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Volume: 19 Issue: 1 January 2021

FULL TEXT

ARTICLE
Nebulized Amphotericin B Dosing Regimen for Aspergillus Prevention After Lung Transplant

Objectives: Lung transplant guidelines recommend nebulized amphotericin B with or without systemic antifungal agents for fungal prophylaxis. However, amphotericin formulation, dosing, and frequency vary between studies. We assessed the safety and effectiveness of nebulized amphotericin B to prevent Aspergillus infection in 2 regimens, ie, twice daily compared with 3 times daily.

Materials and Methods: This was a single-center retrospective cohort study. We included patients at least 14 years old who underwent lung transplant and received nebulized amphotericin B alone or in combination with another antifungal agent either twice daily or 3 times daily. The primary endpoint was the incidence of lung Aspergillus infection, and the secondary endpoints were nebulized amphotericin B side effects and breakthrough Aspergillus infection.

Results: A total of 84 patients were included. The group given nebulized amphotericin twice daily had a higher rate of Aspergillus infection at 17% compared with 4% in the group treated 3 times daily (P = .24). No serious side effects were reported, but coughing and diarrhea were more common in patients who received amphotericin B 3 times daily.

Conclusions: A systemic antifungal agent combined with nebulized amphotericin either twice or 3 times daily has been effective to prevent Aspergillus infection. Nebulized amphotericin twice daily may be a more viable option to increase a patient’s adherence and decrease medication cost and side effects. However, a larger randomized controlled trial is needed to determine the best dosing regimen for nebulized amphotericin B as a fungal prophylaxis after lung transplant.


Key words : Aspergillosis, Post-lung transplantation, Prophylaxis

Introduction

Infection is one of the leading causes of mortality in lung transplant (LT) recipients during the first year after transplant.1 Fungal infections are reported to be a predictor of mortality after LT.1,2 Invasive fungal infections in the early posttransplant period are commonly caused by Candida spp or Aspergillus spp.1 The incidence of Aspergillus infection ranges from 1.7% to 33% during the first 12 months after LT.3-5

This wide range of Aspergillus infection rates has been attributed to differences in immunosuppression regimens, antimicrobial prophylaxis regimens, geographical area, follow-up duration, and definitive diagnostic criteria for Aspergillus infection.3 Factors that may predispose to aspergillosis included the donors, the recipients, and the transplant procedures. After LT, it is a challenge for practitioners to balance a patient’s level of immunosuppression with the risk of fungal infection. Therefore, all LT guidelines and transplant center protocols recommend universal or preemptive antifungal prophylaxis.3,4,6 The Interna­tional Society for Heart and Lung Transplantation guidelines recommend nebulized amphotericin B (nAB), either alone or in combination with systemic antifungal agents, for the first 2 to 4 weeks posttransplant; nAB may be the preferred antifungal agent for prevention because it possesses a broad fungicidal spectrum, lower systemic absorption, and long half-life.7-11 It also provides a site-targeted effect while limiting the risk of harmful drug-to-drug interactions.10 Past studies have demonstrated the efficacy of conventional and liposomal nAB to prevent fungal infections.5,11-13

The dosing regimens of nAB vary widely among studies. Some common nAB deoxycholate dosing regimens are as follows: 10 mg twice daily,14,15 25 mg dosed 3 times per week,16 or 0.5 to 1.5 mg/kg daily.17 However, a worldwide survey of various LT centers found that daily dosing of nAB is the most common frequency used.18 The optimal regimen for dosage, formulation, and duration of nAB for fungal prophylaxis is unknown.8 Thus, practitioners face a challenge when choosing the optimal regimen for fungal prophylaxis.

In the LT center where this study conducted, the institutional LT protocol recommended itraconazole and nAB twice daily for 3 months posttransplant; however, this protocol changed in 2016 to a regimen of 3 times daily, as recommended by the American Society of Transplantation Infectious Disease Community of Practice.19 In this study, over a period of 3 months post-LT, we assessed the safety and effectiveness of nAB to prevent Aspergillus infection in 2 dosage regimens, ie, twice daily compared with 3 times daily.

Materials and Methods

Study population
This was a retrospective cohort study that included all patients 14 years or older who underwent LT (based on the institutional criteria of adults at 14 years old) at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. This center houses the most comprehensive and advanced facility for multiorgan transplant in the Middle East; its LT program is the only one of its kind in the region. At this center, a total of 132 LTs were performed from the beginning of the program on January 1, 2010, until December 31, 2017. However, in this study, only patients who received nAB alone or in combination with another antifungal agent were included. Patients were excluded if they (1) received other solid-organ transplants alone or concomitantly or (2) received nAB for fungal treatment. Data for each patient were obtained from the medical records for 1 year after the transplant date. Ethics approval was obtained from the King Faisal Specialist Hospital and Research Centre Institutional Review Board (RAC No. 218174).

