Interaction of all-trans-retinoic acid with fluconazole in acute promyelocytic leukemia

A rare incidence of severe dermatological toxicities triggered by concomitant administration of all-trans retinoic acid and triazole antifungal in patients with acute promyelocytic leukemia: a case series and review of the literature

BACKGROUND

All-trans retinoic acid (ATRA) is an indispensable part of the treatment of acute promyelocytic leukemia (APL). Although, mild cutaneous toxicities like mucocutaneous xerosis, rash, and pruritus are well reported, ATRA associated severe dermatological toxicities are extremely rare. ATRA is primary metabolized by cytochrome P450 (CYP450) enzyme system, and triazole antifungals are notorious for their strong inhibitory effect on CYP450.

CASE PRESENTATION

Three Asian APL patients experienced rare ATRA-induced severe dermatological toxicities: exfoliative dermatitis (ED) in cases 1 and 2, and necrotic scrotal ulceration in case 3. Both case 1 (33-year-old female), and case 2 (28-year-old male) landed in emergency department with dehydration, generalized skin erythema and xerosis during their induction chemotherapy. Both of these patients also developed invasive aspergillosis and required concomitant triazole antifungals during their chemotherapy. For ED, intravenous fluids and broad-spectrum antibiotics were started along with application of local emollients to prevent transdermal water loss. Although their general condition improved but skin exfoliation continued with complete desquamation of palms and soles. Dermatology was consulted, and clinical diagnosis of ED was established. Discontinuation of ATRA resulted in complete resolution of ED. Case 3 (15-year-old boy) reported two blackish mildly tender scrotal lesions during induction chemotherapy. He also had mucocutaneous candidiasis at presentation and was kept on triazole antifungal. Local bacterial & fungal cultures, and serological testing for herpes simplex virus were reported negative. Despite adequate local care and optimal antibiotic support, his lesions persisted, and improved only after temporary discontinuation of ATRA. After a thorough literature review and considering the temporal association of cutaneous toxicities with triazole antifungals, we speculate that the concomitant use of triazole antifungals inhibited the hepatic metabolism of ATRA, resulting in higher serum ATRA concentration, and markedly accentuated cutaneous toxicities in our patients.

CONCLUSION

By highlighting this crucial pharmacokinetic interaction, we want to caution the fellow oncologists to be mindful of the inhibitory effect of triazole antifungals on CYP450. We propose using a non-myelosuppressive combination of ATRA and arsenic trioxide for management of APL hence, obliterating the need of prophylactic antifungals. However, in the event of invasive fungal infection (IFI), we suggest using alternative class of antifungals.

Papilledema and idiopathic intracranial hypertension due to the possible potentiation of ATRA by posaconazole in a case of acute promyelocytic leukemia

INTRODUCTION

Idiopathic intracranial hypertension (IIH) (pseudotumor cerebri) is a rare side effect of all-trans retinoic acid (ATRA). IIH cases have been observed after the concomitant use of ATRA with azole group antimicrobials such as fluconazole and voriconazole. Here, we discuss about the diagnosis and treatment process of the IIH emerging in a young acute promyelocytic leukemia (APL) case with the ATRA impact, which can be increased by posaconazole.

CASE

A 19-year-old male patient was diagnosed with APL. Headache and blurred vision were developed on the 12^th day of the AIDA (ATRA, 45 mg/m2/day, oral and idarubicin 12 mg/m2, on days 2, 4, 6, 8, intravenous) protocol and posaconazole proflaxis. He was diagnosed IIH along with the existing eye findings and imagings.

MANAGEMENT & OUTCOME

ATRA treatment and posaconazole were interrupted. Systemic acetazolamide and dexamethasone treatment were initiated. After significant clinical response was observed, ATRA treatment was resumed without posaconazole and a similar clinical condition did not recur.

DISCUSSION

The combined use of ATRA and azole group drugs increases the risk of developing IIH. Patients with APL who developed IIH during the concomitant use of ATRA and fluconazole or voriconazole have been reported. To the best of our knowledge, our case is the first APL case with a IIH who treated with ATRA-based therapy and used posaconazole. In case of development of side effects, drugs should be interrupted and this combination should be avoided if possible after appropriate approach and clinical improvement.

Hypercalcemia associated with the interaction between all trans retinoic acid and posaconazole in an acute promyelocytic leukemia case

INTRODUCTION

All-trans retinoic acid (ATRA) is a physiological metabolite of vitamin A and it is used for the treatment of acute promyelocytic leukemia (APL). Hypercalcemia is a rare side effect of ATRA and it may be potentiated after interaction of ATRA with azole group antifungals. Herein, we have reported an APL case with hypercalcemia that is caused by the interaction of ATRA and posaconazole.

CASE REPORT

A 49-year-old female patient was diagnosed as APL after the examinations performed upon the detection of pancytopenia when she had presented with the complaints of widespread bruising and fever. After the initiation of posaconazole and ATRA, her serum calcium levels begin to increase (10.3 to 11.1mg/dl). Her vitamin D level was 21.9 ng/ml and PTH 17.8 pg/ml, both were in the normal ranges. The Drug Interaction Probability Scale score of our case was calculated as 6, indicating that the probable adverse drug reaction. Therefore, the high level of serum calcium was attributed to the interaction between ATRA and posaconazole.

MANAGEMENT & OUTCOME

Although hypercalcemia with ATRA and other antifungal agents have been previously reported in the literature, this is the first report of hypercalcemia with the concomitant use of ATRA and posaconazole.

DISCUSSION

This case highlights the importance of monitoring ATRA's side effects when it is used in combination with drugs inhibiting the cytochrome P450 enzymes. In conclusion, the concomitant use of posaconazole and ATRA may lead to hypercalcemia and serum calcium levels return to normal ranges with the discontinuation of these drugs.

