharmacokinetic samples were collected over 24 hours on days 1 and 8, then analyzed using liquid chromatography-tandem mass spectrometry. The prespecified no-effect range for the 90% confidence interval (CI) of the geometric mean ratio (GMR) of midazolam coadministered with ANS-6637 (day 8) compared with midazolam alone (day 1) was 0.7-1.43. There was an increase in midazolam AUC0-∞ (GMR [90%CI]) that was within the no-effect range (1.26 [1.12-1.425]) and an increase in midazolam Cmax that was outside the range (1.22 [1.03-1.45]). The AUC0-∞ (1.08 [0.91-1.27]) and Cmax (0.95 [0.75-1.2]) of 1-hydroxymidazolam, the primary metabolite of midazolam, were also within the no-effect range. A single grade 3 adverse event (alanine aminotransferase elevation) was identified and resolved following discontinuation of the study drug. Overall, multidose ANS-6637 was well tolerated and did not alter the PK of midazolam beyond a small increase in AUC0-∞ that is unlikely to be clinically significant.

A Randomized Trial of the N-Methyl-d-Aspartate Receptor Glycine Site Antagonist Prodrug 4-Chlorokynurenine in Treatment-Resistant Depression.

BACKGROUND: Ketamine has rapid-acting antidepressant effects but is associated with psychotomimetic and other adverse effects. A 7-chlorokynurenic acid is a potent and specific glycine site N-methyl-d-aspartate receptor antagonist but crosses the blood-brain barrier inefficiently. Its prodrug, L-4-chlorokynurenine (4-Cl-KYN), exerts acute and sustained antidepressant-like effects in rodents and has no reported psychotomimetic effects in either rodents or healthy volunteers. This study examined whether 4-Cl-KYN has rapid antidepressant effects in individuals with treatment-resistant depression. METHODS: After a 2-week drug-free period, 19 participants with treatment-resistant depression were randomized to receive daily oral doses of 4-Cl-KYN monotherapy (1080 mg/d for 7 days, then 1440 mg/d for 7 days) or placebo for 14 days in a randomized, placebo-controlled, double-blind, crossover manner. The primary outcome measure was the Hamilton Depression Rating Scale score, assessed at several time points over a 2-week period; secondary outcome measures included additional rating scale scores. Pharmacokinetic measures of 7-chlorokynurenic acid and 4-Cl-KYN and pharmacodynamic assessments were obtained longitudinally and included 1H-magnetic resonance spectroscopy brain glutamate levels, resting-state functional magnetic resonance imaging, and plasma and cerebrospinal fluid measures of kynurenine metabolites and neurotrophic factors. RESULTS: Linear mixed models detected no treatment effects, as assessed by primary and secondary outcome measures. No difference was observed for any of the peripheral or central biological indices or for adverse effects at any time between groups. A 4-Cl-KYN was safe and well-tolerated, with generally minimal associated adverse events. CONCLUSIONS: In this small crossover trial, 4-Cl-KYN monotherapy exerted no antidepressant effects at the doses and treatment duration studied.ClinicalTrials.gov identifier: NCT02484456.

Utilization of Direct Oral Anticoagulants in People Living with Human Immunodeficiency Virus: Observational Data from the District of Columbia Cohort.