Immunosuppressant regimen
In compliance with our center’s institutional LT protocol, all patients received 500 mg of methylp­rednisolone intravenously per anastomosis at the time of reperfusion as induction therapy. This dose was followed by a daily taper to 20 mg of prednisolone over 6 days. This dose was maintained until 1 month after transplant. Prednisone was then tapered down to 5 mg at 6 months after transplant if there were no signs of graft rejection. All patients were given standard triple immunosuppressant regimens. On the first day after transplant, tacrolimus-based therapy was commenced in combination with mycophenolate mofetil at 1000 mg twice daily. The tacrolimus starting dose was 0.05 to 0.15 mg/kg twice daily, which was then adjusted to maintain the tacrolimus blood concentration between 12 and 15 ng/mL for the first 3 months. If patients were unable to tolerate tacrolimus side effects, then they were switched to cyclosporine.

Antimicrobial prophylaxis
All patients received a preoperative intravenous antibiotic and then de-escalated as needed, depending on donor cultures and surgical cultures. For Pneumocystis pneumonia prophylaxis, all patients received oral trimethoprim-sulfamethoxazole (160 and 800 mg, respectively) 3 times weekly for life. In patients with a positive donor/negative recipient cytomegalo­virus serology, antiviral prophylaxis with valgan­ciclovir at 900 mg/d was maintained for 1 year; for patients with positive-donor/positive-recipient or negative-donor/positive-recipient cytomegalovirus serology, antiviral prophylaxis with 450 mg/d of valganciclovir was maintained for 1 year. Before 2017, patients in the LT program received a dosage of isoniazid that was based on the recipient’s results of the purified protein derivative tuberculin test and QuantiFERON-TB Gold (Qiagen) test; however, after 2017, the program protocol was changed to provide all patients with 300 mg daily of isoniazid plus 50 mg pyridoxine daily for 12 months.

Antifungal prophylaxis
The LT program protocol recommended that patients should receive 200 mg daily of oral itraconazole and 6 mg of nebulized conventional amphotericin B deoxycholate (ie, nAB) delivered via the Respirgard medication nebulizer system (Marquest Medical Products) at a flow of 7 L/min every 12 hours for the first 3 months posttransplant. However, in 2018, the institutional LT program protocol was changed to recommend nAB every 8 hours. At baseline, 1 patient was colonized with Aspergillus that was transmitted from the donor. This patient received 200 mg of voriconazole twice daily instead of itraconazole, 1 month after transplant.

Data collection
We used the Research Electronic Data Capture software (REDCap version 8.9.0) to collect patient data from electronic medical records. Donor data included age, sex, blood type, and history of positive cultures. Recipient data included demographics, operative and postoperative data, and immuno­suppressive regimen. Recipients’ vital measurements and renal and liver function tests were recorded at baseline, at day 7, and at months 3, 6, 9, and 12 posttransplant, during and after a complete course of nAB prophylaxis. The study outcomes were also gathered, including Aspergillus infection, nAB side effects, and rates of survival for patients and allografts within 1 year post-LT.

Clinical outcomes
The study hypothesis was that the rate of lung Aspergillus infection at 1 year after transplant would be lower in patients treated 3 times daily with nAB compared with patients treated twice daily, for 3 months posttransplant. The primary endpoint was the incidence of lung Aspergillus infection after the initiation of antifungal prophylaxis; this endpoint was determined by the isolation of Aspergillus spp. from respiratory cultures 12 months posttransplant. Before start or after the completion of antifungal prophylaxis course, Aspergillus colonization was identified as the presence of a positive Aspergillus culture in the absence of physician documentation of invasive aspergillosis, whereas invasive aspergillosis was defined according to physician documentation in the presence of clinical signs, symptoms, and positive respiratory cultures of Aspergillus spp. Secondary outcomes were based on the assessment of nAB safety and the incidence of Aspergillus breakthrough. Safety was defined by the absence of adverse symptoms indicative of aspergillosis such as bronchospasm, cough, dyspnea, chest tightness, dizziness, dysgeusia, fever, nausea, and vomiting; also, the isolation of Aspergillus spp. during the nAB course was considered to be breakthrough Aspergillus infection. Liver function test values that were 3 times the upper limit of normal were deemed to be indicative of hepatotoxicity.

