COVID-19: A Review of Potential Treatments (Corticosteroids, Remdesivir, Tocilizumab, Bamlanivimab/Etesevimab, and Casirivimab/Imdevimab) and Pharmacological Considerations.

Objectives: In light of the ongoing global pandemic, this paper reviews data on a number of potential and approved agents for COVID-19 disease management, including corticosteroids, remdesivir, tocilizumab, and monoclonal antibody combinations. Dose considerations, potential drug-drug interactions, and access issues are discussed. Key findings: Remdesivir is the first antiviral agent approved for the treatment of COVID-19, based on results from large clinical trials showing reduction in recovery time, faster clinical improvement, and decrease in time to discharge with remdesivir. Dexamethasone and tocilizumab have demonstrated mortality benefits in large, randomized controlled trials. Consequently, the use of corticosteroids has become the standard of care for hospitalized patients with severe or critical COVID-19, while tocilizumab is recommended for use in combination with a corticosteroid in certain hospitalized patients. Recently, monoclonal antibody combinations bamlanivimab/etesevimab and casirivimab/imdevimab received emergency use authorizations for use in non-hospitalized patients with mild-to-moderate COVID-19 at high risk of disease progression. Summary: As data from large clinical trials emerge, the paradigm of COVID-19 treatments has shifted significantly. The use of corticosteroids, remdesivir, and tocilizumab depend on disease severity. Emerging data on monoclonal antibody combinations are promising, but further data are required. Pharmacists can play a role in ensuring appropriate access, correct administration, and safe use of COVID-19 treatments and are encouraged to stay abreast of new developments.

Getting to the Heart of the Matter: A Review of Drug Interactions Between HIV Antiretrovirals and Cardiology Medications.

The past 20 years have seen remarkable advances in the treatment of HIV such that most people diagnosed with HIV today can live long, healthy lives by taking antiretrovirals which are usually life-long. Advancements in antiretroviral therapy include the availability of well tolerated, single tablet regimens that are associated with a lower risk of drug-drug interactions. Despite this, many people living with HIV infection might be taking antiretroviral agents that are associated with significant drug-drug interactions. Because HIV infection itself is associated with cardiovascular complications and this population is living longer, concomitant use of antiretrovirals and medications to treat cardiovascular-related diseases is often required. For this reason, it is imperative that clinicians are aware of the potential for clinically significant drug-drug interactions between antiretroviral agents and cardiac medications as well as the useful HIV drug interaction resources that might provide guidance. Available data on significant interactions are summarized and suggested guidance regarding management is discussed.

Randomized controlled trial of once-daily tenofovir, lamivudine, and lopinavir/ritonavir versus remaining on the same regimen in virologically suppressed HIV-infected patients on their first PI-containing HAART regimen.

PURPOSE: To assess the effects of switching to once-daily (QD) lopinavir/ritonavir (LPV/r)-based combination therapy in HIV-infected patients who are virologically suppressed (HIV viral load <50 copies/mL) on their first protease inhibitor (PI)-containing regimen. METHOD: In this 48-week, prospective, open-label, randomized study, patients were either switched to once-daily LPV/r, tenofovir (TDF), and lamivudine (3TC) (QD arm) or remained on their existing regimen (control arm). The primary endpoint of the study was the proportion of patients maintaining virologic suppression following 48 weeks of treatment. RESULTS: Fifty and 22 patients were randomized to the QD and control arms, respectively. At week 48, there was no significant difference in virological suppression between the QD and control arms using intent-to-treat (missing = failure) analysis (p = .44). There was no significant difference in discontinuation rates between the two arms (p = .66). Significantly more patients randomized to the QD arm reported gastrointestinal adverse events compared with the control arm (p = .009). There were no study drug-related serious adverse events. CONCLUSION: For patients who are already virologically suppressed on their first PI-containing regimen, switching to a QD regimen of TDF+3TC+LPV/r resulted in similar rates of virologic suppression when compared with staying on existing therapy.

CD4+ cell count decline despite HIV suppression: a probable didanosine-valganciclovir interaction.

