Immune reconstitution following alemtuzumab therapy is characterized by exhausted T cells, increased regulatory control of proinflammatory T cells and reduced B cell control

Alemtuzumab is a monoclonal antibody targeting CD52 on the surface of immune cells, approved for the treatment of active relapsing-remitting multiple sclerosis (RRMS). The purpose of this study was to analyze the repopulation of peripheral lymphocytes following alemtuzumab-induced lymphocyte depletion and investigate associations with disease activity and development of secondary autoimmunity. For this, blood samples were collected two years after initiation of alemtuzumab treatment and lymphocytes were subjected to a comprehensive flow cytometry analysis. Included in the study were 40 patients treated with alemtuzumab and 40 treatment-naïve patients with RRMS. Disease activity and development of secondary autoimmune disease was evaluated after three years of treatment. Our study confirms that alemtuzumab treatment profoundly alters the circulating lymphocyte phenotype and describes a reconstituted immune system characterized by T cell activation/exhaustion, an increased regulatory control of IL-17 producing effector T cells and CD20+ T cells, and a reduced control of B cells. There were no obvious associations between immune cell subsets and disease activity or development of secondary autoimmune disease during treatment with alemtuzumab. Our results indicate that the reconstituted immune response is skewed towards a more effective regulatory control of MS-associated proinflammatory T cell responses. Also, the enlarged pool of naïve B cells together with the apparent decrease in control of B cell activity may explain why alemtuzumab-treated patients retain the ability to mount a humoral immune response towards new antigens.

Intrathecal CD8+CD20+ T Cells in Primary Progressive Multiple Sclerosis

BACKGROUND AND OBJECTIVE

Despite accumulating evidence of intrathecal inflammation in patients with primary progressive multiple sclerosis (PPMS), immunomodulatory and suppressive treatment strategies have proven unsuccessful. With this study, we investigated the involvement of CD20⁺ T cells and the effect of dimethyl fumarate on CD20⁺ T cells in PPMS.

METHODS

The main outcomes in this observational, case-control study were flow cytometry assessments of blood and CSF CD20⁺ T cells and ELISA measurements of myelin basic protein and neurofilament light chain in untreated patients with PPMS and patients treated for 48 weeks with dimethyl fumarate or placebo. MRI measures included new and enlarging T2-weighted lesions over 48 weeks and lesion, normal-appearing white matter, cortical, and thalamic volume.

RESULTS

Assessing CD20⁺ T cells in patients with PPMS and controls showed an increased percentage of CD20⁺ T cells in the blood of untreated patients and a strong enrichment in the CSF. In addition, a higher frequency of CD8⁺CD20⁺ T cells in the CSF correlated with a higher concentration of myelin basic protein and T2-weighted lesion volume and with a lower normal-appearing white matter and thalamus volume. Furthermore, CD8⁺CD20⁺ T cells were associated with the development of new T2 lesions. After 48 weeks of treatment with dimethyl fumarate, total T cells in CSF were reduced; however, CD20⁺ T cells were unaffected.

DISCUSSION

This study shows an association between intrathecal CD8⁺CD20⁺ T cells, white matter injury, and thalamic atrophy in PPMS, suggesting a role of CD8⁺CD20⁺ T cells in the immunopathogenesis of PPMS. The results also suggest that limited efficacy of dimethyl fumarate in PPMS may, at least partly, be a consequence of failure to suppress CD8⁺CD20⁺ T cells in CSF.

Cannabis-Based Medicine for Neuropathic Pain and Spasticity-A Multicenter, Randomized, Double-Blinded, Placebo-Controlled Trial

Patients with multiple sclerosis (MS) and spinal cord injury (SCI) commonly sustain central neuropathic pain (NP) and spasticity. Despite a lack of consistent evidence, cannabis-based medicine (CBM) has been suggested as a supplement treatment. We aimed to investigate the effect of CBM on NP and spasticity in patients with MS or SCI. We performed a randomized, double-blinded, placebo-controlled trial in Denmark. Patients aged ≥18 years with NP (intensity >3, ≤9 on a numerical rating scale (NRS0-10) and/or spasticity (>3 on NRS0-10) were randomized to treatment consisting of either delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), a combination of THC&CBD in maximum doses of 22.5 mg, 45 mg and 22.5/45 mg per day, respectively, or placebo. A baseline registration was performed before randomization. Treatment duration was six weeks followed by a one-week phaseout. Primary endpoints were the intensity of patient-reported NP and/or spasticity. Between February 2019 and December 2021, 134 patients were randomized (MS n = 119, SCI n = 15), where 32 were assigned to THC, 31 to CBD, 31 to THC&CBD, and 40 to placebo. No significant difference was found for: mean pain intensity (THC 0.42 (-0.54-1.38), CBD 0.45 (-0.47-1.38) and THC&CBD 0.16 (-0.75-1.08)), mean spasticity intensity (THC 0.24 (-0.67-1.45), CBD 0.46 (-0.74-1.65), and THC&CBD 0.10 (-1.18-1.39), secondary outcomes (patient global impression of change and quality of life), or any tertiary outcomes. We aimed to include 448 patients in the trial; however, due to COVID-19 and recruitment challenges, fewer were included. Nevertheless, in this four-arm parallel trial, no effect was found between placebo and active treatment with THC or CBD alone or in combination on NP or spasticity in patients with either MS or SCI. The trial was registered with the EU Clinical Trials Register EudraCT (2018-002315-98).

Dimethyl fumarate treatment of primary progressive multiple sclerosis: results of an open-label extension study

INTRODUCTION

Dimethyl fumarate treatment is approved in Europe for patients with relapsing-remitting multiple sclerosis (MS) and in the US for relapsing forms of MS. We recently published the results of the first randomized placebo-controlled trial of 48 weeks of treatment with dimethyl fumarate or placebo in primary progressive MS (PPMS) (clinicaltrial.gov NCT02959658). The placebo-controlled phase of the trial did not meet its primary endpoint (reduction in cerebrospinal fluid concentrations of neurofilament light chain [NFL]).

AIM

To investigate the effects of dimethyl fumarate treatment in the open-label extension phase of the trial (week 48-96), where all patients were treated with DMF.

METHODS

Reported data are from screening, week 48, and week 96 visits. Patients were clinically evaluated with Expanded Disability Status Scale (EDSS), 9-Hole Peg Test (9HPT), Timed 25-Foot Walk (T25FW) test, Symbol Digit Modalities Test (SDMT), California Verbal Learning Test, and Brief Visuospatial Memory-Revised. Serum NFL concentrations were measured by single-molecule array analysis. MRI was performed on a 3 tesla MRI scanner and included: new/enlarging lesions, volume of lesions, cortical grey matter, putamen, thalamus, and normal-appearing white matter, and additional diffusion tensor imaging and magnetization transfer ratio measures.

RESULTS

Forty-two patients entered the open-label treatment phase, and 33 patients (61%) had complete data sets at week 96. The remaining 39% did not complete the trial and were not evaluated at week 96. We found no evidence of differences in clinical and MRI measures between patients initially treated with dimethyl fumarate and patients initially treated with placebo from baseline to week 48 and from week 48-96, where all patients were treated with dimethyl fumarate. Serum NFL concentrations remained stable in both groups over 96 weeks. Assessed with either EDSS, T25FW, or 9HPT at week 96, progression was observed for 14 patients (45%). Interestingly, another 15 patients (46%) had improvement in one or more of these domains. Applying a cut-off of 8 points, 2 (6%) patients worsened on SDMT, 25 (78%) did not change, and 5 (16%) improved.

CONCLUSIONS

Dimethyl fumarate treatment showed no effects on neither clinical nor MRI outcomes or changes in serum concentrations of NFL. An expected number of patients showed evidence of progression on standard clinical scales; however, this was matched by an equal number of patients improving. The reasons for the physical improvement in an unexpectedly high proportion of patients must be addressed in future studies.

Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis

BACKGROUND AND OBJECTIVES

It is unclear to what extent intrathecal inflammation contributes to the pathogenesis in primary progressive multiple sclerosis (PPMS). We conducted an exploratory study to investigate the degree of intrathecal inflammation and its association with biomarkers of disease activity and severity in patients with PPMS.

METHODS

We included patients with PPMS who participated in a randomized controlled trial conducted at the Danish Multiple Sclerosis Center, patients with relapsing-remitting multiple sclerosis (RRMS) and healthy controls. We analyzed concentrations of a panel of cytokines in CSF using electrochemiluminescence assays. We then explored the relationship between cytokines found in increased CSF concentrations in patients with PPMS (compared with healthy controls) with CSF concentrations of neurofilament light chain (NFL) and myelin basic protein (MBP), IgG-index, and magnetic resonance imaging (MRI) metrics (volume, magnetization transfer ratio and diffusion tensor imaging) from lesions, normal-appearing white matter, and cortical grey matter.

RESULTS

We included 59 patients with PPMS, 40 patients with RRMS, and 21 healthy controls. In patients with PPMS, CSF concentrations of CC chemokine ligand 3 (CCL-3), CXC chemokine ligand 8 (CXCL-8), CXCL-10, interleukin (IL)-10, IL-15, and vascular endothelial growth factor (VEGF)-A were increased compared with healthy controls and comparable with CSF concentrations in patients with RRMS. In addition, patients with PPMS had increased CSF concentrations of IL-12p40, IL-17A, tumor necrosis factor (TNF)-α, and lymphotoxin (LT)-α compared with healthy controls, but concentrations of these cytokines were even higher in patients with RRMS. For the remaining seven cytokines (CCL22, interferon-γ, IL-5, IL-7, IL-16, IL-22, IL-27), we found no difference between patients with PPMS and healthy controls. CSF concentrations of NFL and MBP correlated weakly with concentrations of IL-15, while the remaining proinflammatory cytokines were not associated with CSF concentrations of NFL or MBP. The IgG-index correlated with four cytokines (IL-10, IL-12p40, TNF-α, and LT-α). We did not observe any significant associations between MRI metrics and CSF biomarkers of inflammation.

DISCUSSION

In this exploratory study, we found few and weak associations between intrathecal inflammation and the extent of neuroaxonal damage and demyelination, and no associations between intrathecal inflammation and MRI metrics, in patients with PPMS. Our findings suggest that, for patients with PPMS, these measures of intrathecal inflammation are not associated with the extent of neuroaxonal injury, demyelination, and disease severity, and these processes may therefore have less relevance in PPMS than in relapsing forms of MS.

Increased Intrathecal Activity of Follicular Helper T Cells in Patients With Relapsing-Remitting Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Follicular helper T (Tfh) cells play a critical role in protective immunity helping B cells produce antibodies against foreign pathogens and are likely implicated in the pathogenesis of various autoimmune diseases. The purpose of this study was to investigate the role of Tfh cells in the pathogenesis of multiple sclerosis (MS).

METHODS

Using flow cytometry, we investigated phenotype, prevalence, and function of Tfh cells in blood and CSF from controls and patients with relapsing-remitting MS (RRMS) and primary progressive MS (PPMS). In addition, an in vitro blood-brain barrier coculture assay of primary human astrocytes and brain microvascular endothelial cells grown in a Boyden chamber was used to assess the migratory capacity of peripheral Tfh cells.

RESULTS

This study identified 2 phenotypically and functionally distinct Tfh cell populations: CD25^- Tfh cells (Tfh1-like) and CD25^int Tfh cells (Tfh17-like). Whereas minor differences in Tfh cell populations were found in blood between patients with MS and controls, we observed an increased frequency of CD25^- Tfh cells in CSF of patients with RRMS and PPMS and CD25^int Tfh cells in patients with RRMS, compared with controls. Increasing frequencies of CSF CD25^- Tfh cells and the CD25^- Tfh/Tfr ratio scaled with increasing IgG index in patients with RRMS. Despite an increased prevalence of intrathecal Tfh cells in patients with MS, no difference in the migratory capacity of circulating Tfh cells was observed between controls and patients with MS. Instead, CSF concentrations of CXCL13 scaled with total counts of Tfh and Tfr cell subsets in the CSF.

DISCUSSION

Our study indicates substantial changes in intrathecal Tfh dynamics, particularly in patients with RRMS, and suggests that the intrathecal inflammatory environment in patients with RRMS promotes recruitment of peripheral Tfh cells rather than the Tfh cells having an increased capacity to migrate to CNS.

Immunotherapy to prevent progression on active surveillance study (IPASS): A phase II, randomized, double-blind, controlled trial of PROSTVAC in prostate cancer patients who are candidates for active surveillance

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Background: Immunotherapy could potentially prevent disease progression for early-stage prostate cancer. In this randomized Phase 2 clinical trial, we evaluated the clinical effects of PROSTVAC, a vaccinia/fowlpox viral vector-based immunotherapy that contains PSA and three T-cell costimulatory molecules, in patients with localized prostate cancer. Methods:154 patients with clinically localized, low- or favorable intermediate-risk prostate cancer active surveillance were randomized (2:1) to receive 7 doses of subcutaneous PROSTVAC or placebo (empty fowlpox vector) over 140 days. Post-intervention prostate biopsy was performed 7-14 days after the last dose. Participants were followed for 6 months post-treatment. The primary outcome was change from baseline to post-vaccination in CD4 and CD8 T cell infiltration in biopsy tumor tissue. Secondary outcomes included changes in prostate biopsy Gleason grade (Grade Group) and serum PSA. Results: There were no differences in CD4 and CD8 densities (count of cells/mm2) in post-treatment biopsy tumor tissue between groups ( p = 0.63 and p = 0.75, respectively). Compared to placebo, patients who received PROSTVAC were less likely to demonstrate upgrading at follow-up biopsy, but this difference did not attain significance (22% vs. 40%, p= 0.08). There was no difference in the change of PSA from baseline to 6 months post-treatment between arms ( p= 0.30). Conclusions: In this first-of-kind trial of immunotherapy for localized prostate cancer, PROSTVAC was well tolerated but did not elicit significant prostate tissue T-cell responses compared to placebo. The favorable post-treatment biopsy grade findings in PROSTVAC patients merit further evaluation and longer-term clinical follow-up. Clinical trial information: NCT02326805.

Peripheral helper T cells in the pathogenesis of multiple sclerosis

BACKGROUND

Peripheral helper T cells (Tph) are likely implicated in the pathogenesis of various inflammatory diseases. Tph cells share functions with follicular helper T cells, including plasma cell differentiation and antibody production.

OBJECTIVE AND METHODS

To investigate a possible role of Tph cells in the pathogenesis of multiple sclerosis (MS), we used flow cytometry to analyze the function, phenotype, and central nervous system (CNS)-recruitment of Tph cells in the blood and cerebrospinal fluid (CSF) from controls and patients with relapsing-remitting (RR) and primary progressive (PP) MS.

RESULT

This study identified two functionally distinct Tph cell populations and a regulatory counterpart, Tpr cells. No differences in blood frequencies, cytokine production, or potential to interact with B cells were found between controls and patients with MS. Along with an equal CNS-migration potential, we found both Tph cell populations enriched in the CSF; and surprisingly, an increased frequency of intrathecal Tph cells in the control group compared to patients with MS.

CONCLUSION

Altogether, we did not find an increased frequency of CSF Tph cells in patients with RRMS or PPMS. Our findings indicate that rather than being involved in MS pathogenesis, Tph cells may be implicated in normal CNS immunosurveillance.

