Characterizing Opioid Prescribing Trends of Medical Oncologists From 2013 to 2019: Analysis From the Centers for Medicare & Medicaid Services Medicare Part D Prescribers Database

PURPOSE

Opioid prescribing trends in medical oncology are poorly defined past 2017, the year after the CDC updated opioid prescription guidelines in noncancer settings. We aim to characterize pain management by medical oncologists by analyzing opioid and gabapentin prescribing trends from 2013 to 2019, identify physician-related factors associated with prescribing patterns, and assess whether CDC guidelines for nononcologic settings changed prescribing patterns.

METHODS

The Centers for Medicare & Medicaid Services (CMS) Medicare Part D Prescribers-by Provider, CMS Medicare Part D Prescribers-by Provider and Drug, and CMS Medicare Physician National Downloadable files from 2013 to 2019 were merged by National Provider Identification. The database included physicians' sex, years of practice, regions, and practice settings. Multivariable binary logistic regression identified significant predictors of total opioid, long-acting opioid, and gabapentin prescriptions.

RESULTS

Binary logistic regression modeling revealed no significant difference in mean daily total opioid prescriptions from 2013 to 2017. Daily opioid prescriptions by medical oncologists decreased significantly after 2017 (P < .001). Increased opioid prescribing was associated with physician male sex (P < .001), practicing over 10 years (P < .001), and practice in nonurban areas (P < .001). Opioid prescribing was greatest in the South and Midwest United States (P < .001). The same patterns were observed with total long-acting opioid prescriptions, whereas gabapentin prescribing increased from 2013 to 2019 (P < .001).

CONCLUSION

Opioid prescriptions by medical oncologists decreased significantly from 2013 to 2019, but this decrease was most substantial from 2017 to 2019. These results may imply that the 2016 CDC guidelines influenced medical oncologists, particularly more junior physicians in urban settings, to manage chronic cancer pain with alternative therapies.

Disparities in lung cancer short- and long-term outcomes after surgery: Analysis from the national cancer database

INTRODUCTION

Social determinants of health are particularly important in lung cancer epidemiology. Previous studies have primarily associated social determinants with long-term outcomes, such as survival, but fail to include short-term outcomes after surgery. The National Cancer Database (NCDB) was used to draw associations between social factors of patients with lung cancer and short-term post-surgical outcomes, while comparing them to prognostic factors, including stage at diagnosis and survival.

METHODS

The 2004-17 NCDB was queried for patients with primary epithelial tumor, squamous cell carcinoma, or adenocarcinoma of the lung treated with curative intent. Linear, binary logistic, Kaplan-Meier, and Cox proportional hazards regression models were utilized.

RESULTS

On logistic regression modeling, male gender, low income, lacking insurance, and facility in the central United States were associated with poor short-term outcomes (<0.05). Increased age, White race, and Black race were associated with increased length of hospital stay and mortality, but negatively correlated with readmission rates (<0.05). Medicare and Medicaid were associated with increased length of stay and mortality, respectively (<0.05). Similar patterns were observed for higher stage at diagnosis (<0.05). Hazard ratios were elevated with increased age, male gender, White race, lacking insurance, Medicaid, and facility in the central United States (<0.05).

CONCLUSION

Many social factors previously associated with poor prognosis after lung cancer diagnosis are also associated with poor short-term outcomes after surgery. This study implies that healthcare providers treating lung cancer should proceed with care while aware that patients with the discussed social factors are predisposed to complicated recoveries.

Female authorship trends and the effect of COVID-19 on cataract and refractive surgery literature

PURPOSE

To evaluate whether gender barriers persist specifically in the cataract and refractive surgery (CRS) literature. In addition, no literature exists investigating the long-term effect of COVID-19 on female authorship in ophthalmology past 2020.

SETTING

Scopus 2015 to 2022.

DESIGN

Retrospective data review.

METHODS

Articles published in the Journal of Refractive Surgery and the Journal of Cataract & Refractive Surgery were recorded from January 2015 to February 2022 from Scopus. Articles with only 1 author or where gender could not be identified were excluded. The first author (FA) gender, senior author (SA) gender, affiliated country, type of literature, and number of citations were collected. Pearson chi-squared tests with phi coefficients and multivariate logistic regression were performed.

