An open-label, randomized, non-inferiority trial of the efficacy and safety of ciprofloxacin versus an aminoglycoside + ciprofloxacin in the treatment of bubonic plague (IMASOY): study protocol for a randomized control trial-an update to the published protocol.

This article reports an update to the protocol of the IMASOY trial, which was prospectively registered on clinicaltrials.gov (NCT04110340) in October 2019.

Crystalline keratopathy secondary to the use of ciprofloxacin after cataract surgery with confirmation by histopathological study: A case report and review of the literature.

OBJECTIVE: To report the case of a 75-year-old patient who presented crystalline keratopathy secondary to the use of topical ciprofloxacin with histopathological verification, after cataract surgery without complications. METHOD: Case report with clinical and photographic follow-up, as well as slides with samples of epithelium and crystalline deposits. RESULTS: Corneal deposits resolved after drug suspension, topical lubricant change, and subsequent surgical debridement. The histopathological examination reported epithelial cells and basophilic particles compatible with drug precipitates. CONCLUSIONS: Crystalline keratopathy is a condition in which crystals of various kinds are deposited in the corneal epithelium and/or in the anterior stroma. It may have an infectious, pharmacological cause or, in rarer cases, corneal dystrophies. Certain factors such as a previous epithelial defect, systemic pathology with diabetes mellitus, ocular surgery and previous dry eye can favor the deposition of ciprofloxacin leading to the formation of a keratopathy.

Safety of Nebulized Ciprodex for Postoperative Management of Tracheal Resection.

OBJECTIVE: Anastomotic complications after tracheal resection/cricotracheal resection (TR/CTR), such as granulation tissue formation, can lead to severe morbidity. The off-label use of nebulized ciprofloxacin-dexamethasone (Ciprodex) for granulation tissue prophylaxis has anecdotally been used after TR/CTR, especially in pediatric patients. However, its use in the adult population, and its safety and side effect profile post-TR/CTR has not been reported. This study aims to characterize the incidence of adverse side effects associated with nebulized Ciprodex in post-TR/CTR patients. METHODS: A retrospective review of all patients who underwent TR/CTR from June 2015 to July 2023 was performed. The use of nebulized Ciprodex (1 mL ciprofloxacin-dexamethasone 0.3%-0.1% otic suspension in 4 mL normal saline) while inpatient was evaluated. Potential side effects were defined as oral thrush, ageusia, arthralgia, and allergic reaction, and were recorded for all patients. RESULTS: Seventy-three patients underwent TR/CTR from June 2015 to July 2023. Of these, 53 (72.6%) had documented Ciprodex administration during their postoperative course. One (1.9%) patient reported at least one side effect, including one instance of skin rash (1.9%) and one instance of allergic reaction (1.9%). There were no other side effects attributed to Ciprodex use. CONCLUSIONS: The incidence of side effects related to the use of nebulized Ciprodex is felt to be minimal in post-TR/CTR. Although Ciprodex may have the potential to treat granulation tissue in the airway, further studies are needed to verify its efficacy and safety. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:3695-3697, 2024.

Aplastic anaemia following antibiotic use for urinary tract infection.

Aplastic anaemia is often associated with recent viral illnesses to include EBV and parvovirus along with certain medications such as anticonvulsants and sulfa containing antibiotics. We describe a case report of a female patient in her 70s who presented with pancytopenia after being treated with nitrofurantoin and ciprofloxacin for suspected urinary tract infection. She underwent an extensive workup to rule out alternative aetiologies of her pancytopenia to include a broad viral, autoimmune and malignancy evaluation which were unrevealing. Given her recent exposure to ciprofloxacin and nitrofurantoin and marrow recovery following removal of these agents, it was presumed that antibiotic exposure was the underlying cause of her aplastic anaemia.

Assessing National Trends and Perceived Safety of Off-Label Ciprofloxacin-Dexamethasone Use by Pediatric Otolaryngologists.