The Effects of Voriconazole on Metabolism of All-Trans Retinoic Acid in the Treatment of Acute Promyelocytic Leukemia: A Case Report

All-trans retinoic acid (ATRA) is a derivative of vitamin A and is the mainstay treatment of acute promyelocytic leukemia (APL). Hypercalcemia is a rare yet important side-effect of ATRA, especially when it is used concomitantly with a medication that impedes its metabolism by inhibiting cytochrome P-450 in the liver and thus increasing the duration of exposure to ATRA. Azole antifungal drugs such as voriconazole are frequently used in patients undergoing chemotherapy due to a high incidence of fungal infections. These medications inhibit two vital enzymes of cytochrome P-450, CYP2C9 and CYP3A4, potentiating the effects of ATRA on calcium metabolism. We present a case of a nine-year-old girl who underwent chemotherapy with all-trans retinoic acid for acute promyelocytic leukemia. The patient was given an anti-fungal cover with voriconazole for extensive fungal chest infection simultaneously. She was found to have asymptomatic hypercalcemia on routine follow-up during the consolidation phase. Both medications were stopped. Subsequently, she was admitted to the ward and managed conservatively with hydration. Serum calcium levels were returned to normal within six days after stopping the combination of ATRA and voriconazole. We underscore that the use of anti-fungal medications should be limited while using ATRA. However, strict monitoring must be done when a combination of these drugs is started, if necessary.

The Ascidian Embryo Teratogenicity assay in Ciona intestinalis as a new teratological screening to test the mixture effect of the co-exposure to ethanol and fluconazole

The aim of this work was to evaluate the Ascidian Embryo Teratogenicity assay (AET) as new alternative invertebrate model to test the developmental effects of the co-exposure to ethanol and fluconazole. Ciona intestinalis embryos were exposed to the azolic fungicide fluconazole, (FLUCO, 7.8-250μM), to ethanol (Eth, 0.01-0.5%) and to their mixture (0.01% Eth+FLUCO 7.8-250μM) from neurula to larval stage. At the end of the exposure period, larvae were morphologically evaluated and benchmark analysis performed by using the PROAST modelling software. Both compounds were teratogenic in a concentration-related manner, particularly affecting the pigmented organs. The co-exposure to Eth enhanced the effects of FLUCO, the additive hypothesis was not rejected by the modelling. The results demonstrated that AET could be considered a good vertebrate-free alternative model for toxicological investigation in embryos.

Bromuconazole-induced hepatotoxicity is accompanied by upregulation of PXR/CYP3A1 and downregulation of CAR/CYP2B1 gene expression

Despite widespread use of bromuconazole as a pesticide for food crops and fruits, limited studies have been done to evaluate its toxic effects. Here, we evaluated the hepatotoxic effect of bromuconazole using classical toxicological (biochemical analysis and histopathological examination) and gene-based molecular methods. Male rats were treated either orally or topically with bromuconazole at doses equal to no observed adverse effect level (NOAEL) and 1/10 LD50 for 90 d. Bromuconazole increased activities of liver enzymes (ALT, AST, ALP, and ACP), and levels of bilirubin. It also induced hepatic oxidative stress as evidenced by significant decrease in the activities of superoxide dismutase (SOD), and significant increase in levels of malondialdehyde (MDA) in liver. In addition, bromuconazole caused an increase in liver weights and necrobiotic changes (vacuolation and hepatocellular hypertrophy). It also strongly induced the expression of PXR and its downstream target CYP3A1 gene as well as the activity of CYP3A1. However, it inhibited the expression of CAR and its downstream target CYP2B1 gene without significant changing in CYP2B1 activity. Overall, the oral route showed higher hepatotoxic effect and molecular changes than the dermal route and all changes were dose dependent. This is the first investigation to report that bromuconazole-induced liver oxidative damage is accompanied by upregulation of PXR/CYP3A1 and downregulation of CAR/CYP2B1.

Zebrafish as an Alternative Vertebrate Model for Investigating Developmental Toxicity-The Triadimefon Example

Triadimefon is a widely used triazole fungicide known to cause severe developmental defects in several model organisms and in humans. The present study evaluated in detail the developmental effects seen in zebrafish embryos exposed to triadimefon, confirmed and expanded upon previous phenotypic findings and compared them to those observed in other traditional animal models. In order to do this, we exposed embryos to 2 and 4 µg/mL triadimefon and evaluated growth until 120 h post-fertilization (hpf) through gross morphology examination. Our analysis revealed significant developmental defects at the highest tested concentration including somite deformities, severe craniofacial defects, a cleft phenotype along the three primary neural divisions, a rigorously hypoplastic or even absent mandible and a hypoplastic morphology of the pharyngeal arches. Interestingly, massive pericardial edemas, abnormal shaped hearts, brachycardia and inhibited or absent blood circulation were also observed. Our results revealed that the presented zebrafish phenotypes are comparable to those seen in other organism models and those derived from human observations as a result of triadimefon exposure. We therefore demonstrated that zebrafish provide an excellent system for study of compounds with toxic significance and can be used as an alternative model for developmental toxicity studies to predict effects in mammals.

Comparison of the ligand binding site of CYP2C8 with CYP26A1 and CYP26B1: a structural basis for the identification of new inhibitors of the retinoic acid hydroxylases

The CYP26s are responsible for metabolizing retinoic acid and play an important role in maintaining homeostatic levels of retinoic acid. Given the ability of CYP2C8 to metabolize retinoic acid, we evaluated the potential for CYP2C8 inhibitors to also inhibit CYP26. In vitro assays were used to evaluate the inhibition potencies of CYP2C8 inhibitors against CYP26A1 and CYP26B1. Using tazarotenic acid as a substrate for CYP26, IC₅₀ values for 17 inhibitors of CYP2C8 were determined for CYP26A1 and CYP26B1, ranging from ∼20 nM to 100 μM, with a positive correlation observed between IC₅₀s for CYP2C8 and CYP26A1. An evaluation of IC₅₀'s versus in vivo C_max values suggests that inhibitors such as clotrimazole or fluconazole may interact with CYP26 at clinically relevant concentrations and may alter levels of retinoic acid. These findings provide insight into drug interactions resulting in elevated retinoic acid concentrations and expand upon the pharmacophore of CYP26 inhibition.