Smoking, cardiovascular risk factors and LRP2 gene variation: Associations with disease severity, cognitive function and brain structure in primary progressive multiple sclerosis

BACKGROUND

Smoking, cardiovascular risk factors, and genetic factors can have adverse effects in MS.

OBJECTIVE

To determine if smoking after disease onset, cardiovascular risk factors, and genetic variants influence primary progressive MS (PPMS).

METHOD

In this cross-sectional study, smoking habits, Framingham Risk Score (FRS), genetic variants, including the low-density lipoprotein receptor-related protein 2 (LRP2) SNP rs12988804 and MRI were collected in 60 PPMS trial participants. Disability and cognition were assessed with the Age-Related Multiple Sclerosis Severity (ARMSS) score, the Progressive-Onset MS Multiple Sclerosis Severity Score, and the Brief International Cognitive Assessment for MS.

RESULTS

Smoking after PPMS onset was significantly associated with higher ARMSS (95% CI 0.8-2.4, p = 0.00016) statistically significant after Bonferroni correction. Lower magnetization transfer ratio in lesions was also significantly associated with smoking after onset of PPMS after correction (95% CI -0.9--4.4, p = 0.0035). Pack-years in people who smoked after onset was likewise significantly associated with higher ARMSS score (b = 0.06 95% CI 0.02-0.09, p = 0.0021) as well as lower Symbol Digit Modalities Test scores (b = -0.40; 95% CI -0.66--0.13, p = 0.0037), both statistically significant after Bonferroni correction. The LRP2 risk allele was associated with decreased performance on the California Verbal Learning Test 2 after correction (CC vs. CT+TT 95% CI -14.2--3.4, p = 0.0018).

CONCLUSION

If validated, these findings suggest that intervention regarding smoking may be beneficial in PPMS. If confirmed, assessment of the LRP2 gene variant may aid in the understanding of underlying pathological mechanisms in PPMS.

Dimethyl Fumarate Treatment in Patients With Primary Progressive Multiple Sclerosis: A Randomized, Controlled Trial

Background and Objective

To study whether dimethyl fumarate is superior to placebo in decreasing CSF concentrations of neurofilament light chain (NFL) in patients with primary progressive MS (PPMS).

Methods

In the double-blind, placebo-controlled phase 2 study dimethyl FUMArate treatment in Progressive Multiple Sclerosis (FUMAPMS), patients with PPMS were randomly assigned to treatment with 240 mg dimethyl fumarate or placebo in a 1:1 ratio for 48 weeks. The primary endpoint was change in concentration of NFL in the CSF. Secondary endpoints included other CSF biomarkers and clinical and MRI measures. Efficacy was evaluated for the full data set by multiple imputations to account for missing data. Safety was assessed for the full data set.

Results

Fifty-four patients (mean age 54.9 years [SD 6.1], median Expanded Disability Status Scale 4.0 [nterquartile range 4.0–6.0], disease duration 14.1 [SD 9.4], and 21 [39%] female) were randomized to either placebo (n = 27) or dimethyl fumarate (n = 27) therapy. At screening CSF concentrations, adjusted for age and sex, of NFL, myelin basic protein (MBP), soluble CD27, chitinase 3-like 1, and B-cell maturation antigen were higher than in a group of symptomatic controls. Twenty-six patients (96%) in the dimethyl fumarate group and 24 patients (89%) in the placebo group completed the randomized phase. Mean change in CSF concentrations of NFL did not differ between groups (mean difference 99 ng/L; 95% CI −292 to 491 ng/L). MBP in CSF decreased in the treatment group (−182 ng/L, 95% CI −323 to −41 ng/L compared with placebo). The difference observed in the multiple imputation data set was not significant in a per protocol analysis. This was nominally significant in the multiple imputation data set but not in the per protocol analysis This was not found in the per protocol analysis Other secondary and tertiary outcomes were not affected. Various infections, lymphopenia, flushing, and gastrointestinal side effects were more frequent in the dimethyl fumarate group. Serious adverse events were similar between groups.

Discussion

Dimethyl fumarate treatment for 48 weeks had no effect on any of the investigated efficacy measures in patients with PPMS. We did not observe adverse events not anticipated for dimethyl fumarate treatment.

Trial Registration Information

Clinicaltrials.gov identifier NCT02959658.

Classification of Evidence

This study provides Class I evidence that for patients with PPMS, dimethyl fumarate treatment has no effect on CSF NFL levels compared with placebo treatment.

MAIT cell subtypes in multiple sclerosis

In patients with multiple sclerosis (MS) and healthy controls (HC) we studied circulating MAIT cells and MAIT cell subtypes expressing CXCR3 and CCR6 by flow cytometry. Absolute numbers of MAIT cells and specifically Tc17-like MAIT cells were lower in patients with primary progressive MS (PPMS) than in controls. Low numbers of Tc17-like MAIT cells were associated with smoking and high concentrations of myelin basic protein in the cerebrospinal fluid. Treatment with alemtuzumab and dimethyl fumarate decreased MAIT cell frequencies. Altogether, we have identified specific MAIT cell subtypes related to PPMS, smoking and demyelination, and MAIT cell effects of MS therapies.

Dimethyl fumarate therapy reduces memory T cells and the CNS migration potential in patients with multiple sclerosis

BACKGROUND

Dimethyl fumarate (DMF) is a disease-modifying therapy for patients with relapsing-remitting multiple sclerosis (RRMS). T cells are major contributors to the pathogenesis of RRMS, where they regulate the pathogenic immune response and participate in CNS lesion development.

OBJECTIVES

In this study we evaluate the therapeutic effects of DMF on T cell subpopulations, their CNS migration potential and effector functions.

METHODS

Blood and CSF from untreated and DMF-treated patients with RRMS and healthy donors were analyzed by flow cytometry.

RESULTS

DMF reduced the prevalence of circulating proinflammatory CD4+ and CD8+ memory T cells, whereas regulatory T cells were unaffected. Furthermore, DMF reduced the frequency of CD4+ T cells expressing CNS-homing markers. In coherence, we found a reduced recruitment of CD4+ but not CD8+ T cells to CSF. We also found that monomethyl fumarate dampened T cell proliferation and reduced the frequency of TNF-α, IL-17 and IFN-γ producing T cells.

CONCLUSION

DMF influences the balance between proinflammatory and regulatory T cells, presumably favoring a less proinflammatory environment. DMF also reduces the CNS migratory potential of CD4+ T cells whereas CD8+ T cells are less affected. Altogether, our study suggests an anti-inflammatory effect of DMF mainly on the CD4+ T cell compartment.

Dimethyl fumarate therapy suppresses B cell responses and follicular helper T cells in relapsing-remitting multiple sclerosis

Background:

Dimethyl fumarate (DMF) is a disease-modifying therapy used for patients with relapsing-remitting multiple sclerosis (RRMS). B cells are important contributors to the pathogenesis of RRMS, where they regulate the inflammatory immune responses and participate in development of lesions in the central nervous system (CNS). The impact of DMF on B cell subpopulations remains incompletely understood.

Objectives:

In this study, we evaluated the effects of DMF on B cell subpopulations and their effector functions.

Methods:

Blood from 21 DMF-treated and 18 untreated patients with RRMS was analyzed by flow cytometry.

Results:

We found that DMF reduces the frequency of circulating antigen–experienced B cells, a reduction likely related to a reduced frequency of follicular helper T (TFH) cells and an increased frequency of follicular regulatory T (TFR) cells. Studying the impact of monomethyl fumarate (MMF), the primary metabolite of DMF, on B cell effector function in vitro showed that MMF increased the frequency of transforming growth factor (TGF)-β-producing B cells and decreased the frequency of B cells secreting lymphotoxin (LT)-α, tumor necrosis factor (TNF)-α, interleukin (IL)-6, and to a lesser extent IL-10.

Conclusion:

In summary, these data suggest an anti-inflammatory role of DMF and its metabolite MMF on the B cell compartment.