OBJECTIVES: Off-label use of Ciprodex® (ciprofloxacin-dexamethasone: CPD), an antibiotic-steroid combination solution, in the airway has been reported by pediatric otolaryngologists with anecdotal success. We examined national trends regarding off-label CPD use including prevalence, common indications, prescriber patterns, adverse events, and accessibility. METHODS: 15-item cross-sectional survey was distributed to American Society of Pediatric Otolaryngology members from January-April 2022. Univariate analyses were performed to compare responses for users of off-label CPD versus non-users. Ease of access was compared across geographies and practice types using multivariate logistic regressions. RESULTS: Of the 163 complete responses (26.6% response rate), 156 (95.7%) reported using off-label CPD. Most common indications for off-label CPD were tracheal granulation (87.8%, n = 137) and choanal atresia (82.1%, n = 128). Ease of access was significantly increased in the Midwest (OR:18.79, 95%CI:3.63-1.24, p = 0.001) and West (OR:29.92, 95%CI:3.55-682.00, p = 0.006). Ease of access was significantly lower at tertiary referral centers (OR:0.11, 95%CI:0.01-0.64, p = 0.041) and private practices (OR:0.04, 95%CI:0.002-0.33, p = 0.009) compared to academic free-standing children's hospitals. Two-thirds of respondents reported feeling "Very Comfortable" with the safety profile of off-label CPD; 99.4% (n = 156) felt that the benefits outweighed the risks of off-label use. Seven respondents (4.5%) reported adverse events (e.g., local allergic reaction, cushingoid symptoms) from off-label use. CONCLUSIONS: Our findings (26.6% response rate) suggest that off-label CPD is commonly used by pediatric otolaryngologists, many of whom reported feeling that the benefits of off-label CPD outweigh the risks. Our results establish a baseline for future efforts to assess the efficacy and safety of off-label CPD and to improve its accessibility. LEVEL OF EVIDENCE: V Laryngoscope, 134:2922-2930, 2024.

Multivariate guard-bands and total risk assessment on multiparameter evaluations with correlated and uncorrelated measured values

Abstract The quality, efficacy, and safety of medicines are usually verified by analytical results. Measurement uncertainty is a critical aspect for the reliability of these analytical results. The pharmacopeial compendia usually adopt a simple acceptance rule that does not consider information from measurement uncertainty. In this work, we compared decision-making using simple acceptance and decision rules with the use of guard-band for multiparameter evaluation of ofloxacin ophthalmic solution and acyclovir topical cream. Ciprofloxacin ophthalmic solution and acyclovir topical cream samples were subject to pharmacopeial tests and assays. Multivariate guard-band widths were calculated by multiplying the standard uncertainty (u) by an appropriate multivariate coverage factor (k'). The multivariate coverage factor (k') was obtained by the Monte Carlo method. According to the simple acceptance rule, all the results obtained for ciprofloxacin ophthalmic solution and acyclovir topical cream are within the specification limits. However, the risk of false conformity decisions increases for ciprofloxacin tests. Decisions made using the simple acceptance rule and decision rules with the use of guard-band may differ. The simple acceptance rule may increase the risk of false conformity decisions when the measured value is close to the regulatory specification limits and/or when the measurement uncertainty value is inappropriately high. Nevertheless, the guard-band decision rule will always reduce the risk of false conformity decisions. Therefore, using information on measurement uncertainty in conformity assessment is highly recommended to ensure the proper efficacy, safety, and quality of medicines.

Syndrome of inappropriate antidiuretic hormone secretion as an adverse reaction of ciprofloxacin: a case report and literature review.

Antidiuretic hormone (ADH) is secreted by the posterior pituitary gland. Unsuppressed release of ADH leads to hyponatremia. This condition is referred to as syndrome of inappropriate antidiuretic hormone secretion (SIADH). Hereby, a case report is presented on ciprofloxacin-induced SIADH. A 67-year-old male patient was examined in the emergency room with symptoms of lethargy, headache, lack of attention, and a generally depressed mood lasting for three days. One week prior, empirical antimicrobial therapy involving ciprofloxacin for prostatitis was initiated. Laboratory analysis showed no relevant abnormalities except for hyponatremia (Na = 129 mmol/L). Chronic hyponatremia, thyroid dysfunction, and adrenal dysfunction were ruled out. Serum osmolality was 263 mOsmol/kg, urine osmolality was 206 mOsmol/kg, and urine sodium was 39 mmol/L. Given that all criteria for SIADH were met, ciprofloxacin was discontinued, and fluid restriction was advised. Four days later, the patient's serum sodium concentrations nearly normalized (Na = 135 mmol/L), and all symptoms resolved. The Naranjo Scale yielded a score of 8, supporting the likelihood of a probable adverse reaction to ciprofloxacin. This case is presented to raise awareness among clinicians about the potential of ciprofloxacin to cause even mild hyponatremia.

Neurobehavioral impairments in ciprofloxacin- treated osteoarthritic adult rats.