OBJECTIVE: To describe a case of significant CD4+ cell decline despite complete viral suppression in an HIV-positive patient receiving didanosine and valganciclovir. CASE SUMMARY: A 68-year-old woman diagnosed with HIV and cytomegalovirus (CMV) enteritis (CD4+ cell count 22 cells/mm(3), viral load 88,898 [4.95 log] copies/mL) was treated with valganciclovir and began lamivudine, didanosine, and lopinavir/ritonavir. Three months later, her viral load was less than 50 copies/mL and CD4+ cell count was 317 cells/mm(3). Over the next 9 months, her viral load remained suppressed, but the CD4+ cell count declined to 83 cells/mm(3) and she experienced ongoing symptoms of didanosine toxicity. Didanosine was replaced with abacavir, leading to a complete CD4+ cell recovery and resolution of symptoms. DISCUSSION: Paradoxical declines in CD4+ cell counts have been reported in HIV-infected patients virally suppressed on tenofovir/didanosine regimens, presumably via inhibition of purine nucleoside phosphorylase (PNP) by tenofovir and enhancement of didanosine toxicity. Ganciclovir and its prodrug valganciclovir also inhibit PNP and increase didanosine concentrations; thus, a similar immunological effect with this combination is possible. This hypothesis is consistent with observations from a historic multicenter CMV retinitis study, where a negative CD4+ cell response was observed in patients receiving ganciclovir, while those treated with foscarnet experienced a CD4+ cell increase and a mortality advantage. Of the subjects who received any type of nucleoside therapy during this study, didanosine use was proportionally higher in the ganciclovir arm versus the foscarnet arm. According to the Naranjo probability scale, our patient experienced a probable adverse reaction associated with the combination of didanosine and valganciclovir. CONCLUSIONS: Patients receiving didanosine-containing highly active antiretroviral therapy and ganciclovir or valganciclovir for treatment of CMV infection should be monitored for didanosine toxicity and unexpected CD4+ cell loss or failure of CD4+ cell recovery. Reduction of didanosine dosage or substitution with an alternative antiretroviral may be necessary.

Interactions between antiretrovirals and antineoplastic drug therapy.

Despite the established impact of highly active antiretroviral therapy (HAART) in reducing HIV-related morbidity and mortality, malignancy remains an important cause of death. Patients who receive the combination of cancer chemotherapy and HAART may achieve better response rates and higher rates of survival than patients who receive antineoplastic therapy alone. However, the likelihood of drug interactions with combined therapy is high, since protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) are substrates and potent inhibitors or inducers of the cytochrome P450 (CYP) system. Since many antineoplastic drugs are also metabolised by the CYP system, coadministration with HAART could result in either drug accumulation and possible toxicity, or decreased efficacy of one or both classes of drugs. Although formal, prospective pharmacokinetic interaction studies are not available in most instances, it is possible to infer the nature of drug interactions based on the metabolic fates of these agents. Paclitaxel and docetaxel are both metabolised by the CYP system, although differences exist in the nature of the isoenzymes involved. Case reports describing adverse consequences of concomitant taxane-antiretroviral therapy exist. Although other confounding factors may have been present, these cases serve as reminders of the vigilant monitoring necessary when taxanes and HAART are coadministered. Similarly, vinca alkaloids are substrates of CYP3A4 and are, thus, vulnerable to PI- or NNRTI-mediated changes in their pharmacokinetics. Interactions with the alkylating agents cyclophosphamide and ifosfamide are complicated as a result of the involvement of the CYP3A4 and CYP2B6 isoenzymes in both the metabolic activation of these drugs and the generation of potentially neurotoxic metabolites. Existing data regarding the metabolic fate of the anthracyclines doxorubicin and daunorubicin suggest that clinically detrimental interactions would not be expected with coadministered HAART. Commonly used endocrine therapies are largely substrates of the CYP system and may, therefore, be amenable to modulation by concomitant HAART. In addition, tamoxifen itself has been associated with reduced concentrations of both anastrozole and letrozole, raising the concern that similar inducing properties may adversely affect the outcome of PI- or NNRTI-based therapy. Similarly, dexamethasone is both a substrate and concentration-dependent inducer of CYP3A4; enhanced corticosteroid pharmacodynamics may result with CYP3A4 inhibitors, while the efficacy of concomitant HAART may be compromised with prolonged dexamethasone coadministration. Since PIs and NNRTIs may also induce or inhibit the expression of P-glycoprotein, the potential for additional interactions to arise via modulation of this transporter also exists. Further research delineating the combined safety and pharmacokinetics of antiretrovirals and antineoplastic therapy is necessary.

Tenofovir: a nucleotide analog for the management of human immunodeficiency virus infection.

