Alice Tseng

Rifabutin-Associated Uveitis

Objective: To review rifabutin-associated uveitis and discuss the mechanism and potential role of drug interactions with clarithromycin and fluconazole in contributing to this adverse event. Data Sources: A MEDLINE search (1991 through September 1994) of English-language literature using the main MeSH headings “rifabutin” and “uveitis” and the subheadings “adverse effects” and “chemically induced.” Relevant articles also were selected from references of identified articles. Abstracts from recent medical conferences of infectious diseases, pharmacology, and HIV were screened for additional data. Study Selection and Data Extraction: All articles and abstracts reporting uveitis potentially related to rifabutin were considered for inclusion. Fifty-four cases were identified. Pertinent information from the case reports, as judged by the authors, was selected and synthesized for discussion. Data Synthesis: Rifabutin is being prescribed increasingly for the treatment and prophylaxis of Mycobacterium avium complex (MAC) infection in the HIV-infected population. Uveitis was initially thought to be a rare, dose-limited complication of rifabutin therapy. In an early dose-ranging tolerance study, uveitis was associated with daily doses of 1200 mg or more. Because this toxicity appeared to be dose-related, lower dosages (300–600 mg/d) of rifabutin were selected for study in subsequent clinical trials. More recent reports noting the association of uveitis with these lower dosages of rifabutin have raised concerns about the prevalence of this adverse event. In the 54 identified cases, patients presented with symptoms of unilateral or bilateral uveitis from 2 weeks to more than 7 months following initiation of rifabutin therapy. In all reported cases, patients were receiving concurrent therapy with clarithromycin and/or fluconazole, both of which have inhibitory effects on rifabutin metabolism. In most cases, uveitis resolved within 1–2 months following discontinuation of rifabutin with or without administration of topical corticosteroids. Conclusions: Rifabutin is prescribed frequently for the prophylaxis and treatment of MAC infection, especially in patients with HIV. Uveitis is a rare, dose-related toxicity of this therapy. The risk of rifabutin-associated uveitis may be increased in patients receiving concurrent therapy with clarithromycin or fluconazole because of drug interactions. Patients receiving therapy with combinations of any of these agents should be warned about signs and symptoms of uveitis and be monitored closely for the development of rifabutin toxicity. If uveitis develops, rifabutin therapy should be discontinued promptly.

Association of Age With Polypharmacy and Risk of Drug Interactions With Antiretroviral Medications in HIV-Positive Patients

Background: Interactions between antiretroviral (ARV) therapy and medications to treat age-related comorbidities are a growing concern in the aging HIV population. Objective: To investigate the association of age with potential drug-drug interactions (PDDIs) involving ARVs. Methods: We studied ARV-treated patients attending a tertiary care center. PDDIs were classified as “red flag” (contraindicated) or “orange flag” (use with caution or dose adjustment). Logistic regression was used to determine the association of age with the occurrence of ≥1 PDDI. Results: Of 914 patients (78% male, median age 49 years), older patients (age ≥50 years) were on more drugs than younger patients (total 9 vs 7; P < .0001) and were more likely to be on ritonavir-boosted protease inhibitors (PIs), integrase inhibitors, and non-ARV medications. Older patients were more likely to have ≥1 orange flag PDDI (71% vs 55%, P < .0001) and to have a red flag PDDI (5% vs 2%, P = .07), although the latter did not reach statistical significance. A 10-year increase in age was associated with an increased likelihood of ≥1 PDDI (odds ratio [OR] = 1.72; P < .0001) after adjusting for gender, race and number and class of ARVs. The effect of age was diminished after adjusting further for the number of non-ARV medications (OR = 1.28; P = .02) and use of cardiovascular drugs (OR = 1.16; P = .21). Conclusions: In our clinic population, older patients were more likely to have a PDDI because of the greater number of non-ARV medications, particularly cardiovascular agents.

A pharmacokinetic study of intermittent rifabutin dosing with a combination of ritonavir and saquinavir in patients infected with human immunodeficiency virus

Our primary aim was to evaluate the plasma exposures and safety of rifabutin and its active 25‐O‐desacetyl metabolite during concomitant therapy of intermittent rifabutin dosing regimens with a combination of ritonavir and saquinavir.