Pseudotumor Cerebri in Acute Promyelocytic Leukemia Patients on Intergroup Protocol 0129: Clinical Description and Recommendations for New Diagnostic Criteria

BACKGROUND

Multiple randomized trials have demonstrated a benefit for all-trans retinoic acid (ATRA) in patients with acute promyelocytic leukemia (APL). Pseudotumor cerebri (PTC) is an infrequently reported adverse effect of ATRA.

METHODS

We examined the incidence, clinical course, and outcomes of patients with APL treated on Intergroup Protocol 0129 (I0129) who developed PTC. This trial evaluated the role of ATRA alone during induction and/or as maintenance therapy.

RESULTS

Of the patients on trial, 240 received ATRA during induction, maintenance, or both; 8 had a clinical suspicion for PTC. Upon review of individual cases, this was felt to be "probable" in 4 patients, "possible" in 1 and "unlikely" in 3 due to lack of diagnostic criteria or presence of a more likely alternate diagnosis.

CONCLUSIONS

"Probable" PTC occurred in 1.7% of patients who received ATRA during induction and/or maintenance therapy. In agreement with previous reports, the incidence of PTC in APL patients receiving ATRA was higher in the pediatric population. Here, we discuss the method for diagnosing PTC in the setting of ATRA therapy and management strategies.

High pseudotumor cerebri incidence in tretinoin and arsenic treated acute promyelocytic leukemia and the role of topiramate after acetazolamide failure

Dual differentiation therapy with arsenic trioxide and tretinoin (all-trans-retinoic acid; ATRA) for the management of low and intermediate risk acute promyelocytic leukemia has recently been recommended by the National Comprehensive Cancer Network. Some less common toxicities of the combination may have yet to be fully realized. Of ten patients we have treated thus far, five (50%) have developed pseudotumor cerebri. In one patient, temporary discontinuation of ATRA and initiation of acetazolamide controlled symptoms. In four patients, topiramate was substituted for acetazolamide to relieve symptoms and allow ATRA dose re-escalation. We conclude that providers should monitor for pseudotumor cerebri and consider topiramate if acetazolamide fails.

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We identify five cases of pseudotumor cerebri during arsenic and tretinoin therapy.

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We report four cases of pseudotumor cerebri successfully treated with topiramate.

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Topiramate may have a role in the management of pseudotumor cerebri.

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Addition of arsenic trioxide to tretinoin may potentiate pseudotumor cerebri.

All-trans-retinoic acid-induced pseudotumor cerebri in acute promyelocytic leukemia

All-trans-retinoic acid is an integral part in the treatment strategy of acute promyelocytic leukemia (APL). Here we describe a case of pseudotumor cerebri associated with all-trans-retinoic acid (ATRA) during the induction therapy in an adult with acute promyelocytic leukemia (APL).

Therapeutic potential of the inhibition of the retinoic acid hydroxylases CYP26A1 and CYP26B1 by xenobiotics

Retinoic acid (RA), the active metabolite of vitamin A, is an important endogenous signaling molecule regulating cell cycle and maintenance of epithelia. RA isomers are also used as drugs to treat various cancers and dermatological diseases. However, the therapeutic uses of RA isomers are limited due to side effects such as teratogenicity and resistance to treatment emerging mainly from autoinduction of RA metabolism. To improve the therapeutic usefulness of retinoids, RA metabolism blocking agents (RAMBAs) have been developed. These inhibitors generally target the cytochrome P450 (CYP) enzymes because RA clearance is predominantly mediated by P450s. Since the initial identification of inhibitors of RA metabolism, CYP26 enzymes have been characterized as the main enzymes responsible for RA clearance. This makes CYP26 enzymes an attractive target for the development of novel therapeutics for cancer and dermatological conditions. The basic principle of development of CYP26 inhibitors is that endogenous RA concentrations will be increased in the presence of a CYP26 inhibitor, thus, potentiating the activity of endogenous RA in a cell-type specific manner. This will reduce side effects compared to administration of RA and allow for more targeted therapy. In clinical trials, inhibitors of RA metabolism have been effective in treatment of psoriasis and other dermatological conditions as well as in some cancers. However, no CYP26 inhibitor has yet been approved for clinical use. This review summarizes the history of development of RAMBAs, the clinical and preclinical studies with the various structural series and the available knowledge of structure activity relationships of CYP26 inhibitors.

Incidence of invasive aspergillosis following remission-induction chemotherapy for acute leukemia: a retrospective cohort study in a single Canadian tertiary care centre

BACKGROUND

The decision to use universal primary antimould prophylaxis to prevent invasive aspergillosis in patients with acute leukemia depends on the incidence of infection at individual centres. We determined our institution's incidence of invasive aspergillosis among patients who received remission-induction chemotherapy for acute leukemia to evaluate the potential benefits of primary antimould prophylaxis.

METHODS

We conducted this retrospective cohort study at a Canadian tertiary care centre. From the central pharmacy registries, we retrieved records for all adult patients for whom remission-induction chemotherapy for acute leukemia was prescribed between 2008 and 2010. We retrieved clinical, microbiologic, pathologic and radiologic data from the patients' medical charts. The primary outcome was a diagnosis of probable or proven invasive aspergillosis up to 180 days after resolution of aplasia.