BACKGROUND: Direct oral anticoagulants (DOACs) have become first-line treatment for venous thrombotic events. DOAC prescribing trends among people living with human immunodeficiency virus (PWH) are not well described. The coadministration of DOACs with the antiretroviral (ARV) pharmacokinetic boosters ritonavir (RTV) or cobicistat (COBI) may be complicated by pharmacokinetic interactions. METHODS: A longitudinal cohort study was conducted using the D.C. Cohort Database in Washington, D.C., from January 2011 to March 2017, to describe oral anticoagulant prescribing among PWH ≥ 18 years old and the prevalence of DOAC use with RTV or COBI. Data collection included demographic and clinical characteristics, ARV and anticoagulant prescriptions, and International Classification of Diseases Ninth and Tenth Edition diagnosis codes. RESULTS: Among 8315 PWH, there were 236 anticoagulant prescriptions (96 DOAC, 140 warfarin) for 206 persons. PWH prescribed anticoagulants were predominantly Black (82%) and male (82%), with a mean age at anticoagulant initiation of 56 years. DOAC use increased from 3% of total anticoagulant prescribing in 2011 to 43% in 2016, accounting for 64% of all newly recorded anticoagulant prescriptions by 2016. There were 19 bleeding events recorded among 16 individuals. Despite the Food and Drug Administration label recommendation to avoid rivaroxaban with boosted ARVs, 41% remained on boosted ARVs after rivaroxaban initiation. CONCLUSIONS: DOAC use increased substantially in PWH by 2016. Although rivaroxaban is not recommended with RTV or COBI, concomitant use was recorded in 41% of rivaroxaban recipients in this cohort. As DOAC usage increases, clinicians need to be aware of potential DOAC/ARV interactions in order to select the most appropriate oral anticoagulant and monitoring plan for PWH.

Rapid Development of High-Level Resistance to Dolutegravir With Emergence of T97A Mutation in 2 Treatment-Experienced Individuals With Baseline Partial Sensitivity to Dolutegravir.

HIV integrase mutation T97A emerges after suboptimal therapy with integrase strand transfer inhibitors (INSTIs), but the contribution of T97A to dolutegravir resistance remains uncertain. Here we report >10-fold increase in dolutegravir resistance after the single addition of T97A in 2 individuals with prior INSTI resistance receiving dolutegravir salvage therapy.

Cytokine-Mediated Systemic Adverse Drug Reactions in a Drug-Drug Interaction Study of Dolutegravir With Once-Weekly Isoniazid and Rifapentine.

Background: Once-weekly isoniazid and rifapentine for 3 months is a treatment option in persons with human immunodeficiency virus and latent tuberculosis infection. This study aimed to examine pharmacokinetic drug-drug interactions between this regimen and dolutegravir, a first-line antiretroviral medication. Methods: This was a single-center, open-label, fixed-sequence, drug-drug interaction study in healthy volunteers. Subjects received oral dolutegravir 50 mg once daily alone (days 1-4) and concomitantly with once-weekly isoniazid 900 mg, rifapentine 900 mg, and pyridoxine 50 mg (days 5-19). Dolutegravir concentrations were measured on days 4, 14, and 19, and rifapentine, 25-desacetyl-rifapentine, and isoniazid concentrations were measured on day 19. Cytokines and antidrug antibodies to isoniazid and rifapentine were examined at select time points. Results: The study was terminated following the development of flu-like syndrome and elevated aminotransferase levels in 2 of 4 subjects after the third isoniazid-rifapentine dose. Markedly elevated levels of interferon-γ, CXCL10, C-reactive protein, and other cytokines were temporally associated with symptoms. Antidrug antibodies were infrequently detected. Dolutegravir area under the curve (AUC) was decreased by 46% (90% confidence interval, 27-110%; P = .13) on day 14. Rifapentine and 25-desacetyl rifapentine levels on day 19 were comparable to reference data, whereas isoniazid AUCs were approximately 67%-92% higher in the subjects who developed toxicities. Conclusions: The combined use of dolutegravir with once-weekly isoniazid-rifapentine resulted in unexpected and serious toxicities that were mediated by endogenous cytokine release. Additional investigations are necessary to examine the safety and efficacy of coadministering these medications. Clinical Trials Registration: NCT02771249.

Test Dose Pharmacokinetics in Pediatric Patients Receiving Once-Daily IV Busulfan Conditioning for Hematopoietic Stem Cell Transplant: A Reliable Approach?