Progressive multiple sclerosis, cognitive function, and quality of life

Background

Patients with progressive multiple sclerosis (MS) often have cognitive impairment in addition to physical impairment. The burden of cognitive and physical impairment progresses over time, and may be major determinants of quality of life. The aim of this study was to assess to which degree quality of life correlates with physical and cognitive function in progressive MS.

Methods

This is a retrospective study of 52 patients with primary progressive (N = 18) and secondary progressive MS (N = 34). Physical disability was assessed using the Expanded Disability Status Scale, Timed 25 Foot Walk (T25FW) test and 9-Hole Peg Test (9HPT). Cognitive function was assessed using Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test, and Trail Making Test B (TRAIL-B). In addition, quality of life was assessed by the Short Form 36 (SF-36) questionnaire.

Results

Only measures of cognitive function correlated with the overall SF-36 quality of life score and the Mental Component Summary score from the SF-36. The only physical measure that correlated with a measure of quality of life was T25FW test, which correlated with the Physical Component Summary from the SF-36. We found no other significant correlations between the measures of cognitive function and the overall physical measures but interestingly, we found a possible relationship between the 9HPT score for the nondominant hand and the SDMT and TRAIL-B.

Conclusion

Our findings support inclusion of measures of cognitive function in the assessment of patients with progressive MS as these correlated closer with quality of life than measures of physical impairment.

Direct nose-brain transport of benzoylecgonine following intranasal administration in rats

In our previous research, cocaine applied intranasally in rats diffused or was transported directly from the nasal cavity to the brain. However, the direct nose-brain cocaine transport only contributes to an initial increase in the relative cocaine brain exposure. In this study, we have determined the nose-brain transport of a polar metabolite of cocaine, benzoylecgonine, to help understand factors affecting drug transport via this novel pathway. The nasal cavity of male Sprague-Dawley rats was isolated to prevent drainage of nasally applied dosing solution to non-nasal regions. Benzoylecgonine was then administered, either by intranasal administration or by intravenous (iv) injection. At different times postdose, blood and tissues from different regions of the brain were collected from groups of rats (n = 4 for each collection time) and benzoylecgonine concentrations in these samples were analyzed by high-performance liquid chromatography. Benzoylecgonine concentrations in plasma were at maximal levels immediately after iv dosing and declined as a function of time. Following intranasal administration, benzoylecgonine concentrations in plasma reached maximal levels between 15 and 30 min after dosing and declined as a function of time. To allow comparison of brain benzoylecgonine content after iv and intranasal administration, brain benzoylecgonine contents were normalized by plasma benzoylecgonine concentrations. The ratios of the area under the benzoylecgonine concentration-time curve (AUC) between the olfactory bulb and plasma following intranasal administration were 10-100 times higher than those obtained after iv dosing. The olfactory tract-to-plasma benzoylecgonine AUC ratios after intranasal administration were significantly higher than those after iv dosing up to 120 min following dosing. The brain tissue-to-plasma AUC ratios in cerebellum, brain stem, and cerebral cortex after intranasal administration were significantly higher than the corresponding ratios after iv administration up to 30 min following dosing. We conclude than nasally administered benzoylecgonine was transported directly from the nasal cavity to the brain and that the significant increase in brain levels was sustained for a prolonged period of time. Factors contributing to the observed differences in the nose-brain transport of cocaine and benzoylecgonine are discussed.

Phase I pharmacokinetic study of tea polyphenols following single-dose administration of epigallocatechin gallate and polyphenon E

Green tea has been shown to exhibit cancer-preventive activities in preclinical studies. Its principal active components include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC), and epicatechin gallate, of which EGCG is the most abundant and possesses the most potent antioxidative activity. We performed a Phase I pharmacokinetic study to determine the systemic availability of green tea catechins after single oral dose administration of EGCG and Polyphenon E (decaffeinated green tea catechin mixture). Twenty healthy subjects (five subjects/dose level) were randomly assigned to one of the dose levels (200, 400, 600, and 800 mg based on EGCG content). All subjects were randomly crossed-over to receive the two catechin formulations at the same dose level. Blood and urine samples were collected for up to 24 h after oral administration of the study medication. Tea catechin concentrations in plasma and urine samples were determined using high-performance liquid chromatography with the coulometric electrode array detection system. After EGCG versus Polyphenon E administration, the mean area under the plasma concentration-time curves (AUC) of unchanged EGCG were 22.5 versus 21.9, 35.4 versus 52.2, 101.9 versus 79.7, and 167.1 versus 161.4 min x microg/ml at the 200-, 400-, 600-, and 800-mg dose levels, respectively. EGC and EC were not detected in plasma after EGCG administration and were present at low/undetectable levels after Polyphenon E administration. High concentrations of EGC and EC glucuronide/sulfate conjugates were found in plasma and urine samples after Polyphenon E administration. There were no significant differences in the pharmacokinetic characteristics of EGCG between the two study medications. The AUC and maximum plasma concentration (Cmax) of EGCG after the 800-mg dose of EGCG were found to be significantly higher than those after the 200- and 400-mg dose. The AUC and Cmax of EGCG after the 800-mg dose of Polyphenon E were significantly higher than those after the three lower doses. We conclude that the two catechin formulations resulted in similar plasma EGCG levels. EGC and EC were present in the body after the Polyphenon E administration; however, they were present predominantly in conjugated forms. The systemic availability of EGCG increased at higher doses, possibly due to saturable presystemic elimination of orally administered green tea polyphenols.

Effect of subacute ibuprofen dosing on rectal mucosal prostaglandin E2 levels in healthy subjects with a history of resected polyps

Nonsteroidal antiinflammatory drugs are among the most promising chemopreventive agents for colorectal cancer. Although the mechanism by which nonsteroidal antiinflammatory drugs exert such effects remains to be further characterized, their best known pharmacological effect is inhibition of prostaglandin synthetase, which leads to decreases in tissue prostaglandin levels. We conducted a randomized, double-blind, controlled study to examine the effect of daily ibuprofen treatment on the rectal mucosal prostaglandin E2 (PGE2) levels in healthy subjects with a history of resected polyps. Study participants (n = 27) completed a 2-week run-in period and were then randomized to take a single, daily dose of ibuprofen (300 or 600 mg) or of a placebo for 4 weeks. Rectal biopsy specimens were taken before and after the run-in period and at 2 and 4 weeks after the ibuprofen/placebo treatment. Notably large between- and within-subject variability in the rectal mucosal PGE2 content was seen. The changes in PGE2 levels after ibuprofen/placebo treatment correlated with the baseline PGE2 content. After adjustment of the baseline values, 2 weeks of 300 mg/day of ibuprofen treatment resulted in significantly more suppression of PGE2 levels than that observed after the placebo treatment (55% versus 22% suppression from baseline; P = 0.033). Although other ibuprofen treatment schedules and doses appeared to result in suppression in the PGE2 levels, the suppression was not statistically significant because of the large variability in this measurement. Because lower doses are associated with fewer adverse effects, a dose of 300 mg of ibuprofen/day should be considered for future Phase II chemoprevention studies. Stratifying study participants, based on their baseline PGE2 levels and inclusion of a larger number of study subjects, are recommended for future trials where the rectal mucosal PGE2 level is to be used as a surrogate end point biomarker.

Tissue disposition of zidovudine and its phosphorylated metabolites in zidovudine-treated healthy and retrovirus infected mice

PURPOSE

The purpose of this study was to examine the effect of chronic AZT treatment on the in vivo tissue disposition of the phosphorylated AZT metabolites in healthy and retrovirus infected mice.

