Possible interaction between intravenous azithromycin and oral cyclosporine

Combination of Hydroxychloroquine Plus Azithromycin As Potential Treatment for COVID-19 Patients: Safety Profile, Drug Interactions, and Management of Toxicity

The coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2, has recently emerged worldwide. In this context, there is an urgent need to identify safe and effective therapeutic strategies for treatment of such highly contagious disease. We recently reported promising results of combining hydroxychloroquine and azithromycin as an early treatment option. Although ongoing clinical trials are challenging the efficacy of this combination, many clinicians claim the authorization to or have already begun to use it to treat COVID-19 patients worldwide. The aim of this article is to share pharmacology considerations contributing to the rationale of this combination, and to provide safety information to prevent toxicity and drug-drug interactions, based on available evidence.

Drug Interactions between Antimicrobial and Immunosuppressive Agents in Solid Organ Transplant Recipients

The number of allogeneic solid organ and bone marrow transplants is increasing all over the world. To prevent transplant rejection and treat acute rejection of transplant, immunosuppressant drugs are used. The outcomes of solid organ transplants have dramatically improved over last 30 years, due to availability of multiple immunosuppressive agents, with varied mechanisms of action. The use of intense immunosuppression makes the individual having undergone solid organ transplant at the risk of several serious infections, which may prove fatal. To prevent and treat these infections (when they occur), patients are often given antimicrobial prophylaxis and therapy. The use of antimicrobials can interfere with the metabolism of the immunosuppressants, and may put the patient at risk of developing severe adverse effects due to unwanted increase or decrease in the serum levels of immunosuppressive agents. Knowledge of these interactions is essential for successful management of solid organ transplant patients. We therefore decided to review the literature and present the interactions that commonly occur between these two life-saving groups of drugs.

How to cite this article: Bhagat V, Pandit RA, Ambapurkar S, Sengar M, Kulkarni AP. Drug Interactions between Antimicrobial and Immunosuppressive Agents in Solid Organ Transplant Recipients. Indian J Crit Care Med 2021;25(1):67–76.

Identification of Antibiotic Administration as a Potentially Novel Factor Associated With Tacrolimus Trough Variability in Kidney Transplant Recipients: A Preliminary Study

Supplemental Digital Content is available in the text.

Tacrolimus trough variability is an important risk factor for kidney allograft outcomes. Recent evidence suggests that the gut microbiota is associated with tacrolimus dosing requirements and direct metabolism of tacrolimus. We hypothesize that administration of antibiotics, which are known to alter the gut microbiota, is associated with tacrolimus trough variability.

Interactions between anti-infective agents and immunosuppressants-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation provide an update on potential drug-drug interactions between anti-infectives and immunosuppressants, which are most notable with calcineurin and mTOR inhibitors. Drug-drug interactions may occur through pharmacokinetic mechanisms leading to altered drug concentrations of either the anti-infective or immunosuppressive drug, or by pharmacodynamic interactions increasing or decreasing the efficacy or toxicity of the medications. Many of the significant pharmacokinetic interactions occur through inhibition or induction of the cytochrome 3A4 system by anti-infective agents leading to increased or decreased immunosuppressive agent levels, respectively. The membrane transporter P-glycoprotein is also often involved in drug interactions. Since the last iteration of these guidelines, multiple new hepatitis C virus direct-acting antivirals have become available for use in SOT recipients. Of these agents, some are substrates of cytochrome and drug transporter systems, while others inhibit these systems and may affect immunosuppressive agents. Due to the high risk for drug-drug interactions in the solid organ transplant population, practitioners must be aware of potential interactions and be vigilant in monitoring and adjusting drug dosing when appropriate.

Proposal for a New Tool to Evaluate Drug Interaction Cases

The assessment of causation for a potential drug interaction requires thoughtful consideration of the properties of both the object and precipitant drugs, patient-specific factors, and the possible contribution of other drugs that the patient may be taking. The Naranjo nomogram was designed to evaluate single-drug adverse events, not drug–drug interactions. Several of the questions on the Naranjo nomogram do not apply to potential drug–drug interactions, while others do not specify object or precipitant drug. Nevertheless, it has been inappropriately used to evaluate drug–drug interactions. The Drug Interaction Probability Scale (DIPS) was developed to provide a guide to evaluating drug interaction causation in a specific patient. It is intended to be used to assist practitioners in the assessment of drug interaction–induced adverse outcomes. The DIPS uses a series of questions relating to the potential drug interaction to estimate a probability score. An accurate assessment using the DIPS requires knowledge of the pharmacologic properties of both the object and precipitant drugs. Inadequate knowledge of either the drugs involved or the basic mechanisms of interaction will be a limitation for some users. The DIPS can also serve as a guide in the preparation of articles describing case reports of drug interactions, as well as in the evaluation of published case reports.