Intravenous (IV) busulfan test dose pharmacokinetics (PK) has been shown to accurately predict once-daily dose requirements and improve outcomes in adult transplant patients, but there are limited data to support this approach in children. Test doses of busulfan ∼0.8 mg/kg were infused over 2 to 3 hours, followed by serial sampling to 4-6 hours postinfusion in pediatric hematopoietic stem cell transplant recipients (n = 5). Once-daily busulfan doses were calculated based on a myelosuppressive area under the concentration-time curve (AUC) target of ∼3700 to 4000 µmol·min/L and assumed dose-proportionality to the test dose. PK analysis was then repeated at full daily doses within 6-8 days of test dose administration. Plasma PK samples collected under test and full-dose conditions were analyzed using validated commercial assays and noncompartmental methods. In 4 out of 5 patients, PK estimates after once-daily IV busulfan administration differed in comparison to test dose estimates (AUC range -38.2% to +49.7%, clearance range -34.3% to +61.8%). Patients 1, 2, and 3 required increases in remaining daily busulfan doses to achieve AUC targets, and no adjustment was required in patient 4. Patient 5's AUC was 49.7% higher than expected, and he subsequently developed fatal sinusoidal obstruction syndrome. In our experience with pediatric patients, test dose PK failed to reliably predict daily dosing requirements with large discrepancies from predicted AUC targets. This article highlights the necessity for therapeutic drug monitoring of IV busulfan and inadvisability of relying solely on test-dose busulfan PK in pediatric patients. Furthermore, clinicians should consider strategies to expedite dose adjustments in real time.

Differential Influence of the Antiretroviral Pharmacokinetic Enhancers Ritonavir and Cobicistat on Intestinal P-Glycoprotein Transport and the Pharmacokinetic/Pharmacodynamic Disposition of Dabigatran.

Dabigatran etexilate (DE) is a P-glycoprotein (P-gp) probe substrate, and its active anticoagulant moiety, dabigatran, is a substrate of the multidrug and toxin extrusion protein-1 (MATE-1) transporter. The antiretroviral pharmacokinetic enhancers, ritonavir and cobicistat, inhibit both these transporters. Healthy volunteers received single doses of DE at 150 mg alone, followed by ritonavir at 100 mg or cobicistat at 150 mg daily for 2 weeks. DE was then given 2 h before ritonavir or cobicistat. One week later, DE was given simultaneously with ritonavir or cobicistat. No significant increases in dabigatran pharmacokinetic (PK) exposure or thrombin time (TT) measures were observed with the simultaneous administration of ritonavir. Separated administration of ritonavir resulted in a mean decrease in dabigatran PK exposure of 29% (90% confidence interval [CI], 18 to 40%) but did not significantly change TT measures. However, cobicistat increased dabigatran PK exposure (area under the concentration-versus-time curve from time zero to infinity and maximum plasma concentration) by 127% each (90% CI, 81 to 173% and 59 to 196%, respectively) and increased TT measures (33% for the area-under-the-effect curve from time zero to 24 h [90% CI, 22 to 44%] and 51% for TT at 24 h [90% CI, 22 to 78%]) when given simultaneously with dabigatran. Similar increases were observed when cobicistat was administered separately by 2 h from the administration of dabigatran. In all comparisons, no significant increase in the dabigatran elimination half-life was observed. Therefore, it is likely safe to coadminister ritonavir with DE, while there is a potential need for reduced dosing and prudent clinical monitoring with the coadministration of cobicistat due to the greater net inhibition of intestinal P-gp transport and increased bioavailability. (This study has been registered at ClinicalTrials.gov under identifier NCT01896622.).

Decreased Absorption of Dolutegravir and Tenofovir Disoproxil Fumarate, But Not Emtricitabine, in an HIV-Infected Patient Following Oral and Jejunostomy-Tube Administration.

The use of enteral feeding tubes to administer antiretroviral medications is necessary in certain patients with human immunodeficiency virus (HIV) infection. However, adequacy of drug exposures after these administration routes are largely unknown, making dosing recommendations and the attainment of viral suppression challenging in this patient population. This report describes a patient with advanced HIV infection and a complicated medical history including long-term intractable nausea/vomiting necessitating antiretroviral medication administration via a Roux-en-Y jejunostomy (J)-tube. Pharmacokinetic assessments were performed to compare differences in antiretroviral drug absorption and plasma exposure following oral and J-tube administration of dolutegravir, tenofovir disoproxil fumarate, and emtricitabine. Results were also compared with published pharmacokinetic data in HIV-infected individuals. Exposure to dolutegravir and tenofovir were similar between J-tube and oral administration routes, whereas emtricitabine exposure was 38% lower when administered via J-tube. However, in comparison with reference data in HIV-infected individuals taking these medications orally, exposure to dolutegravir and tenofovir was 75-76% and 55-61% lower, respectively, following both routes of administration. Emtricitabine exposure was similar to and 71% higher than reference data following J-tube and oral administration, respectively. This report highlights the importance of performing pharmacokinetic assessments in patients with the potential for impaired drug absorption to ensure antiretroviral treatment success.