The evolution of three decades of antiretroviral therapy: challenges, triumphs and the promise of the future.

The evolution of human immunodeficiency virus (HIV) treatment has improved our understanding and management of complex pharmacological issues that have driven improved outcomes and quality of life of the HIV-infected patient. These issues include adherence, long- and short-term toxicities, pharmacoenhancement, pharmacogenomics, therapeutic drug monitoring, differential penetration of drugs into sanctuary sites, such as the central nervous system, genital tract and small bowel, and drug-drug and drug-food interactions related to cytochrome P450 drug-metabolizing enzymes, uridine diphosphate glucuronyltransferases and drug transporters, to name a few. There is future promise, as an increased understanding of the immunopathogenesis of HIV and global public health initiatives are driving novel treatment approaches with goals to prevent, control and, ultimately, eradicate HIV.

Non-nucleoside reverse transcriptase inhibitor failure impairs HIV-RNA responses to efavirenz-containing salvage antiretroviral therapy.

In a retrospective cohort study of salvage antiretroviral combination therapy including efavirenz, 60% of 51 patients were able to suppress HIV RNA by at least 1 log10 or to less than 50 copies/ml. A lack of the previous use of non-nucleoside reverse transcriptase inhibitors was the only factor predictive of response on multivariate analysis. No patient with a viral isolate with an increased IC50 to efavirenz by virtual phenotype had a virological response

Clinical impact of double protease inhibitor boosting with Lopinavir/Ritonavir and Amprenavir as part of salvage antiretroviral therapy

Abstract Purpose: Double protease inhibitor (PI) boosting is being explored as a new strategy in salvage antiretroviral (ARV) therapy. However, if a negative drug interaction leads to decreased drug levels of either or both PIs, double PI boosting could lead to decreased virologic response. A negative drug interaction has been described between amprenavir (APV) and lopinavir/ritonavir (LPV/r). This observational cohort study assessed the virologic impact of the addition of APV to a salvage ARV regimen, which also contains LPV/r, compared to a regimen containing LPV/r alone. Method: Patients initiated on a salvage ARV regimen that included LPV/r obtained from the expanded access program in Toronto, Canada, were evaluated. APV (600-1,200 mg bid) was added at the discretion of the treating physician. Results: Using multivariate Cox proportional hazards models, we found that the addition of APV to a LPV/r-containing salvage regimen was not significantly associated with time to virologic suppression (< 50 copies/mL; adjusted hazard ratio [HR] = 0.75, p = .12) or with time to virologic rebound (adjusted HR = 1.46, p = .34). Those patients who received higher doses of APV had an increased chance of virologic suppression (p = .03). In a subset of 27 patients, the median LPV Ctrough was significantly lower in patients receiving APV (p = .04), and the median APV Ctrough was reduced compared to reported controls. Conclusion: Our data do not support an additional benefit in virologic reduction of double boosting with APV and LPV/r relative to LPV/r alone in salvage ARV therapy. Our studys limitations include its retrospective nature and the imbalance between the two groups potentially confounding the results. Although these factors were adjusted for in the multivariate analysis, a prospective randomized controlled trial is warranted to confirm our findings.

Iritis Associated with Intravenous Cidofovir

OBJECTIVE: To report two patients with AIDS and cytomegalovirus retinitis who developed iritis after receiving intravenous cidofovir. Both experienced recurrent symptoms upon rechallenge. CASE SUMMARIES: Two HIV-positive patients with cytomegalovirus retinitis infections previously controlled with intravenous ganciclovir or foscarnet were treated with intravenous cidofovir. Symptoms of iritis developed after the second or third dose of cidofovir. One patient experienced symptoms unilaterally, while the other patient had bilateral symptoms. In both patients, the iritis resolved with topical ophthalmic therapy, but recurred following subsequent infusions of cidofovir. Therapy with cidofovir was discontinued, and no further recurrences of iritis were noted. One patient had post-inflammatory fixed dilated pupils. CONCLUSIONS: Iritis can uncommonly occur in patients receiving intravenous cidofovir and oral probenecid. With prompt drug discontinuation and administration of topical corticosteroids and/or mydriatic agents, symptoms are usually reversible.