Medical Management of Cyclosporine-Induced Gingival Overgrowth Using Oral Azithromycin in Six Dogs

Gingival overgrowth is an uncommon adverse effect of cyclosporine administration in veterinary species. In people, gingival overgrowth is a common complication of cyclosporine administration for immunosuppression, generally following transplant procedures. Azithromycin has been used successfully for managing gingival overgrowth in human transplant patients when cyclosporine administration cannot be reduced or discontinued. This case series describes six dogs being administered cyclosporine for various dermatologic diseases that developed gingival overgrowth. The dogs were prescribed systemic azithromycin, with or without concurrent dose reduction of cyclosporine. Oral administration of 6.6-10.8 mg/kg of azithromycin once daily for 4-14 weeks was effective for complete clinical resolution of gingival overgrowth. In most cases, gingival overgrowth did not recur even with continued cyclosporine administration long-term. Adverse events of long-term azithromycin administration did not occur in any of the dogs. This series highlights a potentially beneficial medical treatment option for gingival overgrowth even when cyclosporine dose reduction is not possible or elected, without the need for surgical resection of proliferative gingival tissue.

Evaluation of azithromycin in systemic and toothpaste forms for the treatment of ciclosporin-associated gingival overgrowth in dogs

BACKGROUND

Gingival overgrowth is an adverse effect of ciclosporin therapy. Azithromycin (AZI) in capsule and toothpaste form is an effective treatment for ciclosporin-associated gingival overgrowth (CsAGO) in humans.

HYPOTHESIS/OBJECTIVES

To evaluate AZI in a systemic and a toothpaste form for the treatment of CsAGO in dogs. The secondary objective was to determine which treatment is more effective.

ANIMALS

Thirty-six client-owned dogs with CsAGO.

METHODS

Dogs were randomly assigned to the following four groups: AZI capsule; AZI toothpaste; placebo capsule; and placebo toothpaste. Treatments were for 4 weeks, and measurements of gingival sulcus depth, tooth length and subjective global scores were taken at weeks 0, 2, 4 and 8. The AZI dose was 10 mg/kg daily, and brushing (8.5% AZI) was once daily.

RESULTS

There was a significant decrease in gingival sulcus depth for the AZI capsule group at week 8 and for the AZI toothpaste group at weeks 2, 4 and 8. The mean decrease in gingival sulcus depth was significantly greater in active versus placebo groups (P = 0.0356). The tooth length and subjective global scores were not significantly different for any groups. Gastrointestinal adverse events occurred in all groups, but more frequently in the AZI capsule group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Azithromycin improved CsAGO in only one measured parameter, gingival sulcus depth. Only one dog in the AZI capsule group had complete resolution of CsAGO. Further studies are warranted. Azithromycin capsules were associated with the most gastrointestinal adverse effects.

Predicting concentrations of trace organic compounds in municipal wastewater treatment plant sludge and biosolids using the PhATE™ model

This article presents the capability expansion of the PhATE™ (pharmaceutical assessment and transport evaluation) model to predict concentrations of trace organics in sludges and biosolids from municipal wastewater treatment plants (WWTPs). PhATE was originally developed as an empirical model to estimate potential concentrations of active pharmaceutical ingredients (APIs) in US surface and drinking waters that could result from patient use of medicines. However, many compounds, including pharmaceuticals, are not completely transformed in WWTPs and remain in biosolids that may be applied to land as a soil amendment. This practice leads to concerns about potential exposures of people who may come into contact with amended soils and also about potential effects to plants and animals living in or contacting such soils. The model estimates the mass of API in WWTP influent based on the population served, the API per capita use, and the potential loss of the compound associated with human use (e.g., metabolism). The mass of API on the treated biosolids is then estimated based on partitioning to primary and secondary solids, potential loss due to biodegradation in secondary treatment (e.g., activated sludge), and potential loss during sludge treatment (e.g., aerobic digestion, anaerobic digestion, composting). Simulations using 2 surrogate compounds show that predicted environmental concentrations (PECs) generated by PhATE are in very good agreement with measured concentrations, i.e., well within 1 order of magnitude. Model simulations were then carried out for 18 APIs representing a broad range of chemical and use characteristics. These simulations yielded 4 categories of results: 1) PECs are in good agreement with measured data for 9 compounds with high analytical detection frequencies, 2) PECs are greater than measured data for 3 compounds with high analytical detection frequencies, possibly as a result of as yet unidentified depletion mechanisms, 3) PECs are less than analytical reporting limits for 5 compounds with low analytical detection frequencies, and 4) the PEC is greater than the analytical method reporting limit for 1 compound with a low analytical detection frequency, possibly again as a result of insufficient depletion data. Overall, these results demonstrate that PhATE has the potential to be a very useful tool in the evaluation of APIs in biosolids. Possible applications include: prioritizing APIs for assessment even in the absence of analytical methods; evaluating sludge processing scenarios to explore potential mitigation approaches; using in risk assessments; and developing realistic nationwide concentrations, because PECs can be represented as a cumulative probability distribution. Finally, comparison of PECs to measured concentrations can also be used to identify the need for fate studies of compounds of interest in biosolids.