Drug interactions in HIV treatment: complementary & alternative medicines and over-the-counter products.

INTRODUCTION: Use of complementary and alternative medicines (CAMs) and over-the-counter (OTC) medications are very common among HIV-infected patients. These products can cause clinically significant drug-drug interactions (DDIs) with antiretroviral (ARV) medications, thereby increasing risk for negative outcomes such as toxicity or loss of virologic control. Areas covered: This article provides an updated review of the different mechanisms by which CAM and OTC products are implicated in DDIs with ARV medications. Expert commentary: Much of the literature published to date involves studies of CAMs interacting with older ARV agents via the cytochrome P450 (CYP450) system. However, the HIV treatment and prevention arsenal is continually evolving. Furthermore, our elucidation of the role of non-CYP450 mediated DDIs with ARV medications is greatly increasing. Therefore, clinicians are well served to understand the various mechanisms and extent by which new ARV therapies may be involved in drug interactions with CAMs and OTC medications.

Antiretroviral therapy: current drugs.

The rapid advances in drug discovery and the development of antiretroviral therapy is unprecedented in the history of modern medicine. The administration of chronic combination antiretroviral therapy targeting different stages of the human immunodeficiency virus' replicative life cycle allows for durable and maximal suppression of plasma viremia. This suppression has resulted in dramatic improvement of patient survival. This article reviews the history of antiretroviral drug development and discusses the clinical pharmacology, efficacy, and toxicities of the antiretroviral agents most commonly used in clinical practice to date.

Impact of pharmacy technician-centered medication reconciliation on optimization of antiretroviral therapy and opportunistic infection prophylaxis in hospitalized patients with HIV/AIDS.

PURPOSE: This study aimed to examine the role of a pharmacy technician-centered medication reconciliation (PTMR) program in optimization of medication therapy in hospitalized patients with HIV/AIDS. METHODS: A chart review was conducted for all inpatients that had a medication reconciliation performed by the PTMR program. Adult patients with HIV and antiretroviral therapy (ART) and/or the opportunistic infection (OI) prophylaxis listed on the medication reconciliation form were included. The primary objective is to describe the (1) number and types of medication errors and (2) the percentage of patients who received appropriate ART. The secondary objective is a comparison of the number of medication errors between standard mediation reconciliation and a pharmacy-led program. RESULTS: In the PTMR period, 55 admissions were evaluated. In all, 50% of the patients received appropriate ART. In 27of the 55 admissions, there were 49 combined ART and OI-related errors. The most common ART-related errors were drug-drug interactions. The incidence of ART-related medication errors that included drug-drug interactions and renal dosing adjustments were similar between the pre-PTMR and PTMR groups (P = .0868). Of the 49 errors in the PTMR group, 18 were intervened by a medication reconciliation pharmacist. CONCLUSION: A PTMR program has a positive impact on optimizing ART and OI prophylaxis in patients with HIV/AIDS.

The impact of enzyme-inducing antiepileptic drugs on antiretroviral drug levels: a case-control study.

PURPOSE: To evaluate the impact of enzyme-inducing antiepileptic drugs (EI-AEDs) on serum antiretroviral (ARV) levels in patients with HIV. METHODS: Data from the U.S. Military HIV Natural History Study were screened to identify participants taking ARVs with EI-AEDs and controls taking ARVs with non enzyme-inducing AEDs (NEI-AEDs). The proportion of serum ARV levels below the recommended minimum concentrations (C(min)) was compared between these groups. RESULTS: ARV levels were available for 10 individuals exposed to 16 intervals on combined ARVs/EI-AEDs (phenytoin and carbamazepine) and for 25 controls exposed to 30 overlap intervals on combined ARVs/NEI-AEDs. The percentage of overlap intervals with ≥1 ARV levels below C(min) was higher in the EI-AED group than in controls (37.5% vs. 23.3%; p=0.124). After excluding intervals associated with serum levels of EI-AEDs below the reference range (n=6), the proportion of intervals with ≥1 ARV level below C(min) was significantly greater among EI-AED recipients (60%) compared to controls (23.3%; p=0.008). CONCLUSIONS: ARV levels below C(min) were more common in participants receiving EI-AEDs, the difference being statistically significant for intervals associated with EI-AED levels within the reference range. These data suggest that, in agreement with current guidelines, EI-AEDs should be avoided in patients receiving ARV therapy.