RESULTS

3153 articles were included in analysis. There were 910 works with female FAs and 648 with female SAs. Gender did not predict publishing in one journal over the other (P > .050). Women made up less than 30% of authorship of all types of literature, except for prospective/observational studies as FA (31.3%). Compared with before 2020, female FAs from 2020 onward were associated with increased retrospective analysis (phi = 0.072, P = .030) and letters/editorials (phi = 0.134, P < .001) but decreased case reports (phi = 0.087, P = .009) and "others" (phi = -0.164, P < .001). Similar associations were observed for female SAs. Females were more likely to publish in Asian countries. Female SAs predicted an increased likelihood of female FAs (odds ratio, 1.401, 95% CI, 1.165-1.684, P < .001).

CONCLUSIONS

Gender disparities exist in authorship of the CRS literature. COVID-19 has altered the types of literature published by women, but men still publish most of all types of CRS research.

Multi-omic alterations of the SWI/SNF complex define a clinical subgroup in lung adenocarcinoma

SWI/SNF complexes are major targets of mutations in cancer. Here, we combined multiple “-omics” methods to assess SWI/SNF composition and aberrations in LUAD. Mutations in lung SWI/SNF subunits were highly recurrent in our LUAD cohort (41.4%), and over 70% of the mutations were predicted to have functional impact. Furthermore, SWI/SNF expression in LUAD suffered an overall repression that could not be explained exclusively by genetic alterations. Finally, SWI/SNF mutations were associated with poorer overall survival in TCGA-LUAD. We propose SWI/SNF-mutant LUAD as a separate clinical subgroup with practical implications.

30 Informant-Reported Decline Associates with Silent Acute Stroke Lesions and Worse Small Vessel Disease in Mild Stroke Patients

Introduction

Small vessel disease (SVD) commonly causes stroke and dementia. Early clinical predictors of disease progression are lacking. We aimed to determine whether informant reports of chronic cognitive/functional decline, prerequisites for dementia diagnosis, are associated with (a)baseline SVD burden, measured by Fazekas scores and (b)SVD change, measured by incident subcortical Diffusion-weighted Imaging (DWI) lesions.

Method

We prospectively recruited patients with mild ischaemic stroke, performed diagnostic MRI, and invited participants to repeat MRI 3- to 6-monthly. Informants completed the Informant Questionnaire for Cognitive Decline in the Elderly (IQCODE) prior to baseline visit, a 16-item questionnaire which assesses patients’ cognitive and functional decline in the preceding ten years. Scores range from 1–5: a score above 3.3 has high sensitivity/specificity for dementia post-stroke. We conducted linear regression with IQCODE as the dependent variable, adjusting for age, sex, baseline MoCA, disability (modified Rankin Scale).

Results

We recruited 106 participants (mean age 67 years;range 40–86;33% female). Ninety-three informant questionnaires were returned. IQCODE associated with baseline Fazekas score; Fazekas 6 (β = 0.28, p = 0.04) vs. Fazekas 3 (β = 0.03, p = 0.67), R2 = 0.11, adjusted for age, sex, baseline MoCA, disability.

Incident DWI lesions were common (15/106; 14/15 subcortical; no active embolic sources; median 67 days post-stroke). Four were asymptomatic, two reported stroke-like symptoms and nine had neuropsychiatric/non-focal symptoms. IQCODE was higher in those with a new lesion vs. without (β = 0.21, p = 0.02), R2 = 0.09, while age (β = −0.004, p = 0.19), MoCA (β = −0.006, p = 0.56) and disability (β = 0.06, p = 0.2) were not.

Conclusions

Higher SVD burden and incident, mostly “silent” stroke lesions associate more strongly with informant concerns of cognitive/functional decline than age or objective cognitive tests. These findings are novel in an ischaemic stroke population and the first to assess IQCODE/SVD progression. Future work should determine whether combining informant reports with imaging features of small vessel disease improves early detection of dementia.

In the Privacy of Their Own Homes: Using the Internet to Assess Racial Bias

Recent studies suggest that research participants show reduced distortion of their taboo attitudes and behaviors when they take part in Internet-based procedures from outside the laboratory. We explored whether such procedures would reduce distortion in the assessment of racial bias. In Study 1, White participants who completed the study in the laboratory evaluated Black targets more favorably than White targets. This unexpected “outgroup-favoring” pattern occurred in both pencil-and-paper and Internet versions of the study, showing that modality did not produce it; but when participants worked outside the laboratory via the Internet, this pattern disappeared. Study 2 replicated the above findings and further indicated that the reduced distortion in Internet-based studies was due to the removal of the experimenter rather than removing the participants from the laboratory environment. The implications of these findings for the study of controlled processes of prejudice and the nature of Internet-based social communication are discussed.