Tenofovir disoproxil fumarate, an acyclic nucleotide analog of adenosine monophosphate, is the most recent addition to the antiretroviral arsenal. After conversion to tenofovir by diester hydrolysis, subsequent phosphorylation by cellular enzymes to form the active tenofovir diphosphate is necessary for antiretroviral activity. Preliminary data suggest that tenofovir is as safe and efficacious as stavudine when given in combination with lamivudine and efavirenz for the treatment of antiretroviral-naïve patients. In antiretroviral-experienced patients, the addition of tenofovir to stable background antiretroviral therapy resulted in approximately a 0.6 log10 copies/ml reduction in viral load relative to placebo. Extended follow-up suggests that such virologic gains may be durable. In vitro, recombinant human immunodeficiency virus (HIV) expressing the K65R mutation showed a 3-4-fold increase in the 50% inhibitory concentrations of tenofovir when compared with wild type. In vivo, this mutation thus far appears to occur infrequently and is associated with variable virologic responses. Response rates to tenofovir vary with the number and pattern of thymidine analog mutations present before starting treatment with this agent. Tenofovir appears to be a well-tolerated agent in patients who are heavily pretreated and who have advanced disease. The main adverse effects appear to be gastrointestinal in nature and include nausea, vomiting, and diarrhea. In animals, osteomalacia and nephrotoxicity have occurred with tenofovir at exposures much higher than those observed in humans. Although no patient had to discontinue therapy as a result of elevated creatinine levels or hypophosphatemia through 58 weeks of treatment, the toxicities associated with long-term tenofovir therapy in humans are unknown. Concomitant administration of tenofovir and didanosine increases the area under the concentration-time curve of the latter by 44-60%; monitoring for signs and symptoms of didanosine toxicity is recommended. The approved dosage of tenofovir is 300 mg (one tablet) once/day with meals. Given the ease of administration and relative safety from the perspectives of adverse effects and drug interactions, tenofovir has the potential to assume a large role in the treatment of patients with HIV infection.

Significant interaction between activated charcoal and antiretroviral therapy leading to subtherapeutic drug concentrations, virological breakthrough and development of resistance.

A 42-year-old, treatment-experienced woman, virologically suppressed on tenofovir/emtricitabine and boosted atazanavir, experienced virological breakthrough, drop in CD4(+) T-cell count and undetectable drug concentrations. Adherence to treatment was confirmed, but repeat testing yielded similar results. After 2 months, the patient stated that she had been taking activated charcoal to manage gastrointestinal symptoms associated with her combination antiretroviral therapy, but she had recently discontinued the charcoal. Atazanavir concentrations were therapeutic but the patient's viral load rebounded and genotype testing revealed new reverse transcriptase mutations. The patient was changed to zidovudine, lamivudine, and boosted darunavir and achieved viral suppression. At 1 year follow-up, her viral load remained <40 copies/ml. According to the drug interaction probability scale, our patient experienced a probable drug interaction between activated charcoal and atazanavir/ritonavir leading to virological breakthrough and development of resistance.

Steady-state pharmacokinetics and tolerability of indinavir-lopinavir/r combination therapy in antiretroviral-experienced patients.

Six HIV-positive antiretroviral experienced patients initiating therapy with a regimen including lopinavir/ritonavir (400/100 mg twice per day) and indinavir (800 mg twice per day) underwent steady-state pharmacokinetic analysis. The AUC0-12 h of indinavir when combined with lopinavir/ritonavir was comparable with previously published data on indinavir/ritonavir 800/100 mg twice per day in HIV-infected individuals. However, lopinavir AUC0-12 h, Cmax, and C12 h were lower than previously reported in the absence of indinavir. The regimen was well tolerated, although 2 patients developed grade 3 hypertriglyceridemia. No patient discontinued the regimen because of indinavir-related urologic or retinoid-type adverse effects. Further study of the regimen with larger cohorts of patients is necessary.

Evaluation of HIV drug interaction web sites.

BACKGROUND: Clinicians frequently consult HIV drug interaction Web sites of unknown quality. OBJECTIVE: To systematically review and identify HIV drug interaction Web sites of high quality and usefulness for healthcare professionals. METHODS: Relevant Web sites were identified through a structured search on commonly used search engines. An assessment tool containing 4 domains (content, reliability, access restrictions, ease of navigation) was developed. English and French Web sites were selected for review if they included HIV drug interaction information directed to healthcare professionals. Web sites were excluded if antiretroviral interaction data were not available or were out of date. Commercial online databases and sites that required payment were not included. Seventeen HIV pharmacists from across Canada participated in the review. The Web sites were ranked with total mean scores. Mean scores for each domain were then analyzed. Interrater agreement and ANOVA using the rater as a covariate were determined. RESULTS: Nine Web sites met the criteria for review. Web sites from Toronto General Hospital (Canada), HIVinSite (beta version) (US), and the University of Liverpool (UK) ranked highest for total mean scores and for content. Other Web sites were found to be reliable, accessible, and easy to navigate; however, they did not consistently include unpublished data or data on herbal preparations, recreational drugs, or multiple interactions. CONCLUSIONS: Three HIV interaction Web sites of high quality were identified that can be valuable tools for HIV and non-HIV health-care professionals. Regular reviews are necessary in order to keep pace with the growing body of HIV interaction data and the constant evolution of Web sites.