RESULTS

We retrieved records for 123 patients with acute leukemia. Twenty-two of these patients did not receive the prescribed chemotherapy and were excluded from the analysis. Of the 101 patients included, 77 (76.2%) had acute myeloid leukemia. Overall, 136 courses of chemotherapy were administered, with more than 1 course administered to 26 (25.7%) of the 101 patients. In 9 of the patients (8.9%; 95% confidence interval 4.2%-16.2%), invasive aspergillosis was diagnosed (3 proven and 6 probable cases) a median of 19 (range 11-34) days after initiation of chemotherapy. In 7 (78%) of these 9 patients, invasive aspergillosis occurred during the first course of chemotherapy. Three patients died within the first year after diagnosis of invasive aspergillosis.

INTERPRETATION

We found a high incidence (8.9%) of invasive aspergillosis at our centre. This finding triggered the introduction of targeted antimould prophylaxis for patients with acute leukemia who were undergoing remission-induction chemotherapy.

Safety of fluconazole in paediatrics: a systematic review

PURPOSE

To determine the safety of fluconazole in neonates and other paediatric age groups by identifying adverse events (AEs) and drug interactions associated with treatment.

METHODS

A search of EMBASE (1950-January 2012), MEDLINE (1946-January 2012), the Cochrane database for systematic reviews and the Cumulative Index to Nursing and Allied Health Literature (1982-2012) for any clinical study about fluconazole use that involved at least one paediatric patient (≤17 years) was performed. Only articles with sufficient quality of safety reporting after patients' exposure to fluconazole were included.

RESULTS

We identified 90 articles, reporting on 4,209 patients, which met our inclusion criteria. In total, 794 AEs from 35 studies were recorded, with hepatotoxicity accounting for 378 (47.6 %) of all AEs. When fluconazole was compared with placebo and other antifungals, the relative risk (RR) of hepatotoxicity was not statistically different [RR 1.36, 95 % confidence interval (CI) 0.87-2.14, P = 0.175 and RR 1.43, 95 % CI 0.67-3.03, P = 0.352, respectively]. Complete resolution of hepatoxicity was achieved by 84 % of patients with follow-up available. There was no statistical difference in the risk of gastrointestinal events of fluconazole compared with placebo and other antifungals (RR 0.81, 95 % CI 0.12-5.60, P = 0.831 and RR 1.23, 95 %CI 0.87-1.71, P = 0.235, respectively). There were 41 drug withdrawals, 17 (42 %) of which were due to elevated liver enzymes. Five reports of drug interactions occurred in children.

CONCLUSION

Fluconazole is relatively safe for paediatric patients. Hepatotoxicity and gastrointestinal toxicity are the most common adverse events. It is important to be aware that drug interactions with fluconazole can result in significant toxicity.

Interactions between oral antineoplastic agents and concomitant medication: a systematic review

INTRODUCTION

In recent years, the number of oral antitumoral agents has considerably increased. Oral administration increases the risk of interactions, because most oral anticancer drugs are taken on a daily basis. Interactions can increase exposure to antitumoral agents or cause treatment failure. Many antitumoral drugs undergo enzymatic metabolism by cytochrome P450. As some act as inducers or inhibitors of one or more isoenzymes, they can lead to decreases or increases in plasma concentrations of concomitant drugs. Hence, cytostatic drugs can act not only as victims but also as perpetrators. P-glycoprotein, an efflux transporter, can also be involved in pharmacokinetic interactions.

AREAS COVERED

A Medline search was performed to summarize the available evidence of the most clinically relevant interactions between oral chemotherapy agents and other drugs. The search covered the period from 1966 until August 2012 for each antitumoral drug using the medical subject headings 'Drug Interactions' OR 'Pharmacokinetics'. While the present review is not exhaustive, it aims to increase clinicians' awareness of potential drug-drug interactions.

EXPERT OPINION

As cancer patients are often polymedicated and treated by different physicians, the risk of drug interactions between antitumoral agents and other medications is high. More clinical interaction studies are encouraged to ensure appropriate antineoplastic pharmacokinetics in clinical practice.

All-Trans Retinoic Acid-Induced Pseudotumor Cerebri during Induction Therapy for Acute Promyelocytic Leukemia: A Case Report and Literature Review

All-trans retinoic acid (ATRA), a derivative of vitamin A, is an essential component in the treatment of acute promyelocytic leukemia (APL). Though considered to be a relatively safe drug, use of ATRA can lead to several side effects such as retinoic acid syndrome and pseudotumor cerebri (PC). PC is a rare disorder characterized by neurologic and ocular signs and symptoms of increased intracranial pressure, but with normal cerebrospinal fluid composition and normal brain imaging. Most of the previous studies suggest that PC, as a complication of ATRA therapy, occurs predominantly in the pediatric age group. Herein, we report a rare case of ATRA-induced PC in a 38-year-old woman undergoing induction treatment for APL. Symptoms improved with discontinuation of ATRA and treatment with acetazolamide. Concomitant administration of medications such as triazole antifungals which influence the cytochrome P-450 system can exacerbate this potential complication of ATRA. In this paper, we also review the current literature, provide a descriptive analysis of clinical features, and discuss the principles of management of ATRA-induced PC.

[Acute renal failure in patient treated with ATRA and amphotericin B: case report]

This is a report of the case of a patient with acute promyelocytic leukemia treated with all trans-retinoic acid (ATRA), who had suspected all-trans retinoic acid syndrome (ATRA syndrome). The nonspecific febrile leukopenia observed justified the association with antimicrobial and antifungal therapy. Signs and symptoms contributed to the suspicion of ATRA syndrome, and renal function was impaired by the combination with antifungal agents. The decrease in renal function observed initially contributed to the suspicion of ATRA syndrome and was aggravated by antifungals. Thus, the use of ATRA was discontinued. Eight days after the pneumonia characterization, the possibility of ATRA syndrome was dismissed. In this context, ATR's nephrotoxicity and the synergic adverse effect by the use of nephrotoxic antifungal agents were discussed, particularly amphotericin B, as well as the importance of differential diagnosis between ATRA syndrome and infectious diseases.