The effect of single-file reciprocating systems on Substance P and Calcitonin gene-related peptide expression in human periodontal ligament

AIM

To quantify the effect of two single-file reciprocating root canal preparation systems on Substance P (SP) and Calcitonin gene-related peptide (CGRP) expression in healthy human periodontal ligament (PDL).

METHODOLOGY

Forty PDL samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. Prior to extraction, 20 of these premolars were divided equally in two groups, and then, root canals were prepared using one of two different single-file systems: WaveOne and Reciproc. Ten premolars were prepared with hand files and served as a positive control group. The remaining 10 premolars where extracted without treatment and served as a negative control group. All PDL samples were processed, and SP and CGRP were measured by radioimmunoassay.

RESULTS

Greater SP and CGRP expression were found in the hand instrumentation group (1.220 pmol SP and 0.084 pmol CGRP per mg of PDL), followed by the WaveOne group (0.908 pmol SP and 0.046 pmol CGRP per mg of PDL) and the Reciproc group (0.511 pmol SP and 0.022 pmol CGRP per mg of PDL). The lower SP and CGRP values were associated with the intact control group (0.453 pmol SP and 0.018 pmol CGRP per mg of PDL). The Kruskal-Wallis test revealed significant differences between groups (P < 0.001). Post hoc Tukey HSD tests revealed significant differences in SP and CGRP expression between intact teeth in the control group and all the other groups (P < 0.001) except with the Reciproc group (P = 0.165 and P = 0.42 for SP and CGRP, respectively). Hand instrumentation was associated with significant differences with all the other groups (P < 0.001). Differences between the WaveOne and Reciproc groups were also significant (P < 0.001).

CONCLUSION

Substance P and CGRP expression in PDL cells increased when teeth were prepared with WaveOne as well as with hand instrumentation. Reciproc maintained SP and CGRP levels in line with the negative control group.

Nanogel surface coatings for improved single-molecule imaging substrates

Surfaces that resist protein adsorption are important for many bioanalytical applications. Bovine serum albumin (BSA) coatings and multi-arm poly(ethylene glycol) (PEG) coatings display low levels of non-specific protein adsorption and have enabled highly quantitative single-molecule (SM) protein studies. Recently, a method was developed for coating a glass with PEG-BSA nanogels, a promising hybrid of these two low-background coatings. We characterized the nanogel coating to determine its suitability for SM protein experiments. SM adsorption counting revealed that nanogel-coated surfaces exhibit lower protein adsorption than covalently coupled BSA surfaces and monolayers of multi-arm PEG, so this surface displays one of the lowest degrees of protein adsorption yet observed. Additionally, the nanogel coating was resistant to DNA adsorption, underscoring the utility of the coating across a variety of SM experiments. The nanogel coating was found to be compatible with surfactants, whereas the BSA coating was not. Finally, applying the coating to a real-world study, we found that single ligand molecules could be tethered to this surface and detected with high sensitivity and specificity by a digital immunoassay. These results suggest that PEG-BSA nanogel coatings will be highly useful for the SM analysis of proteins.

Spin order in one-dimensional Kondo and Hund lattices

We study numerically the one-dimensional Kondo and Hund lattices consisting of localized spins interacting antiferromagnetically or ferromagnetically with the itinerant electrons, respectively. Using the density-matrix renormalization group we find, for both models and in the small coupling regime, the existence of new magnetic phases where the local spins order forming ferromagnetic islands coupled antiferromagnetically. Furthermore, by increasing the interaction parameter |J| we find that this order evolves toward the ferromagnetic regime through a spiral-like phase with longer characteristic wavelengths. These results shed new light on the zero temperature magnetic phase diagram for these models.

Phase I pharmacokinetic trial and correlative in vitro phase II tumor kinetic study of Apomine (SR-45023A), a novel oral biphosphonate anticancer drug

PURPOSE

To study the human pharmacokinetics and in vitro cytotoxicity of Apomine, an p.o. administered, nonmyelosuppressive agent that selectively inhibits cell proliferation and induces tumor cell apoptosis through the farnesoid X receptor.