Background and purpose:

Ciprofloxacin (CIP) is a broad-spectrum antibiotic widely used in clinical practice to treat musculoskeletal infections. Fluoroquinolone-induced neurotoxic adverse events have been reported in a few case reports, all the preclinical studies on its neuropsychiatric side effects involved only healthy animals. This study firstly investigated the behavioral effects of CIP in an osteoarthritis rat model with joint destruction and pain, which can simulate inflammation-associated musculoskeletal pain. Furthermore, effects of CIP on regional brain-derived neurotrophic factor (BDNF) expression were examined given its major contributions to the neuromodulation and plasticity underlying behavior and cognition. 

Fourteen days after induction of chronic osteoarthritis, animals were administered vehicle, 33 mg/kg or 100 mg/kg CIP for five days intraperitoneally. Motor activity, behavioral motivation, and psychomotor learning were examined in a reward-based behavioral test (Ambitus) on Day 4 and sensorimotor gating by the prepulse inhibition test on Day 5. Thereafter, the prolonged BDNF mRNA and protein expression levels were measured in the hippocampus and the prefrontal cortex. 

CIP dose-dependently reduced both locomotion and reward-motivated exploratory activity, accompanied with impaired learning ability. In contrast, there were no significant differences in startle reflex and sensory gating among treatment groups; however, CIP treatment reduced motor activity of the animals in this test, too. These alterations were associated with reduced BDNF mRNA and protein expression levels in the hippocampus but not the prefrontal cortex. 

This study revealed the detrimental effects of CIP treatment on locomotor activity and motivation/learning ability during osteoarthritic condition, which might be due to, at least partially, deficient hippocampal BDNF expression and ensuing impairments in neural and synaptic plasticity.

The frequency of, and predisposing risk factors for, ciprofloxacin-induced neuro-psychiatric adverse drug reactions.

OBJECTIVES: Ciprofloxacin induces rare neuro-psychiatric adverse drug reactions (ADRs) that are, as yet, not possible to predict due to unknown predisposition factors. BACKGROUND: The aim of the analysis was to assess the frequency of neuro-psychiatric ADRs and to identify potential risk factors that predisposed patients to ciprofloxacin neurotoxicity. METHODS: This observational retrospective study involved the evaluation of the medical records of patients in the Nephrology department and 3rd Internal Clinic of the General University Hospital in Prague. RESULTS: The overall incidence of neurological ADRs was 3.6 %. No neurological ADRs developed in patients aged less than 70 years. The covariates that were significantly more prevalent in the patients who developed neuropsychiatric ADRs were as follows: higher age, a history of neuropsychiatric disorders and the use of anticonvulsants. The administration of drugs from other ATC groups, gender, weight, body mass index, body surface area, renal functions, level of C-reactive protein at the beginning of treatment and the total daily dose/kg did not differ significantly between the two groups. CONCLUSION: Ciprofloxacin neuropsychiatric ADRs are more frequent in older patients with a history of neurologic or psychiatric disorders. No other tested covariates were proven to predispose patients to neuropsychiatric ADRs during treatment with ciprofloxacin (Tab. 2, Ref. 20).

FOVOCIP study: a multicenter randomized trial of fosfomycin versus ciprofloxacin for febrile neutropenia in hematologic patients-efficacy and microbiologic safety.

BACKGROUND: Multidrug-resistant Gram-negative bacterial (MRGNB) infections represent a major public health threat. Cancer patients and, among them, hematological patients are most vulnerable to these infections. Gut colonization by MRGNB is a common phenomenon occurring during hospitalization and chemotherapy exposure. In the neutropenic phase that occurs after chemotherapy, MRGNB translocation occurs increasing patient's mortality. Fluoroquinolone prophylaxis with ciprofloxacin or levofloxacin efficacy is now being questioned due to the increase of incidence in MRGNB. METHODS: A phase III randomized, controlled, clinical trial, open-label parallel-group with a 1:1 ratio, aimed to demonstrate the non-inferiority of oral fosfomycin versus oral ciprofloxacin for febrile neutropenia prevention in patients with acute leukemia (AL) or hematopoietic cell transplant (HSC) receptors. Weekly surveillance cultures are planned to detect gut colonization. Changes in fecal microbiome at the beginning and end of prophylaxis will also be analyzed. DISCUSSION: This trial will provide evidence of the efficacy of an alternative drug to ciprofloxacin for febrile neutropenia prevention in high-risk hematological patients. The battery of planned microbiological studies will allow us to evaluate prospectively the microbiological safety of both pharmacological strategies in terms of the selection of MRGNB occurring in each arm. In addition, valuable information on the way in which each drug changes the fecal microbiome of the patients throughout the treatment will be generated. TRIAL REGISTRATION: Clinical trials NCT05311254, Registered on 5 April 2022, https://clinicaltrials.gov/ct2/show/NCT05311254?term=FOVOCIP&cntry=ES&draw=2&rank=1 . PROTOCOL VERSION: 3.0, dated 20 May 2022.