Azithromycin maintenance therapy in patients with cystic fibrosis: a dose advice based on a review of pharmacokinetics, efficacy, and side effects

Azithromycin maintenance therapy results in improvement of respiratory function in patients with cystic fibrosis (CF). In azithromycin maintenance therapy, several dosing schemes are applied. In this review, we combine current knowledge about azithromycin pharmacokinetics with the dosing schedules used in clinical trials in order to come to a dosing advise which could be generally applicable. We used data from a recently updated Cochrane meta analysis (2011), the reports of clinical trials and pharmacokinetic studies. Based on these data, it was concluded that a dose level of 22-30 mg/kg/week is the lowest dose level with proven efficacy. Due to the extended half-life in patients with CF, the weekly dose of azithromycin can be divided in one to seven dosing moments, depending on patient preference and gastro-intestinal tolerance. No important side effects or interactions with other CF-related drugs have been documented so far.

Elevated tacrolimus levels associated with intravenous azithromycin and ceftriaxone: a case report

Drug interactions are a common occurrence with calcineurin inhibitors. We describe the case of a heart transplant recipient who developed increased tacrolimus blood levels after the administration of intravenous azithromycin and ceftriaxone. Tacrolimus levels decreased after the discontinuation of ceftriaxone and switch from intravenous to oral azithromycin. Transplant recipients who receive intravenous azithromycin and/or ceftriaxone concomitantly with tacrolimus therapy should be monitored closely for the duration of the antibiotic administration.

Azithromycin is associated with increased survival in lung transplant recipients with bronchiolitis obliterans syndrome

BACKGROUND

Previous studies have suggested that azithromycin improves lung function in lung transplant recipients with bronchiolitis obliterans syndrome (BOS). However, these studies did not include a non-treated BOS control cohort or perform survival analysis. This study was undertaken to estimate the effect of azithromycin treatment on survival in lung transplant recipients with BOS.

METHODS

We conducted a retrospective cohort study of consecutive lung transplant recipients who developed BOS between 1999 and 2007. An association between azithromycin treatment and death was assessed using univariate and multivariate time-dependent Cox regression analysis.

RESULTS

Of the 178 recipients who developed BOS in our study, 78 did so after 2003 and were treated with azithromycin. The azithromycin-treated and untreated cohorts had similar baseline characteristics. Univariate analysis demonstrated that azithromycin treatment was associated with a survival advantage and this beneficial treatment effect was more pronounced when treatment was initiated during BOS Stage 1. Multivariate analysis demonstrated azithromycin treatment during BOS Stage 1 (adjusted hazard ratio = 0.23, p = 0.01) and absolute forced expiratory volume in 1 second (FEV(1)) at the time of BOS Stage 1 (adjusted hazard ratio = 0.52, p = 0.003) were both associated with a decreased risk of death.

CONCLUSIONS

In lung transplant recipients with BOS Stage 1, azithromycin treatment initiated before BOS Stage 2 was independently associated with a significant reduction in the risk of death. This finding supports the need for a randomized, controlled trial to confirm the impact of azithromycin on survival in lung transplant recipients.

Legionella pneumonia in cancer patients

Legionella is an important cause of nosocomial and community-acquired pneumonia in both immunocompetent and immunosuppressed patients worldwide; however, the clinical course and optimal antibiotic therapy of Legionella pneumonia (LP) in patients with cancer is uncertain. We studied retrospectively the risk factors, clinical manifestations, and outcome of 49 cancer patients with a positive Legionella culture or direct fluorescent antibody (DFA) over a 13-year period (1991-2003). The majority of patients (82%) had an underlying hematologic malignancy, and 37% were bone marrow transplant recipients; 80% of the patients had active malignancy. Lymphopenia (47%), use of systemic corticosteroids (41%), and chemotherapy (63%) were the most common underlying conditions. The laboratory diagnosis was established by positive Legionella culture (n = 8, 16%), DFA (n = 29, 59%), or both (n = 12, 25%). In 4 patients (8%), a positive DFA was deemed to represent false-positive results. There was no temporal or geographic clustering of cases. The majority of the cases had multilobar (61%) or bilateral (55%) pulmonary involvement. The mean time to response to therapy was 8 days; 18 patients (37%) developed complications requiring prolonged duration of treatment (mean, 25 d). The case-fatality rate was 31%. Two patients had relapse of LP despite appropriate therapy. Improved outcome, especially in those with severe pneumonia, seemed to correlate with the use of a combination of antibiotics. LP is an uncommon infection in our patient population but is associated with significant morbidity and mortality. Treatment of LP in cancer patients may require a prolonged course with a regimen that includes a newer macrolide or quinolone.