METHODS

Female C57BL/6 mice at 12 weeks after inoculation with LP-BM5 murine leukemia virus as well as age-matched control animals were dosed subcutaneously with 25 mg/kg of AZT twice a day for 8 weeks. At the end of the 8-wk treatment (20 weeks post inoculation), each animal received a final AZT dosing solution containing [3H]-AZT with a specific activity of 87 mCi/mmol. The levels of AZT and its phosphorylated metabolites were determined in tissues collected at different times after the last AZT administration using an analytical method coupling an ion-pair HPLC separation procedure with radioactivity detection following the separation.

RESULTS

The tissue-to-plasma (T/P) AZT ratios in control mice could be ranked in the following order: kidneys > muscle approximately equal to spleen approximately equal to liver approximately equal to heart > lung approximately equal to thymus > lymph nodes >> brain. The distributions of AZT into lymph nodes, lung, and thymus tissues in infected mice increased significantly in comparison with those of control animals. Tissue AZT 5'-monophosphate (AZT-MP) profiles tended to parallel the AZT profiles in most tissues examined. Delays in the appearance of AZT 5'-diphosphate (AZT-DP) and AZT-TP were observed in all tissues tested. The conversion of AZT to AZT metabolites was found to be highest in the spleen and bone marrow samples from both control and infected animals. AZT-TP content was not detectable in any of the brain samples analyzed. The lymph nodes of the control animals showed poor ability to phosphorylate AZT to its active triphosphate moiety. This ability was significantly enhanced in infected animals.

CONCLUSIONS

Comparing these findings with those of our previous study performed following a single dose administration of AZT, the chronic AZT regimen had minimal effect on the in vivo tissue disposition of the phosphorylated AZT metabolites. The therapeutic implications of inadequate maintenance of the level of active AZT metabolite in the lymph nodes and the brain following chronic AZT treatment need to be further explored.

The effect of chronic retrovirus infection and immune dysfunction on the P-450-mediated activation of acetaminophen in mouse liver microsomes

Acute viral infection has long been recognized to down-regulate cytochrome P-450 enzymes and subsequently to result in changes in the pharmacological and toxicological responses to xenobiotics. In our previous research, chronic retrovirus infection induced by inoculating a susceptible strain of mice with LP-BM5 murine leukaemia virus (MuLV) was found to suppress acetaminophen (APAP) induced liver injury. In the present study, we aimed to examine the influence of chronic retrovirus infection and its associated immune dysfunction on the activities of a number of cytochrome P-450 isozymes and the P-450-mediated activation of APAP in mouse liver microsomes. Liver microsomes prepared from female C57BL/6 mice at 8 and 16 weeks after LP-BM5 MuLV inoculation as well as from age-matched controls were used in the study. The catalytic activities of the cytochrome P-450 isozymes 1A family and 2E1, catalysts for the activation of APAP, were measured in different microsomal preparations using O-dealkylation of alkoxyresorufin homologues and oxidation of p-nitrophenol, respectively, as the metabolic markers. The formation of the reactive APAP metabolite trapped as glutathione conjugate in the microsomal preparations was also determined. We demonstrated that there were variable changes in total hepatic P-450 levels and in the activities of a number of P-450 isozymes in animals with chronic retrovirus infection and immune dysfunction. Such changes seemed to be dependent on the stage of the disease and to have resulted in increases or minimal changes in the rate of APAP activation in hepatic microsomes collected from this animal model. This suggests that the P-450-mediated activation of APAP was not down-regulated in animals with chronic retrovirus infection. Enhanced elimination of APAP by detoxification metabolic pathways is more likely to be responsible for the increased resistance to APAP-induced hepatotoxicity observed in our previous research in animals with chronic retrovirus infection.

A physiologically based pharmacokinetic model of zidovudine (AZT) in the mouse: model development and scale-up to humans

After having been used in treating HIV infection for a decade, zidovudine (AZT) continues to be an essential component of antiretroviral regimens. Because antiviral responses and toxicity of AZT seem to be related to cells in specific target tissues, being able to understand and predict the distribution of AZT into different pharmacologically and toxicologically relevant tissues is therefore critically important to improving the efficacy and minimizing the toxicity of AZT therapy. This study was designed to develop a physiologically based pharmacokinetic model to help describe and predict the time course of AZT levels in different tissues. The model was developed in the mouse and then scaled up to predict human situations.

Clearance of 125I-labeled interleukin-6 from brain into blood following intracerebroventricular injection in rats

To test the hypothesis that interleukin-6 (IL-6) induced within the brain can be released into peripheral blood, 125I-labeled IL-6 was injected into the lateral cerebral ventricle of rats, and its concentration in peripheral blood followed serially. Acid-precipitable tracer appeared within 5 min of injection and entered the blood following first-order kinetics (fractional rate, 0.0116 +/- 0.0022/min). Comparison of areas under the curve of intracerebroventricular (icv) vs. iv injection showed that 37.1-46.5% of tracer injected into the lateral cerebral ventricle appeared in the blood over a 4-h period. icv IL-6 exits at least in part via venous drainage (superior sagittal sinus/aortic concentration gradient was 1.47 +/- 0.23 and 3.05 +/- 0.87 in two separate groups). Prior icv injection of human IL-1beta (100 ng) did not alter rate of degradation or of exit ofradioiodine-labeled IL-6 from the brain. These studies indicate that a relatively high proportion of IL-6 that arises in the brain enters the peripheral circulation. Direct secretion of IL-6 from brain to blood may be a mechanism by which the brain modifies peripheral metabolic, endocrine, and immune activity.

Application of neural networks to population pharmacokinetic data analysis

This research examined the applicability of using a neural network approach to analyze population pharmacokinetic data. Such data were collected retrospectively from pediatric patients who had received tobramycin for the treatment of bacterial infection. The information collected included patient-related demographic variables (age, weight, gender, and other underlying illness), the individual's dosing regimens (dose and dosing interval), time of blood drawn, and the resulting tobramycin concentration. Neural networks were trained with this information to capture the relationships between the plasma tobramycin levels and the following factors: patient-related demographic factors, dosing regimens, and time of blood drawn. The data were also analyzed using a standard population pharmacokinetic modeling program, NON-MEM. The observed vs predicted concentration relationships obtained from the neural network approach were similar to those from NONMEM. The residuals of the predictions from neural network analyses showed a positive correlation with that from NONMEM. Average absolute errors were 33.9 and 37.3% for neural networks and 39.9% for NONMEM. Average prediction errors were found to be 2.59 and -5.01% for neural networks and 17.7% for NONMEM. We concluded that neural networks were capable of capturing the relationships between plasma drug levels and patient-related prognostic factors from routinely collected sparse within-patient pharmacokinetic data. Neural networks can therefore be considered to have potential to become a useful analytical tool for population pharmacokinetic data analysis.

In vivo tissue disposition of 3'-azido-3'-deoxythymidine and its anabolites in control and retrovirus-infected mice

At present, 3'-azido-3'-deoxythymidine (AZT; zidovudine) remains the drug of choice for initiating AIDS therapy. This drug in itself is inactive; it needs to be converted intracellularly by a series of cellular kinases to AZT 5'-triphosphate (AZT-TP) to exert antiviral activity. The purpose of this study was to examine the in vivo disposition of the phosphorylated AZT anabolites in different target tissues and to investigate the effects of chronic retrovirus infection on the tissue disposition of AZT anabolites. Female C57BL/6 mice at 20 weeks after inoculation with LP-BM5 murine leukemia virus, as well as age-matched control animals, were dosed subcutaneously with 25 mg/kg of AZT. The dosing solution contained [3H]AZT with a specific activity of 87 mCi/mmol. The levels of AZT and its phosphorylated anabolites were determined in tissues collected at different times after AZT administration using an analytical method coupling an ion-pair HPLC separation procedure with radioactivity detection after the separation. The tissue-to-plasma AZT ratios in control mice could be ranked in the following order: kidneys > muscle approximately equal to spleen approximately equal to liver approximately equal to heart approximately equal to lung > thymus > lymph nodes > brain. Similar rank order was observed in infected animals, with the exception that significantly higher AZT levels were found in the lymph nodes, where the tissue-to-plasma AZT ratios in lymph nodes were higher than those in thymus tissues. Tissue AZT 5'-monophosphate profiles tended to parallel the AZT profiles in most tissues examined. Delays in the appearance of AZT 5'-diphosphate and AZT-TP were observed in all tissues tested. AZT-TP content was not detectable in any of the brain samples analyzed. The conversion of AZT to AZT anabolites was found to be highest in the spleen and bone marrow samples from both control and infected animals. Lymph nodes of the control animals showed poor ability to phosphorylate AZT to its active triphosphate moiety. This ability was significantly enhanced in infected animals. We concluded that the in vivo disposition of AZT anabolites after a single dose administration of AZT is tissue-specific in mice and that experimentally induced chronic retrovirus infection resulted in the most significant changes in the distribution of AZT into the lymph nodes and in the phosphorylation of AZT in this important target tissue. Further studies are needed to relate the tissue-specific disposition of AZT anabolites to the therapeutic problems encountered with AZT treatment.