Statistical analyses
Mean values and standard deviations (SD) were used to describe continuous variables, whereas the frequency and percentages were used to describe the categorical variables. The bivariate chi-square test was used to assess the correlations between categorical variables. The independent group t test was used to evaluate the means of continuous variables for statistically significant differences across the dichotomous variables. We used SPSS software (version 22) to perform all statistical analyses.

Results

Characteristics of LT patient cohort
A total of 84 LT recipients met the inclusion criteria. There were 60 patients in the nAB twice daily group, with 49 receiving this regimen in combination with itraconazole. There were 24 patients in the nAB 3 times daily group, with most (83%) receiving this regimen with concomitant itraconazole treatment. Baseline demographics were similar in both study groups (Table 1). The mean age of recipients was 37 ± 15 years, and the mean age of donors was 38.82 ± 12.7 years.

The most common underlying indicator for transplant was interstitial lung disease (50%) in both groups. Some of the recipients had more than 1 underlying illness. All patients received a triple immunosuppressant regimen. Most patients (n = 49) were on tacrolimus plus mycophenolate mofetil and corticosteroids. Eight patients received cyclosporine instead of tacrolimus, to avoid tacrolimus-related neurotoxic side effects. During the study follow-up period, 31 patients were switched from mycop­henolate mofetil to azathioprine to mitigate severe gastrointestinal intolerance or hematological side effects. Only 1 patient received sirolimus added as a fourth agent to the regimen because of a history of recurrent rejection.

Outcome and prophylaxis effect
During the first year post-LT, 11 patients tested positive for Aspergillus spp. The Aspergillus spp growth was as follows: 5 A niger, 4 A flavus, 1 A terreus, and 1 A fumigaus. A higher rate of Aspergillus growth was seen among patients who received nAB twice daily (n = 10, 16.66%) versus among the 3 times daily group (n = 1, 4.16%) (P = .240). Of those 10 patients who received nAB twice daily, 1 patient had invasive aspergillosis while the remaining 9 patients had Aspergillus colonization (Figure 1). In the group given nAB 3 times daily, only 1 patient had Aspergillus infection while on the nAB regimen; this patient was colonized with Aspergillus at baseline from an Aspergillus-infected lung from the donor. At the time of Aspergillus occurrence, only 2 of the 11 patients were on nAB monotherapy. The mean duration of nAB use for both groups was 97.28 ± 48.05 days, and the mean time of Aspergillus infection occurrence was 44 ± 44.05 days. All of the patients were on the triple immunosuppressant regimen while positive for Aspergillus infection; most of them were on tacrolimus, mycophenolate mofetil, and corticosteroid. Four patients in the nAB twice daily group had breakthrough Aspergillus infection, and the remaining patients tested positive for Aspergillus.

Most of the patients tolerated nAB well. Patients on the twice daily prophylaxis regimen experienced fewer side effects in comparison with the 3 times daily regimen. However, most of the side effects were not significantly higher in the 3 times daily group except for flatulence (P = .004). One patient experien­ced a severe neurological side effect, manifested as “jerky” movements, which led to the discontinuation of nAB in the twice daily group (Table 2).

In the first year after transplant, 22 patients had biopsy-proven rejection. Only 2 of these 22 patients were infected with A flavus. Four patients (4.8%) experienced graft loss, with 1 of these patients colonized with Aspergillus. Patient mortality rate was 8.3% (n = 7). Cause of death was either septic shock, cardiopulmonary arrest secondary to hemorrhage shock, chronic lung allograft dysfunction, respiratory failure, or pulmonary hemorrhage. Among the patients who died, 1 was colonized with Aspergillus.

Discussion

Several studies have supported the use of nAB for fungal prophylaxis in LT recipients, either alone or in combination with systemic antifungal agents.5,10,11 However, nAB dosing and frequency varied among studies and was undefined in the guidelines.6,14-18 Nebulized amphotericin B dosing may also vary depending on whether the liposomal or conventional formulation is used.5,11-13 Thus, practitioners cannot readily choose the safest and most effective dose and frequency of nAB. We believe that our study may be the first to compare various nAB dosing frequencies to determine the optimal dosing regimen of nAB.