Substrate specificity and ligand interactions of CYP26A1, the human liver retinoic acid hydroxylase

All-trans-retinoic acid (atRA) is the active metabolite of vitamin A. atRA is also used as a drug, and synthetic atRA analogs and inhibitors of retinoic acid (RA) metabolism have been developed. The hepatic clearance of atRA is mediated primarily by CYP26A1, but design of CYP26A1 inhibitors is hindered by lack of information on CYP26A1 structure and structure-activity relationships of its ligands. The aim of this study was to identify the primary metabolites of atRA formed by CYP26A1 and to characterize the ligand selectivity and ligand interactions of CYP26A1. On the basis of high-resolution tandem mass spectrometry data, four metabolites formed from atRA by CYP26A1 were identified as 4-OH-RA, 4-oxo-RA, 16-OH-RA and 18-OH-RA. 9-cis-RA and 13-cis-RA were also substrates of CYP26A1. Forty-two compounds with diverse structural properties were tested for CYP26A1 inhibition using 9-cis-RA as a probe, and IC(50) values for 10 inhibitors were determined. The imidazole- and triazole-containing inhibitors [S-(R*,R*)]-N-[4-[2-(dimethylamino)-1-(1H-imidazole-1-yl)propyl]-phenyl]2-benzothiazolamine (R116010) and (R)-N-[4-[2-ethyl-1-(1H-1,2,4-triazol-1-yl)butyl]phenyl]-2-benzothiazolamine (R115866) were the most potent inhibitors of CYP26A1 with IC(50) values of 4.3 and 5.1 nM, respectively. Liarozole and ketoconazole were significantly less potent with IC(50) values of 2100 and 550 nM, respectively. The retinoic acid receptor (RAR) γ agonist CD1530 was as potent an inhibitor of CYP26A1 as ketoconazole with an IC(50) of 530 nM, whereas the RARα and RARβ agonists tested did not significantly inhibit CYP26A1. The pan-RAR agonist 4-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid and the peroxisome proliferator-activated receptor ligands rosiglitazone and pioglitazone inhibited CYP26A1 with IC(50) values of 3.7, 4.2, and 8.6 μM, respectively. These data demonstrate that CYP26A1 has high ligand selectivity but accepts structurally related nuclear receptor agonists as inhibitors.

Toxicologic evaluation of imazalil with particular reference to genotoxic and teratogenic potentials

Imazalil (IMA) is a fungicide that is used extensively in fruit plantations and post-harvest treatments. IMA is suspected to produce craniofacial malformations in vertebrates and scarce data are available about its genotoxicity. Therefore, toxicity tests on embryogenesis of zebrafish (Danio rerio) and genotoxicity biomonitoring assays on human lymphocytes were performed to assess the effects of IMA. For this aim, zebrafish embryos were continually exposed, from 0.5 to 144 h post-fertilization, to a range of concentrations (5, 10, 20, 50 and 100 µM). IMA (0 to 672 µM) were also applied to the whole-blood cultures from two persons. We used chromosomal aberrations (CA) and micronucleus (MN) tests to examine DNA damage by IMA in human peripheral lymphocytes. The fungicide significantly altered zebrafish development even at low concentrations and its effects were dose-dependent. Results of the experiment indicated that IMA concentrations of 10 µM and above negatively affected embryo survival and hatching success. Morphological analysis uncovered a large suite of abnormalities such as less melanin pigmentation, wavy notochord, crooked trunk, tail defect and cardiac edema. The cytogenetic results clearly showed that IMA caused increases of the frequencies of the structural chromosomal aberrations and the rates of MN as compared to controls in a dose-dependent manner. In conclusion, the present findings are of importance in the assessment of the potential risk of fungicides as IMA on aquatic ecosystems and humans.

The relative importance of CYP26A1 in hepatic clearance of all-trans retinoic acid

All-trans retinoic acid (RA) is a critical signaling molecule and its concentration is tightly regulated. Several P450 enzymes including CYP26A1, CYP2C8, and CYP3A4 have been proposed to be responsible for RA clearance in the liver but their quantitative importance has not been demonstrated. To determine the contribution of CYP26A1 to hepatic clearance of RA, CYP26A1 protein was quantified in 37 human liver microsomes (HLMs). CYP26A1 expression ranged from not detectable to 2.80pmol/mg microsomal protein. RA clearance by P450 enzymes abundant in human liver was measured in Supersomes. CYP2C8, CYP3A4, CYP3A5 and CYP3A7 metabolized RA with unbound K(m) values of 3.4-7.2microM and V(max) values of 2.3-4.9pmol/min/pmol P450, but were less efficient than CYP26A1 in clearing RA. Simulations performed for livers with varying P450 expression levels over a range of RA concentrations demonstrated that at both endogenous and therapeutic concentrations of RA, CYP26A1 is the primary enzyme responsible for 4-OH RA formation clearance. HLM incubation data showed that 4-OH RA formation velocity varied from 0.2 to 15.3pmol/min/mg microsomal protein and velocity in HLMs was significantly correlated (p<0.01) to CYP26A1, CYP3A4, and CYP3A5 protein content, but not to CYP2C8. When experimental data were scaled to in vivo clearances, the predicted hepatic clearance of RA (0.07L/min using combined Supersome data) was similar to the published in vivo clearance of RA. These findings suggest that CYP26A1 is the P450 isoform that should be targeted when designing RA metabolism blocking agents.