National survey on continuous and extended infusions of antibiotics.

PURPOSE: A national survey was conducted to evaluate the use of continuous and extended infusions for administering ß-lactams and vancomycin. METHODS: The survey was sent to a random sample of 1000 acute care hospital pharmacists in the United States to evaluate the use of continuous and extended infusions of antibiotics. In addition, the same survey was sent to members of the Society of Infectious Diseases Pharmacists (SIDP) to assess the adoption of these infusion strategies. RESULTS: In the random-sample survey, 29 (11.2%) and 15 (5.8%) hospitals reported using continuous and extended infusions, respectively. Common rationales for adopting continuous and extended infusions were greater efficacy, equal or less toxicity, and cost savings. The SIDP survey revealed that 30 (50%) and 21 (35%) of responding pharmacists have initiated continuous and extended infusions, respectively. Common rationales for adopting continuous and extended infusions were greater efficacy, equal or less toxicity, and cost savings. Both surveys found that penicillins were the antibiotics most frequently administered as continuous and extended infusions. CONCLUSION: The results of a survey sent to a random sample of hospital pharmacists and to SIDP members indicated that the majority did not use either continuous or extended infusions of antibiotics. SIDP survey respondents more frequently reported the use of both continuous and extended infusions than the respondents of the random-sample survey, and the percentage of time above the minimum inhibitory concentration was the most frequently assessed pharmacokinetic-pharmacodynamic parameter for both groups.

Antiepileptic drug selection for people with HIV/AIDS: evidence-based guidelines from the ILAE and AAN.

A joint panel of the American Academy of Neurology (AAN) and the International League Against Epilepsy (ILAE) convened to develop guidelines for selection of antiepileptic drugs (AEDs) among people with HIV/AIDS. The literature was systematically reviewed to assess the global burden of relevant comorbid entities, to determine the number of patients who potentially utilize AEDs and antiretroviral agents (ARVs), and to address AED-ARV interactions. Key findings from this literature search included the following: AED-ARV administration may be indicated in up to 55% of people taking ARVs. Patients receiving phenytoin may require a lopinavir/ritonavir dosage increase of approximately 50% to maintain unchanged serum concentrations (Level C). Patients receiving valproic acid may require a zidovudine dosage reduction to maintain unchanged serum zidovudine concentrations (Level C). Coadministration of valproic acid and efavirenz may not require efavirenz dosage adjustment (Level C). Patients receiving ritonavir/atazanavir may require a lamotrigine dosage increase of approximately 50% to maintain unchanged lamotrigine serum concentrations (Level C). Coadministration of raltegravir/atazanavir and lamotrigine may not require lamotrigine dosage adjustment (Level C). Coadministration of raltegravir and midazolam may not require midazolam dosage adjustment (Level C). Patients may be counseled that it is unclear whether dosage adjustment is necessary when other AEDs and ARVs are combined (Level U). It may be important to avoid enzyme-inducing AEDs in people on ARV regimens that include protease inhibitors or nonnucleoside reverse transcriptase inhibitors because pharmacokinetic interactions may result in virologic failure, which has clinical implications for disease progression and development of ARV resistance. If such regimens are required for seizure control, patients may be monitored through pharmacokinetic assessments to ensure efficacy of the ARV regimen (Level C).

Prolonged infusions of ß-lactam antibiotics: implication for antimicrobial stewardship.