Pharmacokinetic/pharmacodynamic modeling of in vitro activity of azithromycin against four different bacterial strains

The bacterial time-kill curves of azithromycin against four bacterial strains (Streptococcus pneumoniae/penicillin-intermediate, S. pneumoniae/penicillin-sensitive, Haemophilus influenzae and Moraxella catarrhalis) were determined by in vitro infection models. Eighteen different pharmacokinetic/pharmacodynamic models were fitted to the time-kill data using non-linear regression and compared for best fit. A simple, widely used E(max) model was not sufficient to describe the pharmacodynamic effects for the four bacterial strains. Appropriate models that gave good curve fits included additional terms for saturation of the number of bacteria (N(max)), delay in the initial bacterial growth phase and/or the onset of anti-infective activity (1-exp(-zt)) as well as a Hill factor (h) that captures the steepness of the concentration-response profile. Azithromycin was highly effective against S. pneumoniae strains and M. catarrhalis while the efficacy against H. influenzae was poor. Applications of these pharmacokinetic/pharmacodynamic models will eventually provide a tool for rational antibiotic dosing regimen decisions.

Lip hypertrophy secondary to cyclosporine treatment: a rare adverse effect and treatment considerations

Gingival hypertrophy is a well-known and extensively documented undesirable side effect of cyclosporine in posttransplant patients. However, severe lip enlargement associated with cyclosporine is less recognized and has seldom been reported in the literature. Lip enlargement may lead to social, physical, and psychological stress, especially in the older childhood and adolescent age groups. We present a case of marked lip hypertrophy and concomitant gingival hypertrophy secondary to cyclosporine (Neoral) treatment in a pediatric bilateral lung transplant recipient. We also discuss the various side effects and treatment considerations available including more recent substitution therapy. Cyclosporine has most effectively and conclusively enabled transplantation of solid organs by reducing transplant-associated morbidity. We believe clinicians should be knowledgeable and aware of lip hypertrophy associated with cyclosporine use. This rare and less understood adverse effect should be recognized during the clinical evaluation of the posttransplant patient.

Macrolide antibiotics and bronchiolitis obliterans following lung transplantation

The anti-inflammatory effects of macrolide antibiotics are of emerging importance. Over the past 20 years, chronic inflammatory respiratory conditions, including diffuse panbronchiolitis, cystic fibrosis and asthma have benefited from long-term low-dose macrolide therapy. Obliterative bronchiolitis, a form of chronic allograft dysfunction in lung transplant recipients, has been reported to be a condition in which macrolide therapy may be indicated. A number of recent cohort studies have been encouraging. Disease progression was delayed with macrolide antibiotic therapy as patients showed a sustained improvement in pulmonary function tests. Up to now, obliterative bronchiolitis has been resistant to most forms of proposed treatment. This review aims to highlight the etiology of obliterative bronchiolitis, the mechanisms of immunomodulation associated with macrolide therapy and how macrolide therapy may be effective by way of these possible mechanisms.

Infectious risk in pediatric organ transplant recipients: is it increased with the new immunosuppressive agents?

The risk of infection in pediatric organ transplant recipients is determined by several factors, including age, the types of organ transplanted and the immunosuppressive treatment which has dramatically changed over the past 10 yr. Little information has been reported regarding the infectious complications related to the current immunosuppressive protocols used in these children. This paper reviews (i) the immunosuppressive agents, focusing on their mechanisms of action and on the new regimens, (ii) the infections related to excessive immunosuppression and also anti-infectious properties or infectious adverse reactions associated with specific immunosuppressive agents. With the new immunosuppressive protocols, the advances in immunologic monitoring, microbiological diagnosis, anti-infectious prophylactic and preemptive treatments, strategies to minimize the risk of infection related to the immunosuppressive therapy are proposed.