Psychiatric treatment considerations with direct acting antivirals in hepatitis C

BackgroundDespite recent advances in hepatitis C (HCV) treatment, specifically the addition of direct acting antivirals (DAAs), pegylated interferon-alpha remains the backbone of HCV therapy. Therefore, the impact of DAAs on the management of co-morbid psychiatric illness and neuropsychiatric sequalae remains an ongoing concern during HCV therapy. This paper provides a review of the neuropsychiatric adverse effects of DAAs and drug-drug interactions (DDIs) between DAAs and psychiatric medications.MethodsWe conducted a Pubmed search using relevant search terms and hand searched reference lists of related review articles. In addition, we searched abstracts for major hepatology conferences and contacted respective pharmaceutical companies for additional studies.ResultsLimited data is available on the neuropsychiatric adverse effects of DAAs; however, data from major clinical trials suggest that DAAs have minimal neuropsychiatric risk. DAAs can potentially interact with a variety of psychotropic agents via cytochrome P450 and p-glycoprotein interactions. Triazolam, oral midazolam, St. John’s Wort, carbamazepine and pimozide, are contraindicated with DAAs. DDIs between DAAs and antidepressants, anxiolytics, hypnotics, mood stabilizers, antipsychotics and treatments for opioid dependence are summarized.ConclusionsAlthough DAAs do not add significant neuropsychiatric risk, the potential for DDIs is high. Consideration of DDIs is paramount to improving medication adherence and mitigating adverse effects during HCV therapy.

Interactions between antifungal and antiretroviral agents

Importance of the field: Since the advent of combination antiretroviral therapy, the incidence of opportunistic infections has declined and the life expectancy of HIV-infected people has significantly increased. However, opportunistic infections, including fungal diseases, remain a leading cause of hospitalizations and mortality in HIV-infected people. With the availability of several new antiretroviral and antifungal agents, drug–drug interactions emerge as a potential safety concern. Areas covered in this review: Relevant literature was identified using a Medline search of articles published up to March 2010 and a review of conference abstracts. Search terms included HIV, antifungal agents and drug interactions. Original papers and relevant citations were considered for this review. What the reader will gain: Readers will gain an understanding of the pharmacokinetic properties of antiretroviral and antifungal agents, and insight into significant drug–drug interactions which may require dosage adjustments or a change in therapy. Take home message: Azole antifungal drugs, with the exception of fluconazole, pose the greatest risk of two-way interactions with antiretroviral drugs through CYP450 enzymes effects. Limited studies suggest the risk of interactions between antiretroviral drugs and echinocandins is much lower. The combination of tenofovir and amphotericin B should be used with caution and close monitoring of renal function is required.

CIHR Canadian HIV Trials Network Coinfection and Concurrent Diseases Core Research Group: 2016 Updated Canadian HIV/Hepatitis C Adult Guidelines for Management and Treatment.

Background. Hepatitis C virus (HCV) coinfection occurs in 20–30% of Canadians living with HIV and is responsible for a heavy burden of morbidity and mortality. Purpose. To update national standards for management of HCV-HIV coinfected adults in the Canadian context with evolving evidence for and accessibility of effective and tolerable DAA therapies. The document addresses patient workup and treatment preparation, antiviral recommendations overall and in specific populations, and drug-drug interactions. Methods. A standing working group with HIV-HCV expertise was convened by The Canadian Institute of Health Research HIV Trials Network to review recently published HCV antiviral data and update Canadian HIV-HCV Coinfection Guidelines. Results. The gap in sustained virologic response between HCV monoinfection and HIV-HCV coinfection has been eliminated with newer HCV antiviral regimens. All coinfected individuals should be assessed for interferon-free, Direct Acting Antiviral HCV therapy. Regimens vary in content, duration, and success based largely on genotype. Reimbursement restrictions forcing the use of pegylated interferon is not acceptable if optimal patient care is to be provided. Discussion. Recommendations may not supersede individual clinical judgement. Treatment advances published since December 2015 are not considered in this document.