The optimal dosage and administration of antibiotics are not only important measures to combat antimicrobial resistance, but they are also integral to antimicrobial stewardship. In light of a diminishing antibiotic pipeline and an alarming rise in resistance, the optimal dosage and administration of antimicrobial agents have been under a great deal of scrutiny. Prolonged infusions of ß-lactam antibiotics have been proposed as an alternate dosing strategy. To summarize the evidence on prolonged infusions of ß-lactam agents and provide their clinical implications for antimicrobial stewardship, we performed a MEDLINE search (1950-2011) of all relevant articles. This article provides a review of data from Monte Carlo simulations, clinical outcome analyses, and pharmacoeconomic studies. Furthermore, protocol implementation strategies are discussed to address antimicrobial stewardship.

Penetration of anti-infective agents into pulmonary epithelial lining fluid: focus on antifungal, antitubercular and miscellaneous anti-infective agents.

Epithelial lining fluid (ELF) is often considered to be the site of extracellular pulmonary infections. During the past 25 years, a limited number of studies have evaluated the intrapulmonary penetration of antifungal, antitubercular, antiparasitic and antiviral agents. For antifungal agents, differences in drug concentrations in ELF or bronchoalveolar lavage (BAL) fluid were observed among various formulations or routes of administration, and between agents within the same class. Aerosolized doses of deoxycholate amphotericin B, liposomal amphotericin B and amphotericin B lipid complex resulted in higher concentrations in ELF or BAL fluid than after intravenous administration. The mean concentrations in ELF following intravenous administration of both anidulafungin and micafungin ranged between 0.04 and 1.38 µg/mL, and the ELF to plasma concentration ratios (based on the area under the concentration-time curve for total drug concentrations) were between 0.18 and 0.22 during the first 3 days of therapy. Among the azole agents, intravenous administration of voriconazole resulted in the highest mean ELF concentrations (range 10.1-48.3 µg/mL) and ratio of penetration (7.1). The range of mean ELF concentrations of itraconazole and posaconazole following oral administration was 0.2-1.9 µg/mL, and the ELF to plasma concentration ratios were <1. A series of studies have evaluated the intrapulmonary penetration of first- and second-line oral antitubercular agents in healthy adult subjects and patients with AIDS. The ELF to plasma concentration ratio was >1 for isoniazid, ethambutol, pyrazinamide and ethionamide. For rifampicin (rifampin) and rifapentine, the ELF to plasma concentration ratio ranged between 0.2 and 0.32, but in alveolar macrophages the concentration of rifampicin was much higher (145-738 µg/mL compared with 3.3-7.5 µg/mL in ELF). No intrapulmonary studies have been conducted for rifabutin. Sex, AIDS status or smoking history had no significant effects on the magnitude of ELF concentrations of antitubercular agents. Subjects who were slow acetylators had higher plasma and ELF concentrations of isoniazid than those who were fast acetylators. Penetration of dapsone into ELF was very good, with the range of mean ELF to plasma concentration ratios being 0.65-2.91 at individual sampling times over 48 hours. Once-daily dosing of aerosolized pentamidine resulted in higher concentrations in BAL fluid than after intravenous administration. The mean BAL concentrations at 15-32 days after once- or twice-monthly administration of aerosolized pentamidine 300 and 600 mg ranged from 6.5 to 28.4 ng/mL. No differences in pentamidine BAL concentrations were observed in symptomatic patients who developed Pneumocystis jirovecii pneumonia compared with patients who did not. Zanamivir concentrations in ELF were similar in magnitude (range 141-326 ng/mL) following administration by continuous intravenous infusion (3 mg/hour), oral inhalation (10 mg every 12 hours) and intravenous bolus (200 mg every 12 hours). Data from case reports have suggested that concentrations of nelfinavir and saquinavir in ELF are undetectable, whereas tipranavir and lopinavir had measureable ELF concentrations (2.20 µmol/L and 14.4 µg/mL, respectively) when these protease inhibitors were co-administrated with ritonavir. While the clinical significance of ELF or BAL concentrations remains unknown for this group of anti-infective agents, the knowledge of drug penetration into the extracellular space of the lung should assist in re-evaluating and designing specific dosing regimens for use against potential pathogens.