Ciprofloxacin-Induced Anaphylactic Reaction Followed by Negative Provocation Test in Response to Levofloxacin: A Case Report.

Fluoroquinolones are a commonly prescribed class of antibiotics due to their broad spectrum of antimicrobial activity, favorable pharmacokinetic properties, ability to switch from parenteral to oral administration, and global availability. After beta-lactams, they are the second most common antibiotic class associated with drug allergies. The mechanism of fluoroquinolone-induced hypersensitivity reactions has not yet been fully understood, so the true incidence of hypersensitivity reactions remains unknown. Cross-reactivity between fluoroquinolones has been the subject of conflicting and limited clinical research. Due to their similar chemical structure, some argue for close cross-reactivity within the group. However, recent studies have produced contradictory results. We present the case of a young patient who had an anaphylactic reaction to ciprofloxacin but was tolerant to levofloxacin, as determined via a skin prick test followed by a drug provocation test. Our findings support the notion that there is little cross-reactivity between fluoroquinolones. Consequently, exposure to another fluoroquinolone in a hospital setting may be beneficial, particularly for patients who lack adequate antibiotic alternatives. However, additional research on this subject is required.

Three Cases of Myoclonus Secondary to Ciprofloxacin: "Ciproclonus".

OBJECTIVES: Ciprofloxacin is a fluoroquinolone that is used for bacterial infections involving different systems. In some cases, ciprofloxacin was reported to induce myoclonus. METHODS: We performed a chart review of 3 patients with myoclonus secondary to ciprofloxacin and reviewed the literature for similar cases. Written consent for publication was obtained from each patient, and their identities were concealed for ethical reasons. RESULTS: We describe 3 cases of myoclonus secondary to ciprofloxacin, 2 males and a female aged 61, 26, and 48 years, respectively. The myoclonus appeared within 3 days of ciprofloxacin intake. In all 3 cases, ciprofloxacin was prescribed for urinary tract infection. Electroencephalogram and neuroimaging studies were normal and possible causes were excluded. Thus, ciprofloxacin was believed to be the underlying cause and hence it was withdrawn. The patients had complete recovery on follow-up. CONCLUSIONS: Although ciprofloxacin is widely prescribed for different infections, only 13 cases were reported to develop myoclonus secondary to ciprofloxacin. The mean age of patients was 62 years. Fifty-four percent of cases were males. Cessation of ciprofloxacin was the most common management course. All individuals fully recovered after ciprofloxacin withdrawal. The mechanism of ciprofloxacin-induced myoclonus is probably associated with γ-aminobutyric acid and glutamate pathways.

Long-term Cardiovascular Adverse Events Induced by Fluoroquinolones: A Retrospective Case-control Study.

ABSTRACT: A correlation is already established between fluoroquinolones (FQs) use and cardiovascular events (CVEs), such as QT prolongation; however, serious events such as aortic aneurysm and valve regurgitation have also been reported with FQs. Several unstudied factors could contribute to the development of different CVEs that were not previously evaluated with FQ therapy. Therefore, we aimed to assess the incidence of different serious CVEs after completion of FQ therapy and potential associating factors. This was a retrospective case-control study of inpatients who received ciprofloxacin, levofloxacin, or moxifloxacin for ≥3 days. Patients' echocardiograms were evaluated for the development of aortic or valvular disease or worsening of an existing condition after completion of therapy. Of 373 included patients, 83 developed new valvular disease or worsening of an existing disease, where tricuspid valve regurgitation was the most common CVE (50/83; 60.2%), followed by mitral valve diseases (48/83; 57.8%). Aortic valve regurgitation occurred more commonly with moxifloxacin compared with ciprofloxacin and levofloxacin (17.8% vs. 6.7% and 10.7%, respectively; P = 0.01). Median time to CVE detection ranged 93-166 days for all FQs. The receipt of moxifloxacin and elevated baseline QT interval were associated with an increased CVEs risk (adjusted odds ratio 3.26; 95% confidence interval, 1.31-8.11 and adjusted odds ratio 1.02; 95% confidence interval, 1.00-1.04, respectively). Other factors did not show such association. The lack of association of different factors with the occurrence of CVEs indicates that all patients receiving FQ therapy, especially moxifloxacin, should be monitored during the first-year after therapy. Alternatively, other antibiotics with a better safety profile may be considered.