EXPERIMENTAL DESIGN

Seven solid cancer patients who participated in an ongoing Phase I study of Apomine and received the starting dose level of 125 mg/m(2)/day x 14 days every 3 weeks underwent a pharmacokinetic study on day 14 of the first course. Plasma concentrations of Apomine were assayed with a Hewlett Packard gas chromatograph using a nitrogen phosphorus detector and HP-5 15m x 0.32-mm column. Fresh human ovarian cancer tumor samples were obtained during initial exploratory laparotomy from 35 chemotherapy-naive, advanced stage epithelial ovarian cancer patients. Tumor samples were tested for sensitivity to Apomine, carboplatin, cisplatin, paclitaxel, and topotecan using an in vitro clonogenic [(3)H]thymidine end point assay.

RESULTS

Pharmacokinetic analysis revealed a mean Apomine plasma C(max) of 16.4 +/- 9.1 microg/ml (29.1 microM), a mean plasma AUC(0--12 h) of 173.4 +/- 105 microg. h/ml (308 microM. h), and a mean t(1/2 (24--192 h)) of 156.2 +/- 42.9 h. In vitro assay results showed that 63 and 91% of the ovarian cancers were sensitive (i.e., >70% inhibition of tumor cell growth) to Apomine at concentrations of 10 and 20 microM. The sensitivity rates were 91% for carboplatin (270 microM), 88% for cisplatin (33 microM), 41% for paclitaxel (5.9 microM), and 85% for topotecan (2.2 microM).

CONCLUSIONS

These in vitro assay results, taken together with our preliminary plasma pharmacokinetic data, suggest that Apomine should be clinically active at the 125 mg/m(2) dose level.

In vitro phase II comparison of the cytotoxicity of a novel platinum analog, nedaplatin (254-S), with that of cisplatin and carboplatin against fresh, human ovarian cancers

PURPOSE

To compare the in vitro cytotoxicity of nedaplatin, an investigational platinum analog, with that of the standard platinum agents, cisplatin and carboplatin, against fresh human, epithelial ovarian cancers.

METHODS

The Hamburger-Salmon human tumor colony-forming assay (HTCA) was used to measure the chemosensitivity of 36 fresh tumor samples obtained during initial exploratory laparotomy from patients with newly diagnosed stage III-IV epithelial ovarian cancer who had received no prior chemotherapy or radiation therapy. Tumor samples were exposed to the platinum analogs for 1 h at concentrations of 10 and 100 micrograms/ml of nedaplatin and cisplatin and 100 and 1000 micrograms/ml of carboplatin. The resulting survival data were used to estimate the IC50 (drug concentration associated with 50% inhibition of tumor colony forming units, TCFUs) of each of the platinum analogs for each of the tumor samples, as well as the estimated survival following exposure to clinically achievable drug levels (i.e. the ultrafiltrable platinum area under the plasma disappearance curve, AUC, achieved in cancer patients following administration of standard or phase II doses).

RESULTS

At the lowest concentration tested (i.e. 10 micrograms/ml nedaplatin and cisplatin and 100 micrograms/ml carboplatin) the percentages of tumor samples which were sensitive (as defined by 50% or less survival of TCFUs as compared with controls) were 42, 50, and 40% for nedaplatin, cisplatin and carboplatin, respectively. The median IC50 values were 28.5, 12 and 121 micrograms/ml for nedaplatin, cisplatin and carboplatin, respectively. The estimated percentage of tumors sensitive to clinically achievable dose levels was 42% for nedaplatin and 36% for cisplatin and carboplatin. Nedaplatin and carboplatin proved relatively crossresistant with cisplatin in vitro; of the 18 tumor samples which were resistant to cisplatin, only 5 (28%) were sensitive to nedaplatin and 3 of 17 (18%) were sensitive to carboplatin.

CONCLUSION

Nedaplatin was associated with cytotoxicity similar to cisplatin and carboplatin in this study. Although nedaplatin appears to be crossresistant with cisplatin, its high rate of in vitro cytotoxicity, relative lack of neurotoxicity and nephrotoxicity, and large in vivo biovailability establish nedaplatin as a promising platinum analog for further clinical development as a salvage and primary chemotherapeutic agent for patients with advanced ovarian cancer.

New type of charge and magnetic order in the ferromagnetic kondo lattice

We study numerically the one dimensional ferromagnetic Kondo lattice, a model widely used to describe nickel and manganese perovskites. By including a nearest-neighbor Coulomb interaction ( V) and a superexchange interaction between the localized moments ( K), we obtain the phase diagram in parameter space for several dopings at T = 0. Because of the competition between double and superexchange, we find a region where the formation of magnetic polarons induces a charge-ordered state which survives also for V = 0. This mechanism should be taken into account in theories of charge ordering involving spin degrees of freedom.