In this study, patients who received nAB twice daily had a higher rate of Aspergillus infection compared with the patients who received nAB 3 times daily. However, this number was not statistically significant (P = .240). Most patients who tested positive for Aspergillus infection were colonized cases, which is considered a risk factor for invasive aspergillosis in LT recipients.20,21 Patients may acquire Aspergillus colonization from donors. This was the case of the colonized patient in the nAB 3 times daily group who later tested positive for Aspergillus. Another reason for Aspergillus colonization may be related to the recipients themselves, such as the extended use of corticosteroid pretransplant for the underlying lung disease or the history of positive cultures and recent hospital admission.22 The history of intensive care unit (ICU) admission in patients who received nAB 3 times daily was significantly higher (P = .004), which may explain the observation that patients who were prescribed nAB 3 times daily were already critical cases at baseline. The fact that only 1 patient had invasive aspergillosis may suggest the effectiveness of nAB to prevent invasive aspergillosis occurrence regardless of the dosing frequency.

In our study, the overall Aspergillus infection rate during the first year after transplant, at 13.09%, remains within the range of previous reports.3-5 In previous studies, the indicated time of Aspergillus infection was between 3.2 and 8.8 months after transplant.7,23 In contrast, here, the mean time of Aspergillus infection was earlier, at 1.46 months posttransplant, mostly during the time of antifungal prophylaxis use. This occurrence may be caused by the high level of immunosuppressant during that early period post-LT, especially since most patients were on a triple immunosuppressant regimen that included high doses of steroids. Another reason for the early onset of infection in those patients could be the lengthy durations of hospitalization and ICU stays, which may increase the risk of patients acquiring nosocomial infections.

Although the higher frequency of nAB dosing was associated with lower rates of Aspergillus infection, it was also associated with higher rates of nAB side effects. Most of these were tolerable. Contrary to previous studies that reported bronchospasm as the main reason for nAB discontinuation,7 none of the patients reported bronchospasm in our study. Most of the transplant recipients were on multiple immuno­suppressant agents or antimicrobial prophylaxis medications, so we were not able to conclude that the noted side effects were solely caused by nAB. Resistance to nAB is uncommon,24 but in this study 4 of 11 patients tested positive for Aspergillus during the nAB twice daily course. None of these infections, however, was invasive. The use of systemic antifungal agents, in addition to nAB, may synergically reduce the risk of Aspergillus invasive infection and colonization because the state of treatment provided Aspergillus double coverage.

The primary limitation of our study was its single-center retrospective study design, thus making it difficult to distinguish among Aspergillus colonization, contamination, and infection cases. The results may have been confounded by the use of systemic antifungal agents in addition to nAB in most patients. The combination of systemic antifungal agents with nAB may augment the effectiveness of nAB, reduce the infection rate of Aspergillus, and inflate the occurrence of side effects. Moreover, the systemic antifungal agent was not received by all patients, which complicates the assessment of the effectiveness of the nebulized regimens. Reliance on patients to maintain adherence to nAB after hospital discharge may have been affected by some recall bias. Although the size of our sample may be larger than in other previous studies, including this patient population, the small sample size limited our conclusions.

In conclusion, our study was unable to demonstrate the greater effectiveness to prevent Aspergillus infection in the 3 times daily nAB regimen versus the twice daily nAB regimen. Therefore, the choice of the nAB dosing frequency may be dependent on recipient characteristics and donor cultures. The regimen for giving nAB twice daily remains a viable option, as it may increase patient adherence and decrease medication cost and side effects. However, this study can only serve to generate a hypothesis for a larger randomized controlled trial to confirm the results and determine the best dosing regimen for nAB as a fungal prophylaxis post-LT.


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Volume : 19
Issue : 1
Pages : 58 - 63
DOI : 10.6002/ect.2020.0187


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From the 1Pharmaceutical Care Division, King Faisal Specialist Hospital and Research Center; the 2Department of Infectious Disease, King Faisal Specialist Hospital and Research Center; the 3Organ Transplant Center, King Faisal Specialist Hospital and Research Center; and the 4Department of Pharmacy Practice, College of Pharmacy, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
Acknowledgements: This research was funded by the Deanship of Scientific Research at Princess Nourah Bint Abdulrahman University through the Fast-track Research Funding Program. The authors thank Alhanouf Aburas, Edward Devol, Abdelmoneim Eldali, and Razita Mukhtar for help with the statistical analyses. Other than described above, the authors have not received any funding or grants in support of the presented research or for the preparation of this work and have no further declarations of potential interest.
*Dema Alisaa and Ghazwa B. Korayem contributed equally to this work as the first authors.
Corresponding author: Ghazwa B. Korayem, Pharmacy Practice Department, College of Pharmacy, Princess Nourah Bint Abdulrahman University, Al Imam Abdullah Ibn Saud Ibn, Abdul Aziz Road, King Khalid International Airport, Riyadh, Saudi Arabia
E-mail: gbkorayem@pnu.edu.sa