The role of CYP26 enzymes in retinoic acid clearance

Retinoic acid (RA) is a critical signaling molecule that regulates gene transcription and the cell cycle. Understanding of RA signaling has increased dramatically over the past decades, but the connection between whole body RA homeostasis and gene regulation in individual cells is still unclear. It has been proposed that cytochrome P450 family 26 (CYP26) enzymes have a role in determining the cellular exposure to RA by inactivating RA in cells that do not need RA. The CYP26 enzymes have been shown to metabolize RA efficiently and they are also inducible by RA in selected systems. However, their expression patterns in different cell types and a mechanistic understanding of their function is still lacking. Based on preliminary kinetic data and protein expression levels, one may predict that if CYP26A1 is expressed in the liver at even very low levels, it will be the major RA hydroxylase in this tissue. As such, it is an attractive pharmacological target for drug development when one aims to increase circulating or cellular RA concentrations. To further the understanding of how CYP26 enzymes contribute to the regulation of RA homeostasis, structural information of the CYP26s, commercially available recombinant enzymes and good specific and sensitive antibodies are needed.

Hypercalcemia due to all trans retinoic acid in the treatment of acute promyelocytic leukemia potentiated by voriconazole

All-trans-retinoic acid (ATRA) is a new and effective treatment of acute promyelocytic leukemia. It has many side-effects, including the retinoic acid syndrome and Sweet's syndrome. There have been only nine cases of hypercalcemia associated with ATRA described in the literature. We discuss a case of hypercalcemia, which we believe was due to inhibition of cytochrome P450 function by voriconizole when used concomitantly with ATRA.

Fluconazole alters CYP26 gene expression in mouse embryos

Disruption of embryonal retinoic acid homeostasis has been postulated to represent an etiological factor involved in the onset of fluconazole-induced teratogenesis. In the present study the impact of a teratogenic pulse of fluconazole on the gene expression of cytochrome P450 (CYP) 26 isoforms, which plays a central role in maintaining proper retinoic acid levels by mediating its degradation, was investigated. ICR pregnant mice were orally administered with 0 (vehicle) or 700mg/kg of fluconazole on gestation day 8. Embryos were collected 12, 24 and 48h after treatment. Quantitative real-time reverse-transcription polymerase chain reaction (quantitative real-time RT-PCR) assay was used to quantify the mRNA expression of CYP26a1, CYP26b1 and CYP26c1 in embryos. As result, fluconazole exposure was associated to an up-regulation of CYP26a1, CYP26b1, whereas no significant change was identified for the CYP26c1 isoform. This study demonstrates the capacity of fluconazole to alter CYP26 gene expression in mouse embryos.

Acute renal failure during ATRA treatment

All-trans-retinoic acid (ATRA), which is used in acute promyelocytic leukemia, is usually well tolerated, but some side effects can be observed. Retinoic acid syndrome is the most severe side effect. Triazole derivatives such as fluconazole inhibit the NADPH-dependent cytochrome P-450-mediated catabolism of ATRA and are increased plasma levels of ATRA. Here, the authors report a case of APL who developed acute renal failure during ATRA and concurrent use of fluconazole.

Fluconazole induces teratogenic effects in the tunicate Phallusia mammillata

Fluconazole (FLUCO) is an azole derivative used to treat fungal and yeast infections. Embryotoxicity tests on the ascidian Phallusia mammillata were performed to evaluate the effects of this drug. FLUCO proved to have strong consequences on P. mammillata development. Incidence of malformations and of lethality increased in a dose dependent way. Probit analysis showed that FLUCO had a high TI value (Teratogenic Index, LC(50)/TC(50)), thus this substance could be classified as a teratogenic compound for ascidians. Larvae exposed to FLUCO showed a typical phenotype characterized by malformations restricted to the trunk region: the trunk appeared round in shape with flat palps, the sensory vesicle cavity was absent or reduced and the anterior central nervous system failed to correctly differentiate. These anomalies resulted similar to those induced by retinoic acid (RA) treatment. Thus, it could be hypothesized that FLUCO and RA may act with a similar pathogenic mechanism in ascidian larvae, as it has been proposed for mammals.

Krox20 is down-regulated following triazole in vitro embryonic exposure: a polycompetitor-based assay

This study was conducted in order to analyse gene-expression alterations in rat embryos following exposure to triazoles, using an easy-handling approach. Triazole derivatives have been shown to alter the morphology of cranio-facial structures and to induce abnormalities in hindbrain patterning and neural crest cell migration. Specification of hindbrain segments is regulated by retinoic acid and the hox code. Krox20 was chosen as molecular marker for its specific distribution in the anterior neural tube. In fact, this zinc-finger protein is expressed in rhombomere 3 and 5. Mis-regulation of Krox20 levels have shown to induce severe alterations in the correct patterning of the rhomboencephalon and the derived structures. In order to analyse Krox20 mRNA levels in rat embryos exposed in vitro to the triazole derivative triadimefon, a semi-quantitative approach utilising the competitive RT-PCR was chosen. A lambda phage-based plasmid construct that could compete with target and internal standard gene at the same time during enzymatic reaction was generated. Results were confirmed by real-time RT-PCR analysis on the same samples. Our data show a down-regulation of Krox20 transcript levels after exposure to the triazole derivative, implying a key role of this molecule in the pathogenic pathway induced by triazole exposure.