Safety aspects of pegylated liposomal doxorubicin in patients with cancer

Encapsulation in polyethylene glycol-coated (pegylated; Stealth) liposomes alters the pharmacokinetic characteristics, and hence the safety and tolerability profile, of doxorubicin. Pegylated liposomal doxorubicin administered as a single agent is generally well tolerated. Grade III/IV leucopenia, stomatitis and palmar-plantar erythrodysaesthesia affected 16, 6 and 18% of solid tumour patients, respectively. Other adverse effects included nausea and vomiting and alopecia. Acute hypersensitivity infusion reactions have been reported in up to 9% of patients in some studies. Recently published data from a phase II trial in patients with refractory ovarian cancer showed no alopecia or cardiotoxicity and little nausea and vomiting after pegylated liposomal doxorubicin. Unlike free doxorubicin, pegylated liposomal doxorubicin is not a vesicant. Preliminary data, not yet confirmed in comparative studies, suggest that the pegylated liposomal formulation may be less cardiotoxic than free doxorubicin. Mucositis, however, appears to be increased. Studies to determine optimal dosing schedules and safety of pegylated liposomal doxorubicin in combination with other agents are ongoing.

An overview of clinical cancer chemoprevention studies with emphasis on positive phase III studies

Cancer prevention aims to halt or reverse the development and progression of precancerous cells through the use of noncytotoxic nutrients and/or pharmacologic agents during the lengthy time period between tumor initiation and frank malignancy. This paper reviews cancer chemoprevention studies and focuses on Phase III trials, which are large, randomized, placebo-controlled studies that usually last several years. Studies may include multiple agents and dose levels, long-term toxicity evaluations or the modulation of surrogate endpoint biomarkers. Sample sizes of individual studies vary depending on statistical concerns and the demographics of the subject population. Recent Phase III trials include several promising agents: retinol; the retinoids 13-cis retinoic acid, all-trans-retinoic acid and 4-hydroxyphenyl retinamide; beta-carotene; finasteride and tamoxifen. Because one of the many actions of retinoids is the induction of epidermal differentiation, clinical trials with this class of agents have largely been conducted in epithelial or squamous cell tumor types. Several Phase III studies that have targeted the reversal of premalignant lesions or the prevention of second primary tumors have shown promising positive results. In contrast, some studies have shown that chemopreventive agents may have limited activity against the recurrence or progression of cells that have already undergone malignant transformation. Thus, the role of chemoprevention appears to lie in reversal of the premalignant process rather than suppression of malignant growth.

In vitro drug testing of ovarian cancer using the human tumor colony-forming assay: comparison of in vitro response and clinical outcome

The purpose of this study was to assess the prognostic value of in vitro drug chemosensitivity testing using the Hamburger-Salmon human tumor colony-forming assay (HTCA) in fresh tumor samples obtained from newly diagnosed patients with stage II-IV ovarian cancer undergoing maximum cytoreductive surgery and prior to platinum-based chemotherapy. The HTCA was performed on fresh ovarian cancers obtained from 93 patients at their initial exploratory laparotomy to evaluate in vitro sensitivity to cisplatin, carboplatin, and cyclophosphamide following a 1-hr drug exposure. Prospective clinical follow-up was performed on all patients with the primary study endpoints being pathologically proven complete response at second-look surgery and disease-free and overall survival durations. In vitro drug sensitivity was strongly dose-dependent. At a concentration of 5 micrograms/ml only 23% of tumor samples were sensitive (as defined by a > or = 50% decrease in tumor colony-forming units compared to controls) to cisplatin; 13% of tumors were sensitive to carboplatin at a concentration of 50 micrograms/ml and 11% to 4-OH-cyclophosphamide at a concentration of 1 microgram/ml. At doses which were 10 times the previously stated concentrations, the sensitivity rates to cisplatin, carboplatin, and 4-OH-cyclophosphamide increased to 72, 63, and 53%, respectively. Subjects were categorized as having drug-sensitive disease if HTCA results showed in vitro drug sensitivity to at least one of the agents used in their primary chemotherapy. Multivariate analysis failed to show any advantage in clinical response rate, progression-free interval, or survival duration for patients with drug-sensitive disease compared to drug-resistant disease; however, there was evidence of a trend toward an enhanced pathologically proven complete response rate in patients who had chemosensitive tumors in vitro. Second-look surgery was performed in 28 of 55 patients with optimal surgical resections and no clinical evidence of disease at the completion of their primary chemotherapy. Fifty percent (5/10) of patients with drug-sensitive disease achieved a pathologic complete response, while only 3/18 (17%) patients with drug-resistant tumors had a documented pathologic complete response (P = 0.13). As reported in other ovarian cancer studies, patient characteristics which were found to be significantly associated with survival were stage of disease (II-III vs IV), optimal primary surgical resection (i.e., < 1 cm2 residual tumor) vs suboptimal resection, clinical measurability of disease at initiation of chemotherapy, and response to primary chemotherapy. In conclusion, in vitro drug sensitivity, as measured by the HTCA, does not appear to be an independent prognostic factor for survival in patients with stage II-IV epithelial ovarian cancer who undergo standard treatment with tumor debulking surgery and primary platinum-based chemotherapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Salvage chemotherapy in recurrent or refractory squamous cell cancer of the uterine cervix