Drug-Induced Liver Injury with Commonly Used Antibiotics in the All of Us Research Program.

Antibiotics are a known cause of idiosyncratic drug-induced liver injury (DILI). According to the Centers for Disease Control and Prevention, the five most commonly prescribed antibiotics in the United States are azithromycin, ciprofloxacin, cephalexin, amoxicillin, and amoxicillin-clavulanate. We quantified the frequency of acute DILI for these common antibiotics in the All of Us Research Program, one of the largest electronic health record (EHR)-linked research cohorts in the United States. Retrospective analyses were conducted applying a standardized phenotyping algorithm to de-identified clinical data available in the All of Us database for 318,598 study participants. Between February 1984 and December 2022, more than 30% of All of Us participants (n = 119,812 individuals) had been exposed to at least 1 of our 5 study drugs. Initial screening identified 591 potential case patients that met our preselected laboratory-based phenotyping criteria. Because DILI is a diagnosis of exclusion, we then used phenome scanning to narrow the case counts by (i) scanning all EHRs to identify all alternative diagnostic explanations for the laboratory abnormalities, and (ii) leveraging International Classification of Disease 9th revision (ICD)-9 and ICD 10th revision (ICD)-10 codes as exclusion criteria to eliminate misclassification. Our final case counts were 30 DILI cases with amoxicillin-clavulanate, 24 cases with azithromycin, 24 cases with ciprofloxacin, 22 cases with amoxicillin alone, and < 20 cases with cephalexin. These findings demonstrate that data from EHR-linked research cohorts can be efficiently mined to identify DILI cases related to the use of common antibiotics.

Is EMA warning on quinolones and fluoroquinolones really assessed? An EudraVigilance database analysis.

BACKGROUND: On March 11th 2019, European Medicines Agency (EMA) issues a warning after a review of serious, disabling and potentially permanent adverse events (AEs), particularly on musculoskeletal and nervous system, with quinolone (QN) and fluoroquinolone (FQ) antibiotics. Aim of this study was to evaluate the effect of the EMA warning on the rate of AEs after QN and FQ treatments, reported in the EudraVigilance (EV) database. METHODS: EV database is the system for managing and analyzing information on suspected AEs to medicines which have been authorized or being studied in clinical trials in the European Economic Area (EEA). We retrospectively explored the effect of FQs and QNs on musculoskeletal and nervous system from the EMA warning up to now (21 months) and compared these results with the 21 months before the EMA warning. RESULTS: Main part of AEs in EV database were reported for ciprofloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin. Ciprofloxacin total AEs before 21 months till 12 months of EMA warning were 2763. 12 months before EMA Warning they were 2935. Twelve months after EMA Warning they were 3419. Between 12 months till 21 months they were 3174. Musculoskeletal disorders were respectively 574 (21% of the total) 21 months before, 558 (19%) 12 months before, 1048 (31%) after 12 months, 540 (17%) after 21 months of EMA Warning. Nervous system disorders were respectively 606 (22% of the total) 21 months before, 517 (18%) 12 months before, 680 (20%) after 12 months, 560 (18%) after 21 months of EMA Warning (respectively OR 1,16 95%CI 1,10 -1,22, P 0,12 ; OR 0,76 95%CI 0,69-0,83, P 0,27 ; OR 1,01 95%CI 0,96-1,06 P 0,05). CONCLUSIONS: Our analysis clearly showed no significant differences before and after EMA warning, opening new insights in the role of the EMA warning in clinical practice.

Comparative effectiveness and safety of antibiotic prophylaxis during induction chemotherapy in children with acute leukaemia: a systematic review and meta-analysis.