Toxic effects of two pesticides, Imazalil and Triadimefon, on the early development of the ascidian Phallusia mammillata (Chordata, Ascidiacea)

Azole compounds are fungicides used in agriculture and in clinical area and are suspected to produce craniofacial malformations in vertebrates. Toxicity tests on sperm viability, fertilization and embryogenesis of the solitary ascidian Phallusia mammillata were performed to evaluate the effects of two azole derivatives, Imazalil and Triadimefon. Ascidian (Chordata, Ascidiacea) embryos and larvae could provide biological criteria for seawater quality standards because the larvae are lecitotrophic and have a short pelagic period, allowing to run the larval toxicity tests over a short period of time. Imazalil and Triadimefon proved to have strong consequences on P. mammillata. They could influence the reproductive rate of the animal exerting their effects at different levels: acting as spermiotoxic agents, inhibiting fertilization and impairing embryological development. Fertilization rate significantly decreased after 30min exposure of sperm to 25microM Imazalil (P<0.0001) and after exposure of both gametes to 50microM Imazalil (P<0.05) and 1mM Triadimefon (P<0.0001) as compared to controls. Malformations caused by exposure of embryos to both substances were dose dependent. Imazalil median teratogenic concentration (TC50 concentration, the concentration that resulted in 50% malformed larvae) value was 0.67microM and median lethal concentration (LC50, the concentration that resulted in 50% embryos dead before completing the development) value was 10.23microM while for Triadimefon TC50 value was 29.56 and LC50 value was 173.7microM. Larvae developed from embryos treated with Imazalil and Triadimefon showed alterations of the anterior structures of the trunk: papillary nerves and the anterior central nervous system failed to correctly differentiate, as showed by immunostaining with anti-beta-tubulin antibody. Comparing the anomalies caused by retinoic acid, reported in a previous study, it was possible to hypothesize that malformations induced by Imazalil and Triadimefon could be due to a perturbation of the endogenous retinoid content, as it has been proposed for mammals. Ascidians proved to be good models to study the toxic effects of pesticides since they offered both the convenience of working with an invertebrate species and the tissue sensitivity to chemical compound comparable to vertebrates.

Defining critical periods for itraconazole-induced cleft palate, limb defects and axial skeletal malformations in the mouse

The main aim of the study was to identify the critical periods of susceptibility for itraconazole-mediated teratogenesis in the mouse. Pregnant ICR (CD-1) mice received a single oral administration of itraconazole at 50 mg/kg b.w., 150 mg/kg b.w. or 250 mg/kg b.w. on gestation day 8, 9, 10, 11 or 12. Control animals were administered with vehicle on gestation days 8-12. The gestational outcome was evaluated near term, on gestation day 18. Treatment-related morphological findings, as they can be evaluated by external, visceral and skeletal examination, mainly included cleft palate, limb defects and axial skeletal malformations. Cleft palate and limb defects resulted after single exposures between gestation days 9 and 11, with a tendency toward maximal response on gestation day 10. Significant incidences of axial skeletal defects were seen exclusively on gestation days 8 and 9. Exposure on gestation day 12 did not yield significant teratogenic responses. Cleft palate was the most sensitive teratogenic response, being the only developmental lesion associated to exposure to itraconazole at 150 mg/kg b.w.

Postulated pathogenic pathway in triazole fungicide induced dysmorphogenic effects

Triazole fungicides are used in medicine as well as in agricultural treatment of mycoses. The pharmacological mechanism is related to the inhibition of CYP enzymes involved in the formation of the fungal walls. A similar inhibition of human CYP enzymes has been suggested as the cause of triazole side effects in humans. An important role of some CYP isoforms (CYP26 isoforms) expressed during mammalian development is the catabolism of retinoic acid, a known morphogen in vertebrates and invertebrates. The adverse effects on morphogenesis, observed after exposure of mammalian, amphibian and ascidiacea, are compared to the reported effects of triazole in humans. The possible pathogenic pathway in triazole-related teratogenesis is discussed on the basis of different experimental approaches.

Photosensibilisation au voriconazole : 7 cas

BACKGROUND

Voriconazole is a new second-generation fluconazole-derived triazole. With greater potency against susceptible species and a broader spectrum of activity than fluconazole, it is the treatment of choice for invasive pulmonary aspergillosis and other fungal infections (Fusarium, Scedosporium/Pseudalleschezria) is indicated in a visit Candida infections refractory to fluconazole. We describe 7 cases of photosensitivity during treatment with voriconazole in a setting of immunodepression.

CASE REPORTS

The patients comprised 5 women and 2 men with a mean age of 38 years (17-67 years). Five had undergone pulmonary transplantation for mucoviscidosis, one had undergone kidney transplantation for lupus nephroangiosclerosis and one was on long-term systemic steroid treatment for Sjögren's syndrome. All patients had very severe immunosuppression and were receiving voriconazole for pulmonary aspergillosis (6 cases) or Scedosporium infection (1 case). Photosensitization appeared within 5 weeks to 14 months after the start of treatment, and in all cases followed exposure to sun, occasionally at low levels. In all cases, cutaneous lesions rapidly disappeared on discontinuation of treatment.

DISCUSSION

There have been reports in the literature, although rare, of photosensitivity with voriconazole. Patients must be informed of the possibility of this adverse effect and sun protection must be recommended when voriconazole is prescribed, particularly during periods of intensive exposure.

Dysmorphogenic effects of some fungicides derived from the imidazole on rat embryos cultured in vitro

Like triazole-derivatives, imidazole-derivatives exert their antifungal and toxicological properties by inhibiting P450 enzymes (Cyps). At the embryonic level, Cyp enzymes are involved also in the catabolism of the retinoic acid. Specific effects of triazole-derivatives have been reported on developing rodent embryos, and were correlated to an imbalance of the retinoid homeostasis. The aim of this work was to investigate if imidazole-derivatives are able to induce specific malformations similar to those observed after triazole-derivative exposure. Post implantation rat embryos were exposed in vitro to 1,000 microM Imidazole and to 5-100 microM of the imidazole-derivatives Ketoconazole and Enilconazole. After 48 h in culture, the embryos exposed to the imidazole-derivatives showed specific malformations, quite similar to those observed after triazole-derivative exposure. The common dysmorphogenic effects of the azole-derivatives of the two classes could be due to the inhibition of retinoid catabolism. From this point of view, the contemporaneous exposure to these substances or their therapeutic use could be considered as potentially dangerous for human conceptuses.