Squamous cell cancer of the cervix is a relatively drug-resistant tumor. Therefore, chemotherapy is predominantly reserved for cervical cancer patients with recurrent or refractory disease following surgery and/or radiation therapy or for patients who present with far advanced, incurable disease. Objective responses to salvage chemotherapy are generally short lived (4 to 6 months) with few patients surviving more than 1 year. Complete clinical remissions primarily occur at extrapelvic sites (eg, lung, lymph node, and soft tissue metastases). Bulky pelvic tumor in an area of prior irradiation remains largely refractory to further therapy. At present, no chemotherapy regimen has proven superior to single-agent cisplatin, which is associated with an approximately 30% objective response rate. The most effective nonplatinum agents appear to be doxorubicin, ifosfamide, mitolactol, and vincristine. Multiple studies have documented improved partial response rates with platinum-based multiagent chemotherapy, but no regimen has been associated with an improved survival duration. To improve the poor prognosis of this patient group, identification of new agents with at least equivalent activity to cisplatin is mandatory. The development of new platinum-based regimens using currently available agents is unlikely to substantially improve patient survival, although better palliative therapy may result from this approach.

Total platinum dose versus platinum dose intensification in ovarian cancer treatment

Multiple in vitro and in vivo studies demonstrate the importance of platinum dose intensity in chemotherapy of advanced ovarian cancer. The relevant areas discussed in this report include (1) retrospective analysis of platinum dose intensity and outcome of ovarian cancer therapy, (2) in vitro human tumor cell line drug assay data, (3) fresh human ovarian tumor cloning data, (4) platinum pharmacokinetics with an emphasis on the relationship between the platinum concentration x time product and cytotoxicity, and (5) prospective clinical studies designed to test the importance of platinum dose intensity alone or platinum dose intensity and total dose. When attempting to design optimal platinum-based therapies for ovarian cancer, it is important to bear in mind the following considerations: (1) both platinum dose intensity and total dose should be increased; (2) to achieve exponential cytotoxicity (eg, up to 10-fold increases in tumor cell kill) by increasing the platinum dose, it is critical to select a platinum dose capable of overcoming inherent drug resistance; (3) carboplatin may be the platinum analogue of choice for dose intensification studies since, unlike cisplatin, it is rarely associated with cumulative nonhematologic toxicity (and as a result can be escalated up to five to six times the standard dose); and (4) the Calvert formula should be used for determining carboplatin dose to safely and accurately target desired drug exposure (as measured by the concentration x time product) and degree of hematologic toxicity.

Influence of hypoxia on the metabolism and excretion of misonidazole by the isolated perfused rat liver--a model system

The isolated perfused rat liver was evaluated as a model system for the characterization of misonidazole metabolism under hypoxic conditions. Misonidazole metabolism by livers perfused under aerobic conditions was also examined. The clearance of misonidazole was more than three times greater under anaerobic compared to aerobic conditions (4.94 +/- 1.56 vs 1.27 +/- 0.22 ml/min; means +/- S.D., N = 3). Misonidazole metabolites were detected only in the bile. Analysis of these metabolites by reverse-phase high performance liquid chromatography (HPLC) demonstrated that misonidazole metabolism was also qualitatively changed when anaerobic conditions were employed. Misonidazole beta-glucuronide was the major metabolite detected under aerobic conditions, but it was a minor metabolite in anaerobically perfused livers. The three major metabolites produced under anaerobic conditions were not characterized, but desmethyl misonidazole (RO-07-9963) and the 2-amino-imidazole derivative of misonidazole (1-[2-aminoimidazol-1-yl]-3-methoxy-2-propanol) were excluded as possible structures.