BACKGROUND: Bacterial infections are common during induction therapy in children and adolescents with acute leukaemia and may cause infection-related mortality. AIM: To determine the efficacy and safety of prophylactic antibiotics in paediatric patients with acute leukaemia receiving induction chemotherapy. METHODS: From three English databases and four Chinese databases, we searched for randomized controlled trials (RCTs) and cohort studies that compared prophylactic antibiotics to placebo, no prophylaxis, or that compared one antibiotic versus another in paediatric patients with acute leukaemia undergoing induction chemotherapy. Two reviewers independently screened the studies, extracted data, and assessed the risk of bias using Cochrane Risk of Bias 2 tool and Newcastle-Ottawa Scale, and the certainty of evidence using Grading of Recommendations Assessment, Development, and Evaluation (GRADE). FINDINGS: Two RCTs and ten cohort studies were finally included. For children with acute lymphoblastic leukaemia, antibiotic prophylaxis, including levofloxacin, sulfamethoxazole-trimethoprim, or other antibiotics, probably reduced bacteraemia (risk ratio (RR): 0.44; 95% confidence interval (CI): 0.33-0.60; moderate certainty) without significantly increasing Clostridioides difficile infection (CDI) or invasive fungal infection. Levofloxacin reduced the CDI rate (RR: 0.08; 95% CI: 0.01-0.62; high certainty). Ciprofloxacin prophylaxis probably reduced infection-related mortality (RR: 0.12; 95% CI: 0.01-0.97; moderate certainty). In children with acute myeloid leukaemia, ciprofloxacin plus vancomycin may reduce febrile neutropenia (RR: 0.79; 95% CI: 0.66-0.94; low certainty). Individual studies indicated that prophylaxis increased antibiotic exposure but reduced non-preventive antibiotic exposure. CONCLUSION: In children with acute leukaemia undergoing induction therapy, antibiotic prophylaxis may improve the bacterial infection and mortality.

Effect of glyphosate and ciprofloxacin exposure on enteric bacteria of tadpoles.

The high load of agrochemicals and antibiotics present in agricultural aquatic environments represents a risk for wildlife. Since enteric bacteria, which play a key role in the physiological functioning of their hosts, are sensitive to a wide variety of pollutants, their study allows to evaluate the health of organisms. This study aimed to evaluate the effects of commercial formulations of a glyphosate-based herbicide (GBH) and the antibiotic ciprofloxacin (CIP), individually and in mixture, on the bacterial diversity of the intestinal content of common toad (Rhinella arenarum) tadpoles. The diversity of cultivable fast-growing bacteria with low nutritional requirements was evaluated using classic microbiological tests and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry identification. Bacterial diversity varied among treatments. Taxa diversity increased in the GBH-treated group but decreased in the CIP-treated group. Remarkably, Yersinia spp. and Proteus spp. were only found in the GBH-treated group. The prevalence of Klebsiella spp. and Pseudomonas spp. decreased in the intestinal microbiota of the GBH-CIP-treated group. To our knowledge, this is the first report on the alteration of cultivable enteric bacteria of autochthonous tadpoles due to two pollutants of emerging concern. Our results demonstrate that R. arenarum tadpoles can be used as non-conventional model organisms for environmental pollution monitoring. Our preliminary findings would contribute to understanding how the presence of GBH and CIP in freshwaters may represent a threat to wildlife and human health by causing enteric dysbiosis of part of the bacterial community.

Exposure of anti-infective drugs and the dynamic changes of the gut microbiota during gastrointestinal mucositis in autologous stem cell transplant patients: a pilot study.

Gastrointestinal mucositis could potentially compromise drug absorption due to functional loss of mucosa and other pathophysiological changes in the gastrointestinal microenvironment. Little is known about this effect on commonly used anti-infectives. This study aimed to explore the association between different stages of gastrointestinal mucositis, drug exposure, and gut microbiota. A prospective, observational pilot study was performed in HSCT patients aged ≥ 18 years receiving anti-infectives orally. Left-over blood samples and fecal swabs were collected from routine clinical care until 14 days after HSCT to analyze drug and citrulline concentrations and to determine the composition of the gut microbiota. 21 patients with a median age of 58 (interquartile range 54-64) years were included with 252 citrulline, 155 ciprofloxacin, 139 fluconazole, and 76 acyclovir concentrations and 48 fecal swabs obtained. Severe gastrointestinal mucositis was observed in all patients. Due to limited data correlation analysis was not done for valacyclovir and fluconazole, however we did observe a weak correlation between ciprofloxacin and citrulline concentrations. This could suggest that underexposure of ciprofloxacin can occur during severe mucositis. A follow-up study using frequent sampling rather than the use of left-over would be required to investigate the relationship between gastrointestinal mucositis, drug exposure, and gut microbiome.