Immunosuppressants

Immunosuppressants are prescribed to prevent rejection of transplanted tissues and organs and are also used in the treatment of autoimmune disorders. Consultation-liaison psychiatrists increasingly encounter patients taking these agents as the number of transplant recipients increases and the indications for the use of immunosuppressants expands. These drugs have potentially deleterious physical, mental, and biochemical side effects. In addition, transplant recipients and patients with autoimmune disorders commonly have comorbid illnesses that require pharmacologic treatment. The management of these patients is challenging secondary to the severity of these illnesses, the number of medications prescribed, and the potential for adverse drug-drug interactions. Knowledge of the pharmacokinetic properties of these drugs and the potential for serious drug-drug interactions that cause alterations in serum levels of the immunosuppressant medications is essential. Increased serum levels may cause serious toxic effects and decreased serum levels may lead to rejection of the transplanted organ or worsening of the autoimmune disorder. Adverse events may also occur when serum levels of medications prescribed for comorbid illnesses are altered by administration of immunosuppressants. The pharmacokinetic drug-drug interaction profiles of the glucocorticoids, cyclosporine, tacrolimus, sirolimus, mycophenolate mofetil, azathioprine, and monoclonal antibodies are discussed in this review.

Maintenance azithromycin therapy for bronchiolitis obliterans syndrome: results of a pilot study

Bronchiolitis obliterans syndrome remains the leading cause of morbidity and mortality in the pulmonary transplant population. Previous studies show that macrolide antibiotics may be efficacious in the treatment of panbronchiolitis and cystic fibrosis. In the latter, azithromycin decreases the number of respiratory exacerbations, improves FEV1, and improves quality of life. We hypothesized that oral azithromycin therapy may improve lung function in patients with bronchiolitis obliterans syndrome. To test this hypothesis, we conducted an open-label pilot trial using maintenance azithromycin therapy in six lung transplant recipients (250 mg orally three times per week for a mean of 13.7 weeks). In this study, five of these six individuals demonstrated significant improvement in pulmonary function, as assessed by FEV1, as compared with their baseline values at the start of azithromycin therapy. The mean increase in the percentage of predicted FEV1 values in these individuals was 17.1% (p </= 0.05). In addition, the absolute FEV1 increased by 0.50 L (range -0.18 to 1.36 L). These data suggest a potential role for maintenance macrolide therapy in the treatment of bronchiolitis obliterans syndrome in lung transplant recipients.

Influence of P-glycoprotein inhibitors on accumulation of macrolides in J774 murine macrophages

The influence of inhibitors of P-glycoprotein (verapamil [VE], cyclosporine [CY], and GF120918 [GF]) on the cell handling of macrolides (erythromycin [ERY], clarithromycin [CLR], roxithromycin [ROX], azithromycin [AZM], and telithromycin [TEL]) was examined in J774 murine macrophages. The net influx rates of AZM and TEL were increased from 2- to 3.5-fold in the presence of these inhibitors, but their efflux was slowed only marginally. At 3 h, the inhibitors increased the levels of AZM, ERY, and TEL accumulation approximately three- to fourfold (the effect of VE, however, was lower) but did not influence CLR accumulation (the inhibitors had an intermediate behavior on ROX accumulation). The effect was concentration dependent (half-maximal increases in the level of accumulation of AZM were obtained with GF, CY, and VE at 0.5, 5, and 10 micro M, respectively). ATP depletion also caused an approximately threefold increase in the level of accumulation of AZM. Two inhibitors of MRP (probenecid [2.5 mM] and gemfibrozil [0.25 mM]) had no effect. Monensin (a proton ionophore) completely suppressed the accumulation of AZM in control cells as well as in cells incubated in the presence of VE, demonstrating that transmembrane proton gradients are the driving force causing the accumulation of AZM in both cases. Yet, VE did not alter the pH of the lysosomes (approximately 5) or of the cytosol (approximately 7.1). P-glycoprotein was detected by immunostaining at the cell surface as well as in intracellular vacuoles (endosomes and lysosomes). The data suggest that the influx of AZM, ERY, TEL, and ROX is adversely influenced by the activity of P-glycoprotein in J774 macrophages, resulting in suboptimal drug accumulation.

Immunosuppressants

This edition of the Med-Psych Drug-Drug Interactions Update begins a change in format. Starting with this column, each column will feature one drug-drug interaction (DDI) topic that will be explored in depth. This edition features DDIs associated with the commonly used immunosuppressants. These drugs are frequently encountered by consultation-liaison psychiatrists in tertiary care settings. Generally, most of these drugs have narrow safety and therapeutic windows; therefore, other drugs that change their serum levels can have deleterious effects. In this review, the DDI profiles of cyclosporine, tacrolimus, sirolimus, and the corticosteroids are explored.