Comparative pharmacokinetics and interspecies scaling of amphotericin B in several mammalian species

This study employed several interspecies scaling methods, to evaluate the applicability of extrapolating to man, pharmacokinetic information obtained from animals for amphotericin B, an anti-fungal drug. Pharmacokinetic parameters from four animal species (mouse, rat, monkey and dog) and man were obtained from the literature or from analysis of data reported in the literature. The allometric relationships (obtained from four animal species) as a function of species body weight (W; kg) for systemic clearance per maximum life span potential (CLS/MLP), steady-state volume of distribution (VSS), apparent volume of distribution (V beta) and volume of the central compartment (VC) were: 5691W1.096; 2.46W0.839; 3.08W0.948 and 1.07W0.965, respectively. The allometric relationships for half-life (h) and mean residence time (h) did not scale well with body weight. The prediction of pharmacokinetic parameters in man from the allometric equations do not always agree with those reported in the literature which are based upon a limited number of studies with few human subjects. The plasma concentration-time profiles from these animals were adjusted by normalizing the concentration with dose/W0.948, and re-plotted on different pharmacokinetic time scales. The syndesichrons plot produced an almost superimposable profile of adjusted concentrations as a function of adjusted time among the four species.

Site-specific pharmacokinetics and pharmacodynamics of intramuscular meperidine in elderly postoperative patients

OBJECTIVE

To examine and compare the pharmacokinetics and pharmacodynamics of meperidine when administered intramuscularly at gluteal and deltoid sites in elderly postoperative patients.

DESIGN

Prospective, randomized investigation.

SETTING

Tertiary care university teaching hospital.

PATIENTS

Fourteen patients 60 years of age or older who were undergoing general surgery.

INTERVENTION

A single dose of meperidine 0.75 mg/kg given intramuscularly at either a deltoid or gluteal site.

MAIN OUTCOME MEASURES

Pharmacokinetic (based on concentration-time curves) and pharmacodynamic (i.e., pain scales, need for additional pain medication) comparisons were made, based on site of meperidine injection.

RESULTS

No statistically significant differences were found in the maximum plasma concentration, volume of distribution, or clearance of meperidine by site of injection. Substantial interpatient variability in pharmacokinetic parameters was noted for both sites (range of maximum concentrations: 191-500 ng/mL gluteal, 166-374 ng/mL deltoid). Although pain scores were similar for the two groups, four of the patients in the group given gluteal injection required additional breakthrough pain management within 4 hours of meperidine injection compared with one patient in the group given deltoid injection.

CONCLUSIONS

There is no obvious relationship between meperidine pharmacokinetic and pharmacodynamic parameters, regardless of intramuscular injection site. Breakthrough pain is common when patients are given intramuscular injections postoperatively, particularly when the gluteal route is used. When meperidine is used for analgesia in elderly postoperative patients, consideration should be given to more rapid and predictable routes (e.g., intravenous injection) of meperidine administration.

Increased resistance to acetaminophen-induced hepatotoxicity in retrovirus-infected mice

In this research we examined the influence of chronic retrovirus infection on the hepatic metabolism of a model substrate, acetaminophen (APAP), and its induced liver injury in mice inoculated with LP-BM5 murine leukemia viruses. Female C57BL/6 mice at 15-17 wks after LP-BM5 retrovirus inoculation and age-matched control animals were used in the studies. APAP treatment (300 mg kg-1, p.o.) resulted in moderate to severe centrilobular necrosis in control animals, with the necrotic area accounting for 40-60% of the total area. In contrast, the APAP-treated (300 mg kg-1, p.o.) infected animals exhibited mild zonal necrosis with the necrotic area accounting for 1-6% of the total area. In the same study, a statistically significant higher percentage of APAP glucuronide and a lower percentage of unchanged APAP were recovered from the urine of the LP-BM5-inoculated animals than from that of controls. No statistically significant differences between infected and uninfected animals in the urinary recovery of APAP sulfate, APAP cysteine, or APAP mercapturate were observed. The formation of APAP metabolites and APAP-associated biochemical changes were also determined from liver slice preparation to avoid in vivo complicating factors. Consistently more significant depletion of the intracellular glutathione levels and K+ content were observed in slices from the uninfected animals at high concentrations of APAP (1 and 2 mM) than in slices from the retrovirus-infected animals. The differences in APAP-associated biochemical changes were accompanied by a 1.4-1.5-fold increase in the formation of APAP glucuronide, sulfate, and glutathione metabolites in slices prepared from animals inoculated with LP-BM5. We concluded that, based on histological examination and hepatic biochemical measurements, the retrovirus-infected animals were more resistant to APAP-induced liver injury. This could be due, in part, to alterations in the detoxification and activation metabolic pathways of APAP.

Vitamin E deficiency and immune dysfunction in retrovirus-infected C57BL/6 mice are prevented by T-cell receptor peptide treatment

Female C57BL/6 mice were infected with LP-BM5 retrovirus, causing murine acquired immunodeficiency syndrome (AIDS), which is functionally similar to human AIDS. Retrovirus infection inhibited release of T-helper 1 cytokines, stimulated secretion of T-helper 2 cytokines and induced hepatic and cardiac vitamin E deficiency with increased lipid peroxides. We hypothesized that the immune dysfunction caused increased oxidation and loss of vitamin E. Because T-cell receptor (TCR) peptide treatment blocked the excessive stimulation of a T-cell subset by retroviral superantigens, we tested whether maintenance of normal immune function during infection prevented excessive oxidative damage. The TCR peptide treatments with doses > 100 microgram/mouse and administered 2-4 wk postinfection significantly inhibited the retrovirus-induced immune dysfunction, concomitantly reduced tissue oxidative damage and thereby largely maintained vitamin E concentration in the liver and heart. Reducing the dose of peptide or delaying administration until early murine AIDS had developed resulted in severe immune dysfunction that caused elevated tissue lipid peroxidation and loss of vitamin E. The TCR peptide treatment partially maintained production of interleukin-2 (IL-2) and prevented retrovirus-induced elevated production of IL-6 by splenocytes in vitro. In conclusion, TCR peptide treatment during murine retrovirus infection ameliorated immune dysfunction and thus prevented increases in tissue lipid peroxidation and vitamin E loss. T-cell immune dysfunction and its prevention by TCR peptide treatment is important in the therapy of vitamin E deficiency induced by retrovirus infection.