Frequency of potential azole drug-drug interactions and consequences of potential fluconazole drug interactions

PURPOSE

To assess the frequency of potential azole-drug interactions and consequences of interactions between fluconazole and other drugs in routine inpatient care.

METHODS

We performed a retrospective cohort study of hospitalized patients treated for systemic fungal infections with an oral or intravenous azole medication between July 1997 and June 2001 in a tertiary care hospital. We recorded the concomitant use of medications known to interact with azole antifungals and measured the frequency of potential azole drug interactions, which we considered to be present when both drugs were given together. We then performed a chart review on a random sample of admissions in which patients were exposed to a potential moderate or major drug interaction with fluconazole. The list of azole-interacting medications and the severity of interaction were derived from the DRUGDEX System and Drug Interaction Facts.

RESULTS

Among the 4,185 admissions in which azole agents (fluconazole, itraconazole or ketoconazole) were given, 2,941 (70.3%) admissions experienced potential azole-drug interactions, which included 2,716 (92.3%) admissions experiencing potential fluconazole interactions. The most frequent interactions with potential moderate to major severity were co-administration of fluconazole with prednisone (25.3%), midazolam (17.5%), warfarin (14.7%), methylprednisolone (14.1%), cyclosporine (10.7%) and nifedipine (10.1%). Charts were reviewed for 199 admissions in which patients were exposed to potential fluconazole drug interactions. While four adverse drug events (ADEs) caused by fluconazole were found, none was felt to be caused by a drug-drug interaction (DDI), although in one instance fluconazole may have contributed.

CONCLUSIONS

Potential fluconazole drug interactions were very frequent among hospitalized patients on systemic azole antifungal therapy, but they had few apparent clinical consequences.

Study on the common teratogenic pathway elicited by the fungicides triazole-derivatives

Triazole-derivatives alter the pharyngeal apparatus morphogenesis of rodent embryos cultured in vitro. The hindbrain segmentation and the rhombencephalic neural crest cell (NCCs) migration are altered by Fluconazole exposure in vitro. The aim of the present work is to identify if a common pathogenic pathway is detectable also for other molecules of this class of compounds. 9.5 days post coitum (d.p.c.) old rat embryos were exposed in vitro to the teratogenic concentrations of Flusilazole, Triadimefon and Triadimenol and cultured for 24, 48 or 60 h. The expression and localisation of Hox-b1 and Krox-20 proteins (used as markers for hindbrain segmentation) were evaluated after 24 h of culture. The localisation and distribution of NCC was evaluated after 24, 30 and 48 h of culture. The morphology of the embryos was analysed after 48 h, while the branchial nerve structures were evaluated after 60 h of culture. Hindbrain segmentation and NCC migration alteration as well as pharyngeal arch and cranial nerve abnormalities were detected after exposure of the tested molecules. A common severe teratogenic intrinsic property for the tested molecules of this chemical class has been found, acting through alteration of the normal hindbrain developmental pattern.

Teratogenic effects of two antifungal triazoles, triadimefon and triadimenol, on Xenopus laevis development: craniofacial defects

Triadimefon and triadimenol, fungicides used in agriculture, are suspected of producing craniofacial malformations. As the results of FETAX analysis showed that Triadimefon was highly teratogenic, we studied the action of these triazoles on the development of the branchial apparatus in Xenopus, using early molecular markers and analysis of the cartilaginous-muscular elements of tadpoles. Teratogenic effects were observed, after exposure at the neurula stage, at the level of cartilages and muscles of the 1st and 2nd branchial arches. By in situ hybridization, we observed that in exposed specimens the territories of the branchial arches are perturbed. From these results, we considered the craniofacial malformations related to the influence of triazoles on the differentiation of branchial arches. Comparing the anomalies caused by triazoles and by retinoic acid (RA) led us to the conclusion that triazoles can affect endogenous RA content, as has been shown for mammals.

Craniofacial and axial skeletal defects induced by the fungicide triadimefon in the mouse

BACKGROUND

Triadimefon is an antifungal derived from triazole. In in vitro whole-rodent embryo cultures, triazole-derivatives showed specific teratogenic effects at the branchial apparatus. The aim of the present work was to test in vivo triadimefon (FON), in order to verify a relationship between triazole exposure, embryonic abnormalities, and/or fetal malformations.

METHODS

Pregnant CD-1 mice were treated with 0-300 mg/kg FON by gavage on day 8 post coitum (p.c.) at 10:00 AM, and sacrificed on day 8 p.c. at 1:00 PM, on day 9 p.c. at 10:00 AM, on day 10 p.c. at 10:00 AM, and at term of gestation (day 18 p.c.). At midgestation, the embryos were processed for specific immunostainings to visualize the hindbrain segmentation (day 8 p.c.) and the neural crest cell migration (days 8 and 9 p.c.). Fetuses explanted at term were all processed for skeletal examination after double-staining of osseous and cartilaginous tissues.

RESULTS

At midgestation, the immunostaining of rhombomeres 3 and 5 showed a light scattering of the immunostained areas; the neural crest cell migration was unaffected, but their localization at the branchial arch level was abnormal. At term, several severe malformations were observed at the craniofacial and at the axial skeletal level. Ectopic cartilage was observed at the upper jaw.

CONCLUSIONS

Triadimefon is teratogenic. The observed craniofacial malformations could be explained by an alteration of the rhombomeric organization and neural crest migration to the branchial arches; the axial abnormalities could be explained by the abnormal segmental identity specification.