Pharmacokinetics of amphotericin B in rats as a function of dose following constant-rate intravenous infusion

Amphotericin B (AmB) is widely used for the treatment of systemic mycoses. The current therapeutic regimens for this drug are complex and somewhat empirical, in part because of very limited information about the disposition kinetics of this agent. In this study, we examined the disposition kinetics of AmB as a function of dose and estimated clearance values using a steady state study design in an animal model. Groups of male Sprague-Dawley rats were given different two-step infusion regimens to achieve three different steady state concentrations (i.e., three different total infused doses). We observed no significant differences in systemic clearance among the three AmB doses studied. Similarly, only small differences were seen in volumes of distribution as a function of dose. However, renal clearance decreased significantly as the total infused dose was increased (0.76 +/- 0.33, 0.86 +/- 0.24, and 0.37 +/- 0.04 mL min-1 kg-1 for the low-medium and high-dose groups, respectively; p < 0.05). Signs of renal impairment were observed in the high-dose group, as documented by decreased creatinine clearance. Dose-dependent renal clearance may have been due either to nephrotoxicity associated with the high dose of AmB and/or to saturation of an active secretion process. Furthermore, clearance values estimated from steady state conditions were similar to those from time-averaged values (based on the estimation of area under the plasma concentration-time profile). This suggests that clearance calculations from time-averaged concentrations provide reasonable estimates, since steady state plasma concentrations could be reliably determined. However, the possibility that a true tissue steady state condition was not achieved with our study design cannot be ruled out. Further investigation is necessary to identify the renal excretion mechanisms of AmB and to reach steady state tissue concentration to confirm the estimation of systemic clearance.

Quantitative determination of cocaine, cocaethylene (ethylcocaine), and metabolites in plasma and urine by high-performance liquid chromatography

A sensitive HPLC assay was developed to quantitate the relatively nonpolar compounds cocaine, cocaethylene (ethylcocaine), norcocaine, and norcocaethylene, as well as the relatively polar metabolites benzoylecgonine and benzoylnorecgonine, in rat plasma and urine. The assay in plasma employed two successive liquid-liquid extractions and separate injections onto two different columns (C8 and C18) to separate and quantitate the relatively polar and nonpolar compounds. In urine, the procedure employed a liquid-liquid extraction followed by solid-phase extraction (C18 light-load cartridges) and two separate injections as for plasma. The UV absorbance of the effluent was monitored at 235 nm. Linear standard curves were obtained over the concentration ranges of 25 to 1000 ng/mL and 5 to 250 ng/mL in plasma and urine, respectively. The inter- and intraday coefficients of variation for the assay of all compounds in plasma and urine were < 18% at low concentrations (12.5-100 ng/mL) and < 12% at high concentrations (125-250 ng/mL). There was no degradation of these compounds during the extraction procedure or during 2 months of storage at -20 degrees C. The quantitation limits for the assay of the relatively nonpolar and polar compounds in plasma were 25 (2.5 ng in 0.1 mL) and 50 ng/mL (5 ng in 0.1 mL), respectively. For the assay in urine, the quantitation limits were 5 (2.5 ng in 0.5 mL) and 12.5 ng/mL (6.25 ng in 0.5 mL) for the assay of the relatively nonpolar and polar compounds, respectively. The methods have been applied to quantitate those compounds in rat plasma.

Separation and quantitation of the enantiomers of methamphetamine and its metabolites in urine by HPLC: precolumn derivatization and fluorescence detection

To study the disposition kinetics of methamphetamine (MAP), we have developed a sensitive high-performance liquid chromatographic (HPLC) assay to quantitate the enantiomers of MAP and its major metabolites, amphetamine (AP), p-hydroxymethamphetamine (p-OH-MAP), and p-hydroxyamphetamine (p-OH-AP), the latter two of which are hydroxylated metabolites, in rat urine. To determine conjugated hydroxylated metabolites, urine samples were treated with beta-glucuronidase. Both hydrolyzed and nonhydrolyzed p-OH-MAP and p-OH-AP were extracted into ethyl acetate and back extracted with 0.05M HCl. To determine MAP and AP, urine samples were extracted with benzene, followed by back extraction into 0.05M HCl. The acid layer was collected, and to it was added (-)-1-(9-fluorenyl)ethyl chloroformate (FLEC) for the derivatization of MAP and its metabolites. Derivatization was allowed to proceed for 24 h at room temperature. The derivatized products were separated on a C18 column with a mobile phase consisting of acetate buffer (pH 3.6)-acetonitrile-tetrahydrofuran. Quantitation was achieved using a fluorescence detector at an excitation wavelength of 265 nm and an emission wavelength of 330 nm. Linear standard curves were obtained over the concentration range of 5-100 ng/mL. The interday and intraday coefficients of variation for the assay for all eight enantiomers at 10 and 75 ng/mL were less than 13%. The detection limit was 5 ng/mL or 0.5 ng on-column.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitive enantiomer-specific high-performance liquid chromatographic analysis of methamphetamine and amphetamine from serum using precolumn fluorescent derivatization

In order to study the stereoselective disposition of methamphetamine (MAP), a widely abused drug, we have developed a sensitive HPLC assay to separate and quantitate the enantiomers of MAP and amphetamine (AP) in rat serum. Serum samples to which was added aniline sulfate (internal standard) were alkalized with 0.02 M carbonate buffer (pH 10.6) and extracted with ethyl acetate. Following back extraction with hydrochloric acid, neutralization, and reconstitution, the sample was derivatized with (-)-fluorenylethyl chloroformate overnight at room temperature. The derivatized products were separated following injection onto a reversed-phase C18 column. The mobile phase consisted of 0.02 M acetate buffer-acetonitrile-tetrahydrofuran (46:39:15, v/v). The fluorescent intensity of the effluent was monitored at excitation and emission wavelengths of 265 and 330 nm, respectively. The derivatized aniline, R-, S-AP, R- and S-MAP had retention times of 21.0, 22.6, 23.6, 27.7 and 29.0 min, respectively. Linear standard curves were obtained over the concentration range of 5-250 ng/ml. The inter-day and intra-day coefficients of variation for the assay of all four compounds at 12.5, 50.0 and 250 ng/ml were in the range of 2.1-18.6%. The method was applied to quantitate the concentrations of MAP and AP enantiomers in rat serum following a short term intravenous infusion of racemic MAP (15 mg/kg). There were no differences in serum concentrations of MAP enantiomers but the concentrations of S-AP were consistently greater than those of R-AP. These data suggest a stereoselective disposition for the formation and/or elimination of amphetamine.

Disposition kinetics of d- and l-amphetamine following intravenous administration of racemic amphetamine to rats

Amphetamine (AP), a chiral drug, displays stereoselective differences in biological action. The effect of stereochemistry on the disposition kinetics of the enantiomers has not been thoroughly studied. We examined the disposition kinetics of AP in rats using a sensitive precolumn derivatization HPLC method that can separate the enantiomers of AP and its metabolites. Male Sprague-Dawley rats were given a short intravenous infusion of racemic AP (15 mg/kg). The systemic and renal clearances, steady-state volume of distribution, and terminal half-life for l-AP were (mean +/- SD), respectively: 65.6 +/- 9.25 ml/min.kg; 15.4 +/- 2.55 ml/min.kg; 4.33 +/- 0.71 liters/kg; and 0.96 +/- 0.13 hr. The corresponding values for d-AP were: 50.8 +/- 6.88 ml/min.kg; 12.5 +/- 2.02 ml/min.kg; 3.84 +/- 0.55 liters/kg; and 1.12 +/- 0.09 hr. There are statistically significant differences between the enantiomers in all pharmacokinetic parameters except half-life. About 40% of the l-AP dose was excreted in urine as l-p-hydroxyamphetamine and 24% as intact drug. The corresponding values for d-AP were 32% and 26%, respectively. p-Hydroxyamphetamine was primarily excreted into urine as the conjugated form. These data indicate stereoselective differences in the pharmacokinetics of the enantiomers of AP after administration of racemic drug in the rat.

Pharmacokinetics of D-propranolol following oral, intra-arterial and intraportal administration: contrasting effects of oral glucose pretreatment

Several research groups have reported that in man the oral administration of propranolol with food leads to a marked increase (about 50 per cent) in the area under the plasma concentration-time curve (AUCpo) of this well absorbed and highly metabolized drug. An acute change in hepatic metabolic enzyme activity has been postulated as one of the mechanisms which could be responsible for this observed 'food effect'. The administration of simple carbohydrates such as glucose and fructose has been documented to influence hepatic drug metabolism. Therefore, in the present study, the effect of oral glucose (4 g kg-1 as a 50 per cent aqueous solution) on the disposition kinetics of d-propranolol was examined in male Sprague-Dawley rats (8 to 9 per group). Oral glucose treatment caused a statistically significant decrease (50.4 +/- 12.3 vs 36.6 +/- 15.2 min micrograms ml-1; p < 0.05) in the AUCpo of propranolol when this drug was given by oral intubation (10 mg kg-1). This glucose treatment also caused the apparent mean residence time of propranolol after an oral dose to increase from 0.70 +/- 0.08 h to 1.79 +/- 0.29 h (p < 0.05), but did not change its rate of elimination (suggesting collectively a decreased apparent intrinsic clearance and prolonged drug absorption). In a second study, the same oral glucose treatment was demonstrated to have little impact on the steady state concentrations of propranolol when this drug was infused intraarterially at a constant rate. This confirms that the systemic clearance of propranolol is influenced minimally by the glucose treatment. In a third study, propranolol was infused at a constant rate into the portal vein (pyloric vein infusion) bypassing the processes of intestinal metabolism and absorption (i.e. to remove these sources of variability associated with oral administration). Under these conditions, no significant changes in AUC or apparent mean residence time were observed for the two propranolol doses studied (10 mg kg-1 and 5 mg kg-1). We conclude that the oral glucose and oral propranolol interaction appears to be due to an alteration in the input process before drug enters the liver. Furthermore, this experimental series suggests that studies combining accurate assessments of systemic clearance (constant rate intra-arterial infusion studies), intrinsic hepatic clearance (pyloric vein infusion studies), and oral administration supplemented with necessary protein binding studies may be used together to characterize the mechanism responsible for drug-nutrient and drug-drug interactions.

Disposition kinetics of amphotericin B in rats. The influence of dose

Amphotericin B (Am-B), an antifungal drug, has been used for the treatment of most disseminated fungal infections. The current therapeutic regimens for this drug are complex, at least in part as a result of limited pharmacokinetic information. In this study, we examined the disposition of Am-B as a function of dose in rats. Groups of male Sprague-Dawley rats were given Am-B by a 15-min iv infusion at three different doses. We observed no significant differences in systemic clearance among the Am-B doses studied (4.29 +/- 1.42, 3.83 +/- 0.29, and 3.92 +/- 0.68 ml/min.kg for doses of 0.28, 0.45, and 0.84 mg/kg, respectively). Similarly, small differences were seen in volumes of distribution as a function of dose. We conclude that the disposition kinetics of Am-B were linear over the dose range studied.

The influence of vitamin K3 treatment on the pharmacokinetics and metabolism of (+)-propranolol in the rat

The effects of vitamin K3 treatment on the pharmacokinetics and metabolism of (+)-propranolol and the consequences of hepatic injury associated with vitamin K3 treatment were examined in groups of male Sprague-Dawley rats. When vitamin K3 (20 mg/kg) in polyethylene glycol 300 (PEG 300) was coinfused with (+)-propranolol (2 mg/kg) into the pyloric vein (a tributary flowing directly into the hepatic portal vein), a significant decrease in the intrinsic clearance of total drug (CLint) from 94.1 +/- 50.1 to 32.9 +/- 11.5 ml/min/kg was observed (p less than 0.01 vs. vehicle control). However, a lower dose of vitamin K3 (2 mg/kg in PEG 300) had little effect on this parameter. Interestingly, the PEG 300 vehicle control group exhibited a significantly (p less than 0.05) higher CLint than that observed in a saline control group (94.1 +/- 50.1 vs. 45.9 +/- 13.7 ml/min/kg). This difference appeared to be due to an increase in the free fraction of propranolol caused by PEG 300, because in vitro addition of this solvent to serum (at estimated in vivo concentrations) with or without added vitamin K3 doubled propranolol free fraction. Furthermore, rats that received the high dose vitamin K3 (20 mg/kg) treatment exhibited a pronounced increase in the serum concentration of enzymes of hepatic origin (alanine aminotransferase and sorbitol dehydrogenase) and in the incidence of hepatic necrosis. It was also observed that high-dose vitamin K3 treatment caused only minor changes in the urinary recovery of propranolol metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of 4-methylpyrazole on antipyrine clearance in rats

Pyrazole and 4-methylpyrazole (4-MP) are potent, effective inhibitors of alcohol dehydrogenase. Pyrazole and its derivatives also have been shown to affect the cytochrome P-450 dependent monooxygenase system. This study was performed to investigate the effect of 4-MP on the disposition kinetics of antipyrine (AP). Groups of male Fisher 344 rats were given an ip injection of 4-MP (100 mg/kg) or 4-MP HCl (equivalent to 4-MP 100 mg/kg) or an equivalent volume of saline. AP (20 mg/kg) was injected intravenously via the jugular vein catheter 30 minutes later. Blood samples were collected upto 24 hours and assayed by HPLC. 4-MP pretreatment significantly decreased AP clearance from 0.490 +/- 0.032 to 0.095 +/- 0.014 (4-MP HCl) and 0.076 +/- 0.008 (4-MP) L/hr.kg (p less than 0.01). The volume of distribution of AP decreased from 0.82 +/- 0.07 to 0.65 +/- 0.06 (4-MP HCl) and 0.56 +/- 0.04 (4-MP) L/kg (p less than 0.05). Mean residence time increased from 1.68 +/- 0.09 to 6.91 +/- 0.58 (4-MP HCl) and 7.39 +/- 0.56 (4-MP) hr (p less than 0.01). These results demonstrate a significant inhibitory effect of 4-MP on the cytochrome P-450 isozyme(s) which is responsible for AP metabolism in intact animals.

The effects of hypercapnia, hypoxia, exercise and anxiety on the pattern of breathing in man

1. The pattern of breathing, defined as the relations between tidal volume and inspiratory and expiratory times, was measured during the stimulation of breathing by carbon dioxide (hyperoxic rebreathing at rest) in twenty-seven healthy, young volunteers. 2. Most of the patterns (twenty) were divisible into two parts, for low (range 1) and high (range 2) tidal volumes. The relations were curved, inverse proportionalities for both inspiration and expiration in range 2, and for expiration in range 1. The relations for inspiration in range 1 were evenly divided between those with constant inspiratory times (type 1) and those with curved, inverse proportionalities (type 2). 3. In four volunteers, direct proportionalities predominated and the patterns were scattered (type 3). 4. Eight of the volunteers (four type 1, two type 2 and two type 3 patterns) repeated the measurements and one changed from a type 1 to a type 2 pattern. 5. Nine of the volunteers also rebreathed during resting hypoxia. Two altered their patterns, and the others had patterns which were superimposed upon those measured during hyperoxic rebreathing at rest. 6. Eighteen of the volunteers also rebreathed (hyperoxic) during light exercise (25 W). Five entrained their breathing frequency to the exercise rhythm and showed exercise patterns with constant inspiratory and expiratory times. The others had patterns which were extensions of those measured during hyperoxic rebreathing at rest. 7. The pattern of breathing in range 1 was measured by steady-state methods in a further ten volunteers at rest with their eyes closed and open, and during mental arithmetic. The pooled average pattern showed that the stress of mental arithmetic shortened both inspiratory and expiratory times, and changed a type 2 pattern into a type 1 pattern.